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N. Chary Mamillapalli Prof. Govindasamy Sekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18584-18588
Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral CuII/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β‐amino alcohol derivatives. 相似文献
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Dr. Bo Peng Dr. Danny Geerdink Dr. Christophe Farès Prof. Dr. Nuno Maulide 《Angewandte Chemie (International ed. in English)》2014,53(21):5462-5466
A new approach for the fully chemoselective α‐arylation of amides is presented. By means of electrophilic amide activation, aryl groups can be regioselectively introduced α‐ to amides, even in the presence of esters and alkyl ketones. Mechanistic studies reveal key reaction intermediates and emphasize a remarkably subtle base effect in this transformation. 相似文献
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Christopher J. Teskey Pauline Adler Carlos R. Gonalves Nuno Maulide 《Angewandte Chemie (International ed. in English)》2019,58(2):447-451
We report a method for the selective α,β‐dehydrogenation of amides in the presence of other carbonyl moieties under mild conditions. Our strategy relies on electrophilic activation coupled to in situ selective selenium‐mediated dehydrogenation. The α,β‐unsaturated products were obtained in moderate to excellent yields, and their synthetic versatility was demonstrated by a range of transformations. Mechanistic experiments suggest formation of an electrophilic SeIV species. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(40):12475-12479
Compared to the α‐functionalization of aldehydes, ketones, even esters, the direct α‐modification of amides is still a challenge because of the low acidity of α‐CH groups. The α‐functionalization of N−H (primary and secondary) amides, containing both an unactived α‐C−H bond and a competitively active N−H bond, remains elusive. Shown herein is the general and efficient oxidative α‐oxyamination and hydroxylation of aliphatic amides including secondary N−H amides. This transition‐metal‐free chemistry with high chemoselectivity provides an efficient approach to α‐hydroxy amides. This oxidative protocol significantly enables the selective functionalization of inert α‐C−H bonds with the complete preservation of active N−H bond. 相似文献
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Anthony Linden J. E. Florian Magirius Heinz Heimgartner 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(1):1-9
Depsipeptides and cyclodepsipeptides are analogues of the corresponding peptides in which one or more amide groups are replaced by ester functions. Reports of crystal structures of linear depsipeptides are rare. The crystal structures and conformational analyses of four depsipeptides with an alternating sequence of an α,α‐disubstituted α‐amino acid and an α‐hydroxy acid are reported. The molecules in the linear hexadepsipeptide amide in (S)‐Pms‐Acp‐(S)‐Pms‐Acp‐(S)‐Pms‐Acp‐NMe2 acetonitrile solvate, C47H58N4O9·C2H3N, ( 3b ), as well as in the related linear tetradepsipeptide amide (S)‐Pms‐Aib‐(S)‐Pms‐Aib‐NMe2, C28H37N3O6, ( 5a ), the diastereoisomeric mixture (S,R)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe2/(R,S)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe2 (1:1), C32H41N3O6, ( 5b ), and (R,S)‐Mns‐Acp‐(S,R)‐Mns‐Acp‐NMe2, C30H37N3O6, ( 5c ) (Pms is phenyllactic acid, Acp is 1‐aminocyclopentanecarboxylic acid and Mns is mandelic acid), generally adopt a β‐turn conformation in the solid state, which is stabilized by intramolecular N—H…O hydrogen bonds. Whereas β‐turns of type I (or I′) are formed in the cases of ( 3b ), ( 5a ) and ( 5b ), which contain phenyllactic acid, the torsion angles for ( 5c ), which incorporates mandelic acid, indicate a β‐turn in between type I and type III. Intermolecular N—H…O and O—H…O hydrogen bonds link the molecules of ( 3a ) and ( 5b ) into extended chains, and those of ( 5a ) and ( 5c ) into two‐dimensional networks. 相似文献
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Rui Zhang Zhikun Zhang Qi Zhou Lefei Yu Jianbo Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5800-5804
Fluorine‐containing β‐amino acids and their derivatives have attracted significant attention due to their importance in life sciences. Herein the previously unknown difluoroketenimine, the analogue of the elusive difluoroketene, has been generated by the reaction of difluorocarbene and isocyanide, which further undergoes [2+2] cycloaddition with imine. The three‐component reaction affords α,α‐difluoro‐β‐amino amides in good yields. Mechanistic studies reveal the unique properties of the difluoroketenimine in the [2+2] cycloaddition with imine. 相似文献
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Costas N. Costa Costas S. Patrickios 《Journal of polymer science. Part A, Polymer chemistry》1999,37(11):1597-1607
α‐Hydroxy and α,ω‐dihydroxy polymers of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) of various molecular weights were synthesized by group transfer polymerization (GTP) in tetrahydrofuran (THF), using 1‐methoxy‐1‐(trimethylsiloxy)‐2‐methyl propene (MTS) as the initiator and tetrabutylammonium bibenzoate (TBABB) as the catalyst. The hydroxyl groups were introduced by adding one 2‐(trimethylsiloxy) ethyl methacrylate (TMSEMA) unit at one or at both ends of the polymer chain. The ends were converted to 2‐hydroxyethyl methacrylate (HEMA) units after the polymerization by acid‐catalyzed hydrolysis. Gel permeation chromatography (GPC) in THF and proton nuclear magnetic resonance (1H‐NMR) spectroscopy in CDCl3 were used to determine the molecular weight and composition of the polymers. These mono‐ and difunctional methacrylate polymers can be covalently linked at the hydroxy termini to form star polymers and model networks, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1597–1607, 1999 相似文献
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Dr. Filippo Nisic Gaetano Speciale Prof. Dr. Anna Bernardi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(22):6895-6906
A highly stereoselective synthesis of α‐ or β‐glycofuranosyl amides based on the traceless Staudinger ligation of glycofuranosyl azides of the galacto, ribo, and arabino series with 2‐diphenylphosphanyl‐phenyl esters has been developed. Both α‐ and β‐isomers can be obtained with excellent selectivity from a common, easily available precursor. The process does not depend on the anomeric configuration of the starting azide but appears to be controlled by the C2 configuration and by the protection/deprotection state of the substrates. A mechanistic interpretation of the results, supported by 31P NMR experiments, is offered and merged with our previous mechanistic analysis of pyranosyl azide ligation reactions. 相似文献
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Electrophilic Activation of α,β‐Unsaturated Amides: Catalytic Asymmetric Vinylogous Conjugate Addition of Unsaturated γ‐Butyrolactones
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Dr. Ming Zhang Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5525-5529
Although catalytic asymmetric conjugate addition reactions have remarkably advanced over the last two decades, the application of less electrophilic α,β‐unsaturated carboxylic acid derivatives in this useful reaction manifold remains challenging. Herein, we report that α,β‐unsaturated 7‐azaindoline amides act as reactive electrophiles to participate in catalytic diastereo‐ and enantioselective vinylogous conjugate addition of γ‐butyrolactones in the presence of a cooperative catalyst comprising of a soft Lewis acid and a Brønsted base. Reactions mostly reached completion with as little as 1 mol % of catalyst loading to give the desired conjugate adducts in a highly stereoselective manner. 相似文献
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Xiuqin Dong Wen Yang Weimin Hu Jianwei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(2):670-673
The asymmetric fluorination of azolium enolates that are generated from readily available simple aliphatic aldehydes or α‐chloro aldehydes and N‐heterocyclic carbenes (NHCs) is described. The process significantly expands the synthetic utility of NHC‐catalyzed fluorination and provides facile access to a wide range of α‐fluoro esters, amides, and thioesters with excellent enantioselectivity. Pyrazole was identified as an excellent acyl transfer reagent for catalytic amide formation. 相似文献
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N‐Heterocyclic Carbene Catalyzed Enantioselective α‐Fluorination of Aliphatic Aldehydes and α‐Chloro Aldehydes: Synthesis of α‐Fluoro Esters,Amides, and Thioesters
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Dr. Xiuqin Dong Dr. Wen Yang Dr. Weimin Hu Prof. Dr. Jianwei Sun 《Angewandte Chemie (International ed. in English)》2015,54(2):660-663
The asymmetric fluorination of azolium enolates that are generated from readily available simple aliphatic aldehydes or α‐chloro aldehydes and N‐heterocyclic carbenes (NHCs) is described. The process significantly expands the synthetic utility of NHC‐catalyzed fluorination and provides facile access to a wide range of α‐fluoro esters, amides, and thioesters with excellent enantioselectivity. Pyrazole was identified as an excellent acyl transfer reagent for catalytic amide formation. 相似文献
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