Metal-Free Catalytic C–Si Bond Formation in an Aqueous Medium. Enantioselective NHC-Catalyzed Silyl Conjugate Additions to Cyclic and Acyclic α,β-Unsaturated Carbonyls
作者:Jeannette M. O’Brien、Amir H. Hoveyda
DOI:10.1021/ja203031a
日期:2011.5.25
conjugate addition of a dimethylphenylsilyl group to α,β-unsaturated carbonyls is reported. Transformations are catalyzed by a chiral N-heterocyclic carbene (NHC), performed in an aqueous solution (3:1 mixture of water and tetrahydrofuran) and are operationally simpler to perform than the NHC-Cu-catalyzed variant. The chiral catalyst is generated from an enantiomerically pure imidazolinium salt (prepared
报道了一种将二甲基苯基甲硅烷基与 α,β-不饱和羰基进行对映选择性共轭加成的无金属方法。转化由手性 N-杂环卡宾 (NHC) 催化,在水溶液(水和四氢呋喃的 3:1 混合物)中进行,并且在操作上比 NHC-Cu 催化的变体更简单。手性催化剂由对映异构纯的咪唑啉盐(分三步制备)和常见的有机胺碱 (dbu) 生成。NHC 催化的过程在 22°C 下以 5.0-12.5 mol% 的催化剂负载量在 1-12 小时内进行,以 85:15 至 >98:2 的对映体比和 50% 至 >98% 的产率提供所需的 β-甲硅烷基羰基化合物. 环状烯酮或内酯以及无环的 α,β-不饱和酮、酯和醛可用作底物。