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Leming Wang Xinhang Jiang Jiean Chen Yong Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7488-7492
In contrast to well‐established asymmetric hydrogenation reactions, enantioselective protonation is an orthogonal approach for creating highly valuable methine chiral centers under redox‐neutral conditions. Reported here is the highly enantio‐ and diastereoselective hydrofluorination of enals by an asymmetric β‐protonation/α‐fluorination cascade catalyzed by N‐heterocyclic carbenes (NHCs). The two nucleophilic sites of a homoenolate intermediate, generated from enals and an NHC, are sequentially protonated and fluorinated. The results show that controlling the relative rates of protonation, fluorination, and esterification is crucial for this transformation, and can be accomplished using a dual shuttling strategy. Structurally diverse carboxylic acid derivatives with two contiguous chiral centers are prepared in a single step with excellent d.r. and ee values. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(10):2769-2773
A one‐pot N‐Boc deprotection and catalytic intramolecular reductive amination protocol for the preparation of enantiomerically pure tetrahydroisoquinoline alkaloids is described. The iodine‐bridged dimeric iridium complexes displayed superb stereoselectivity to give tetrahydroisoquinolines, including several key pharmaceutical drug intermediates, in excellent yields under mild reaction conditions. Three additives played important roles in this reaction: Titanium(IV) isopropoxide and molecular iodine accelerated the transformation of the intermediate imine to the tetrahydroisoquinoline product; p ‐toluenesulfonic acid contributed to the stereocontrol. 相似文献
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Ya Chen Yan‐Mei He Shanshan Zhang Tingting Miao Qing‐Hua Fan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3849-3853
A rapid construction of enantioenriched benzo‐fused quinolizidines, indolizidines, and their analogues by ruthenium‐catalyzed asymmetric cascade hydrogenation/reductive amination of quinolinyl‐ and quinoxalinyl‐containing ketones has been developed. This reaction proceeds under mild reaction conditions, affording chiral benzo‐fused aliphatic N‐heterocyclic compounds with structural diversity in good yields (up to 95 %) with excellent diastereoselectivity (up to >20:1 dr) and enantioselectivity (up to >99 % ee). Furthermore, this catalytic protocol is applicable to the formal synthesis of (+)‐gephyrotoxin. 相似文献
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Zi‐Jing Zhang Ling Zhang Rui‐Long Geng Jin Song Xiao‐Hua Chen Liu‐Zhu Gong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12318-12322
Highly enantioselective [3+3] and [3+4] annulations of isatin‐derived enals with ethynylethylene carbonates and ethynyl benzoxazinanones are enabled by NHC/cooper cooperative catalysis, leading to a big library of spirooxindole derivatives in high structural diversity and enantioselectivity (up to 99 % ee). Both reactions represent a nicely synergistic integration of NHC and copper catalysis, in which both catalysts activate the substrates and the chiral NHC perfectly controls the stereochemistry. 相似文献
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DennisG. Gillingham AmirH. Hoveyda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2007,119(21):3934-3938
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Guangyang Xu Ping Chen Pei Liu Shengbiao Tang Xinhao Zhang Jiangtao Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(7):2002-2006
A novel rhodium‐catalyzed dearomatization of O‐substituted pyridines to access N‐substituted 2‐pyridones has been developed. A computational study suggests a mechanism involving the formation of a pyridinium ylide followed by an unprecedented 1,4‐acyl migratory rearrangement from O to C. Furthermore, the chiral dirhodium complexes serve as the catalyst for the asymmetric transformation with excellent enantioselective control. DFT calculations indicate the chirality is transferred from axial chirality to the central stereogenic centre. The stronger π–π interaction and CH–π interaction account for the high enantioselectivity. 相似文献
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Ansoo Lee Joshua L. Zhu Taisiia Feoktistova Alexander C. Brueckner Paul H.‐Y. Cheong Karl A. Scheidt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6002-6006
A direct decarboxylative strategy for the generation of aza‐o‐quinone methides (aza‐o‐QMs) by N‐heterocyclic carbene (NHC) catalysis has been discovered and explored. This process requires no stoichiometric additives in contrast with current approaches. Aza‐o‐QMs react with trifluoromethyl ketones through a formal [4+2] manifold to access highly enantioenriched dihydrobenzoxazin‐4‐one products, which can be converted to dihydroquinolones through an interesting stereoretentive aza‐Petasis–Ferrier rearrangement sequence. Complementary dispersion‐corrected density functional theory (DFT) studies provided an accurate prediction of the reaction enantioselectivity and lend further insight to the origins of stereocontrol. Additionally, a computed potential energy surface around the major transition structure suggests a concerted asynchronous mechanism for the formal annulation. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16248-16252
A palladium‐catalyzed asymmetric intramolecular allylic C−H amination controlled by a chiral phosphoramidite ligand was established for the preparation of various substituted chiral hydropyrimidinones, the precursors of hydropyrimidines, in high yields with high enantioselectivities. In particular, dienyl sodium N ‐sulfonyl amides bearing an arylethene‐1‐sulfonyl group underwent a sequential allylic C−H amination and intramolecular Diels–Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidinone frameworks in high yields and with high levels of stereoselectivity. Significantly, this method was used as the key step in an asymmetric synthesis of letermovir. 相似文献
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Xin‐Shen Liang Rui‐Dong Li Xiao‐Chen Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):14023-14027
We have developed a method for the highly diastereo‐ and enantioselective construction of 2,3‐dihydrobenzofurans bearing tetrasubstituted carbon stereocenters by means of annulation reactions between carbenes and 2‐iminyl‐ or 2‐acyl‐substituted phenols through catalysis by readily accessible copper(I)/bisoxazoline catalysts under mild conditions. These reactions feature a unique mechanism in which the copper catalyst serves a dual function: first it reacts with the diazo compound to generate a metal carbene, and second, upon formation of an oxonium ylide, it acts as a Lewis acid to activate the imine or ketone for diastereo‐ and enantioselective cyclization. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(32):9640-9644
The development of a boron/nitrogen‐centered frustrated Lewis pair (FLP) with remarkably high water tolerance is presented. As systematic steric tuning of the boron‐based Lewis acid (LA) component revealed, the enhanced back‐strain makes water binding increasingly reversible in the presence of relatively strong base. This advance allows the limits of FLP's hydrogenation to be expanded, as demonstrated by the FLP reductive amination of carbonyls. This metal‐free catalytic variant displays a notably broad chemoselectivity and generality. 相似文献