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2. All those papers, where do they come from?
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Ross, Haymo, primary
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- 2006
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3. Anionic and Photochemical Behaviour of the Medium-Sized Terpenoid Ketone 8-Dehydro-12-O-methyl-deacylhallerinDedicated to the memory of Anna Ramella PralungoAnd it seems to me you lived your life Like a candle in the wind (“Candle in the wind”, Elton John) We dedicate this paper to the memory of Anna, whose recent death at the tragically early age of 33 came as a profound shock to her friends and colleagues. Anna was a lively and engaging young woman, dynamic, generous and life-loving. She was a committed, hard-working student, when she undertook the research described in this paper, which constitutes the substance of her master’s thesis.
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Croce, Gianluca, Milanesio, Marco, Viterbo, Davide, Clericuzio, Marco, Ugliengo, Piero, and Appendino, Giovanni
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Treatment of the germacrane ketone 8-dehydro-12-O-methyl-deacylhallerin (2) with bases under conditions of thermodynamic enolization resulted in complete epimerization at the adjacent carbon atom C-7, with formation of 3. The conformational features of the epimeric ketones 2 and 3 were investigated by X-ray crystal structure analysis, NMR spectroscopy, molecular mechanics and dynamics simulations and ab initio calculations. While 2 showed temperature-insensitive sharp 1H NMR signals, its epimer 3 showed only broad lines. These spectral features suggest that 2 is monorotameric, while 3 is a mixture of different conformers, as was verified by molecular mechanics and dynamics calculations. Upon UV irradiation, 2 underwent isomerization at the C1–C10 double bond, while 3 was unreactive. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
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- 2006
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4. The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the EnolatesPart 280 of our General Papers. Part 279: Ref.1
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Zimmerman, Howard E. and Pushechnikov, Alexei
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A priori, allenic enolates as reaction intermediates may be protonated to afford (Z)- or (E)-α,β-unsaturated carbonyl products. The allenic enolates are tautomeric with α-vinylcarbanions. The literature on the behavior of these species on protonation is highly varied both in stereochemical outcome and in mechanistic interpretation. The current study has provided an independent mode of generation of the allenic enolates and has investigated the reaction stereochemistry of protonation to afford the stereoisomeric α,β-unsaturated carbonyl products. Under kinetic conditions, these highly reactive species are protonated in the α,β-π plane with preference (E) to the larger β group. Under thermodynamic conditions, addition/elimination equilibrates the two product stereoisomers. The kinetic protonation stereochemistry is a function of solvent, proton donor, and donor concentration. Computations serve to clarify the reaction mechanism. It was found that the stereochemistry of ketonization of allenic enolates follows the reaction course suggested as possible some decades earlier and common to less unique enolates. Additionally, the linear versus the bent enolate structure proves to depend on the countercation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
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- 2006
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5. Exocyclic–Endocyclic N-Acyliminium Ion Equilibration via an Intramolecular α-Thioamidoalkylation in the Synthesis of Fused N,S-Heterocyclic Systems: Some New ParametersPreliminary results in this area, including part of this work, were presented at the American Chemical Society National Meeting, Poster 367, San Francisco, CA, March 26–30, 2000.For the preceding paper in the series see ref.4
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Hucher, Nicolas, Pesquet, Anthony, Netchitaïlo, Pierre, and Daïch, Adam
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The reactivity of N-[aryl(or alkyl)thio(oxo or seleno)alkylamidals 6 bearing the N-(CH2)n-X-(CH2)m-Ar functionality towards neat TFA has been examined. Substrates of type 6 give, together with the products 11, 17, 19, and 25 of the “expected” π-cyclization process, the “unexpected” products 12, 18, and 26 resulting from a new tandem heteroamidoalkylation/isomerization/π-cyclization. The composition of the final isomeric mixture depends on the temperature of the reaction, with a high selectivity in favor of the “expected” π-cyclization product 11 as a thermodynamic isomer. Furthermore, the results demonstrate again the relevance of TFA catalysis and support two reaction pathways involving the formation of an aza-sulfonium cation A as a valuable intermediate which undergoes the π-cyclization process alone or in tandem with the thiocyclization/isomerization to give the cyclized products cited above. For the latter tandem reaction, we have established clearly that the n value should be equal to 1, the process can be performed independently for both the succinimide and phthalimide series, the reaction depends on the nucleophilicity of the heteroatom, and can be generalized to other heterocycles. Only the role of the benzene substitution has still to be totally elucidated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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- 2005
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6. Bending versus Twisting Acenes – A Computational Study
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Amit Manor Armon, Igor Schapiro, Ori Gidron, Anjan Bedi, and Veniamin Borin
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Full Paper ,Aromaticity ,Conjugation ,Band gap ,Chemistry ,Acenes ,Organic Chemistry ,Bending ,Full Papers ,Planarity testing ,Delocalized electron ,Organic electronic materials ,Atomic orbital ,Chemical physics ,Curved aromatics ,Physical and Theoretical Chemistry ,Triplet state ,HOMO/LUMO ,Astrophysics::Galaxy Astrophysics - Abstract
Polycyclic aromatic hydrocarbons (PAHs) are widely used in organic electronic devices. The electronic, magnetic, and optical properties of PAHs can be tuned by structural modifications to the aromatic backbone to introduce an inherent distortion from planarity, such as bending or twisting. However, it remains difficult to isolate and control the effects of such distortions. Here, we sought to understand how backbone twisting and bending affect the electronic properties of acenes, as models for larger PAHs. We found that, even when highly distorted from planarity (30° per ring), acenes maintain their aromatic character and π orbital delocalization with minor mixing of the σ and π orbitals. In addition, the energy gap between the HOMO and LUMO decreases with increasing twist, while the gap is hardly affected by bending, since the energy of both orbitals increase to a similar extent. For bent acenes in the triplet state, the spin becomes more localized with increasing bend, whereas twisting produces an evenly distributed spin delocalization. These findings can guide the synthesis of PAHs with tailored properties., A computational study performed on nonplanar acenes demonstrates the different effects of bending and twisting on the effect on their electronic properties.
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- 2021
7. Reactivity of 5‐(Alkynyl)dibenzothiophenium Salts: Synthesis of Diynes, Vinyl Sulfones, and Phenanthrenes
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Tianshu Liu, Manuel Alcarazo, Christopher Golz, Tobias Heilmann, Christian J. Rugen, and Kevin Kafuta
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Vinyl sulfones ,Sulfonium ,Alkyne ,010402 general chemistry ,Sulfonium salts ,01 natural sciences ,Medicinal chemistry ,Radical cyclization ,Addition reactions ,Diynes ,chemistry.chemical_compound ,Nucleophile ,Very Important Paper ,Reactivity (chemistry) ,Electrophilic alkynylation ,Physical and Theoretical Chemistry ,chemistry.chemical_classification ,Addition reaction ,Full Paper ,010405 organic chemistry ,Organic Chemistry ,Full Papers ,0104 chemical sciences ,chemistry ,Michael reaction ,Phenanthrenes - Abstract
The reactivity of 5‐(alkynyl)dibenzothiophenium salts 1 is explored in the presence of different nucleophiles, dienes, and under photochemical conditions. Reaction with lithium acetylides affords diynes in moderate yields; while depending on the substitution pattern, the reaction with sulfinates delivers either the alkyne transfer products, alkynyl sulfones, or β‐(sulfonium) vinyl sulfones through addition to the C−C triple bond. Similar behavior is observed when tosylamines are used as nucleophiles. Salts of general formula 1 also react with dienes to render the corresponding Diels‐Alder cycloadducts. The vinyl sulfonium salts obtained by these routes further react with nucleophiles through a Michael addition, dibenzothiophene elimination sequence. Alternatively, they also engage in photoinduced radical cyclizations to produce substituted phenanthrenes. Attempts to use this specific addition/radical cyclization sequence for the construction of the 6a,7‐dehydroaporphine skeleton present in several families of alkaloids are also described., The synthetic potential of 5‐(alkynyl)benzothiophenium salts is further evaluated. In addition to their reactivity as electrophilic alkynylation reagents, they undergo regioselective additions to the C−C triple bond. The products thus obtained can be used for the synthesis of Z‐vinyl sulfones and 9,10‐substituted phenanthrenes.
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- 2021
8. Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages
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Jeroen P. J. Bruekers, Paul Tinnemans, Roeland J. M. Nolte, Johannes A. A. W. Elemans, Wybren Jan Buma, Nicolas Vanthuyne, Jeanne Crassous, Matthijs A. Hellinghuizen, Pieter J. Gilissen, Jean-Valère Naubron, Radboud University [Nijmegen], Institut des Sciences Moléculaires de Marseille (ISM2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), University of Amsterdam [Amsterdam] (UvA), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), European Research Council (ERC) European Research Council (ERC) [740295 ENCOPOL], Dutch Ministry of Education, Culture and Science [024.001.035], Ministere de l'Education Nationale, de la Recherche et de la Technologie, Centre National de la Recherche Scientifique (CNRS) Centre National de la Recherche Scientifique (CNRS), Rennes Metropole Region Bretagne, project Equip@Meso of the program \'Investissements d'Avenir\'French National Research Agency (ANR) [ANR-10-EQPX-29-01], ANR-14-CE25-0018,Fast Relax,Approximation rapide et fiable(2014), Radboud university [Nijmegen], Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), and Molecular Spectroscopy (HIMS, FNWI)
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Circular dichroism ,Cooperativity ,010402 general chemistry ,01 natural sciences ,Porphyrin ,chemistry.chemical_compound ,medicine ,[CHIM]Chemical Sciences ,Physical and Theoretical Chemistry ,Allostery ,Host–guest chemistry ,FELIX Condensed Matter Physics ,Full Paper ,010405 organic chemistry ,Scanning Probe Microscopy ,Organic Chemistry ,Viologen ,Full Papers ,0104 chemical sciences ,3. Good health ,Crystallography ,chemistry ,Vibrational circular dichroism ,Zirconium ,Enantiomer ,Chirality (chemistry) ,Host-guest chemistry ,Physical Organic Chemistry ,medicine.drug - Abstract
Chiral zirconium(IV) double cage sandwich complex Zr(1)2 has been synthesized in one step from porphyrin cage H21. Zr(1)2 was obtained as a racemate, which was resolved by HPLC and the enantiomers were isolated in >99.5 % ee. Their absolute configurations were assigned on the basis of X‐ray crystallography and circular dichroism spectroscopy. Vibrational circular dichroism (VCD) experiments on the enantiomers of Zr(1)2 revealed that the chirality around the zirconium center is propagated throughout the whole cage structure. The axial conformational chirality of the double cage complex displayed a VCD fingerprint similar to the one observed previously for a related chiral cage compound with planar and point chirality. Zr(1)2 shows fluorescence, which is quenched when viologen guests bind in its cavities. The binding of viologen and dihydroxybenzene derivatives in the two cavities of Zr(1)2 occurs with negative allostery, the cooperativity factors α (=4 K2/K1) being as low as 0.0076 for the binding of N,N’‐dimethylviologen. These allosteric effects are attributed to a pinching of the second cavity as a result of guest binding in the first cavity., Starting from achiral porphyrin cage compounds, chiral zirconium(IV) double decker porphyrin cages have been prepared and their enantiomers resolved. The binding of two viologen guests in the double decker porphyrin cages occurs via a strongly negative allosteric effect, resulting in an almost 3 orders of magnitude weaker binding of the second viologen guest compared to that of the first.
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- 2021
9. Double Porphyrin Cage Compounds
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Kathleen Stout, Roeland J. M. Nolte, Mathijs F. J. Mabesoone, Fabian L L Visschers, Jeroen van den Berg, Joëlle-Rose Klop, Alan E. Rowan, Theo P. J. Peters, Eline M Meijer, Johannes A. A. W. Elemans, and Paul B. White
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Synthetic Organic Chemistry ,DABCO ,010402 general chemistry ,01 natural sciences ,Porphyrin compounds ,Axial ligands ,chemistry.chemical_compound ,Polymer chemistry ,Molecule ,Porphyrin‐Based Receptors ,Physical and Theoretical Chemistry ,Host–guest chemistry ,Alkyl ,Octane ,chemistry.chemical_classification ,Full Paper ,010405 organic chemistry ,Ligand ,Molecular Materials ,Organic Chemistry ,Diastereomer ,Full Papers ,Porphyrin ,0104 chemical sciences ,chemistry ,Physical Organic Chemistry - Abstract
The synthesis and characterization of double porphyrin cage compounds are described. They consist of two porphyrins that are each attached to a diphenylglycoluril‐based clip molecule via four ethyleneoxy spacers, and are linked together by a single alkyl chain using “click”‐chemistry. Following a newly developed multistep synthesis procedure we report three of these double porphyrin cages, linked by spacers of different lengths, i.e. 3, 5, and 11 carbon atoms. The structures of the double porphyrin cages were fully characterized by NMR, which revealed that they consist of mixtures of two diastereoisomers. Their zinc derivatives are capable of forming sandwich‐like complexes with the ditopic ligand 1,4‐diazabicyclo[2,2,2]octane (dabco)., The synthesis of double porphyrin cage compounds based on glycoluril is described. Through a multistep synthesis, three double cage compounds linked by spacers of variable length are obtained. The binding and conformational properties of their zinc derivatives towards the ditopic ligand dabco have been investigated into detail.John Wiley & Sons, Ltd.
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- 2020
10. Oxidative Cleavage of Alkene C=C Bonds Using a Manganese Catalyzed Oxidation with H2O2 Combined with Periodate Oxidation
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Mecozzi, Francesco, Dong, Jia Jia, Angelone, Davide, Browne, Wesley R., Eisink, Niek N. H. M., Polymer Chemistry and Bioengineering, and Molecular Inorganic Chemistry
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MECHANISM ,Manganese ,Full Paper ,DIOLS ,Full Papers ,Alkenes ,Homogeneous catalysis ,Ozonolysis ,RUPTURE ,Oxidation ,EPOXIDES ,OLEFINS ,SODIUM PERIODATE ,Alkene Cleavage - Abstract
A one‐pot multi‐step method for the oxidative cleavage of alkenes to aldehydes/ketones under ambient conditions is described as an alternative to ozonolysis. The first step is a highly efficient manganese catalyzed epoxidation/cis‐dihydroxylation of alkenes. This step is followed by an Fe(III) assisted ring opening of the epoxide (where necessary) to a 1,2‐diol. Carbon–carbon bond cleavage is achieved by treatment of the diol with sodium periodate. The conditions used in each step are not only compatible with the subsequent step(s), but also provide for increased conversion compared to the equivalent reactions carried out on the isolated intermediate compounds. The described procedure allows for carbon–carbon bond cleavage in the presence of other alkenes, oxidation sensitive moieties and other functional groups; the mild conditions (r.t.) used in all three steps make this a viable general alternative to ozonolysis and especially for use under flow or continuous batch conditions., A one‐pot multi‐step method for the oxidative cleavage of alkenes to aldehydes/ketones under ambient conditions is reported. Combining a highly efficient manganese catalyzed epoxidation/cis‐dihydroxylation with Fe(III)(ClO4)3 assisted ring opening is followed by periodiate cleavage of the resulting diol.John Wiley & Sons, Ltd.
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- 2019
11. Synthesis and Evaluations of '1,4‐Triazolyl Combretacoumarins' and Desmethoxy Analogs
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Jessica D. Hess, Mahesh K. Lakshman, Padmanava Pradhan, Robert Snoeck, Renato J. Aguilera, Dominique Schols, Tashrique A. Khandaker, and Graciela Andrei
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Triazole ,Alkyne ,Heterocycles ,Coumarin ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,chemistry.chemical_compound ,Hexafluorophosphate ,Reactivity (chemistry) ,Phosphonium ,Physical and Theoretical Chemistry ,Solubility ,Combretastatin ,chemistry.chemical_classification ,Full Paper ,Click chemistry ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Full Papers ,0104 chemical sciences ,Alkynes ,Copper ,Derivative (chemistry) - Abstract
1,4‐Triazolyl combretacoumarins have been prepared by linking the trimethoxyarene unit of combretastatin A4 with coumarins, via a 1,2,3‐triazole. For this, 4‐azidocoumarins were accessed by a sequential two‐step, one‐pot reaction of 4‐hydroxycoumarins with (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), followed by reaction with NaN3. In the reaction with BOP, a coumarin‐derived phosphonium ion intermediate seems to form, leading to an O 4‐(benzotriazolyl)coumarin derivative. For the CuAAC reaction of azidocoumarins with 5‐ethynyl‐1,2,3‐trimethoxybenzene, catalytic [(MeCN)4Cu]PF6 in CH2Cl2/MeOH with 2,6‐lutidine, at 50 oC, was suitable. The 4‐azidocoumarins were less reactive as compared to PhN3 and the NBO coefficients of the azido groups were compared by DFT analysis. Compound solubility was a problem in biological assays. On the basis of the biological and solubility data of one 1,4‐triazolyl combretacoumarin, four analogs lacking one or two methoxy groups were synthesized. Reactivity differences among the phenylacetylenes were noted and the NBO coefficients of the alkynes were compared by DFT analysis. In cytotoxicity assays, 1‐phenyl‐4‐(3,4,5‐trimethoxyphenyl)‐1H‐1,2,3‐triazole showed activity in CEM and MDA‐MB‐231 cell lines by apoptosis. The desmethoxy 6‐bromo‐4‐(4‐(4‐methoxyphenyl)‐1H‐1,2,3‐triazol‐1‐yl)‐2H‐chromen‐2‐one also showed cytotoxicity against the two cell lines, but this did not appear to be consistent with apoptosis. The antiviral activity of the compounds was unremarkable., A facile, one‐pot synthesis of 4‐azidocoumarins from 4‐hydroxycoumarins has been developed. Cu‐catalyzed azide‐alkyne cycloaddition of these compounds with 5‐ethynyl‐1,2,3‐trimethoxybenzene or mono and dimethoxy phenylacetylenes gave a series of 1,4‐triazolyl combretacoumarins and desmethoxy analogs. These were analyzed for their antiproliferative and antiviral properties.John Wiley & Sons, Ltd.This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.
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- 2019
12. Rare‐Earth‐Metal‐Catalyzed Kinetic Resolution of Chiral Aminoalkenes via Hydroamination: The Effect of the Silyl Substituent of the Binaphtholate Ligand on Resolution Efficiency
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Hiep N. Nguyen and Kai C. Hultzsch
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inorganic chemicals ,Reaction mechanism ,Reaction mechanisms ,Substituent ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Hydroamination ,Catalysis ,Kinetic resolution ,chemistry.chemical_compound ,Asymmetric catalysis ,Rare earths ,Physical and Theoretical Chemistry ,Full Paper ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Enantioselective synthesis ,Substrate (chemistry) ,Full Papers ,0104 chemical sciences ,Intramolecular force ,Asymmetric Hydroamination - Abstract
The kinetic resolution of α‐substituted aminopentenes via intramolecular hydroamination was investigated using various 3,3′‐silyl‐substituted binaphtholate yttrium catalysts. High efficiencies in the kinetic resolution were observed for methyl‐, benzyl‐, and phenyl‐substituted substrates utilizing the cyclohexyldiphenylsilyl‐substituted catalyst 2c with resolution factors reaching as high as 90(5) for hex‐5‐en‐2‐amine (3a). Kinetic analysis of the enantioenriched substrates with the matching and mismatching catalyst revealed that the efficiency of catalyst 2c benefits significantly from a favorable Curtin–Hammett pre‐equilibrium and by a large kfast/kslow ratio. Other binaphtholate catalysts were less efficient due to a less favorable Curtin–Hammett pre‐equilibrium, which often favored the mismatching substrate‐catalyst combination. Cyclization of the matched substrate proceeds generally with large trans‐selectivity, whereas the trans/cis‐ratio for mismatched substrates is significantly diminished, favoring the cis‐cyclization product isomer in some instances.
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- 2019
13. Visible Light‐Promoted Beckmann Rearrangements: Separating Sequential Photochemical and Thermal Phenomena in a Continuous Flow Reactor
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Chen, Yuesu, Cantillo, David, and Kappe, C. Oliver
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Full Paper ,Chemical generator ,Continuous flow ,Beckmann rearrangement ,Flow Photochemistry ,Vilsmeier–Haack reagent ,Full Papers ,Photoredox catalysis - Abstract
The Beckmann rearrangement of oximes to amides typically requires strong acids or highly reactive, hazardous electrophiles and/or elevated temperatures to proceed. A very attractive alternative is the in situ generation of Vilsmeier-Haack reagents, by means of photoredox catalysis, as promoters for the thermal Beckmann rearrangement. Investigation of the reaction parameters for this light-induced method using a one-pot strategy has shown that the reaction is limited by the different temperatures required for each of the two sequential steps. Using a continuous flow reactor, the photochemical and thermal processes have been separated by integrating a flow photoreactor unit at low temperature for the electrophile generation with a second reactor unit, at high temperature, where the rearrangement takes place. This strategy has enabled excellent conversions and yields for a diverse set of oximes, minimizing the formation of side products obtained with the original one-pot method.
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- 2019
14. A Revised Modular Approach to (–)‐trans‐Δ8‐THC and Derivatives Through Late‐Stage Suzuki–Miyaura Cross‐Coupling Reactions
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Bloemendal, Victor R. L. J., Sondag, Daan, Elferink, Hidde, Boltje, Thomas J., van Hest, Jan. C. M., and Rutjes, Floris P. J. T.
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Cannabis derivatives ,Full Paper ,Tetrahydrocannabinol ,Suzuki–Miyaura coupling ,Cascade reactions ,Heterocycles ,Full Papers - Abstract
A revised modular approach to various synthetic (–)‐trans‐Δ8‐THC derivatives through late‐stage Suzuki–Miyaura cross‐coupling reactions is disclosed. Ten derivatives were synthesized allowing both sp2‐ and sp3‐hybridized cross‐coupling partners with minimal β‐hydride elimination. Importantly, we demonstrate that a para‐bromo‐substituted THC scaffold for Suzuki–Miyaura cross‐coupling reactions has been initially reported incorrectly in recent literature.
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- 2019
15. The Red Color of Life Transformed – Synthetic Advances and Emerging Applications of Protoporphyrin IX in Chemical Biology
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Mathias O. Senge and Elisabeth Sitte
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Protoporphyrin IX ,Chemical biology ,Porphyrinoids ,Review ,Heme ,010402 general chemistry ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Chemical Biology ,Physical and Theoretical Chemistry ,chemistry.chemical_classification ,biology ,010405 organic chemistry ,Porphyrinoids | Very Important Paper ,Cytochrome c ,Biomolecule ,Organic Chemistry ,Porphyrin ,Combinatorial chemistry ,ddc ,0104 chemical sciences ,Heme B ,chemistry ,Sensing ,biology.protein ,Oxygen binding - Abstract
Protoporphyrin IX (PPIX) is the porphyrin scaffold of heme b, a ubiquitous prosthetic group of proteins responsible for oxygen binding (hemoglobin, myoglobin), electron transfer (cytochrome c) and catalysis (cytochrome P450, catalases, peroxidases). PPIX and its metallated derivatives frequently find application as therapeutic agents, imaging tools, catalysts, sensors and in light harvesting. The vast toolkit of accessible porphyrin functionalization reactions enables easy synthetic modification of PPIX to meet the requirements for its multiple uses. In the past few years, particular interest has arisen in exploiting the interaction of PPIX and its synthetic derivatives with biomolecules such as DNA and heme‐binding proteins to evolve molecular devices with new functions as well as to uncover potential therapeutic toeholds. This review strives to shine a light on the most recent developments in the synthetic chemistry of PPIX and its uses in selected fields of chemical biology., The use of the heme precursor protoporphyrin IX for biological applications has experienced a steep increase in recent years. Herein, we review possibilities for synthetic modification of this porphyrin scaffold and discuss its emerging key uses in the field of chemical biology.John Wiley & Sons, Ltd.
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- 2020
16. Ammonium Salt-Catalyzed Ring-Opening of Aryl-Aziridines with β-Keto Esters
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Mario Waser, Viktoria Kreuzer, Maximilian Tiffner, Bernhard Spingler, and Victoria Haider
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Full Paper ,Alkylation ,010405 organic chemistry ,Organocatalysis ,Aryl ,Organic Chemistry ,Enantioselective synthesis ,food and beverages ,Regioselectivity ,Full Papers ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Bifunctional ammonium salt ,Ammonium ,Aziridine Opening ,Physical and Theoretical Chemistry ,Bifunctional - Abstract
We herein report an ammonium salt‐catalyzed protocol for the regioselective ring opening of aryl‐aziridines with β‐keto esters. The reaction gives access to a variety of highly functionalized target molecules with two consecutive stereogenic centers and can be rendered enantioselective (up to e.r. = 91:9) by using bifunctional chiral ammonium salt catalysts., The quaternary ammonium salt‐catalyzed addition of β‐keto esters to aryl‐aziridines gives access to structurally diverse target molecules with two consecutive stereocenters.John Wiley & Sons, Ltd.
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- 2020
17. Asymmetric α-Chlorination of β-Keto Esters Using Hypervalent Iodine-Based Cl-Transfer Reagents in Combination with Cinchona Alkaloid Catalysts
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Johannes Schörgenhumer, Christopher Mairhofer, Lotte Stockhammer, and Mario Waser
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inorganic chemicals ,Cinchona ,Cinchona Alkaloids ,010402 general chemistry ,01 natural sciences ,Catalysis ,Nucleophile ,Cinchona alkaloids ,polycyclic compounds ,Organic chemistry ,Chlorination ,heterocyclic compounds ,Physical and Theoretical Chemistry ,Hypervalent iodine reagents ,biology ,Full Paper ,010405 organic chemistry ,Chemistry ,Organocatalysis ,organic chemicals ,Organic Chemistry ,Hypervalent molecule ,Full Papers ,biology.organism_classification ,0104 chemical sciences ,Reagent ,Electrophile ,Nucleophilic catalysis - Abstract
We herein report an unprecedented strategy for the asymmetric α‐chlorination of β‐keto esters with hypervalent iodine‐based Cl‐transfer reagents using simple Cinchona alkaloid catalysts. Our investigations support an α‐chlorination mechanism where the Cinchona species serves as a nucleophilic catalyst by reacting with the chlorinating agent to generate a chiral electrophilic Cl‐transfer reagent in situ. Using at least 20 mol‐% of the alkaloid catalyst allows for good yields and enantioselectivities for a variety of different β‐keto esters under operationally simple conditions., Simple Cinchona alkaloids serve as nucleophilic organocatalysts to facilitate the enantioselective α‐chlorination of β‐keto esters by using hypervalent iodine‐based Cl‐transfer reagentsJohn Wiley & Sons, Ltd.
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- 2020
18. Synthesis and Structure of
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Nitika, Grover, Ganapathi, Emandi, Brendan, Twamley, Bhavya, Khurana, Vincent, Sol, and Mathias O, Senge
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Full Paper ,Expanded porphyrins ,Porphyrinoids ,Photosensitizer ,Non‐aromatic ,Full Papers ,Expanded Porphyrinoids | Very Important Paper ,Homoporphyrins - Abstract
Bench‐stable meso‐substituted di(p/m‐benzi)homoporphyrins were synthesized through acid‐catalyzed condensation of dipyrrole derivatives with aryl aldehydes. The insertion of a 1,1,2,2‐tetraphenylethene (TPE) or but‐2‐ene‐2,3‐diyldibenzene unit in the porphyrin framework results in the formation of dibenzihomoporphyrins, merging the features of hydrocarbons and porphyrins. Single crystal X‐ray analyses established the non‐planar structure of these molecules, with the phenylene rings out of the mean plane, as defined by the dipyrromethene moiety and the two meso‐carbon atoms. Spectroscopic and structural investigations show that the macrocycles exhibit characteristics of both TPE or but‐2‐ene‐2,3‐diyldibenzene and dipyrromethene units indicating the non‐aromatic characteristics of the compounds synthesized. Additionally, the dibenzihomoporphyrins were found to generate singlet oxygen, potentially allowing their use as photosensitizers., A series of dibenzihomoporphyrins were synthesized by incorporation of phenylene para‐ and meta‐linkages into the macrocycles. Structural elucidation revealed non‐aromatic property due to a lack of effective π‐conjugation and non‐planarity of the macrocycles. Furthermore, these macrocycles were shown to act as photosensitizers for singlet oxygen generation.John Wiley & Sons, Ltd.
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- 2020
19. An Insight into Non-Covalent Interactions on the Bicyclo[1.1.1]pentane Scaffold
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Mathias O. Senge, Keith J. Flanagan, Cristina Trujillo, Christopher J. Kingsbury, and Nitika Grover
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Hydrogen bonding ,Bioisosteres ,Noncovalent interactions ,Bicyclo[1.1.1]pentane ,Stacking ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Non-covalent interactions ,Physical and Theoretical Chemistry ,Benzene ,chemistry.chemical_classification ,Halogen bond ,Full Paper ,Bicyclic molecule ,010405 organic chemistry ,Hydrogen bond ,Organic Chemistry ,Full Papers ,ddc ,0104 chemical sciences ,Pentane ,Crystallography ,Monomer ,chemistry ,Halogen bonding - Abstract
Bicyclo[1.1.1]pentane (BCP) is studied extensively as a bioisosteric component of drugs. Not found in nature, this molecular unit approximates the distance of a para‐disubstituted benzene which is replaced in medicines as a method of improving treatments. Predicting interactions of these drugs with specific active sites requires knowledge of the non‐covalent interactions engaged by this subunit. Structure determinations and computational analysis (Hirshfeld analysis, 2D fingerprint plots, DFT) of seven BCP derivatives chosen to probe specific and directional interactions. X‐ray analysis revealed the presence of various non‐covalent interactions including I ⋅⋅⋅ I, I ⋅⋅⋅ N, N−H ⋅⋅⋅ O, C−H ⋅⋅⋅ O, and H−C ⋅⋅⋅ H−C contacts. The preference of halogen bonding (I ⋅⋅⋅ I or I ⋅⋅⋅ N) in BCP 1–4 strictly depends upon the electronic nature and angle between bridgehead substituents. The transannular distance in co‐crystals 2 and 4 was longer as compared to monomers 1 and 3. Stronger N−H ⋅⋅⋅ O and weaker C−H ⋅⋅⋅ O contacts were observed for BCP 5 while the O ⋅⋅⋅ H interaction was a prominent contact for BCP 6. The presence of 3D BCP units prevented the π ⋅⋅⋅ π stacking between phenyl rings in 3, 4, and 7. The BCP skeleton was often rotationally averaged, indicating fewer interactions compared to bridgehead functional groups. Using DFT analysis, geometries were optimized and molecular electrostatic potentials were calculated on the BCP surfaces. These interaction profiles may be useful for designing BCP analogs of drugs., The effect of bridgehead substitutions on non‐covalent interactions was investigated for seven BCP derivatives. The X‐ray analyses show 3D‐structures and a combination of non‐covalent interactions including HB, XB, and CH ⋅⋅⋅ HC contacts. QTAIM analysis and MEP graphs show the presence of bond critical points and σ‐holes.
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- 2020
- Full Text
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20. Cu and Hydroquinone for the Trifluoromethylation of Unprotected Phenols
- Author
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Christoph Koeberl, Jakob Pletz, Michael Fuchs, Walter Goessler, Oliver Steiner, and Wolfgang Kroutil
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Iodide ,Hydroquinone ,010402 general chemistry ,01 natural sciences ,Fluorinated Compounds ,Catalysis ,chemistry.chemical_compound ,Organic chemistry ,Phenols ,Physical and Theoretical Chemistry ,Laccase ,chemistry.chemical_classification ,Trifluoromethylation ,Trifluoromethyl ,Full Paper ,Phenol ,010405 organic chemistry ,Organic Chemistry ,Full Papers ,0104 chemical sciences ,chemistry ,Reagent ,Copper - Abstract
Fluorination and trifluoromethylation are indispensable tools in the preparation of modern pharmaceuticals and APIs. Herein we present a concept for the introduction of a trifluoromethyl group into unprotected phenols employing catalytic copper(I) iodide and hydroquinone, tBuOOH, and the Langlois' reagent. The method proceeds under mild conditions and exhibits an extended substrate scope compared to the biocatalytic trifluoromethylation using laccase from Agaricus bisporus. Various functional groups such as aldehydes, esters, ethers, ketones and nitriles were tolerated. The hydroquinone-mediated trifluoromethylation reaction allowed accessing trifluoromethylated phenols, which are cumbersome to prepare via previously known chemical methods.
- Published
- 2018
21. A Kinetic Photometric Assay for the Quantification of the Open-Chain Content of Aldoses
- Author
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Alexander Reichetseder, Florian Rudroff, Hubert Kalaus, Marko D. Mihovilovic, Christian Stanetty, and Verena Scheibelreiter
- Subjects
chemistry.chemical_classification ,Aldehydes ,Communication ,Organic Chemistry ,Kinetics ,Carbohydrates ,Aldehyde ,Communications ,Adduct ,chemistry.chemical_compound ,Ultraviolet visible spectroscopy ,chemistry ,Computational chemistry ,Very Important Paper ,Analytical methods ,Moiety ,Hemiacetal ,Reactivity (chemistry) ,UV/Vis spectroscopy ,Physical and Theoretical Chemistry ,Plate reader - Abstract
Aldoses exist predominantly in the cyclic hemiacetal form, which is in equilibrium with the open‐chain aldehyde form. The small aldehyde content hampers reactivity when chemistry addresses the carbonyl moiety. This low concentration of the available aldehyde is generally difficult to ascertain. Herein, we demonstrate a new kinetic determination of the (minute) open‐chain content (OCC) of aldoses. This kinetic approach exploits the aldehyde‐selectivity of 2‐aminobenzamidoxime (ABAO), which furnishes a strongly UV‐active adduct. Simple formation curves can be measured in a photometer or plate reader for high‐throughput screening. Under pseudo‐first order kinetics, these curves correlate with a prediction model yielding the relative OCC. The OCCs of all parent aldoses (pentoses and hexoses) were determined referencing against the two tetroses with exceptionally high OCCs and were in very good agreement with literature data. Additionally, the assay was extended towards higher‐carbon sugars with unknown OCC and also applied to rationalise a lack of reactivity observed in a recent synthetic investigation., An operationally simple UV‐based kinetic assay allows the accurate determination of the minute proportions (
- Published
- 2020
22. Anionic and Photochemical Behaviour of the Medium-Sized Terpenoid Ketone 8-Dehydro-12-O-methyl-deacylhallerinDedicated to the memory of Anna Ramella PralungoAnd it seems to me you lived your life Like a candle in the wind (“Candle in the wind”, Elton John) We dedicate this paper to the memory of Anna, whose recent death at the tragically early age of 33 came as a profound shock to her friends and colleagues. Anna was a lively and engaging young woman, dynamic, generous and life-loving. She was a committed, hard-working student, when she undertook the research described in this paper, which constitutes the substance of her master’s thesis.
- Author
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Gianluca Croce, Marco Milanesio, Davide Viterbo, Marco Clericuzio, Piero Ugliengo, and Giovanni Appendino
- Published
- 2006
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23. Dihalohydration of Alkynols: A Versatile Approach to Diverse Halogenated Molecules
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Samantha M, Gibson, Jarryl M, D'Oyley, Joe I, Higham, Kate, Sanders, Victor, Laserna, Abil E, Aliev, and Tom D, Sheppard
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Halogenated Molecules ,Full Paper ,Halogenation ,Alkynes ,Alcohols ,Heterocycles ,Full Papers ,Ketones - Abstract
In this paper we outline how dihalohydration reactions of propargylic alcohols can be used to access a wide variety of useful halogenated building blocks. A novel procedure for dibromohydration of alkynes has been developed, and a selection of dichloro and dibromo diols and cyclic ethers were synthesized. The dihalohydration of homo‐propargylic alcohols provides a useful route to 3‐halofurans, which were shown to readily undergo cycloaddition reactions under mild conditions. Finally, a novel ring expansion of propargylic alcohols containing a cyclopropylalkyne provides access to halogenated alkenylcyclobutanes.
- Published
- 2018
24. Balancing Bulkiness in Gold(I) Phosphino-triazole Catalysis
- Author
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Zhao, Yiming, Wakeling, Matthew G., Meloni, Fernanda, Sum, Tze Jing, van Nguyen, Huy, Buckley, Benjamin R., Davies, Paul W., and Fossey, John S.
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Keytopic: Bulky Ligands ,Full Paper ,Click chemistry ,Gold ,Full Papers ,Triazoles ,Homogeneous catalysis ,Phosphane ligands - Abstract
The syntheses of a series of 1‐phenyl‐5‐phosphino 1,2,3‐triazoles are disclosed, within which, the phosphorus atom (at the 5‐position of a triazole) is appended by one, two or three triazole motifs, and the valency of the phosphorus(III) atom is completed by two, one or zero ancillary (phenyl or cyclohexyl) groups respectively. This series of phosphines was compared with tricyclohexylphosphine and triphenylphosphine to study the effect of increasing the number of triazoles appended to the central phosphorus atom from zero to three triazoles. Gold(I) chloride complexes of the synthesised ligands were prepared and analysed by techniques including single‐crystal X‐ray diffraction structure determination. Gold(I) complexes were also prepared from 1‐(2,6‐dimethoxy)‐phenyl‐5‐dicyclohexyl‐phosphino 1,2,3‐triazole and 1‐(2,6‐dimethoxy)‐phenyl‐5‐diphenyl‐phosphino 1,2,3‐triazole ligands. The crystal structures thus obtained were examined using the SambVca (2.0) web tool and percentage buried volumes determined. The effectiveness of these gold(I) chloride complexes to serve as precatalysts for alkyne hydration were assessed. Furthermore, the regioselectivity of hydration of but‐1‐yne‐1,4‐diyldibenzene was probed.
- Published
- 2019
25. The Intermediates in Lewis Acid Catalysis with Lanthanide Triflates
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Guilherme L, Tripodi, Thiago C, Correra, Célio F F, Angolini, Bruno R V, Ferreira, Philippe, Maître, Marcos N, Eberlin, and Jana, Roithová
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Lewis acid catalysis ,Reactive intermediates ,Catalysis Intermediates ,Full Paper ,Reaction mechanisms ,Structure elucidation ,Full Papers ,Lanthanide triflates - Abstract
Lanthanide triflates are effective Lewis acid catalysts in reactions involving carbonyl compounds due to their high oxophilicity and water stability. Despite the growing interest, the identity of the catalytic species formed in lanthanide catalysed reactions is still unknown. We have therefore used mass spectrometry and ion spectroscopy to intercept and characterize the intermediates in a reaction catalysed by ytterbium and dysprosium triflates. We were able to identify a number of lanthanide intermediates formed in a simple condensation reaction between a C‐acid and an aldehyde. Results show correlation between the reactivity of lanthanide complexes and their charge state and suggest that the triply charged complexes play a key role in lanthanide catalysed reactions. Spectroscopic data of the gaseous ions accompanied by theoretical calculations reveal that the difference between catalytic efficiencies of ytterbium and dysprosium ions can be explained by their different electrophilicity., Knoevenagel condensation can be accelerated by addition of Lewis acids. This work shows a number of intermediates along the reaction path catalyzed by ytterbium and dysprosium and compares relative reaction rates. The main conclusion is: the larger the electrostatic field of the Lewis acid, the more activated the intermediates, and the faster the reaction.John Wiley & Sons, Ltd.
- Published
- 2019
26. Effect of Chirality on the Binding of Viologen Guests in Porphyrin Macrocycles
- Author
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Varghese, Shaji, Spierenburg, Bram, Bruekers, Jeroen P. J., Swartjes, Anne, White, Paul B., Elemans, Johannes A. A. W., and Nolte, Roeland J. M.
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Full Paper ,Host–Guest Complexation ,Porphyrinoids ,Threading ,Host–guest systems ,Cage compounds ,Full Papers ,Chirality ,Pseudo‐rotxanes - Abstract
As part of a project aimed at the development of chiral processive catalysts that can write information on a polymer chain we describe the synthesis of two optically active porphyrin macrocycles, which are prepared in 3 steps from an achiral precursor compound. Fluorescence and 1H‐NMR studies show that one of the macrocycles displays selectivity in the binding of chiral viologen guest molecules.
- Published
- 2019
- Full Text
- View/download PDF
27. Direct Stereoselective Aziridination of Cyclohexenols with 3-Amino-2-(trifluoromethyl)quinazolin-4(3
- Author
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Marta, Artola, Shirley, Wouters, Sybrin P, Schröder, Casper, de Boer, Yurong, Chen, Rita, Petracca, Adrianus M C H, van den Nieuwendijk, Johannes M F G, Aerts, Gijsbert A, van der Marel, Jeroen D C, Codée, and Herman S, Overkleeft
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3‐amino‐quinazolin‐4(3H)‐ones ,Full Paper ,Aziridines ,Glycosidase inhibitors ,Full Papers ,Glycosidases ,Stereoselective Aziridination ,Cyclophellitol - Abstract
Cyclophellitol aziridine and its configurational and functional isomers are powerful covalent inhibitors of retaining glycosidases, and find application in fundamental studies on glycosidases, amongst others in relation to inherited lysosomal storage disorders caused by glycosidase malfunctioning. Few direct and stereoselective aziridination methodologies are known for the synthesis of cyclophellitol aziridines. Herein, we present our studies on the scope of direct 3‐amino‐2‐(trifluoromethyl)quinazolin‐4(3H)‐one‐mediated aziridination on a variety of configurational and functional cyclohexenol isosters. We demonstrate that the aziridination can be directed by an allylic or homoallylic hydroxyl through H‐bonding and that steric hindrance plays a key role in the diastereoselectivity of the reaction., This work describes direct aziridination reactions on differently substituted glycoside configured cyclohexenes with 3‐amino‐2‐(trifluoromethyl)quinazolin‐4(3H)‐one as nitrogen donor. It is shown that aziridination can be directed by allylic or homoallylic hydroxyls through H‐bonding, and that steric hindrance plays an essential role in the diastereoselective outcome of the final cyclitols aziridines.John Wiley & Sons, Ltd.
- Published
- 2018
28. Nucleophilic Aromatic Substitution (S
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Harry C, Sample and Mathias O, Senge
- Subjects
Nucleophilic Aromatic Substitution | Very Important Paper ,Aromaticity ,Porphyrinoids ,Review ,Nucleophilic Aromatic Substitution - Abstract
The nucleophilic substitution of aromatic moieties (SNAr) has been known for over 150 years and found wide use for the functionalization of (hetero)aromatic systems. Currently, several “types” of SNAr reactions have been established and notably the area of porphyrinoid macrocycles has seen many uses thereof. Herein, we detail the SNAr reactions of seven types of porphyrinoids with differing number and type of pyrrole units: subporphyrins, norcorroles, corroles, porphyrins, azuliporphyrins, N‐confused porphyrins, and phthalocyanines. For each we analyze the substitution dependent upon: a) the type of nucleophile and b) the site of substitution (α, β, or meso). Along with this we evaluate this route as a synthetic strategy for the generation of unsymmetrical porphyrinoids. Distinct trends can be identified for each type of porphyrinoid discussed, regardless of nucleophile. The use of nucleophilic substitution on porphyrinoids is found to often be a cost‐effective procedure with the ability to yield complex substituent patterns, which can be conducted in non‐anhydrous solvents with easily accessible simple porphyrinoids., An up to date review regarding the SNAr of seven different types of porphyrinoids, each containing differing numbers and types of pyrrole rings and meso positions is presented. The reactivity and mechanistic analysis of subporphyrins, norcorroles, corroles, porphyrins, azuliporphyrins, N‐confused porphyrins, and phthalocyanines shows a bright future for the generation of unsymmetrical porphyrinoids via this reaction mechanism.John Wiley & Sons, Ltd.
- Published
- 2020
29. How to Synthesise High Purity, Crystalline d‐Glucaric Acid Selectively
- Author
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Armstrong, Robert D., Kariuki, Benson M., Knight, David W., and Hutchings, Graham J.
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chemistry.chemical_classification ,Glucaric acid ,010405 organic chemistry ,Chemistry ,Communication ,Organic Chemistry ,D-Glucaric Acid ,Glucaric Acid Synthesis | Very Important Paper ,Carbohydrates ,Polymer ,010402 general chemistry ,01 natural sciences ,Glucaric Acid ,Communications ,0104 chemical sciences ,Chemoselectivity ,Azeotrope ,Yield (chemistry) ,Molecule ,Organic chemistry ,Physical and Theoretical Chemistry ,Platform molecule - Abstract
Glucaric acid has potential applications in food, pharmaceutical and polymer industries yet no methodology exists within the public domain for isolation of this key bio-derived platform molecule as a pure, crystalline solid. Here we demonstrate the difficulties, which arise in doing so and report development of a process for derivation of free-glucaric acid from its Ca2+/K+ glucarate salts, which are both commercially available. Employing Amberlyst-15 (H+) exchange resin and azeotrope drying, powdered glucaric acid is prepared at > 99.96 % purity in 98.7 % dry yield.
- Published
- 2017
30. Efficient O‐Acylation of Alcohols and Phenol Using Cp2TiCl as a Reaction Promoter
- Author
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Rosario Hernández-Galán, José Manuel Botubol-Ares, Isidro G. Collado, María Jesús Durán-Peña, James R. Hanson, and Química Orgánica
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Acylation ,chemistry.chemical_element ,Manganese ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Acyl chloride ,Organic chemistry ,Phenol ,Physical and Theoretical Chemistry ,Titanium ,Primary (chemistry) ,Full Paper ,010405 organic chemistry ,Radical reactions ,Organic Chemistry ,Titanocene dichloride ,Esters ,Transesterification ,Full Papers ,0104 chemical sciences ,chemistry ,Halohydrins - Abstract
A method has been developed for the conversion of primary, secondary, and tertiary alcohols, and phenol, into the corresponding esters at room temperature. The method uses a titanium(III) species generated from a substoichiometric amount of titanocene dichloride together with manganese(0) as a reductant, as well as methylene diiodide. It involves a transesterification from an ethyl ester, or a reaction with an acyl chloride. A radical mechanism is proposed for these transformations.
- Published
- 2016
31. Synthesis of a Crushed Fullerene C60H24 through Sixfold Palladium‐Catalyzed Arylation
- Author
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Dorel, Ruth, de Mendoza, Paula, Calleja, Pilar, Pascual, Sergio, González‐Cantalapiedra, Esther, Cabello, Noemí, and Echavarren, Antonio M.
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Full Paper ,Mass spectrometry ,Fullerenes ,Full Papers ,Truxene ,Arylation ,Palladium - Abstract
The synthesis of a new C 3v‐symmetric crushed fullerene C60H24 (5) has been accomplished in three steps from truxene through sixfold palladium‐catalyzed intramolecular arylation of a syn‐trialkylated truxene precursor. Laser irradiation of 5 induces cyclodehydrogenation processes that result in the formation of C60, as detected by LDI‐MS.
- Published
- 2016
32. Synthesis of 3-Amino-1-benzothiophene-1,1-diones by Alkyne Directed Hydroarylation and 1/N→3/C-Sulfonyl Migration
- Author
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Ivan, Bernar, Daniel, Blanco-Ania, Sophie J, Stok, Lia, Sotorríos, Enrique, Gómez-Bengoa, and Floris P J T, Rutjes
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Full Paper ,Ynamines ,Synthetic methods ,C–H Activation ,C–H activation ,Full Papers ,Homogeneous catalysis ,Palladium - Abstract
A completely regioselective and highly stereoselective palladium‐catalyzed intramolecular hydroarylation of arenesulfonyl ynamines to benzothiazoles was developed. The presence of an electron‐withdrawing group on the triple bond of the sulfonyl ynamine was crucial for the success of the reaction and our mechanistic studies suggest an alkyne‐directed 5‐exo‐dig cyclization pathway. The products easily underwent photoinduced rearrangement to 3‐amino‐1‐benzothiophene‐1,1‐diones (up to 35 % yields after two steps).
- Published
- 2018
33. Reagent Controlled Stereoselective Assembly of α-(1,3)-Glucans
- Author
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Liming, Wang, Herman S, Overkleeft, Gijsbert A, van der Marel, and Jeroen D C, Codée
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carbohydrates (lipids) ,Glycosylation ,Full Paper ,α‐1,3‐Glucan ,Oligosaccharides ,Stereoselectivity ,Additive ,Full Papers ,Glycosylations - Abstract
Pre‐activation based glycosylations have become a very powerful tool in the assembly of oligosaccharides and the use of nucleophilic additives allows for the in situ generation of reactive intermediates with tailored reactivity. We here use a glycosylation strategy that is based on the use of per‐benzylated imidate building blocks for the fully stereoselective construction of a spacer equipped Aspergillus fumigatus α‐1,3‐octaglucan. We have used the trimethylsilyl iodide (TMSI)‐triphenylphosphine oxide (Ph3P=O) for the stereoselective installation of an azidopropanol spacer and triflic acid (TfOH)‐dimethyl formamide (DMF) enabled glycosylations for the coupling reactions with the secondary glucosyl C‐3‐alcohols. An operationally simple in situ activation coupling procedure is introduced and used for the final glycosylation events towards the octasaccharide.
- Published
- 2018
34. Air-Stable CpCo
- Author
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Fabian, Fischer and Marko, Hapke
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Earth‐abundant metals ,Full Paper ,Synthetic methods ,Pyridines ,Catalyst activation ,[2+2+2] Cycloadditions ,Cobalt ,Full Papers ,Microwave ,Cycloaddition - Abstract
The robust CoI precatalyst [CpCo(P{OEt}3)(trans‐MeO2CHC=CHCO2Me)] was investigated in cyclotrimerizations, furnishing benzenes and pyridines from triynes, diynes and nitriles, comparing the influence of different ways of energy supply; namely, irradiation and conventional (thermal) or microwave heating. The precatalyst was found to work under all conditions, including the possibility to catalyze cyclotrimerizations at room temperature under photochemical conditions at longer reaction times. Performance of the reactions in a microwave reactor proved to be the most time‐efficient way to rapidly assemble the expected reaction products; however, careful selection of reaction conditions can be required. The synthesis of pyridines and isoquinolines successfully involved the utilization of versatile functionalized nitriles, affording structurally interesting reaction products. Comparison with the known and often applied precatalyst CpCo(CO)2 demonstrated the significantly higher reactivity of the CpCoI–phosphite–olefin precatalyst.
- Published
- 2018
35. Generation of Dynamic Combinatorial Libraries Using Hydrazone-Functionalized Surface Mimetics
- Author
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Sarah H, Hewitt and Andrew J, Wilson
- Subjects
chemistry.chemical_classification ,Porphyrins ,Full Paper ,010405 organic chemistry ,Organic Chemistry ,Supramolecular chemistry ,Hydrazones ,Hydrazone ,Dynamic combinatorial chemistry ,Full Papers ,010402 general chemistry ,Hydrazide ,Hydrazone DCLs | Very Important Paper ,01 natural sciences ,Porphyrin ,Combinatorial chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,Aniline ,chemistry ,Protein surface mimetics ,Physical and Theoretical Chemistry ,Surface protein - Abstract
Dynamic combinatorial chemistry (DCC) represents an approach, whereby traditional supramolecular scaffolds used for protein surface recognition might be exploited to achieve selective high affinity target recognition. Synthesis, in situ screening and amplification under selection pressure allows the generation of ligands, which bear different moieties capable of making multivalent non‐covalent interactions with target proteins. Generic tetracarboxyphenyl porphyrin scaffolds bearing four hydrazide moieties have been used to form dynamic combinatorial libraries (DCLs) using aniline‐catalyzed reversible hydrazone exchange reactions, in 10 % DMSO, 5 mm NH4OAc, at pH 6.75. High resolution mass spectrometry (HRMS) was used to monitor library composition and establish conditions under which equilibria were established.
- Published
- 2018
36. The Conformation of the Mannopyranosyl Phosphate Repeating Unit of the Capsular Polysaccharide of Neisseria meningitidis Serogroup A and Its Carba-Mimetic
- Author
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Ilaria Calloni, Luca Unione, Gonzalo Jiménez-Osés, Francisco Corzana, Linda Del Bino, Alessio Corrado, Olimpia Pitirollo, Cinzia Colombo, Luigi Lay, Roberto Adamo, and Jesús Jiménez-Barbero
- Subjects
Natural products ,Full Paper ,Structure elucidation ,Synthesis design · ,Glycomimetics ,Conformation analysis ,macromolecular substances ,Full Papers ,Synthesis design ,NMR ,Glycomimetics · · - Abstract
Neisseria meningitidis serogroup A (MenA) is an aerobic diplococcal Gram‐negative bacterium responsible for epidemic meningitis disease. Its capsular polysaccharide (CPS) has been identified as the primary virulence factor of MenA. This polysaccharide suffers from chemical lability in water. Thus, the design and synthesis of novel and hydrolytically stable structural analogues of MenA CPS may provide additional tools for the development of therapies against this disease. In this context, the structural features of the natural phosphorylated monomer have been analyzed and compared to those of its carba‐analogue, where the endocyclic oxygen has been replaced by a methylene moiety. The lowest energy geometries of the different molecules have been calculated using a combination of quantum mechanical techniques and molecular dynamics simulations. The predicted results have been compared and validated using NMR experiments. The results indicate that the more stable designed glycomimetics may adopt the conformation adopted by the natural monomer, although they display a wider flexibility around the torsional degrees of freedom.
- Published
- 2018
- Full Text
- View/download PDF
37. The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the EnolatesPart 280 of our General Papers. Part 279: Ref.1.
- Author
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Howard E. Zimmerman and Alexei Pushechnikov
- Published
- 2006
- Full Text
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38. ExocyclicEndocyclic N-Acyliminium Ion Equilibration via an Intramolecular a-Thioamidoalkylation in the Synthesis of Fused N,S-Heterocyclic Systems: Some New ParametersPreliminary results in this area, including part of this work, were presented at the American Chemical Society National Meeting, Poster 367, San Francisco, CA, March 2630, 2000.For the preceding paper in the series see ref.4
- Author
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Nicolas Hucher, Anthony Pesquet, Pierre Netchitalo, and Adam Dach
- Published
- 2005
- Full Text
- View/download PDF
39. Enamine Ltd.: The Science and Business of Organic Chemistry and Beyond.
- Subjects
ORGANIC chemistry ,COMPUTER-assisted drug design ,CONTRACT research organizations - Abstract
In two recent Nature papers co-authored by Enamine scientists, this strategy was implemented to discover unique nanomolar hits for various biological targets.[6,7] GLO:5AG/21dec21:ejoc202101210-fig-0003.jpg PHOTO (COLOR): 3 Enamine stock and tangible compound collections. This Guest Editorial opens a special issue dedicated to the 30th anniversary of Enamine Ltd. - a worldwide supplier of chemical compounds and services originating from Kyiv, Ukraine. Enamine started as a supplier of screening compounds for the pharmaceutical and agrochemical industry, but significantly expanded its business portfolio over the last three decades. [Extracted from the article]
- Published
- 2021
- Full Text
- View/download PDF
40. Electrochemically‐Enabled Construction of N‐Acyl Iminophosphoranes.
- Author
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Wang, Wei, Cao, Shujie, Wang, Yike, Hu, Boxin, Zhu, Xuehua, Sun, Yanyan, and Wang, Yang
- Subjects
- *
RADICAL anions , *PHOSPHAZENES , *RADICALS (Chemistry) , *ELECTROSYNTHESIS , *GRAPHITE - Abstract
N‐acyl iminophosphoranes have shown significant potentials in various areas. This paper presents two electrochemical strategies for the successful construction of a series of substituted N‐acyl iminophosphoranes using electrochemical activation of hydroxylamines or dioxazolones to generate unprotected amide radicals and radical anions. The simple undivided cell with inexpensive electrode setups (graphite felts, carbon rods, and copper sheets) provides excellent substrates tolerance under mild conditions. This simple electrochemical construction of N‐acyl iminophosphoranes also has good scalability, practicability and extensibility. Furthermore, synthetic transformations of the N‐acyl iminophosphorane products have demonstrated the application potentials of the P=N bond. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
41. Recent Advances in the Synthesis of Chiral Allenes via Asymmetric 1,4‐Difunctionalization of 1,3‐Enynes.
- Author
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Li, Sijia, Yuan, Kaiyao, Zhang, Guozhu, and Guo, Rui
- Subjects
- *
ALLENE , *TRANSITION metals , *CHEMICAL properties , *NATURAL products , *CATALYSIS - Abstract
Allenes represent a distinctive class of organic molecules characterized by their unique physical and chemical properties. Among them, chiral allenes play a significant role in modern chemistry. They not only serve as pivotal frameworks for natural products and drug molecules but also are essential building blocks in organic synthesis. Over the years, numerous remarkable and efficient methods have been developed for the synthesis of chiral allenes. Notably, the catalytic synthesis of chiral allenes using transition metals in conjunction with chiral ligands has garnered considerable attention. This review paper aims to provide an overview of recent advancements in the synthesis of chiral allenes through asymmetric 1,4‐difunctionalization of 1,3‐enynes, in which two distinct strategies including non‐radical and radical processes are highlighted. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. Oxidation of Vicinal Diols to α-Hydroxy Ketones with H
- Author
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Francesco, Mecozzi, Jia Jia, Dong, Pattama, Saisaha, and Wesley R, Browne
- Subjects
inorganic chemicals ,Manganese Catalysis ,Earth‐abundant metals ,Manganese ,Full Paper ,organic chemicals ,Oxidation ,Full Papers ,Homogeneous catalysis ,Hydrogen peroxide ,Hydroxyl ketone - Abstract
α‐Hydroxy ketones are valuable synthons in organic chemistry. Here we show that oxidation of vic‐diols to α‐hydroxy ketones with H2O2 can be achieved with an in situ prepared catalyst based on manganese salts and pyridine‐2‐carboxylic acid. Furthermore the same catalyst is effective in alkene epoxidation, and it is shown that alkene oxidation with the MnII catalyst and H2O2 followed by Lewis acid ring opening of the epoxide and subsequent oxidation of the alkene to α‐hydroxy ketones can be achieved under mild (ambient) conditions.
- Published
- 2017
43. Divergent Synthesis of Cyclopropane-Containing Lead-Like Compounds, Fragments and Building Blocks through a Cobalt Catalyzed Cyclopropanation of Phenyl Vinyl Sulfide
- Author
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Stephen J, Chawner, Manuel J, Cases-Thomas, and James A, Bull
- Subjects
chemistry.chemical_classification ,Cyclopropanes ,Sulfide ,Full Paper ,010405 organic chemistry ,Cyclopropanation ,Negishi coupling ,Organic Chemistry ,Homogeneous catalysis ,Sulfoxide ,Full Papers ,010402 general chemistry ,Small ring systems ,01 natural sciences ,0104 chemical sciences ,Cyclopropane ,chemistry.chemical_compound ,chemistry ,Sulfoxides ,Molecular diversity ,Electrophile ,Organic chemistry ,Physical and Theoretical Chemistry ,Divergent synthesis - Abstract
Cyclopropanes provide important design elements in medicinal chemistry and are widely present in drug compounds. Here we describe a strategy and extensive synthetic studies for the preparation of a diverse collection of cyclopropane‐containing lead‐like compounds, fragments and building blocks exploiting a single precursor. The bifunctional cyclopropane (E/Z)‐ethyl 2‐(phenylsulfanyl)‐cyclopropane‐1‐carboxylate was designed to allow derivatization through the ester and sulfide functionalities to topologically varied compounds designed to fit in desirable chemical space for drug discovery. A cobalt‐catalyzed cyclopropanation of phenyl vinyl sulfide affords these scaffolds on multigram scale. Divergent, orthogonal derivatization is achieved through hydrolysis, reduction, amidation and oxidation reactions as well as sulfoxide–magnesium exchange/functionalization. The cyclopropyl Grignard reagent formed from sulfoxide exchange is stable at 0 °C for > 2 h, which enables trapping with various electrophiles and Pd‐catalyzed Negishi cross‐coupling reactions. The library prepared, as well as a further virtual elaboration, is analyzed against parameters of lipophilicity (ALog P), MW and molecular shape by using the LLAMA (Lead‐Likeness and Molecular Analysis) software, to illustrate the success in generating lead‐like compounds and fragments.
- Published
- 2017
44. Synthesis of Chiral Tetrahydrofurans and Pyrrolidines by Visible-Light-Mediated Deoxygenation
- Author
-
Daniel, Rackl, Viktor, Kais, Eugen, Lutsker, and And Oliver, Reiser
- Subjects
Electron transfer ,Full Paper ,Photochemistry ,Radical reactions ,Deoxygenative Photocyclizations | Very Important Paper ,Heterocycles ,Full Papers ,Photocatalysis - Abstract
The synthesis of chiral tetrahydrofurans and pyrrolidines starting from 1,2‐diols or β‐amino alcohols, respectively, by visible‐light‐mediated deoxygenation is described. Easily accessible monoallylated/propargylated substrates were activated either as inexpensive ethyl oxalates or as recyclable 3,5‐bis(trifluoromethyl)benzoates to generate alkyl radicals suitable for 5‐exo‐trig/5‐exo‐dig cyclizations under visible‐light irradiation.
- Published
- 2017
45. Total Synthesis of Blennolide Mycotoxins: Design, Synthetic Routes and Completion
- Author
-
Carl Friedrich Nising, Arantxa Encinas, Emilie M. C. Singer, Martin Nieger, Hülya Sahin, Stefan Bräse, and Anne C. Meister
- Subjects
Chemistry ,Biological property ,Organic Chemistry ,Total synthesis ,Organic chemistry ,Physical and Theoretical Chemistry ,Combinatorial chemistry ,Domino ,Full paper ,Blennolide C ,3. Good health - Abstract
Mycotoxins of the tetrahydroxanthone class of natural products possess a large number of interesting biological properties. In this full paper, we present our synthetic strategy to some members of this class of compounds, namely the blennolides A and C. We disclose the scope and limitations of the functionalization of various xanthones derived from a domino oxa-Michael-aldol condensation and pursue dimerization of these xanthones. Furthermore, the first crystal structure of blennolide C has been obtained.
- Published
- 2014
46. Stereoselective Synthesis of Functionalized Bicyclic Scaffolds by Passerini 3-Center-2-Component Reactions of Cyclic Ketoacids
- Author
-
Răzvan C, Cioc, Verónica, Estévez, Daan J, van der Niet, Christophe M L, Vande Velde, Nikolaus G, Turrini, Mélanie, Hall, Kurt, Faber, Eelco, Ruijter, and Romano V A, Orru
- Subjects
Ketoacids ,Diastereoselectivity ,Lactones ,Full Paper ,Cyclization ,Multicomponent reactions ,Rearrangement ,Full Papers ,Isocyanide Chemistry - Abstract
We report the use of bifunctional starting materials (ketoacids) in a diastereoselective Passerini three‐center‐two‐component reaction. Study of the reaction scope revealed the required structural features for stereoselectivity in the isocyanide addition. In this system, an interesting isomerization of the primary Passerini product – the α‐carboxamido lactone – into an atypical product, an α‐hydroxy imide, was found to occur under acidic conditions. Furthermore, enantioenriched Passerini products can be generated from an enantioenriched ketoacid obtained by chemoenzymatic synthesis.
- Published
- 2016
47. Optimising Terpene Synthesis with Flow Biocatalysis
- Author
-
Xiaoping, Tang, Rudolf K, Allemann, and Thomas, Wirth
- Subjects
Full Paper ,Flow Chemistry ,Synthetic methods ,Terpenoids ,Biocatalysis ,Enzyme catalysis ,Segmented flow ,Full Papers - Abstract
Sesquiterpenes are an important family of natural products, many of which exhibit important pharmaceutical and agricultural properties. They are biosynthesised from farnesyl diphosphate in sesquiterpene synthase catalysed reactions. Here, we report the development of a highly efficient segmented flow system for the enzyme‐catalysed continuous flow production of sesquiterpenes. Design of experiment (DoE) methods were used to optimise the performance of the flow biocatalysis, and quantitative yields were achieved by using an operationally simple but highly effective segmented flow system.
- Published
- 2016
48. Small Molecular Chromogenic Sensors for Hg2+: A Strong 'Push-Pull' System Exists after Binding
- Author
-
Yanyan Fu, Hongxiang Li, and Wenping Hu
- Subjects
Aqueous solution ,Filter paper ,Chromogenic ,Chemistry ,Organic Chemistry ,Analytical chemistry ,Azine ,chemistry.chemical_compound ,Molecular recognition ,Aniline ,Proton NMR ,Organic chemistry ,Naked eye ,Physical and Theoretical Chemistry - Abstract
Two small molecular chromogenic sensors 1 and 2 for detection of Hg2+ are described. After coordination with Hg2+, a red shift of about 100 nm was observed in the UV/Vis spectra and the color of the solution changed from pale yellow to red which could easily be detected by the naked eye. The results indicate a strong push-pull system was formed after coordination of Hg2+. The 1H NMR spectra and control experiments showed the binding sites of 1 and 2 to be the aniline groups rather than the azine bridge. Moreover, mercury test papers were made by adsorbing 1 onto filter paper, allowing heterogeneous sensing of Hg2+ in aqueous solution.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
- Published
- 2007
49. Ether Cleavage Re-Investigated: Elucidating the Mechanism of BBr3-Facilitated Demethylation of Aryl Methyl Ethers
- Author
-
Kosak, Talon M, Conrad, Heidi A, Korich, Andrew L, and Lord, Richard L
- Subjects
Density functional calculations ,Reaction mechanisms ,Full Papers ,Ether cleavage - Abstract
One of the most well-known, highly utilized reagents for ether cleavage is boron tribromide (BBr3), and this reagent is frequently employed in a 1:1 stoichiometric ratio with ethers. Density functional theory calculations predict a new mechanistic pathway involving charged intermediates for ether cleavage in aryl methyl ethers. Moreover, these calculations predict that one equivalent of BBr3 can cleave up to three equivalents of anisole, producing triphenoxyborane [B(OPh)3] prior to hydrolysis. These predictions were validated by gas chromatography analysis of reactions where the BBr3:anisole ratio was varied. Not only do we confirm that sub-stoichiometric equivalents may be used for ether demethylation, but the findings also support our newly proposed three cycle mechanism for cleavage of aryl methyl ethers.
- Published
- 2015
50. Crossed McMurry Coupling Reactions for Porphycenic Macrocycles: Non-Statistical Selectivity and Rationalisation
- Author
-
Cowie, Thomas Y, Kennedy, Lorna, Żurek, Justyna M, Paterson, Martin J, and Bebbington, Magnus W P
- Subjects
McMurry coupling ,Heterocyclic chemistry ,Redox chemistry ,Photochemistry ,Full Papers ,Porphycenes ,Macrocycles - Abstract
Crossed McMurry reactions of bifuran- or bithiophenedicarbaldehydes with bipyrroledicarbaldehydes have been studied for the first time. Only those porphycenic macrocycles derived from homocoupled McMurry products were formed. The results are explained by using both density functional theory and electron propagator computations to model the electron affinity of the dialdehyde starting materials. It was predicted that bifuran\bithiophene cross-coupling would indeed occur, and this was demonstrated by the first synthesis of a novel dioxa,dithio hetero-porphycenoid annulene. This approach will allow the prior identification of viable substrates for related crossed McMurry reactions.
- Published
- 2015
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