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Enantioselective Formation of All‐Carbon Quaternary Stereocenters from Indoles and Tertiary Alcohols Bearing A Directing Group 下载免费PDF全文
Dr. Wanxiang Zhao Zhaobin Wang Boyang Chu Prof. Jianwei Sun 《Angewandte Chemie (International ed. in English)》2015,54(6):1910-1913
Described is an efficient catalytic asymmetric intermolecular C? C bond‐formation process to generate acyclic all‐carbon quaternary stereocenters. The reactions overcome the unfavorable steric hindrance around reactive centers, and the competitive elimination (E1), to form a range of useful indole products with excellent efficiency and enantioselectivity. 相似文献
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Enantioselective Construction of Vicinal Tetrasubstituted Stereocenters by the Mannich Reaction of Silyl Ketene Imines with Isatin‐Derived Ketimines 下载免费PDF全文
Jiannan Zhao Bing Fang Weiwei Luo Xiaoyu Hao Prof. Dr. Xiaohua Liu Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2015,54(1):241-244
A highly enantioselective Mannich reaction of silyl ketene imines with isatin‐derived ketimines has been realized by using a chiral N,N′‐dioxide/ZnII catalyst. A variety of β‐amino nitriles containing congested vicinal tetrasubstituted stereocenters were obtained with excellent outcomes (up to 98 % yield, >19:1 d.r. and 99 % ee). Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction. 相似文献
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Organocatalytic Asymmetric 1,6‐Addition/1,4‐Addition Sequence to 2,4‐Dienals for the Synthesis of Chiral Chromans 下载免费PDF全文
Pernille H. Poulsen Karla Santos Feu Bruno Matos Paz Prof. Dr. Frank Jensen Prof. Dr. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2015,54(28):8203-8207
A novel asymmetric organocatalytic 1,6‐addition/1,4‐addition sequence to 2,4‐dienals is described. Based on a 1,6‐Friedel–Crafts/1,4‐oxa‐Michael cascade, the organocatalyst directs the reaction of hydroxyarenes with a vinylogous iminium‐ion intermediate to give only one out of four possible regioisomers, thus providing optically active chromans in high yields and 94–99 % ee. Furthermore, several transformations are presented, including the formation of an optically active macrocyclic lactam. Finally, the mechanism for the novel reaction is discussed based on computational studies. 相似文献
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Dr. Taichi Kano Dr. Taiga Yurino Prof. Keiji Maruoka 《Angewandte Chemie (International ed. in English)》2013,52(44):11509-11512
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Na Shao Xueyang Liu Dr. Valérie Monnier Dr. Laurence Charles Dr. Jean Rodriguez Dr. Cyril Bressy Dr. Adrien Quintard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(5):e202103874
Elaboration of enantioenriched complex acyclic stereotriads represents a challenge for modern synthesis even more when fluorinated tetrasubstituted stereocenters are targeted. We have been able to develop a simple strategy in a sequence of two unprecedented steps combining a diastereoselective aldol-Tishchenko reaction and an enantioselective organocatalyzed kinetic resolution. The aldol-Tishchenko reaction directly generates a large panel of acyclic 1,3-diols possessing a fluorinated tetrasubstituted stereocenter by condensation of fluorinated ketones with aldehydes under very mild basic conditions. The anti 1,3-diols featuring three contiguous stereogenic centers are generated with excellent diastereocontrol (typically >99 : 1 dr). Depending upon the precursors both diastereomers of stereotriads are accessible through this flexible reaction. Furthermore, from the obtained racemic scaffolds, development of an organocatalyzed kinetic resolution enabled to generate the desired enantioenriched stereotriads with excellent selectivity (typically er >95 : 5). 相似文献
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Hao Wu Li‐Li Zhang Zhi‐Qing Tian Dr. Yao‐Dong Huang Prof. Yong‐Mei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1747-1753
Bispirooxindole derivatives containing three stereocenters, including two spiro quaternary centers, were synthesized in a high‐yielding, atypically rapid, and stereocontrolled cascade Michael–cyclization reaction between methyleneindolinones and isothiocyanato oxindoles catalyzed by a bi‐ or multifunctional organocatalyst. Mild conditions were used to construct bispirooxindoles with excellent enantio‐ and diastereomeric purities within less than 1 min. Catalyst reconfiguration offered access to the opposite enantiomer. This exceptionally highly efficient procedure will allow diversity‐oriented syntheses of this intriguing class of compounds with potential biological activities. 相似文献
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Morita–Baylis–Hillman Reaction of β,β‐Disubstituted Enones: An Enantioselective Organocatalytic Approach for the Synthesis of Cyclopenta[b]annulated Arenes and Heteroarenes 下载免费PDF全文
Bishnupada Satpathi Prof. Dr. S. S. V. Ramasastry 《Angewandte Chemie (International ed. in English)》2016,55(5):1777-1781
The first enantioselective organocatalytic intramolecular Morita–Baylis–Hillman (MBH) reaction of sterically highly demanding β,β‐disubstituted enones is presented. The MBH reaction of β,β‐disubstituted‐α,β‐unsaturated electron‐withdrawing systems was previously considered to be unfeasible. Towards this end, designer substrates, which under simple and practical reaction conditions generate a variety of cyclopenta[b]annulated arenes and heteroarenes in excellent enantiopurities and near‐quantitative yields in remarkably short reaction times, are described. The reason for the unusually facile nature of this reaction is attributed to the synergy guided and entropically favored intramolecular reaction. Further, this strategy provides easy access to a substantial number of bioactive natural products and pharmaceutically significant compounds. 相似文献
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Enantio‐ and Diastereoselective Access to Distant Stereocenters Embedded within Tetrahydroxanthenes: Utilizing ortho‐Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalysis 下载免费PDF全文
M. Sc. Chien‐Chi Hsiao M. Sc. Hsuan‐Hung Liao Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2014,53(48):13258-13263
A protocol for the highly enantioselective synthesis of 9‐substituted tetrahydroxanthenones by means of asymmetric Brønsted acid catalysis has been developed. A chiral binol‐based N‐triflyphosphoramide was found to promote the in situ generation of ortho‐quinone methides and their subsequent reaction with 1,3‐cyclohexanedione to provide the desired products with excellent enantioselectivities. In addition, a highly enantio‐ and diastereoselective Brønsted acid catalyzed desymmetrization of 5‐monosubstituted 1,3‐dicarbonyl substrates with ortho‐quinone methides gives rise to valuable tetrahydroxanthenes containing two distant stereocenters. 相似文献
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Yi‐Ming Cao Prof. Dr. Rui Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1184-1188
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Organocatalytic Enantioselective Cross‐Vinylogous Rauhut–Currier Reaction of Methyl Coumalate with Enals 下载免费PDF全文
Qiwen Liu Prof. Dr. Liansuo Zu 《Angewandte Chemie (International ed. in English)》2018,57(30):9505-9509
The organocatalytic enantioselective intermolecular cross‐vinylogous Rauhut–Currier (RC) reaction of methyl coumalate with α,β‐unsaturated aldehydes is reported, and the enals are activated by iminium catalysis to serve as the Michael acceptors and methyl coumalate is used as an activated diene to generate a latent enolate. The excellent selectivity is driven by the aromaticity of methyl coumalate, and the post transformation of this heterocyclic structure into other electron‐deficient arenes and heterocycles have addressed, in part, the challenging selectivity issues of the intermolecular cross‐RC reactions and the limited scope of iminium catalysis. 相似文献
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Asymmetric Synthesis of Fully Substituted Cyclopentane‐Oxindoles through an Organocatalytic Triple Michael Domino Reaction 下载免费PDF全文
Dr. Liang‐Hua Zou Arne R. Philipps Prof. Dr. Gerhard Raabe Prof. Dr. Dieter Enders 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1004-1008
An efficient, highly stereoselective asymmetric synthesis of fully functionalized cyclopentanes bearing an oxindole moiety and several other functional groups in one pot has been developed. Key step is an organocatalytic triple Michael domino reaction forming three C?C bonds and six stereocenters, including a quaternary one. Starting from equimolar amounts of simple substrates, a high molecular complexity can be reached after a Wittig olefination in one pot. The new protocol can easily be scaled up to gram amounts. 相似文献
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Catalytic Asymmetric 1,6‐Conjugate Addition of para‐Quinone Methides: Formation of All‐Carbon Quaternary Stereocenters 下载免费PDF全文
Dr. Zhaobin Wang Yuk Fai Wong Prof. Jianwei Sun 《Angewandte Chemie (International ed. in English)》2015,54(46):13711-13714
Described herein is a general and mild catalytic asymmetric 1,6‐conjugate addition of para‐quinone methides (p‐QMs), a class of challenging reactions with previous limited success. Benefiting from chiral Brønsted acid catalysis, which allows in situ formation of p‐QMs, our reaction expands the scope to general p‐QMs with various substitution patterns. It also enables efficient intermolecular formation of all‐carbon quaternary stereocenters with high enantioselectivity. 相似文献
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Dr. Xingguang Li Prof. Jianwei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17197-17202
An organocatalytic enantioconvergent synthesis of chiral tetrasubstituted allenes is disclosed. With suitable chiral phosphoric acid catalysts, a range of racemic indole-substituted propargylic alcohols reacted with nucleophiles to provide efficient access to a series of enantioenriched allenes with high enantioselectivities. Control experiments suggested a mechanism involving remotely controlled asymmetric 1,8-addition of the in situ generated indole imine methide via a bifunctional transition state. 相似文献
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