15,894 results on '"ADDUCT"'
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2. Oxidative dehalogenation of halophenols by high-valent nonheme iron(<scp>iv</scp>)-oxo intermediates
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Devesh Kumar, Chivukula V. Sastri, Prasenjit Barman, Gourab Mukherjee, Jagnyesh Kumar Satpathy, Sam P. de Visser, and Umesh Kumar Bagha
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biology ,Chemistry ,Iron ,Active site ,Halogenation ,Heme ,Hydrogen atom abstraction ,Redox ,Medicinal chemistry ,Adduct ,Oxidative Stress ,Nucleophile ,biology.protein ,medicine ,Ferric ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Oxidation-Reduction ,medicine.drug - Abstract
Mononuclear high-valent iron(IV)-oxo intermediates are excellent oxidants towards oxygenation reactions by heme and nonheme metalloenzymes and their model systems. One of the most important functions of these intermediates in nature is to detoxify various environmental pollutants. Organic substrates such as halogenated phenols are known to be water pollutants which can be degraded to their less hazardous forms through an oxidation reaction by iron(IV)-oxo complexes. Metalloproteins in the Nature utilize various types of second-coordination sphere interactions to anchor the substrate in the vicinity of the active site. This concept of substrate-binding is well-known for natural enzymes, but quite elusive for the relevant biomimetic model systems. Herein, we report the oxidative reactivity patterns of an iron(IV)-oxo intermediate, [FeIV(O)(2PyN2Q)]2+, (2PyN2Q = 1,1-di(pyridin-2yl)-N, N-bis(quinolin-2-ylmethyl)methanamine) with a series of mono-, di- and tri-halophenols. A detailed experimental study shows that the dehalogenation reactions of the halophenols by such iron(IV)-oxo intermediates proceed via an initial hydrogen atom abstraction from the phenolic O-H group. Further, based on the size and nucleophilicity of the halophenol, an intermediate substrate-bound species forms , that is a phenolate adduct to the ferric species - which thereafter leads to the formation of the corresponding products. more...
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- 2022
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Catalog
3. Preferential formation of mono‐dimethyl disulfide adducts for determining double bond positions of poly‐unsaturated fatty acids
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Yongsong Huang and Sian Liao
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chemistry.chemical_classification ,chemistry.chemical_compound ,Double bond ,chemistry ,General Chemical Engineering ,Organic Chemistry ,Dimethyl disulfide ,Isomerization ,Medicinal chemistry ,Adduct - Published
- 2021
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4. Effect of Lewis Acids on the Catalyst Activity for Alkene Metathesis, Z-/E- Selectivity and Stability of Tungsten Oxo Alkylidenes
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J. Haydée Merino, Xavier Solans-Monfort, and Jesús Bernad
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chemistry.chemical_classification ,Steric effects ,Catalyst deactivation ,Chemistry ,Alkene ,Ligand ,General Chemistry ,Metal alkylidenes ,Metathesis ,Medicinal chemistry ,Lewis acid ,Catalysis ,Adduct ,Density functional theory ,Electronic effect ,heterocyclic compounds ,Olefn metathesis ,Lewis acids and bases - Abstract
Lewis acids increase the catalytic activity of classical heterogeneous catalysts and molecular d0 tungsten oxo alkylidenes in a variety of olefin metathesis processes. The formation of labile adducts between the metal complex and the Lewis acid has been observed experimentally and suggested to be involved in the catalyst activity increase. In this contribution, DFT (M06) calculations have been performed to determine the role of Lewis acids on catalyst activity, Z-/E- selectivity and stability by comparing three W(E)(CHR)(2,5-dimethylpyrrolide)(O-2,6-dimesithylphenoxide) (E = oxo, imido or oxo-Lewis acid adduct) alkylidenes. Results show that the formation of the alkylidene—Lewis acid adducts influences the reactivity of tungsten oxo alkylidenes due to both steric and electronic effects. The addition of the Lewis acid on the E group increases its bulkiness and this decreases catalyst Z-selectivity. Moreover, the interaction between the oxo ligand and the Lewis acid decreases the donating ability of the former toward the metal. This is important when the oxo group has either a ligand in trans or in the same plane that is competing for the same metal d orbitals. Therefore, the weakening of oxo donating ability facilitates the cycloaddition and cycloreversion steps and it stabilizes the productive trigonal bipyramid metallacyclobutane isomer. The two factors increase the catalytic activity of the complex. The electron donating tuneability by the coordination of the Lewis acid also applies to catalyst deactivation and particularly the key β-hydride elimination step. In this process, the transition states show a ligand in pseudo trans to the oxo. Therefore, the presence of the Lewis acid decreases the Gibbs energy barrier significantly. Overall, the optimization of the E group donating ability in each step of the reaction makes tungsten oxo alkylidenes more reactive and this applies both for the catalytic activity and catalyst deactivation. more...
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- 2021
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5. Electrochemical Properties and Reactivity Study of [MnV(O)(μ-OR–Lewis Acid)] Cores
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Sayantan Paria, Satadal Paul, Geetika Gupta, and Moumita Bera
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Inorganic Chemistry ,Reaction rate ,Reaction mechanism ,Ligand ,Chemistry ,Metal ions in aqueous solution ,Electrophile ,Reactivity (chemistry) ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Medicinal chemistry ,Adduct - Abstract
A mononuclear manganese(V) oxo complex of a bis(amidate)bis(alkoxide) ligand, (NMe4)[MnV(HMPAB)(O)] [2; H4HMPAB = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene], was synthesized and structurally characterized. A Mn-Oterm distance of 1.566(4) A was observed in the solid-state structure of 2, consistent with the Mn≡O formulation. The reaction of redox-inactive metal ions (Mn+ = Li+, Ca2+, Mg2+, Y3+, and Sc3+) with 2 resulted in the formation of 2-Mn+ species, which were characterized by UV-vis, 1H NMR, cyclic voltammetry, and in situ IR spectroscopy. Theoretical calculations suggested that the alkoxide oxygen atoms of the ligand scaffold are energetically most favorable for coordinating the Mn+ ions in 2. Complex 2 revealed one-electron-reduction potential at -0.01 V versus ferrocenium/ferrocene, which shifted anodically upon coordination of Mn+ ions to 2, and such a shift became more prominent with stronger Lewis acids. The oxygen-atom transfer (OAT) reactivities of 2 and 2-Mn+ species with triphenylphosphine were compared, which exhibited a systematic increase of the reaction rate with increasing Lewis acidity of Mn+ ions, and a plot of log k2 versus Lewis acidity of Mn+ ions (ΔE) followed a linear relationship. It was observed that 2-Sc3+ was ca. 3200 times more reactive toward the OAT reaction compared to 2. Hammett analysis of 2 exhibited a V-shaped plot, indicating a change of the reaction mechanism upon going from electron-rich to electron-deficient Ar3P substrates. In contrast, 2-Ca2+ and 2-Sc3+ showed an electrophilic nature toward the OAT reaction, thus demonstrating the role of the Lewis acid in controlling the OAT mechanism. The hydrogen-atom abstraction reaction of 2 and 2-Mn+ adducts with 1-benzyl-1,4-dihydronicotinamide was investigated, and it was observed that the rate of reaction did not vary considerably with the Lewis acidity of Mn+ ions. On the basis of Eyring analysis of 2 and 2-Mn+ adducts, we hypothesized an entropy-controlled hydrogen-atom-transfer reaction for 2-Sc3+, which is different from the reaction mechanism of 2 and 2-Ca2+. more...
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- 2021
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6. Crystal structures of the gold NHC complex bis(4-bromo-1,3-diethylimidazol-2-ylidene)gold(I) iodide and its 1:1 adduct with trans-bis(4-bromo-1,3-diethyl-imidazol-2-ylidene)diiodidogold(III) iodide
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Rolf Büssing, Peter G. Jones, and Ingo Ott
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crystal structure ,halogen bonds ,Iodide ,Crystal structure ,Medicinal chemistry ,Article ,Adduct ,Veröffentlichung der TU Braunschweig ,General Materials Science ,ddc:5 ,chemistry.chemical_classification ,Halogen Bonds ,Crystallography ,n-heterocyclic carbene ,N-heterocyclic Carbene ,General Chemistry ,gold ,Condensed Matter Physics ,chemistry ,ddc:54 ,QD901-999 ,Gold ,ddc:543 ,Publikationsfonds der TU Braunschweig ,ddc:546 - Abstract
The first title compound, [Au(C7H11BrN2)2]I, crystallizes in the space group P\overline{1} without imposed symmetry. The cations and anions are linked to form chains by Br...I...Br halogen-bond linkages. The second title compound, [Au(C7H11BrN2)2][AuI2(C7H11BrN2)2]I2, is an adduct of the first and its formally I2-oxidized AuIII analogue. It also crystallizes in space group P\overline{1}, whereby both gold atoms occupy inversion centres. The extended structure is a reticular layer involving Br...I...Br and I...I...Au linkages. more...
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- 2021
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7. Reactivity of the Bicyclic Amido‐Substituted Silicon(I) Ring Compound Si 4 {N(SiMe 3 )Mes} 4 with FLP‐Type Character
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Felicitas Lips, Kevin Schwedtmann, Jörn Droste, Alexander Hepp, Milica Feldt, Benedikt J. Guddorf, Jan Keuter, Michael Ryan Hansen, and Michael Quest
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Bicyclic molecule ,Chemistry ,Organic Chemistry ,Protonation ,General Chemistry ,Medicinal chemistry ,Catalysis ,Frustrated Lewis pair ,Adduct ,chemistry.chemical_compound ,Reactivity (chemistry) ,Lewis acids and bases ,Carbene ,Diphenylacetylene - Abstract
The bicyclic amido-substituted silicon(I) ring compound Si4 {N(SiMe3 )Mes}4 2 (Mes=Mesityl=2,4,6-Me3 C6 H2 ) features enhanced zwitterionic character and different reactivity from the analogous compound Si4 {N(SiMe3 )Dipp}4 1 (Dipp=2,6-i Pr2 C6 H3 ) due to the smaller mesityl substituents. In a reaction with the N-heterocyclic carbene NHC Me4 (1,3,4,5-tetramethyl-imidazol-2-ylidene), we observe adduct formation to give Si4 {N(SiMe3 )Mes}4 ⋅ NHC Me4 (3). This adduct reacts further with the Lewis acid BH3 to yield the Lewis acid-base complex Si4 {N(SiMe3 )Mes}4 ⋅ NHC Me4 ⋅ BH3 (4). Coordination of AlBr3 to 2 leads to the adduct 5. Calculated proton affinities and fluoride ion affinities reveal highly Lewis basic and very weak Lewis acidic character of the low-valent silicon atoms in 1 and 2. This is confirmed by protonation of 1 and 2 with Brookharts acid yielding 6 and 7. Reaction with diphenylacetylene only occurs at 111 °C with 2 in toluene and is accompanied by fragmentation of 2 to afford the silacyclopropene 8 and the trisilanorbornadiene species 9. more...
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- 2021
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8. Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination
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David Scheschkewitz, Cem B. Yildiz, Michael Zimmer, Volker Huch, Ramakirushnan Suriya Narayanan, Kaustubh R. Mote, Pankaj Kalita, Debabrata Dhara, Vadapalli Chandrasekhar, Anukul Jana, Subhadip Mondal, and Aksaray Teknik Bilimler Meslek Yüksekokulu more...
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Phosphine oxide ,010405 organic chemistry ,Chemistry ,Diphosphene ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Adduct ,Catalysis ,chemistry.chemical_compound ,Hydrolysis ,Reactivity (chemistry) ,Carbene - Abstract
Diphosphene TerMesP = PTerMes (1; TerMes = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) and NHCMe42 (NHCMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHCMe4-coordinated diphosphene 3. While uncoordinated 1 is inert to hydrolysis, the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHCMe4. On this basis, conditions suitable for the catalytic use of NHCMe4 were identified. Similarly, while the hydrogenation of free diphosphene 1 with H3N·BH3 is very slow, 3 reacts instantaneously with H3N·BH3 at room temperature to afford a dihydrodiphosphane. © 2018 The Royal Society of Chemistry., Department of Science and Technology Tata Institute of Fundamental Research, This work is supported by the Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad-500107, Telan-gana, India, SERB-DST (EMR/2014/001237), India, Research Group Linkage Programme of Alexander von Humboldt Foundation, Germany, and Saarland University, Germany. VC is thankful to the Department of Science and Technology, New Delhi, India, for a National J. C. Bose fellowship. We thank the reviewers for their comments to improve the manuscript. more...
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- 2022
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9. DFT (density functional theory) studies on cycloisomerization of 15–membered triazatriacetylenic macrocycle
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Nader Zabarjad Shiraz, Mansooreh Movahedi, Marjaneh Samadizadeh, Mohamad Reza Talei Bavil Olyai, and Ali Ezabadi
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DFT (density functional theory) ,triazatriacetyle ,Ene–Reaction ,General Chemistry ,Sigmatropic reaction ,Medicinal chemistry ,Article ,Cycloaddition ,Catalysis ,Adduct ,[2+2+2] reaction ,chemistry.chemical_compound ,Cycloisomerization ,chemistry ,cycloisomerization ,Pd ,Moiety ,Ene reaction ,Pyrrole - Abstract
The mechanism as well the stereochemistry of cascade cycloisomerization of 15–membered triazatriacetylenic macrocycle was investigated theoretically by using M062X/6–31+G(d,p) and M062X/LANL2DZ calculations. The results showed that the mechanism and outcome of the reaction depended on the absence and presence of a transition metal catalyst. So that, in thermal-induced condition, the reaction had to experience several suprafacial concerted reactions including Ene-reaction (DG#=35.38 kcal/mol), Diels–Alder cycloaddition (DG# = 17.16 kcal/mol), and sigmatropic H-shift rearrangement (DG# = 56.21 kcal/mol) to produce diastereoselective fused cis–tetracyclic aromatic bearing a pyrrole moiety by following kinetic considerations. Also, the [2+2+2] cycloaddition mechanism was neglected in thermal–induced conditions because of high activation free Gibbs energy (DG# = 63.90 kcal/mol). In the presence of palladium catalyst, Pd(0) formed an adduct by coordinating to C = C bonds and decreased the DG# of the process to 29.58 kcal/mol, and consequently provided a facilitated media for the reaction to follow the [2+2+2] to produce more stable fused tetracyclic benzenoid aromatic by passing through the lower energy barrier. more...
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- 2021
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10. Lewis Acid‐Promoted Oxidative Addition at a [Ni 0 (diphosphine) 2 ] Complex: The Critical Role of a Secondary Coordination Sphere
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David J. Nelson, Maeve C. Dufour, Joseph A. Zurakowski, Denis M. Spasyuk, Marcus W. Drover, and Brady J. H. Austen
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Coordination sphere ,010405 organic chemistry ,Ligand ,Chemistry ,Organic Chemistry ,Iodobenzene ,Context (language use) ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Oxidative addition ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,Adduct ,chemistry.chemical_compound ,QD ,Reactivity (chemistry) ,Lewis acids and bases - Abstract
Oxidative addition represents a critical elementary step in myriad catalytic transformations. Here, the importance of thoughtful ligand design cannot be overstated. In this work, we report the intermolecular activation of iodobenzene (PhI) at a coordinatively saturated 18-electron [Ni 0(diphosphine) 2] complex bearing a Lewis acidic secondary coordination sphere. Whereas alkyl-substituted diphosphine complexes of Group 10 are known to be unreactive in such reactions, we show that [Ni 0(P 2B Cy 4) 2] (P 2B Cy 4=1,2-bis(di(3-dicyclohexylboraneyl)-propylphosphino)ethane) is competent for room-temperature PhI cleavage to give [Ni II(P 2B Cy 4)(Ph)(I)]. This difference in oxidative addition reactivity has been scrutinized computationally – an outcome that is borne out in ring-opening to provide the reactive precursor – for [Ni 0(P 2B Cy 4) 2], a “boron-trapped” 16-electron κ 1-diphosphine Ni(0) complex. Moreover, formation of [Ni II(P 2B Cy 4)(Ph)(I)] is inherent to the P 2B Cy 4 secondary coordination sphere: treatment of the Lewis adduct, [Ni 0(P 2B Cy 4) 2(DMAP) 8] with PhI provides [Ni II(P 2B Cy 4) 2(DMAP) 8(I)]I via iodine-atom abstraction and not a [Ni II(Ph)(I)(diphosphine)] compound – an unusual secondary sphere effect. Finally, the reactivity of [Ni 0(P 2B Cy 4) 2] with 4-iodopyridine was surveyed, which resulted in a pyridyl-borane linked oligomer. The implications of these outcomes are discussed in the context of designing strongly donating, and yet labile diphosphine ligands for use in a critical bond activation step relevant to catalysis. more...
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- 2021
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11. Interconversion of Molybdenum or Tungsten d2 Styrene Complexes with d0 1-Phenethylidene Analogues
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Maxime Boudjelel, Charlene Tsay, Richard R. Schrock, Matthew P. Conley, and Sumeng Liu
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Diastereomer ,chemistry.chemical_element ,Protonation ,General Chemistry ,Biochemistry ,Medicinal chemistry ,Catalysis ,Adduct ,Styrene ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Deprotonation ,chemistry ,Molybdenum ,Pyridinium - Abstract
Upon addition of 5-15% PhNMe2H+X- (X = B(3,5-(CF3)2C6H3)4 or B(C6F5)4) to Mo(NAr)(styrene)(OSiPh3)2 (Ar = N-2,6-i-Pr2C6H3) in C6D6 an equilibrium mixture of Mo(NAr)(styrene)(OSiPh3)2 and Mo(NAr)(CMePh)(OSiPh3)2 is formed over 36 h at 45 °C (Keq = 0.36). A plausible intermediate in the interconversion of the styrene and 1-phenethylidene complexes is the 1-phenethyl cation, [Mo(NAr)(CHMePh)(OSiPh3)2]+, which can be generated using [(Et2O)2H][B(C6F5)4] as the acid. The interconversion can be modeled as two equilibria involving protonation of Mo(NAr)(styrene)(OSiPh3)2 or Mo(NAr)(CMePh)(OSiPh3)2 and deprotonation of the α or β phenethyl carbon atom in [Mo(NAr)(CHMePh)(OSiPh3)2]+. The ratio of the rate of deprotonation of [Mo(NAr)(CHMePh)(OSiPh3)2]+ by PhNMe2 in the α position versus the β position is ∼10, or ∼30 per Hβ. The slow step is protonation of Mo(NAr)(styrene)(OSiPh3)2 (k1 = 0.158(4) L/(mol·min)). Proton sources such as (CF3)3COH or Ph3SiOH do not catalyze the interconversion of Mo(NAr)(styrene)(OSiPh3)2 and Mo(NAr)(CMePh)(OSiPh3)2, while the reaction of Mo(NAr)(styrene)(OSiPh3)2 with pyridinium salts generates only a trace (∼2%) of Mo(NAr)(CMePh)(OSiPh3)2 and forms a monopyridine adduct, [Mo(NAr)(CHMePh)(OSiPh3)2(py)]+ (two diastereomers). The structure of [Mo(NAr)(CHMePh)(OSiPh3)2]+ has been confirmed in an X-ray study; there is no structural indication that a β proton is activated through a CHβ interaction with the metal. W(NAr)(CMePh)(OSiPh3)2 is also converted into a mixture of W(NAr)(CMePh)(OSiPh3)2 and W(NAr)(styrene)(OSiPh3)2 (Keq = 0.47 at 45 °C in favor of the styrene complex) with 10% [PhNMe2H][B(C6F5)4] as the catalyst; the time required to reach equilibrium is approximately the same as in the Mo system. more...
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- 2021
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12. Enantioselective Cross-Coupling of Electron-Deficient Alkenes via Ir-Catalyzed Vinylic sp2 C–H Alkylation
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Masafumi Kojima, Sahoko Onoda, Takanori Shibata, and Mamoru Ito
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Chemistry ,Yield (chemistry) ,Organic Chemistry ,Enantioselective synthesis ,Electron ,Physical and Theoretical Chemistry ,Alkylation ,Biochemistry ,Medicinal chemistry ,Catalysis ,Adduct ,Conjugate - Abstract
A chiral Ir-catalyzed reaction of α-aryl-α,β-unsaturated amides with β-substituted acrylates proceeded to give formal conjugate adducts in high yield and ee (up to 99% yield and up to 95% ee). This is the first example of the enantioselective cross-coupling of two different electron-deficient alkenes via vinylic sp2 C-H activation, and polyfunctionalized chiral compounds were obtained. more...
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- 2021
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13. Dirhodium‐Catalyzed Enantioselective B−H Bond Insertion of gem ‐Diaryl Carbenes: Efficient Access to gem ‐Diarylmethine Boranes
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Yu-Xuan Su, Shou-Fei Zhu, Xiao-Yu Li, Liang-Liang Yang, Yu-Tao Zhao, and Ming-Yao Huang
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Diazomethane ,Enantioselective synthesis ,chemistry.chemical_element ,Boranes ,General Medicine ,General Chemistry ,Borane ,Medicinal chemistry ,Catalysis ,Rhodium ,Adduct ,chemistry.chemical_compound ,Stereospecificity ,chemistry ,Carbene - Abstract
The scarcity of reliable methods for synthesizing chiral gem-diarylmethine borons limits their applications. Herein, we report a method for highly enantioselective dirhodium-catalyzed B-H bond insertion reactions with diaryl diazomethanes as carbene precursors. These reactions afforded chiral gem-diarylmethine borane compounds in high yield (up to 99 % yield), high activity (turnover numbers up to 14 300), high enantioselectivity (up to 99 % ee) and showed unprecedented broad functional group tolerance. The borane compounds synthesized by this method could be efficiently transformed into diaryl methanol, diaryl methyl amine, and triaryl methane derivatives with good stereospecificity. Mechanistic studies suggested that the borane adduct coordinated to the rhodium catalyst and thus interfered with decomposition of the diazomethane, and that insertion of a rhodium carbene (generated from the diaryl diazomethane) into the B-H bond was most likely the rate-determining step. more...
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- 2021
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14. Copper-Catalyzed Cyclization of N-Propargyl Ynamides with Borane Adducts through B–H Bond Insertion
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Tong-Yi Zhai, Xiao Li, Chong-Yang Shi, Guang-Yu Zhu, Xin-Qi Zhu, and Long-Wu Ye
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Hydrogen bond ,Organic Chemistry ,Substrate (chemistry) ,Borane ,Biochemistry ,Medicinal chemistry ,Adduct ,chemistry.chemical_compound ,chemistry ,Functional group ,Copper catalyzed ,Physical and Theoretical Chemistry ,Vinyl cation ,N-propargyl - Abstract
An efficient copper-catalyzed cyclization of N-propargyl ynamides with borane adducts through B-H bond insertion has been developed. A series of valuable organoboron compounds are constructed in generally good yields with a wide substrate scope and good functional group tolerance under mild reaction conditions. Importantly, this protocol via vinyl cation intermediates constitutes a novel way of B-H bond insertion. more...
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- 2021
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15. Spectroscopic Evidence for a Cobalt-Bound Peroxyhemiacetal Intermediate
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Yeongjin Son, Aleksandr Pereverzev, Jaeheung Cho, Guilherme L. Tripodi, Kyungmin Kim, Seonghan Kim, and Jana Roithová
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chemistry.chemical_classification ,Letter ,Direct evidence ,aldehyde deformylation ,chemistry.chemical_element ,Aldehyde ,Medicinal chemistry ,Adduct ,bioinorganic chemistry ,Metal ,Isotopic labeling ,Chemistry ,chemistry ,Nucleophile ,peroxyhemiacetal species ,dichotomic reactivity ,visual_art ,visual_art.visual_art_medium ,Spectroscopy and Catalysis ,Reactivity (chemistry) ,Cobalt ,QD1-999 ,cobalt-dioxygen adduct - Abstract
Aldehyde deformylation reactions by metal dioxygen adducts have been proposed to involve peroxyhemiacetal species as key intermediates. However, direct evidence of such intermediates has not been obtained to date. We report the spectroscopic characterization of a mononuclear cobalt(III)-peroxyhemiacetal complex, [Co(Me3-TPADP)(O2CH(O)CH(CH3)C6H5)]+ (2), in the reaction of a cobalt(III)-peroxo complex (1) with 2-phenylpropionaldehyde (2-PPA). The formation of 2 is also investigated by isotope labeling experiments and kinetic studies. The conclusion that the peroxyhemiacetalcobalt(III) intermediate is responsible for the aldehyde deformylation is supported by the product analyses. Furthermore, isotopic labeling suggests that the reactivity of the cobalt(III)-peroxo complex depends on the second reactant. The aldehyde inserts between the oxygen atoms of 1, whereas the reaction with acyl chlorides proceeds by a nucleophilic attack. The observation of the peroxyhemiacetal intermediate provides significant insight into the initial step of aldehyde deformylation by metalloenzymes. more...
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- 2021
16. N‐Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Adducts of Antimony(III)
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Udo Radius, Krzysztof Radacki, Michael Philipp, and Mirjam J. Krahfuss
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Inorganic Chemistry ,chemistry.chemical_classification ,chemistry.chemical_compound ,Antimony ,Chemistry ,chemistry.chemical_element ,ddc:546 ,Medicinal chemistry ,Carbene ,Alkyl ,Adduct - Abstract
A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with antimony(III) chlorides of the general formula SbCl\(_{2}\)R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me\(_{2}\)Im\(^{Me}\) (1,3,4,5-tetra-methyl-imidazolin-2-ylidene), iPr\(_{2}\)Im\(^{Me}\) (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Mes\(_{2}\)Im, Dipp\(_{2}\)Im (R\(_{2}\)Im=1,3-di-organyl-imidazolin-2-ylidene; Mes=2,4,6-trimethylphenyl, Dipp=2,6-di-isopropylphenyl) and cAAC\(^{Me}\) with antimony(III) compounds SbCl\(_{2}\)R (R=Cl (1), Ph (2) and Mes (3)) yields the adducts NHC ⋅ SbCl\(_{2}\)R (R=Cl (4), Ph (5) and Mes (6); NHC=Me\(_{2}\)Im\(^{Me}\) (a), iPr\(_{2}\)Im\(^{Me}\) (b), Dipp\(_{2}\)Im (c) and Mes\(_{2}\)Im (d)) and cAAC\(^{Me}\) ⋅ SbCl\(_{2}\)R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp\(_{2}\)Im) ⋅ SbCl\(_{2}\)Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated \(^{a}\)NHC-adduct \(^{a}\)Dipp\(_{2}\)Im ⋅ SbCl\(_{2}\)Ar (Ar=Mes (7) and Ph (8)) (\(^{"a"}\) denotes “abnormal” coordination mode of the NHC) in high yields. One of the chloride substituents at antimony of 7 can be abstracted by GaCl3 or Ag[BF\(_{4}\)] to obtain the imidazolium salts [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][BF\(_{4}\)] (9) and [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][GaCl\(_{4}\)] (10). more...
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- 2021
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17. Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: AuIII–Cl versus AuIII–OH
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Brendan Twamley, Aidan R. McDonald, Robert Gericke, and Marta Lovisari
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010405 organic chemistry ,Ligand ,Halide ,chemistry.chemical_element ,Oxidative phosphorylation ,Hydrogen atom ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Oxygen ,Article ,3. Good health ,0104 chemical sciences ,Adduct ,Inorganic Chemistry ,Metal ,chemistry ,visual_art ,Transfer mechanism ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry - Abstract
High-valent metal–halides have come to prominence as highly effective oxidants. A direct comparison of their efficacy against that of traditional metal–oxygen adducts is needed. [AuIII(Cl)(terpy)](ClO4)2 (1; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O–H and C–H bonds via a hydrogen atom transfer mechanism. A direct comparison with [AuIII(OH)(terpy)](ClO4)2 (2) showed that 1 was a kinetically superior oxidant with respect to 2 for all substrates tested. We ascribe this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand., We report a direct comparison of the efficacy of metal−halide oxidants to those of traditional metal−oxygen adducts. AuIII−Cl and AuIII−OH oxidants, supported by the same ancillary ligand, readily oxidized substrates via a hydrogen atom transfer mechanism. The AuIII−Cl oxidant was kinetically superior for all substrates. We ascribed this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand. more...
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- 2021
18. Bifunctional Fluorophosphonium Triflates as Intramolecular Frustrated Lewis Pairs: Reversible CO 2 Sequestration and Binding of Carbonyls, Nitriles and Acetylenes
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Jan J. Weigand, Jannis Fidelius, Antonio Bauzá, Felix Hennersdorf, Kai Schwedtmann, Antonio Frontera, Chun-Xiang Guo, and Arne Dickschat
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chemistry.chemical_compound ,Chemistry ,Tetrahedral carbonyl addition compound ,Intramolecular force ,Organic Chemistry ,Electrophile ,General Chemistry ,Bifunctional ,Medicinal chemistry ,Catalysis ,Cycloaddition ,Frustrated Lewis pair ,Adduct - Abstract
Electrophilic fluorophosphonium triflates bearing pyridyl (3[OTf]) or imidazolyl (4[OTf])-substituents act as intramolecular frustrated Lewis pairs (FLPs) and reversibly form 1 : 1 adducts with CO2 (5+ and 6+ ). An unusual and labile spirocyclic tetrahedral intermediate (72+ ) is observed in CO2 -pressurized (0.5-2.0 bar) solutions of cation 4+ at low temperatures, as demonstrated by variable-temperature NMR studies, which were confirmed crystallographically. In addition, cations 3+ and 4+ actively bind carbonyls, nitriles and acetylenes by 1,3-dipolar cycloaddition, as shown by selected examples. more...
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- 2021
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19. Maillard Browning Inhibition by Ellagic Acid via Its Adduct Formation with the Amadori Rearrangement Product
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Khizar Hayat, Chi-Tang Ho, Ziyan Wang, Yan Xu, Qiang Zhang, Mengyu Ma, Heping Cui, and Xiaoming Zhang
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Glycation End Products, Advanced ,Xylose ,Melanoidin ,General Chemistry ,Medicinal chemistry ,Maillard Reaction ,Adduct ,Hydrolysis ,chemistry.chemical_compound ,Maillard reaction ,symbols.namesake ,Ellagic Acid ,chemistry ,Tandem Mass Spectrometry ,Yield (chemistry) ,Amadori rearrangement ,Browning ,symbols ,General Agricultural and Biological Sciences ,Ellagic acid - Abstract
The Maillard reaction performed under a stepwise increase of temperature was applied for researching the inhibition of Maillard browning caused by ellagic acid. Ellagic acid was found effective for the inhibition of melanoidin formation in the xylose-glycine Maillard reaction but depended on its dosage and the point of time it was added in the reaction system. The lightest color of the Maillard reaction products was observed when ellagic acid was added at the 90th min, which was the point of time when the Amadori rearrangement product (ARP) developed the most. LC-ESI-MS/MS analysis results showed a significant tendency of the ellagic acid hydrolysis product to react with the predominant intermediate ARP to yield an adduct. The adduct stabilized the ARP and delayed its decomposition and inhibited the downstream reactions toward browning. After the ARP was depleted, ellagic acid also showed an effect on scavenging some short-chain dicarbonyls which contributed to the inhibition of Maillard browning. more...
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- 2021
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20. Sharp difference in the rate of formation and stability of the Diels–Alder reaction adducts with 2,3‐dicyano‐1,4‐benzoquinone and N‐phenylimide‐1,4‐benzoquinone‐2,3‐dicarboxylic acid
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Anastasia O. Kolesnikova, Vladimir D. Kiselev, Alexey A. Shulyatiev, Ildar F. Dinikaev, and Dmitry A. Kornilov
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Inorganic Chemistry ,1,4-Benzoquinone ,chemistry.chemical_classification ,chemistry.chemical_compound ,Dicarboxylic acid ,Reaction rate constant ,chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry ,Biochemistry ,Medicinal chemistry ,Adduct ,Diels–Alder reaction - Published
- 2021
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21. Syntheses, Structures, Reactivities, and Basicities of Quinolinyl and Isoquinolinyl Complexes of an Electron Rich Chiral Rhenium Fragment and Their Electrophilic Addition Products
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Dante A. Castillo Molina, Michael B. Hall, Taveechai Wititsuwannakul, Frank Hampel, and John A. Gladysz
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Steric effects ,Chemistry ,Electrophilic addition ,Ligand ,Organic Chemistry ,chemistry.chemical_element ,Protonation ,General Chemistry ,Crystal structure ,Rhenium ,Medicinal chemistry ,Catalysis ,Adduct ,Nucleophile - Abstract
Reactions of Li+ [(η5 -C5 H5 )Re(NO)(PPh3 )]- with 2- and 4-chloroquinoline or 1-chloroisoquinoline give the corresponding σ quinolinyl and isoquinolinyl complexes 3, 6, and 8. With 3 and 8 there is further protonation to yield HCl adducts, but additions of KH give the free bases. Treatment of 3 with HBF4 ⋅OEt2 or H(OEt2 )2+ BArf- gives the quinolinium salts [(η5 -C5 H5 )Re(NO)(PPh3 )(C(NH)C(CH)4 C(CH)(CH))]+ X- (3-H+ X- ; X- =BF4- /BArf- , 94-98 %). Addition of CF3 SO3 CH3 to 3, 6, or 8 affords the corresponding N-methyl quinolinium salts. In the case of [(η5 -C5 H5 )Re(NO)(PPh3 )(C(NCH3 )C(CH)4 C(CH)(CH))]+ CF3 SO3- (3-CH3+ CF3 SO3- ), addition of CH3 Li gives the dihydroquinolinium complex (SRe RC ,RRe SC )-[(η5 -C5 H5 )Re(NO)(PPh3 )(C(NCH3 )C(CH)4 C(CHCH3 )(CH2 ))]+ CF3 SO3- ((SRe RC ,RRe SC )-5+ CF3 SO3- , 76 %) in diastereomerically pure form. Crystal structures of 3-H+ BArf- , 3-CH3+ CF3 SO3- , (SRe RC , RRe SC )-5+ Cl- , and 6-CH3+ CF3 SO3- show that the quinolinium ligands adopt Re⋅⋅⋅C conformations that maximize overlap of their acceptor orbitals with the rhenium fragment HOMO, minimize steric interactions with the bulky PPh3 ligand, and promote various π interactions. NMR experiments establish the Bronsted basicity order 3>8>6, with Ka (BH+ ) values >10 orders of magnitude greater than the parent heterocycles, although they remain less active nucleophilic catalysts in the reactions tested. DFT calculations provide additional insights regarding Re⋅⋅⋅C bonding and conformations, basicities, and the stereochemistry of CH3 Li addition. more...
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- 2021
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22. Simple Synthesis of Complex Amines from the Diels–Alder Adducts of (–)-Cytisine
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Oleg Lukin, Grygoriy Dolgonos, Volodymyr Fetyukhin, Alexey Chuyko, and Alexander Shivanyuk
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chemistry.chemical_classification ,Double bond ,Hydrogen ,Organic Chemistry ,chemistry.chemical_element ,Medicinal chemistry ,Catalysis ,Adduct ,chemistry.chemical_compound ,Cytisine ,chemistry ,Yield (chemistry) ,Benzyl group ,Derivative (chemistry) ,Diels–Alder reaction - Abstract
The Diels–Alder reaction of N-benzylcytisine with N-methyl- and N-benzylmaleimides is 100% endo-selective and gives the corresponding syn- and anti-diastereomers in 11–42% isolated yields. The studies of the reaction progress with LCMS and NMR along with detailed quantum chemical calculations revealed that some Diels–Alder adducts are kinetically and their isomers are thermodynamically controlled products. The Pd/C-catalyzed hydrogenation of benzyl-protected cytisine amine derivatives resulted in the removal of the benzyl group and the addition of hydrogen to the C=C double bond to give the corresponding secondary amines in 45–84% yield. The complete reduction of carbonyl groups in a cytisine derivative with LiAlH4 in THF under reflux afforded the respective tricyclic triamine. Quantum mechanical calculations for the mechanism of the Diels–Alder reaction between the simplest model compounds are presented. more...
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- 2021
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23. Crystal structure of 2-(2,6-diisopropylphenyl)-N,N-diethyl-3,3-dimethyl-2-azaspiro[4.5]decan-1-amine: a diethylamine adduct of a cyclic(alkyl)(amino)carbene (CAAC)
- Author
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Roxanne A. Naumann, Allegra L. Liberman-Martin, and Joseph W. Ziller
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crystal structure ,Crystallography ,chemistry.chemical_element ,cyclic(alkyl)(amino)carbene ,General Chemistry ,Crystal structure ,Condensed Matter Physics ,Medicinal chemistry ,Research Communications ,Adduct ,chemistry.chemical_compound ,carbene reactivity ,Deprotonation ,chemistry ,n—h bond activation ,QD901-999 ,hemic and lymphatic diseases ,Amide ,cyclic(alkyl)(amino)carbene ,General Materials Science ,Amine gas treating ,Lithium ,Carbene ,Monoclinic crystal system - Abstract
A diethylamine adduct of a cyclic(alkyl)(amino)carbene was synthesized and characterized by single-crystal X-ray diffraction and NMR spectroscopy., The structure of the title compound, C27H46N2, at 93 K has monoclinic (P21/n) symmetry. The title compound was prepared by treatment of 2-(2,6-diisopropylphenyl)-3,3-dimethyl-2-azaspiro[4.5]dec-1-en-2-ium hydrogen dichloride with two equivalents of lithium diethylamide. Characterization of the title compound by single-crystal X-ray diffraction and 1H and 13C NMR spectroscopy is presented. Formation of the diethylamine adduct of the cyclic(alkyl)(amino)carbene (CAAC) was unexpected, as deprotonation using lithium diisopropylamide results in free CAAC formation. more...
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- 2021
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24. [Ni(NHC) 2 ] as a Scaffold for Structurally Characterized trans [H−Ni−PR 2 ] and trans [R 2 P−Ni−PR 2 ] Complexes
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Michael K. Whittlesey, Sara Sabater, William J. M. Blackaby, Heidi Née Schneider Schmidt, Mary F. Mahon, Nasir A. Rajabi, Udo Radius, Stuart MacGregor, Maximilian W. Kuntze-Fechner, Thomas Zell, Harry Grieve, David Schmidt, John P. Lowe, and Connie J. Isaac more...
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Ligand ,Organic Chemistry ,Substituent ,chemistry.chemical_element ,General Chemistry ,Medicinal chemistry ,Catalysis ,Adduct ,chemistry.chemical_compound ,Nickel ,chemistry ,Diphosphines ,Moiety ,Carbene ,Phosphine - Abstract
The addition of PPh2 H, PPhMeH, PPhH2 , P(para-Tol)H2 , PMesH2 and PH3 to the two-coordinate Ni0 N-heterocyclic carbene species [Ni(NHC)2 ] (NHC=IiPr2 , IMe4 , IEt2 Me2 ) affords a series of mononuclear, terminal phosphido nickel complexes. Structural characterisation of nine of these compounds shows that they have unusual trans [H-Ni-PR2 ] or novel trans [R2 P-Ni-PR2 ] geometries. The bis-phosphido complexes are more accessible when smaller NHCs (IMe4 >IEt2 Me2 >IiPr2 ) and phosphines are employed. P-P activation of the diphosphines R2 P-PR2 (R2 =Ph2 , PhMe) provides an alternative route to some of the [Ni(NHC)2 (PR2 )2 ] complexes. DFT calculations capture these trends with P-H bond activation proceeding from unconventional phosphine adducts in which the H substituent bridges the Ni-P bond. P-P bond activation from [Ni(NHC)2 (Ph2 P-PPh2 )] adducts proceeds with computed barriers below 10 kcal mol-1 . The ability of the [Ni(NHC)2 ] moiety to afford isolable terminal phosphido products reflects the stability of the Ni-NHC bond that prevents ligand dissociation and onward reaction. more...
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- 2021
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25. Oxidative cyclization of 5-aryl-1-benzyl-1,2,3-triazoles bearing electron-rich aromatic groups: ortho/ortho and ortho/ipso coupling
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Mastaneh Safarnejad Shad, S. S. Zhokhov, Victor B. Rybakov, Maksim А. Boichenko, Olga A. Ivanova, Konstantin V. Anisovich, Igor V. Truhskov, and Wim Dehaen
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Coupling (electronics) ,Reaction conditions ,Oxidative cyclization ,chemistry.chemical_compound ,Chemistry ,Intramolecular force ,Aryl ,Organic Chemistry ,Oxidative coupling of methane ,Medicinal chemistry ,Boron trifluoride ,Adduct - Abstract
The intramolecular oxidative coupling of electron-rich aromatic groups in 5-(het)aryl-1-(het)arylalkyl-1 H -1,2,3-triazoles was studied in detail. Under treatment with phenyliodoso bis(trifluoroacetate) and boron trifluoride etherate these substrates afforded products of either ortho/ortho or ortho/ipso coupling depending on the nature of aromatic groups and reaction conditions applied. It was found that for substrates which are capable for both types of coupling, ortho-/ipso -adducts are formed under kinetic control while ortho-/ortho -products are formed under thermodynamic control. The developed procedures allow preparation of complex polycyclic azaheterocycles from simple precursors in two steps only. more...
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- 2021
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26. Reaction of 2- and 4-(Arylmethylideneamino)phenols with Methyl 1-Bromocyclohexanecarboxylate and Zinc
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Nikolay F. Kirillov, E. A. Nikiforova, Maksim V. Dmitriev, D. V. Baibarodskikh, and D. P. Zverev
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chemistry.chemical_classification ,Schiff base ,Double bond ,Chemistry ,Organic Chemistry ,Intramolecular cyclization ,chemistry.chemical_element ,Zinc ,Medicinal chemistry ,Adduct ,chemistry.chemical_compound ,Nucleophile ,Reagent ,Phenols - Abstract
2- and 4-(Arylmethylideneamino)phenols react with Reformatsky reagent, obtained from methyl 1-bromocyclohexanecarboxylate and zinc, to form 3-aryl-2-[2-(or 4-)hydroxyphenyl]-2-azaspiro[3.5]nonan-1-ones. The reaction involves the initial addition of the organozinc reagent across the C=N double bond of the Schiff base and the subsequent intramolecular cyclization of the adduct via the nucleophilic attack of the nitrogen atom on the ester carbonyl carbon atom. The structures of the products were confirmed by X-ray diffraction analysis. more...
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- 2021
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27. Reactions of (1-Bromoethenyl)(diphenyl)phosphine Oxide with NH-, OH-, and SH-Nucleophiles
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G. Ts. Gasparyan, H. M. Stepanyan, L. V. Derdzyan, M. Zh. Ovakimyan, A. S. Poghosyan, R. E. Muradyan, and A. S. Bichakhchyan
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Antitumor activity ,Phosphine oxide ,chemistry.chemical_compound ,chemistry ,Nucleophile ,organic chemicals ,technology, industry, and agriculture ,Triazole ,Imidazole ,General Chemistry ,Pyrazole ,Medicinal chemistry ,Adduct - Abstract
The reactions of (1-bromoethenyl)(diphenyl)phosphine oxide with NH-, OH-, SH-nucleophiles were studied. The reaction of phosphine oxide with alcohols and alkanethiols led to the formation of the corresponding adducts, while in reactions with pyrazole, imidazole and triazole (E)-(vinyl)(diphenyl)phosphine oxide 2-(azol-1-yl)-derivatives were formed. Antibacterial and antitumor activity of (1-bromoethenyl)(diphenyl)phosphine oxide and its derivatives was studied. more...
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- 2021
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28. Anionic Diels–Alder Chemistry of Cyclic Sodium Dien-1-olates Delivering Highly Stereoselective and Functionalized Polycyclic Adducts
- Author
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Kak-Shan Shia and Jing-Kai Huang
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chemistry.chemical_classification ,Letter ,Base (chemistry) ,Chemistry ,Sodium ,fungi ,Organic Chemistry ,chemistry.chemical_element ,Ion pairs ,Biochemistry ,Medicinal chemistry ,Adduct ,Diels alder ,Stereoselectivity ,Physical and Theoretical Chemistry - Abstract
Anionic Diels-Alder chemistry of electron-deficient cross-conjugated vinylogous alkenones, providing highly stable sodium dienolate ion pairs as electron-rich dienes in the presence of a weak sodium base in THF, has been newly developed, leading to a single Diels-Alder adduct, in racemic form, in moderate to high yields (up to 97%, 37 examples). more...
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- 2021
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29. Frustrated Lewis‐Pair Neighbors at the Xanthene Framework: Epimerization at Phosphorus and Cooperative Formation of Macrocyclic Adduct Structures
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Karel Škoch, Marcel A. Müller, Stefan Grimme, Sebastian Ehlert, Gerhard Erker, Constantin G. Daniliuc, and Gerald Kehr
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Xanthene ,Electron pair ,Organic Chemistry ,Diastereomer ,General Chemistry ,Borane ,Medicinal chemistry ,Catalysis ,Frustrated Lewis pair ,Adduct ,chemistry.chemical_compound ,chemistry ,Bifunctional ,Derivative (chemistry) - Abstract
Attachment of a pair of P-stereogenic mesityl(alkynyl)phosphanyl groups at the 4- and 5-positions of a 9,9-dimethylxanthene framework gave mixtures of the respective rac- and meso-bisphosphanyl diastereoisomers. They slowly epimerized in a thermally induced reaction with Gibbs activation barriers of about 25 kcal mol-1 at room temperature (measured and DFT calculated). The reaction of the meso-mesityl(tert-butylethynyl)phosphanyl derivative with two molar equivalents of Piers' borane [HB(C6 F5 )2 ] led to the formation of the alkylidene-bridged geminal bisphosphane/borane-frustrated Lewis pair system. The compound was obtained enriched (>85 %) in the rac diastereoisomer. With a variety of bifunctional donor substrates, the rac-bis-P/B FLP formed macrocyclic compounds. They were all formally derived from meso-configurated diastereoisomers of the bisphosphanylxanthene backbone. more...
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- 2021
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30. Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C–X Bonds
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Hendrik Tinnermann, Rowan D. Young, Simon Sung, Craig Fraser, Zhi Hao Toh, and Dániel Csókás
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Colloid and Surface Chemistry ,Chemistry ,Cleave ,Intramolecular force ,General Chemistry ,Alkali metal ,Biochemistry ,Medicinal chemistry ,Catalysis ,Stoichiometry ,Adduct - Abstract
We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation. more...
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- 2021
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31. Hydrolysis of Small Oxo/Hydroxo Molecules Containing High Oxidation State Actinides (Th, Pa, U, Np, Pu): A Computational Study
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Lauren M. Tatina, Eddy M. Lontchi, David A. Dixon, Monica Vasiliu, Alyssa C. Caccamo, John K. Gibson, and Amber N. Gomez
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Chemistry ,Molecular ,Ionic bonding ,Atomic ,Endothermic process ,Medicinal chemistry ,Bond order ,Adduct ,Hydrolysis ,Particle and Plasma Physics ,Theoretical and Computational Chemistry ,Oxidation state ,Molecule ,Nuclear ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Physical Chemistry (incl. Structural) - Abstract
The energetics of hydrolysis reactions for high oxidation states of oxo/hydroxo monomeric actinide species (ThIVO2, PaIVO2, UIVO2, PaVO2(OH), UVO2(OH), UVIO3, NpVIO3, NpVIIO3(OH), and PuVIIO3(OH)) were calculated at the CCSD(T) level. The first step is the formation of a Lewis acid/base adduct with H2O (hydration), followed by a proton transfer to form a dihydroxide molecule (hydrolysis); this process is repeated until all oxo groups are hydrolyzed. The physisorption (hydration) for each H2O addition was predicted to be exothermic, ca. -20 kcal/mol. The hydrolysis products are preferred energetically over the hydration products for the +IV and +V oxidation states. The compounds with AnVI are a turning point in terms of favoring hydration over hydrolysis. For AnVIIO3(OH), hydration products are preferred, and only two waters can bind; the complete hydrolysis process is now endothermic, and the oxidation state for the An in An(OH)7 is +VI with two OH groups each having one-half an electron. The natural bond order charges and the reaction energies provide insights into the nature of the hydrolysis/hydration processes. The actinide charges and bond ionicity generally decrease across the period. The ionic character decreases as the oxidation state and coordination number increase so that covalency increases moving to the right in the actinide period. more...
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- 2021
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32. Binary-Acid Catalysis with Sc(OTf)3/TfOH in the Alkenylation of Arenes with Alkynes
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Jiaying Sun, Linrui Xiang, Wen Si, Jian Lv, Wenxuan Zhang, Ran Song, and Daoshan Yang
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Chemistry ,Yield (chemistry) ,Organic Chemistry ,Binary acid ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Carbocation ,Biochemistry ,Medicinal chemistry ,Trifluoromethanesulfonate ,Catalysis ,Adduct - Abstract
Herein we report binary acid Sc(OTf)3/TfOH-catalyzed alkenylation of arenes with alkynes. In this system, the high-energy vinyl carbocations with activated and weakly coordinating trifluoromethanesulfonate anions by Lewis acid Sc(III) can undergo facile Friedel-Crafts reactions with arenes to give the desired adducts in up to 90% yield and with high Z-selectivity. more...
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- 2021
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33. Synthesis, crystal structure and properties of hepta(ammonium) penta(1H-imidazol-3-ium) paratungstate B tetrahydrate
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Savita A. Kundaikar, Sudesh M Morajkar, Christian Näther, Wolfgang Bensch, and Bikshandarkoil R. Srinivasan
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chemistry.chemical_compound ,Tetrahydrate ,chemistry ,Materials Chemistry ,Imidazole ,Ammonium ,Crystal structure ,Physical and Theoretical Chemistry ,Medicinal chemistry ,Tungsten trioxide ,Adduct - Abstract
An attempted isolation of the elusive diammonium tetraoxidotungstate (NH4)2[WO4] as its imidazole (Im) adduct resulted in the serendipitous formation of hepta(ammonium) penta(1H-imidazol-3-ium) par... more...
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- 2021
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34. Regioselective Preparation of Fullerene Bis‐adducts from Cleavable Macrocyclic Bis‐malonates
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Sebastiano Guerra, Jean-François Nierengarten, Michel Holler, Eric Meichsner, Franck Schillinger, Iwona Nierengarten, Uwe Hahn, and Thi Minh Nguyet Trinh
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Fullerene ,Chemistry ,Organic Chemistry ,Regioselectivity ,Bingel reaction ,Physical and Theoretical Chemistry ,Medicinal chemistry ,Adduct - Published
- 2021
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35. Dissecting Transmetalation Reactions at the Molecular Level: Role of the Coordinated Anion in Gas-Phase Models for the Transmetalation Step of the Hiyama Cross-Coupling Reaction
- Author
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Geethika K. Weragoda, Howard Z. Ma, George N. Khairallah, Adam W. E. Stewart, Richard A. J. O'Hair, and Allan J. Canty
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010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Coupling reaction ,0104 chemical sciences ,Adduct ,Inorganic Chemistry ,Propene ,chemistry.chemical_compound ,Transmetalation ,chemistry ,Transition metal ,Molecule ,Organic synthesis ,Physical and Theoretical Chemistry ,Palladium - Abstract
Palladium-catalyzed cross-coupling protocols have become a cornerstone in organic synthesis. Here, a gas-phase model of the Hiyama cross-coupling reaction was designed to shed light on the roles of coordinated anions (fluoride versus chloride) in transmetalation from Si to Pd. A combination of mass spectrometry experiments and DFT calculations was used. The ligated palladium fluoride and chloride cationic complexes, [(phen)Pd(X)]+ (X = F and Cl), readily react with vinyltrimethylsilane, Me3Si(CH═CH2), via transmetalation to give [(phen)Pd(CH═CH2)]+ as the major product. DFT calculations reveal that this transmetalation reaction is concerted and proceeds via a four-centered transition state, illustrating the role of coordinated halide in this gas-phase system. Two minor side products are observed corresponding to transmetalation to give [(phen)Pd(CH3)]+ and [(phen)Pd(SiMe2X)]+. DFT calculations suggest that these arise from the same initial Si to Pd methyl transmetalation pathway to give the [(phen)Pd(CH3) + Me2(CH═CH2)SiX]+ intermediate, which either then loses Me2(CH═CH2)SiX or reacts via C–C bond coupling to ultimately yield propene and [(phen)Pd(SiMe2X)]+. [(phen)Pd(CH═CH2)]+ undergoes a reaction with a second molecule of vinyltrimethylsilane to form an adduct, which upon collision-induced dissociation liberates 1,3-butadiene to form [(phen)Pd(SiMe3)]+. DFT calculations suggest a mechanism in which C–C bond formation is followed by migration of SiMe3 from C to Pd. Links between the observed gas-phase chemistry and solution-phase Pd-mediated homocoupling reactions of vinyltrimethylsilanes are explored. more...
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- 2021
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36. 1,3‐Bis(tricyanoborane)imidazoline‐2‐ylidenate Anion—A Ditopic Dianionic N‐Heterocyclic Carbene Ligand
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Maik Finze, Udo Radius, and Ludwig Zapf
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Steric effects ,Carbenes | Hot Paper ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,Adduct ,chemistry.chemical_compound ,Imidazolate ,Pyridine ,cyanoborate ,Research Articles ,010405 organic chemistry ,Ligand ,General Chemistry ,0104 chemical sciences ,Nickel ,anionic carbene ,chemistry ,boron ,ddc:546 ,N-heterocyclic carbene ,Carbene ,imidazolate ,Research Article ,Methyl iodide - Abstract
The 1,3‐bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)3−pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H5O2 + salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N‐heterocyclic carbene (NHC), 1,3‐bis(tricyanoborane)imidazoline‐2‐ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)4] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ‐donor and π‐acceptor ability, make NHC 3 a unique and promising ligand and building block., Unprecedentedly stable salts of the 1,3‐bis(tricyanoborane)imidazolate ion with different types of counterions were obtained on large scale. Deprotonation of the imidazolate ion provided access to the corresponding dianionic NHC that acts as ditopic ligand. more...
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- 2021
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37. Facile Access to Alkylideneborane and Diborabutadiene N-Heterocyclic Carbene Complexes
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Ping Cui, Ling Bing Kong, Hao Gao, Chen-Ho Tung, and Qianli Li
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Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,010405 organic chemistry ,Dimethyl sulfide ,Density functional theory ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Carbene ,0104 chemical sciences ,Adduct - Abstract
A facile route to synthesis of B═C double-bonded systems has been developed. Specifically, both dibromofluorenylborane (FluH-BBr2) and a 1,1-dibromo-2,2-difluorenyldiborane/dimethyl sulfide adduct [(FluH)2B-BBr2(SMe2)] could be smoothly dehydrobrominated and subsequently coordinated by N-heterocyclic carbenes (NHCs) with formation of the respective alkylideneborane 1 and diborabutadiene 3. The electronic structures of 1 and 3 are interrogated and compared with those of base-free counterparts through density functional theory calculations. more...
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- 2021
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38. Synthesis of β-Methyl Alcohols: Influence of Alkyl Chain Length on Diastereoselectivity and New Attractants of Rhynchophorus ferrugineus
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Van-Dung Le, Cong-Hao Nguyen, Thanh-Danh Nguyen, Hong-Ung Nguyen, and Chi-Hien Dang
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0106 biological sciences ,chemistry.chemical_classification ,Steric effects ,Addition reaction ,biology ,010401 analytical chemistry ,Diastereomer ,General Chemistry ,biology.organism_classification ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Adduct ,Rhynchophorus ,chemistry ,Reagent ,Stereoselectivity ,General Agricultural and Biological Sciences ,Alkyl ,010606 plant biology & botany - Abstract
The diastereoselectivity of adducts in the addition reaction via the Felkin-Anh model is affected significantly by the steric effect of bulky groups. However, the influence of steric alkyl chain length has not been studied for the diastereoselectivity. In this work, we present a new strategy for the racemic synthesis of β-methyl alcohols to obtain various diastereomer ratios using the Felkin-Anh model. The addition of alkyl Grignard reagents to α-methyl aldehydes afforded diastereomer ratios of threo/erythro ≈ 2:1, while the reduction in structurally related ketones using LiAlH4 afforded ratios of threo/erythro ≈ 1:1. The experimental data showed no effect of alkyl chain length on either side on the stereoselectivity of adducts. All synthesized analogues were evaluated for attractiveness to Rhynchophorus ferrugineus weevils in the field. Five novel derivatives, including two alcohols and three ketones, were found to attract weevils in the field trials. Among them, 3-methyldecan-4-one (5b) and 4-methyldecan-5-ol (11a) were found to be the most attractive to the insects. more...
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- 2021
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39. Photocatalytic C–H activation and the subtle role of chlorine radical complexation in reactivity
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Qiaomu Yang, Patrick J. Carroll, Yu-Heng Wang, Eric J. Schelter, Patrick J. Walsh, Yusen Qiao, and Michael R. Gau
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Alkane ,chemistry.chemical_classification ,Cerium ,Multidisciplinary ,Chemistry ,Radical ,Photodissociation ,Alkoxy group ,Photocatalysis ,chemistry.chemical_element ,Reactivity (chemistry) ,Medicinal chemistry ,Adduct - Abstract
A complex role for chlorine radicals Radicals are atoms or molecules that are highly reactive because they have an unpaired electron. A common means of investigating whether they are involved in a particular reaction is to try to trap them with an acceptor compound. Yang et al. reinvestigated a photoinduced alkane oxidation reaction for which a trapping study had previously implicated alkoxy radicals. Their spectroscopic, kinetic, and isotopic labeling studies revealed that chlorine, rather than alkoxy, was the key radical intermediate; the prior trapping results had stemmed from its complexation with alcohols. Science , abd8408, this issue p. 847 more...
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- 2021
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40. Synthesis, characterization and antimicrobial activity of copper(II) Schiff base adducts of some p-substituted aniline Schiff bases
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Sheriff Adewuyi, R. O. Shaibu, A. O. Sobola, Gareth M. Watkins, and S. A. Amolegbe
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Schiff base ,chemistry.chemical_element ,General Chemistry ,Medicinal chemistry ,Copper ,Adduct ,Metal ,chemistry.chemical_compound ,Aniline ,chemistry ,Salicylaldehyde ,visual_art ,visual_art.visual_art_medium ,Chelation ,Methanol - Abstract
The synthesis, characterization and antimicrobial activity of Cu(II) complexes of some p-substituted aniline Schiff base ligands have been carried out. The Schiff bases were obtained from salicylaldehyde and o-vanillin. The Cu(II) complexes have been characterized by elemental analysis, conductivity measurement, infrared and electronic spectral data. The complexes were obtained either as metal chelates [Cu(L)2] or Schiff base adducts (CuCl2.2LH).xH2O. The metal chelates were non-electrolytes while the Schiff base adducts exhibited 1:1 or 2:1 electrolytes in methanol. The Cu(II) complexes exhibited slight antimicrobial activity against Escherichia coli ATCC® 8739™*, Staphylococcus aureus subsp. aureus ATCC® 6538™*, Bacillus subtilis subsp. spizizenii ATCC® 6633™* and Candida albicans ATCC® 2091™*. The complexes exhibited significant antifungal activity. KEY WORDS: Metal Chelates, Schiff bases, Adducts, Cu(II) complexes, Salicylaldimines Bull. Chem. Soc. Ethiop. 2021, 35(1), 33-42. DOI: https://dx.doi.org/10.4314/bcse.v35i1.3 more...
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- 2021
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41. Trimethylsilyl Pseudohalide Adducts of GaCl 3 and B(C 6 F 5 ) 3
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Axel Schulz, Kevin Bläsing, Steffen Maurer, Alexander Villinger, and Jonas Bresien
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Inorganic Chemistry ,chemistry.chemical_compound ,Trimethylsilyl ,chemistry ,Medicinal chemistry ,Adduct - Published
- 2021
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42. Aromaticity-Driven Access to Cycloalkyl-Fused Naphthalenes
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Karekar Sanjeev, Silver Raju, and Srivari Chandrasekhar
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010405 organic chemistry ,Chemistry ,Decarboxylation ,Organic Chemistry ,Aromatization ,Aromaticity ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Aryne ,Cycloaddition ,0104 chemical sciences ,Adduct ,Yield (chemistry) ,Intramolecular force ,Physical and Theoretical Chemistry - Abstract
We report the efficient synthesis of cycloalkyl-fused naphthalenes through the [4 + 2]-cycloaddtion/decarboxylative aromatization of alkyne-tethered aryne insertion adducts. These scaffolds were difficult to synthesize using conventional reactions. The reaction proceeds via the formation of a benzopyrylium intermediate followed by intramolecular [4 + 2] cycloaddition and a subsequent decarboxylation pathway. This method is also compatible with allene-tethered substrates to afford similar products. In addition, the one-pot synthesis of polysubstituted naphthalenes via aryne insertion/benzannulation has also been developed in good yield. more...
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- 2021
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43. Hydrosilane σ‐Adduct Intermediates in an Adaptive Zinc‐Catalyzed Cross‐dehydrocoupling of Si−H and O−H Bonds
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Uddhav Kanbur, Arkady Ellern, Smita Patnaik, and Aaron D. Sadow
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dehydrogenative cross-coupling ,sigma-adducts ,Silanes ,Full Paper ,010405 organic chemistry ,saturation kinetics ,Organic Chemistry ,Alcohol ,General Chemistry ,Full Papers ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,Transition state ,0104 chemical sciences ,Adduct ,Silyl ether ,zinc catalysis ,chemistry.chemical_compound ,Reaction rate constant ,chemistry ,Salt metathesis reaction ,silyl ethers - Abstract
Three‐coordinate PhBOXMe2 ZnR (PhBOXMe2 =phenyl‐(4,4‐dimethyl‐oxazolinato; R=Me: 2 a, Et: 2 b) catalyzes the dehydrocoupling of primary or secondary silanes and alcohols to give silyl ethers and hydrogen, with high turnover numbers (TON; up to 107) under solvent‐free conditions. Primary and secondary silanes react with small, medium, and large alcohols to give various degrees of substitution, from mono‐ to tri‐alkoxylation, whereas tri‐substituted silanes do not react with MeOH under these conditions. The effect of coordinative unsaturation on the behavior of the Zn catalyst is revealed through a dramatic variation of both rate law and experimental rate constants, which depend on the concentrations of both the alcohol and hydrosilane reactants. That is, the catalyst adapts its mechanism to access the most facile and efficient conversion. In particular, either alcohol or hydrosilane binds to the open coordination site on the PhBOXMe2 ZnOR catalyst to form a PhBOXMe2 ZnOR(HOR) complex under one set of conditions or an unprecedented σ‐adduct PhBOXMe2 ZnOR(H−SiR′3) under other conditions. Saturation kinetics provide evidence for the latter species, in support of the hypothesis that σ‐bond metathesis reactions involving four‐centered electrocyclic 2σ–2σ transition states are preceded by σ‐adducts., σ‐Silane adducts and alcohol adducts are kinetically detected intermediates in zinc‐catalyzed σ‐bond metathesis‐type dehydrocoupling reactions. These intermediates feature prominently in the reactivity of coordinatively unsaturated zinc centers, which efficiently mediate Si−O bond formation. The catalyst is responsive to reaction conditions, adapting as a function of concentration to follow the kinetically preferred mechanism. more...
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- 2021
44. Polar Solvent–Mediated Synthesis of Terminal Alkyne Derivatives of Thiazoles and Evaluation of Their Antidiabetic Activity
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Ranjan C. Khunt, Khushal M. Kapadiya, and A. J. Jivani
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chemistry.chemical_classification ,010405 organic chemistry ,Organic Chemistry ,Formaldehyde ,Alkyne ,Phenacyl ,Mass spectrometry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Adduct ,Solvent ,Benzaldehyde ,chemistry.chemical_compound ,chemistry ,medicine ,Acarbose ,medicine.drug - Abstract
Two new pharmacologically active series of N-alkyne-substituted indole–thiazoles and C-alkyne-substituted benzylidene–thiazoles were synthesized by a two-step procedure involving initial reactions of thiosemicarbazide with, respectively, [1-(prop-2-yne-1-yl)oxy)-1H-indol-3-yl]formaldehyde and 2-(prop-2-yne-1-yloxy)benzaldehyde, followed by the reactions of the resulting hydrazine-1-carbothioamides with a variety of substituted phenacyl bromides. The synthesized adducts composition and structure were established by elemental analysis and IR and 1H and 13C NMR spectroscopy and mass spectrometry. In vitro antidiabetic activity screening by the α-amylase inhibition assay with Acarbose as a reference drug revealed an excellent antidiabetic potency in four-terminal alkyne-substituted benzylidene–and indole–thiazoles derived from dichloro- and bromophenacyl bromides. more...
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- 2021
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45. Bis(pertrifluoromethylcatecholato)silane: Extreme Lewis Acidity Broadens the Catalytic Portfolio of Silicon
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Thaddäus Thorwart, Daniel Roth, and Lutz Greb
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Trifluoromethyl ,Silanes ,Full Paper ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Lewis superacids ,deoxygenation ,silicon ,Homogeneous catalysis ,General Chemistry ,Disiloxane ,Full Papers ,catechol ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Silane ,homogeneous catalysis ,Catalysis ,0104 chemical sciences ,Adduct ,chemistry.chemical_compound ,Benzophenone ,Lewis acids and bases - Abstract
Given its earth abundance, silicon is ideal for constructing Lewis acids of use in catalysis or materials science. Neutral silanes were limited to moderate Lewis acidity, until halogenated catecholato ligands provoked a significant boost. However, catalytic applications of bis(perhalocatecholato)silanes were suffering from very poor solubility and unknown deactivation pathways. In this work, the novel per(trifluoromethyl)catechol, H2catCF3, and adducts of its silicon complex Si(catCF3)2 (1) are described. According to the computed fluoride ion affinity, 1 ranks among the strongest neutral Lewis acids currently accessible in the condensed phase. The improved robustness and affinity of 1 enable deoxygenations of aldehydes, ketones, amides, or phosphine oxides, and a carbonyl‐olefin metathesis. All those transformations have never been catalyzed by a neutral silane. Attempts to obtain donor‐free 1 attest to the extreme Lewis acidity by stabilizing adducts with even the weakest donors, such as benzophenone or hexaethyl disiloxane., The extremely electron‐deficient tetratrifluorocatechol is synthesized and installed at silicon, providing a Lewis superacid that ranks among the strongest fluoride ion acceptors accessible in the condensed phase. The compound enables silicon‐catalyzed deoxygenation of ketones, aldehydes, amides and phosphine oxides and the first silicon catalyzed carbonyl‐olefin metathesis. more...
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- 2021
46. C–N and C–H Activation of an N-Heterocyclic Carbene by Magnesium(II) Hydride and Magnesium(I) Complexes
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Cameron Jones, Laurent Maron, Ambre Carpentier, K. Yuvaraj, Cory D. Smith, School of Chemistry, Monash University [Clayton], Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Australian Research Council more...
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Steric effects ,010405 organic chemistry ,Hydride ,Magnesium ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Adduct ,Inorganic Chemistry ,IMes ,chemistry.chemical_compound ,chemistry ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Isostructural ,Carbene ,Mesitylene - Abstract
International audience; Reactions of the hindered N-heterocyclic carbene, :C{(MesNCH)(2)} (IMes; Mes = mesityl), with a series of beta-diketiminatomagnesium(II) hydride and dimagnesium(I) complexes were carried out at 80 degrees C. The reactions involving the magnesium hydrides, [{((Ar)Nacnac)Mg(mu-H)}(2)] [(Ar)Nacnac = [(ArNCMe)(2)CH](-), where Ar = 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)], proceeded via activation of an exocyclic C-N bond of IMes, giving magnesium imidazolyl compounds [((Ar)Nacnac)Mg(mu-H)(mu-Imid)Mg((Ar)Nacnac)] (Imid = [NC2H2N-(Mes)C](-)) and mesitylene. A low-yield IMes methyl C-H activation product, [((Dep)Nacnac)Mg(IMes(-H))], was also obtained, via H-2 elimination, from the reaction between IMes and [{((Dep)Nacnac)Mg(mu-H)}(2)]. Reactions between IMes and dimagnesium(I) compounds [{((Ar)Nacnac)Mg}(2)] [Ar = 2,6-dimethylphenyl (Xyl) or Mes] afforded isostructural C-H activation products [((Ar)Nacnac)Mg(IMes(-H))] but in higher yields. Density functional theory calculations suggest that the reactions do not progress via stable adduct complex intermediates, which are sterically inaccessible. more...
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- 2021
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47. Isoselective Polymerization of rac ‐Lactide by Aluminum Complexes of N‐Heterocyclic Carbene‐Phosphinidene Adducts
- Author
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Dirk Bockfeld, Jayeeta Bhattacharjee, Matthias Tamm, and Marius Peters
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ring-opening polymerization ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Ring-opening polymerization ,Catalysis ,Adduct ,chemistry.chemical_compound ,phosphinidenes ,N-heterocyclic carbenes ,Lactide ,010405 organic chemistry ,Communication ,Organic Chemistry ,General Chemistry ,Toluene ,Communications ,0104 chemical sciences ,IMes ,chemistry ,Polymerization ,Phosphinidene ,aluminum ,N‐Heterocyclic Carbenes ,poly(lactic acid) ,Carbene - Abstract
The N‐heterocyclic carbene‐phosphinidene adducts (NHC)PH were reacted with AlMe3 in toluene to afford the monoaluminum complexes [{(IDipp)PH}AlMe3] and [{(IMes)PH}AlMe3] (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene, IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene). In contrast, the dialuminum complex [{(MeIMes)PH}(AlMe3)2] was obtained for MeIMes=1,3‐bis(2,4,6‐trimethylphenyl)‐4,5‐dimethylimidazolin‐2‐ylidene. These complexes served as initiators for the efficient ring‐opening polymerization of rac‐lactide in toluene at 60 °C. High degrees of isoselectivity were found for the poly(rac‐lactide) obtained in the presence of the monoaluminum complexes (P m up to 0.92, T m up to 191 °C), whereas almost atactic polymers were produced by the dialuminum complex. Detailed mechanistic studies reveal that the polymerization proceeds via a coordination‐insertion mechanism with the carbene‐phosphinidene ligands acting as stereodirecting groups., N‐Heterocyclic carbene‐phosphinidene trimethylaluminum (AlMe3) complexes can promote the isoselective ring‐opening polymerization of rac‐lactide, which proceeds via insertion into the aluminum‐carbon bonds with the monodentate, prochiral phosphorus ligand acting as a stereo‐directing group. more...
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- 2021
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48. Indirect Access to Carbene Adducts of Bismuth- and Antimony-Substituted Phosphaketene and Their Unusual Thermal Transformation to Dipnictines and [(NHC)2OCP][OCP]
- Author
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Robert J. Gilliard, Guo-Cang Wang, Jacob E. Walley, Zoltán Benkő, Diane A. Dickie, Levi S. Warring, and Erik Kertész
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010405 organic chemistry ,Ligand ,chemistry.chemical_element ,Infrared spectroscopy ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Article ,0104 chemical sciences ,Adduct ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Antimony ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Carbene ,Pnictogen - Abstract
The synthesis and thermal redox chemistry of the first antimony (Sb)– and bismuth (Bi)–phosphaketene adducts are described. When diphenylpnictogen chloride [Ph2PnCl (Pn = Sb or Bi)] is reacted with sodium 2-phosphaethynolate [Na[OCP]·(dioxane)x], tetraphenyldipnictogen (Ph2Pn–PnPh2) compounds are produced, and an insoluble precipitate forms from solution. In contrast, when the N-heterocyclic carbene adduct (NHC)–PnPh2Cl is combined with [Na[OCP]·(dioxane)x], Sb– and Bi–phosphaketene complexes are isolated. Thus, NHC serves as an essential mediator for the reaction. Immediately after the formation of an intermediary pnictogen–phosphaketene NHC adduct [NHC–PnPh2(PCO)], the NHC ligand transfers from the Pn center to the phosphaketene carbon atom, forming NHC–C(O)P-PnPh2 [Pn = Sb (3) or Bi (4)]. In the solid state, 3 and 4 are dimeric with short intermolecular Pn–Pn interactions. When compounds 3 and 4 are heated in THF at 90 and 70 °C, respectively, the pnictogen center PnIII is thermally reduced to PnII to form tetraphenyldipnictines (Ph2Pn–PnPh2) and an unusual bis-carbene-supported OCP salt, [(NHC)2OCP][OCP] (5). The formation of compound 5 and Ph2Pn–PnPh2 from 3 or 4 is unique in comparison to the known thermal reactivity for group 14 carbene–phosphaketene complexes, further highlighting the diverse reactivity of [OCP]− with main-group elements. All new compounds have been fully characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy (1H, 13C, and 31P), infrared spectroscopy, and elemental analysis (1, 2, and 5). The electronic structure of 5 and the mechanism of formation were investigated using density functional theory (DFT)., An N-heterocyclic carbene (NHC) was used to support the otherwise unstable Ph2Sb—P=C=O and Ph2Bi—P=C=O moieties. Exploration of the thermal chemistry of these NHC−phosphaketene adducts reveals the formation of the salt [NHC2OCP][OCP]. This present work demonstrates the thermal chemistry of the 2-phospaethynolate anion with heavier pnictogens (Sb and Bi). more...
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- 2021
49. Boron Lewis reagent with nitrogen and oxygen adducts: synthesis of aza-belted diazabicyclo[n.n.5.5]alkane derivatives
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Guodong Su, Fuyan Xiao, and Guofan Jin
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Alkane ,chemistry.chemical_classification ,Absorption spectroscopy ,010405 organic chemistry ,Chemical shift ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Adduct ,chemistry ,Reagent ,Yield (chemistry) ,Halogen ,Boron - Abstract
A novel belt shape of multi-phenyl groups around a diazabicyclo[n.n.5.5]alkane center combined with boron, nitrogen, and oxygen adducts was prepared in good yield in two steps starting from phenylethylamine and 1,2-bis(chloromethyl)benzenes. The halogen boron adduct, XFY-3, 4, 5 and 6, showed unique nuclear magnetic resonance (NMR) spectroscopic properties. A series of 1H, 13C, 11B, and 19F NMR spectroscopy analysis revealed the change in chemical shifts were due to an interaction between the functional groups, and the XFY-6 was characteristic bands were analyzed by ultraviolet–visible absorption spectrum and fluorescence spectra. In particular, XFY-6 was an electron-rich compound because of its unique structure and excellent stability in terms of chemical reactivity. more...
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- 2021
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50. Copper-Catalyzed Cycloaddition of Heterobicyclic Alkenes with Diaryl Disulfides to Synthesize Dihydrobenzo[b]thiophene Derivatives
- Author
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Lin Wang, Qifu Lin, Wen Yang, Dingqiao Yang, Yue Li, and Yongqi Yao
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010405 organic chemistry ,Chemistry ,Organic Chemistry ,Copper catalyzed ,Substrate (chemistry) ,010402 general chemistry ,01 natural sciences ,Thiophene derivatives ,Medicinal chemistry ,Cycloaddition ,0104 chemical sciences ,Adduct - Abstract
A novel copper-catalyzed cycloaddition of diaryl disulfides to heterobicyclic alkenes has been developed. The C-S and C-C bonds can be formed simultaneously on the C═C bond of the olefins via a single-step cycloaddition to afford a series of 2,3-dihydrobenzo[b]thiophene derivatives. This reaction exhibits excellent diastereoselectivity and relatively broad substrate scope. Various functional groups attached to the substrates are tolerated in this protocol to give the corresponding exo adducts in moderate yields. more...
- Published
- 2021
- Full Text
- View/download PDF
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