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Abstract: An efficient one-pot multicomponent synthesis of 3,4- dihydropyrimidin-2(1H)-ones has been developed from aldehyde bisulfite adducts, ethyl acetoacetate and urea using recyclable polymer- supported sulfonic acid catalyst. This new method provides several advantages over the previous synthesis, including high product yields, commercially viable, minimal workup operations and sustainable chemical practices.

The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam. By strategically using the in situ generated Appel's salt or Mitsunobu's zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this method have been demonstrated.

Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation.

Here in we report Ag(I)-promoted homo-dimerization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes for the synthesis of structurally novel and functionalized naphthalene derivatives. This transformation has exhibited a broad scope for the alkyl as well as aryl groups present on alkynes. Observations made from the control experiments, had suggested the possible mechanism as i) homo-dimerization of in situ generated benzopyrylium ion intermediates through a head–tail [4+2] cycloaddition, followed by ii) the competitive aromative ring-opening vs. decarbonylative aromatization of the adduct to give the formylated and deformylated naphthalenes respectively.

Thiolate adducts of dirhodium(II) tetraacetate have proven difficult to prepare. We isolated a stable, paramagnetic Ni4Rh2 adduct containing Ni-based metallothiolates bound in axial positions of the Rh24+ core. The adduct formation is accompanied by a change of the magnetic exchange interaction in the dinuclear Ni2 subunits.

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.

The installation of (benzo)thiophene-containing biaryls via coupling reactions has become a staple in designing photoelectric materials. Undeniably, C-H/C-H cross-coupling reactions between two (hetero)aromatics would be a shortcut toward these structural fragments. While more reliable cross-coupling technologies are well-established to provide C2-arylated (benzo)thiophenes, efficient methods that arylate the C3-position remain underdeveloped. Herein we provide insight into the factors that determine regioselectivity switching for these cross-coupling reactions. X-ray crystallographic analysis gives solid evidence for the key roles of triflate in regioselective dearomatization and acetate in base-assisted anti-β-deprotonated rearomatization. The first isolation and X-ray characterization of a medium-sized dearomatized cyclometalated adduct involving both substrates provide extra insight into aerobic oxidative Ar-H/Ar-H cross-coupling reactions. The mechanistic breakthrough incubates the first example, enabling C-H/C-H-type C3-arylation of benzothiophenes. Finally, this chemistry is used to design blue-emitting thermally activated delayed fluorescence (TADF) materials with a helicene conformation that exhibit a high maximum external quantum efficiency of 25.4% in OLED.

Two pairs of enantiomeric diarylheptanoid-phenylpropanoid adducts bearing a cyclohexenone core, (±)-saccardianones A and B (1 and 2), an alkaloidal diarylheptanoid-phenylpropanoid adduct bearing a 4-piperidone core, (±)-saccardianine A (3), a pair of enantiomeric dimeric diarylheptanoid alkaloids bearing a tetrahydropyridine core, (±)-saccardianine B (4), and a suspected degradation product, saccardianine C (5), in addition to a known diarylheptanoid, platyphyllenone (6), were isolated from the leaves of Pellacalyx saccardianus. Their chemical structures were elucidated based on detailed analyses of the NMR and MS data. The structure of (±)-(1) was also confirmed by X-ray diffraction analysis. Compounds (±)-2 and 6 exhibited selective cytotoxicity towards the AsPC-1 and PANC-1 pancreatic cancer cell lines, respectively.

The structures of 1:1 and 1:2 adducts of phosphanetricarbo­nitrile with 1,4-di­aza­bicyclo­[2.2.2]octane are reported., In the structures of 1:1 and 1:2 adducts of phosphanetricarbo­nitrile (C3N3P) with 1,4-di­aza­bicyclo­[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the ortho­rhom­bic space group, Pbcm, with four formula units in the unit cell (Z′ = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phospho­rus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octa­hedral with the lone pair on the phospho­rous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phospho­rus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z’ = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) mol­ecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P⋯N inter­actions and consequently the mol­ecular geometry of the phospho­rus atom is distorted octa­hedral. This must mean that the lone pair of electrons on the phospho­rus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phospho­rus atom and one of the terminal nitro­gen atoms from the C≡ N moiety, forming chains in the a-axis direction. In addition there are weak C—H⋯N inter­actions between a terminal nitro­gen atoms from the C≡N moiety and the C6H12N2 mol­ecules, which form sheets perpendicular to the a axis.

Mycobacterium tuberculosis (Mtb) cells are known to synthesize very long chain (C60-90) structurally complex mycolic acids with various functional groups. In this study, we applied linear ion-trap (LIT) multiple-stage mass spectrometry (MSn), combined with high-resolution mass spectrometry to study the mechanisms underlying the fragmentation processes of mycolic acid standards desorbed as lithiated adduct ions by ESI. This is followed by structural characterization of a Mtb mycolic acid family (Bovine strain). Using the insight fragmentation processes gained from the study, we are able to achieve a near complete characterization of the whole mycolic acid family, revealing the identity of the α-alkyl chain, the location of the functional groups including methyl, methoxy, and keto groups along the meroaldehyde chain in each lipid species. This study showcased the power of LIT MSn toward structural determination of complex lipids in a mixture, which would be otherwise very difficult to define using other analytical techniques.

Mutagenic agents such as aromatic amines undergo metabolic activation and produce DNA adducts at C8 position of guanine bases. N-2-acetylaminofluorene (AAF) generates different mutational outcomes when placed at G1, G2, and G3 of a NarI sequence (-G1G2CG3CC/T-). These outcomes are dictated by the conformations adopted by these adducts. Detection of such lesions is of considerable interest owing to their hazardous effects. Here, we report the synthesis of three cyclometalated [Ir(L)2dppz]+ complexes (L = 2-phenylpyridine (ppy) 1; benzo[h]quinoline (bhq) 2; 2-phenylquinoline (pq) 3; dppz = dipyrido[3,2-a:2',3'-c]phenazine) and their interaction with AAF adducted NarI DNA. Remarkably, complexes 1 and 2 displayed dominant 3LC transition characteristic of polar environment despite binding to the adducted sites. On the other hand, complex 3 binds to NarI sequences and behaves as a luminescent reporter for AAF-modified DNA. The results reported here emphasize that molecular light switching phenomenon can be stimulated by switching ancillary ligands and might act as potential probes for covalent-DNA defects.

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.

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+.

A direct general method for the preparation of α-oxyacylated vinyl ketones using Koser's hypervalent iodine reagent is reported. A variety of acyloxy groups from long-chain aliphatic, aromatic, α,β-unsaturated carboxylic acids have been installed efficiently for the first time. The oxyacylated adducts were used for the preparation of densely functionalized chiral δ-lactones and cyclopentenes using carbene organocatalysis.

Quinones are potent genotoxic agents through generating reactive oxygen species or undergo covalent bonding to modify the nucleobases of DNA. The formation of DNA adducts is an early indication of cancer, as it may lead to gene mutation, thereby initiating tumor development. The present review aims to summarize different types of quinone-induced DNA damages and the corresponding DNA adducts. In addition to the considerably stable naphthoquinone and halobenzoquinones in the environment, quinones are also metabolically activated from estrogen, bisphenol A, ochratoxin A, polychlorinated biphenyls, benzo[a]pyrene and polybrominated diphenyl ethers, in which the inducement from these pollutants to produce DNA adducts were systematically discussed. Liquid chromatography-mass spectrometry (LC-MS)-based method with high accuracy and sensitivity for the detection of DNA adducts in mononucleotides, DNA duplexes, and biological samples was methodically summarized. It is believed that the presence of dione moiety in quinones is an imperative element that induce the formation of DNA adducts. The investigation on DNA adducts is helpful for understanding the generation, transformation, and repair of DNA damages, and for elucidating the underlying mechanism of carcinogenesis. This review provides a new perspective to assess the toxicological potential of quinones, and intends to put forward strategies of analyzing DNA adducts, which act as biomarkers, for indicating the potential health risks of multiDNA damages.

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.

New silicone based adducts were synthesized by reacting equimolar ratio of carbinol polydimethylsiloxane (CPDMS), 2,4-toluene diisocyanate (TDI) and polyethylene glycol (PEG, having a molecular weight of 300, 600, 1000, 2000 or 6000 Da) at 100 °C for 90 min. Only the PEG 600, 1000, and 2000 based adducts are self-water dispersible. The chemical structure of the CPDMS/TDI/PEG1000 adduct was confirmed via FTIR analysis while TEM analysis assured that the particles size of its emulsion ranges from 8 to 22 nm. The higher the PEG molecular weight of adduct, the higher is the adduct emulsion particles size. Incorporation of the aforementioned adducts emulsions as textile softeners in easy care finishing formulation of cotton fabric gives rise to an enhancement in functional properties of treated fabric namely softness and anti-crease, an improvement in percent nitrogen, tear strength, and flexibility as well as a reduction in whiteness index and wettability of treated fabric. The CPDMS/TDI/PEG1000 adduct emulsion treated fabric was characterized via SEM and EDX analysis. Combining of that adduct emulsion with triclosan, as bio-active additives, in the soft/resin finishing formulation of cotton fabric results in durable antibacterial properties of treated fabric.

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.

This work describes that a sterically bulky o-carboranylsilylene can significantly enhance the stability of the resultant carboranylsilylene-borane adducts. Removal of one halide from the boron cen...

In polynuclear biological active sites, multiple electrons are needed for turnover, and the distribution of these electrons among the metal sites is affected by the structure of the active site. However, the study of the interplay between structure and redox distribution is difficult not only in biological systems but also in synthetic polynuclear clusters since most redox changes produce only one thermodynamically stable product. Here, the unusual chemistry of a sterically hindered trichromium complex allowed us to probe the relationship between structural and redox isomerism. Two structurally isomeric trichromium imides were isolated: asymmetric terminal imide (tbsL)Cr3(NDipp) and symmetric, μ3-bridging imide (tbsL)Cr3(μ3–NBn) ((tbsL)6− = (1,3,5-C6H9(NC6H4-o-NSitBuMe2)3)6−). Along with the homovalent isocyanide adduct (tbsL)Cr3(CNBn) and the bisimide (tbsL)Cr3(μ3–NPh)(NPh), both imide isomers were examined by multiple-wavelength anomalous diffraction (MAD) to determine the redox load distribution by the free refinement of atomic scattering factors. Despite their compositional similarities, the bridging imide shows uniform oxidation of all three Cr sites while the terminal imide shows oxidation at only two Cr sites. Further oxidation from the bridging imide to the bisimide is only borne at the Cr site bound to the second, terminal imido fragment. Thus, depending on the structural motifs present in each [Cr3] complex, MAD revealed complete localization of oxidation, partial localization, and complete delocalization, all supported by the same hexadentate ligand scaffold., Application of high-resolution Multiwavelength Anomalous Diffraction (MAD) allows the assignment of localized, partly delocalized, and fully delocalized oxidation in a series of trichromium imide isomers.

Functionalization-induced phase transitions in polymer systems in which a postpolymerization reaction drives polymers to organize into colloidal aggregates are a versatile method to create nanoscal...

The reaction of manganese(II) acetate hydrate with cymantrenecarboxylic acid under inert atmosphere gave the complex [Mn(Thf)2(OH2)4][OOCC5H4Mn(CO)3]2 (I), which was highly unstable to air oxygen and temperature of the adduct, in which the anions occupy the outer-sphere positions. The oxidation of the mother liquor after isolation of the single crystals of I afforded the complex Mn6(µ4-O)2[µ,η2-OOCC5H4Mn(CO)3]2[µ-OOCC5H4Mn(CO)3]8(OH2)4·5C6H6·THF·3H2O (II). According to X-ray diffraction data, the metal core of II was a hexanuclear cluster $${\text{Mn}}_{4}^{{{\text{II}}}}{\text{Mn}}_{2}^{{{\text{III}}}}$$ containing mixed-valence metal atoms. Apart from X-ray diffraction, the obtained unstable complexes were characterized by elemental analysis and IR spectroscopy (powders).

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.

Mycotoxin monitoring is critical to ensure that foods are safe for human and animal consumption, so highly sensitive and selective detection methods are required by regulatory agencies. In this work, a new method for the analysis of patulin in fruit products was developed based on the high reactivity of the mycotoxin with sodium benzene-1,2-bis(thiolate). This previously unknown reaction occurs in buffered aqueous solution and results in a stable adduct that can be sensitively determined by tandem time-of-flight mass spectrometry. The proposed method is performed by a simple dilute-and-shoot procedure without the use of organic solvents and was able to determine patulin with an instrumental detection limit of 0.5 μg L−1. When the method was applied to the analysis of fortified apple and pear products, recovery values ranged from 95 to 100%. Finally, the applicability under real conditions was demonstrated by the successful analysis of reference and quality control materials., This work was supported by the Spanish Ministerio de Economía y Competitividad (AGL2015-64488), Ministerio de Ciencia e Innovación (RTI2018-096121 and PID2019-108070RB-I00ALI) and cofinanced by European Regional Development Funds. HD was supported by a predoctoral Grant (BES-2016-078159) from the Spanish Ministerio de Industria, Economía y Competitividad.