共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Catalytic Asymmetric Oxidative γ‐Coupling of α,β‐Unsaturated Aldehydes with Air as the Terminal Oxidant 下载免费PDF全文
Line Næsborg Vasco Corti Lars Astrup Leth Dr. Pernille H. Poulsen Prof. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2018,57(6):1606-1610
A novel concept for catalytic asymmetric coupling reactions is presented. Merging organocatalysis with single‐electron oxidation by using a catalytic amount of a copper(II) salt and air as the terminal oxidant, we have developed a highly stereoselective carbon–carbon oxidative coupling reaction of α,β‐unsaturated aldehydes. The concept relies on the generation of a dienamine intermediate, which is oxidized to an open‐shell activated species that undergoes highly selective γ‐homo‐ and γ‐heterocoupling reactions. In the majority of examples presented, only a single stereoisomer was formed. 相似文献
3.
Direct Catalytic Asymmetric Doubly Vinylogous Michael Addition of α,β‐Unsaturated γ‐Butyrolactams to Dienones 下载免费PDF全文
Xiaodong Gu Tingting Guo Yuanyuan Dai Allegra Franchino Jie Fei Chuncheng Zou Prof. Dr. Darren J. Dixon Prof. Dr. Jinxing Ye 《Angewandte Chemie (International ed. in English)》2015,54(35):10249-10253
An asymmetric doubly vinylogous Michael addition (DVMA) of α,β‐unsaturated γ‐butyrolactams to sterically congested β‐substituted cyclic dienones with high site‐, diastereo‐, and enantioselectivity has been achieved. An unprecedented DVMA/vinylogous Michael addition/isomerization cascade reaction affords chiral fused tricyclic γ‐lactams with four newly formed stereocenters. 相似文献
4.
5.
On the Mechanism of the Organocatalytic Asymmetric Epoxidation of α,β‐Unsaturated Aldehydes 下载免费PDF全文
Dr. Rebecca L. Davis Dr. Kim L. Jensen Dr. Björn Gschwend Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):64-67
Mechanistic studies on the organocatalytic epoxidation of α,β‐unsaturated aldehydes explore the autoinductive behavior of the reaction and establish that the hydrate/peroxyhydrate of the product is acting as a phase‐transfer catalyst. Based on these studies, an improved methodology that provides high selectivities and decreased catalyst loading, through the addition of chloral hydrate, is developed. 相似文献
6.
Asymmetric γ‐Allylation of α,β‐Unsaturated Aldehydes by Combined Organocatalysis and Transition‐Metal Catalysis 下载免费PDF全文
Line Næsborg Kim Søholm Halskov Dr. Fernando Tur Sofie M. N. Mønsted Prof. Dr. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2015,54(35):10193-10197
The first asymmetric regio‐ and diastereodivergent γ‐allylation of cyclic α,β‐unsaturated aldehydes based on combined organocatalysis and transition‐metal catalysis is disclosed. By combining an aminocatalyst with an iridium catalyst, both diastereomers of branched allylated products can be achieved in moderate to good yields and excellent regio‐ and stereoselectivities. Furthermore, by replacing the iridium catalyst with a palladium catalyst, the linear allylated products are formed in good yields and excellent regio‐ and enantioselectivities. The developed method thus provides selective access to all six isomers of the γ‐allylated product in a divergent fashion by choosing the appropriate combination of organocatalyst, transition‐metal catalyst, and ligand. 相似文献
7.
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
8.
Direct Catalytic Asymmetric Vinylogous Conjugate Addition of Unsaturated Butyrolactones to α,β‐Unsaturated Thioamides 下载免费PDF全文
Dr. Liang Yin Dr. Hisashi Takada Shaoquan Lin Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》2014,53(21):5327-5331
Soft Lewis acid/Brønsted base cooperative catalysts have enabled direct catalytic asymmetric vinylogous conjugate addition of α,β‐ and β,γ‐unsaturated butyrolactones to α,β‐unsaturated thioamides with perfect atom economy. When using α‐angelica lactone and its derivatives as pronucleophiles, as little as 0.5 mol % catalyst loading was sufficient to complete the reaction necessary to construct consecutive tri‐ and tetrasubstituted stereogenic centers in a highly diastereo‐ and enantioselective fashion. 相似文献
9.
Silvia Reboredo Prof. Efraím Reyes Prof. Jose L. Vicario Prof. Dr. Dolores Badía Prof. Luisa Carrillo Dr. Abel de Cózar Prof. Dr. Fernando P. Cossío 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7179-7188
The catalytic enantioselective [3+2] cycloaddition between azomethine ylides and α,β‐unsaturated aldehydes catalyzed by α,α‐diphenylprolinol has been studied in detail. In particular, the reaction has been extended to the use of 2‐alkenylidene aminomalonates generated in situ as azomethine ylide precursors. These reactions lead to the formation of pyrrolidines containing a 5‐alkenyl side chain with potential for chemical manipulation. Moreover, a detailed and concise computational study has been carried out to understand the exact nature of the mechanism of this reaction and especially the consequences derived from the incorporation of the chiral secondary amine catalyst on the reaction pathway. 相似文献
10.
Direct Asymmetric Michael Reaction of α,β‐Unsaturated Aldehydes and Ketones Catalyzed by Two Secondary Amine Catalysts 下载免费PDF全文
Prof. Dr. Yujiro Hayashi Nariyoshi Umekubo 《Angewandte Chemie (International ed. in English)》2018,57(7):1958-1962
A direct asymmetric Michael reaction of α,β‐unsaturated aldehydes and ketones proceeded in the presence of two pyrrolidine‐type catalysts, a diphenylprolinol silyl ether and hydroxyproline, to afford synthetically useful δ‐keto aldehydes with excellent diastereo‐ and enantioselectivity. Although there are several iminium ions and enamines in the reaction mixture, the iminium ion generated by the former catalyst reacts preferentially with the enamine generated by the latter catalyst. 相似文献
11.
12.
Highly Asymmetric Michael Addition to α,β‐Unsaturated Ketones Catalyzed by 9‐Amino‐9‐deoxyepiquinine
Jian‐Wu Xie Wei Chen Rui Li Mi Zeng Wei Du Lei Yue Ying‐Chen Chen Prof. Dr. Yong Wu Prof. Dr. Jin Zhu Prof. Jin‐Gen Deng Prof. Dr. 《Angewandte Chemie (International ed. in English)》2007,46(27):5049-5049
13.
Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
14.
Diphenylprolinol Silyl Ether Catalyzed Asymmetric Michael Reaction of Nitroalkanes and β,β‐Disubstituted α,β‐Unsaturated Aldehydes for the Construction of All‐Carbon Quaternary Stereogenic Centers 下载免费PDF全文
Prof. Dr. Yujiro Hayashi Yuya Kawamoto Masaki Honda Daichi Okamura Shigenobu Umemiya Yuka Noguchi Takasuke Mukaiyama Prof. Dr. Itaru Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12072-12082
The asymmetric Michael reaction of nitroalkanes and β,β‐disubstituted α,β‐unsaturated aldehydes was catalyzed by diphenylprolinol silyl ether to afford 1,4‐addition products with an all‐carbon quaternary stereogenic center with excellent enantioselectivity. The reaction is general for β‐substituents such as β‐aryl and β‐alkyl groups, and both nitromethane and nitroethane can be employed. The addition of nitroethane is considered a synthetic equivalent of the asymmetric Michael reaction of ethyl and acetyl substituents by means of radical denitration and Nef reaction, respectively. The short asymmetric synthesis of (S)‐ethosuximide with a quaternary carbon center was accomplished by using the present asymmetric Michael reaction as the key step. The reaction mechanism that involves the E/Z isomerization of α,β‐unsaturated aldehydes, the retro‐Michael reaction, and the different reactivity between nitromethane and nitroethane is discussed. 相似文献
15.
Lewis base‐catalyzed cyclization reactions of allenoates with electron‐deficient olefins and imines have been demonstrated by the preparation of biologically active natural products and pharmaceutically interesting substances and have emerged as powerful synthetic tools in the rapid construction of cyclic molecular complexity. In contrast to phosphine‐containing Lewis bases, nitrogen‐containing Lewis base amines display markedly different reaction profiles; however, this area is not well‐developed. Herein we summarize the recent progress in this emerging field and outline the challenges ahead. 相似文献
16.
17.
Dr. Cheng‐Kui Pei Yu Jiang Yin Wei Prof. Dr. Min Shi 《Angewandte Chemie (International ed. in English)》2012,51(45):11328-11332
18.
19.
20.
Shaoquan Lin Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3296-3299
We report a direct catalytic asymmetric Mannich‐type addition of α,β‐unsaturated γ‐butyrolactam to α‐ethoxycarbonyl ketimines promoted by a soft Lewis acid/Brønsted base cooperative catalyst. A thiophosphinoyl group on the nitrogen of ketimines was crucial for both electrophilic activation and α‐addition of γ‐butyrolactams. The obtained aza‐Morita–Baylis–Hillman‐type products bear an α‐amino acid architecture with a tetra‐substituted stereogenic center. 相似文献