The Use ofN-Alkyl-2,2′-bipyrrolidine Derivatives as Organocatalysts for the Asymmetric Michael Addition of Ketones and Aldehydes to Nitroolefins
作者:Olivier Andrey、Alexandre Alexakis、Axel Tomassini、Gerald Bernardinelli
DOI:10.1002/adsc.200404037
日期:2004.8
The direct Michael addition of aldehydes and ketones to nitroolefins, catalyzed by N-i-Pr-2,2′-bipyrrolidine, is described. The desired 1,4-adducts are obtained in excellent yields with enantioselectivities up to 95% ee and dr up to 95 : 5 of the syn aldehyde addition product. An unexpected inversion of diastereoselectivity was observed for the addition of α-hydroxy ketones to β-arylnitroolefins with
描述了由Ni -Pr-2,2'-联吡咯烷催化的醛和酮直接迈克尔加成到硝基烯烃上。以优异的产率获得所需的1,4-加合物,其对映体选择性高达合成醛加成产物的95%ee和dr:95:5 。对于以高达98%ee的对映选择性将α-羟基酮添加到β-芳基硝基烯烃中,观察到了非预期的非对映选择性反转。在α-羟基酮的OH基和催化剂的叔氮之间形成内部氢键导致形成刚性的顺式烯胺中间体,这解释了预期的非对映选择性和非常高的ee。