Chiral Squaramide-Catalyzed Enantioselective Conjugate Michael Addition of Various Thiols to α,β-Unsaturated N-Acylated Oxazolidin-2-ones
作者:Le Dai、Hongjun Yang、Fener Chen
DOI:10.1002/ejoc.201100403
日期:2011.9
A highly enantioselective sulfa-Michael addition (SMA) of variousthiols to α,β-unsaturatedN-acylated oxazolidinones has been achieved with a chiral squaramide catalyst under very mild reaction conditions. In addition, the conversion of the β-thio-substituted adduct to the corresponding methyl β-tosylbutanoate was demonstrated in high yield through a methanolysis/oxidation sequence.
A convenient Fe(OTf)2-catalyzed Michael additionreaction of thiols to α,β-unsaturated carbonyl compounds was developed. The use of a simple procedure (EtOH, room temperature, air atmosphere) allowed to set up effective green catalytic conditions for the C–S bond formation. The scope of the reaction was demonstrated using various substituted thiols and original Michael acceptors. The corresponding
Asymmetric Sulfa-Michael Addition of α,β-Unsaturated Esters/Amides Using a Chiral N-Heterocyclic Carbene as a Noncovalent Organocatalyst
作者:Jiean Chen、Yong Huang、Pengfei Yuan、Sixuan Meng
DOI:10.1055/s-0035-1561843
日期:——
We report an asymmetric sulfa-Michael reaction of α,β-unsaturated amides and estersusing a chiral N-heterocyclic carbene as the HOMO-raising organocatalyst. We discovered an interesting correlation between 13C NMR shifts of substrates and ee of their products. More electron-deficient Michael acceptors afforded higher enantioselectivity.
我们报告了使用手性 N-杂环卡宾作为 HOMO 提升有机催化剂的 α,β-不饱和酰胺和酯的不对称磺胺-迈克尔反应。我们发现底物的 13C NMR 位移与其产物的 ee 之间存在有趣的相关性。更多缺电子迈克尔受体提供更高的对映选择性。
Catalytic Asymmetric Conjugate Addition of Simple Alkyl Thiols to α,β-Unsaturated <i>N</i>-Acylated Oxazolidin-2-ones with Bifunctional Catalysts
作者:Yan Liu、Bingfeng Sun、Baomin Wang、Matthew Wakem、Li Deng
DOI:10.1021/ja8085092
日期:2009.1.21
In this communication, we describe an unprecedented highly enantioselective catalytic conjugateaddition of simple alkyl thiols to alpha,beta-unsaturated N-acylatedoxazolidin-2-ones catalyzed by acid-base bifunctional catalysis. This reaction provides a useful catalytic method for the synthesis of optically active chiral sulfur compounds that are otherwise difficult to prepare by asymmetric catalysis
The enantioselective conjugate addition of thiols to (E)-3-crotonoyloxazolidin-2-one was effectively catalyzed by the Fe(BF4)(2)center dot 6H(2)O/(S,S)-ip-pybox catalyst. and the addition product was obtained with up to a 95% ee. Furthermore, the CO(ClO4)(2)center dot 6H(2)O/(S,S)-ip-pybox catalyst also catalyzed the same reaction with a high enantioselectivity. (c) 2008 Elsevier Ltd. All rights reserved.