Catalytic Enantioselective Cross-Couplings of Secondary Alkyl Electrophiles with Secondary Alkylmetal Nucleophiles: Negishi Reactions of Racemic Benzylic Bromides with Achiral Alkylzinc Reagents
作者:Jörg T. Binder、Christopher J. Cordier、Gregory C. Fu
DOI:10.1021/ja308460z
日期:2012.10.17
We have developed a nickel-catalyzed method for the asymmetric cross-coupling of secondary electrophiles with secondary nucleophiles, specifically, stereoconvergent Negishi reactions of racemic benzylic bromides with achiral cycloalkylzinc reagents. In contrast to most previous studies of enantioselective Negishi cross-couplings, tridentate pybox ligands are ineffective in this process; however, a
我们开发了一种镍催化的方法,用于二级亲电试剂与二级亲核试剂的不对称交叉偶联,特别是外消旋苄基溴与非手性环烷基锌试剂的立体聚合 Negishi 反应。与之前大多数对映选择性 Negishi 交叉偶联的研究相比,三齿 pybox 配体在此过程中无效;然而,一种新的、易于获得的双齿异喹啉-恶唑啉配体提供了出色的 ee 和良好的产率。使用无环烷基锌试剂作为偶联伙伴导致发现了一种非常不寻常的异构化,该异构化可从未支化的亲核试剂中产生大量的支化交叉偶联产物。