Stereocontrolled Construction of Quaternary Stereocenters by Inter- and Intramolecular Nitro-Michael Additions Catalyzed by Bifunctional Thioureas
作者:Rubén Manzano、José M. Andrés、María D. Muruzábal、Rafael Pedrosa
DOI:10.1002/adsc.201000612
日期:2010.12.17
A highly diastereo- and enantioselectiveconjugateaddition of β-keto esters to nitroolefins, catalyzed by a chiral thiourea prepared from L-valine is described. The formation of two contiguous tertiary and quaternary stereocenters occurs in high yield and excellent diastereo- and enantioselection with only 2 mol% of catalyst loading. The reaction is general and different β-keto esters and aryl- and
Catalyticasymmetric1,4-addition of β-ketoesters to nitroalkenes is described. 2.5 mol % of a homobimetallic Lewis acid/Brønsted base bifunctional Co2-Schiff basecomplex smoothly promoted the reaction in excellent yield (up to 99%), diastereoselectivity, and enantioselectivity (up to >30:1 dr and 98% ee). Catalyst loading was successfully reduced to 0.1 mol %. Mechanistic studies suggested that
描述了 β-酮酯与硝基烯烃的催化不对称 1,4-加成反应。2.5 mol% 的均双金属路易斯酸/Brønsted 碱双功能 Co2-Schiff 碱配合物以优异的产率(高达 99%)、非对映选择性和对映选择性(高达 >30:1 dr 和 98% ee)顺利促进反应。催化剂负载成功地降低到 0.1 mol%。机理研究表明,两个 Co 金属中心的分子内协同功能对于高催化活性和立体选择性很重要。