Bifunctional Iminophosphorane Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α-Substituted Acrylate Esters
作者:Alistair J. M. Farley、Christopher Sandford、Darren J. Dixon
DOI:10.1021/jacs.5b10226
日期:2015.12.30
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated α-substituted acrylate esters catalyzed by a bifunctional iminophosphorane organocatalyst under mild conditions is described. The strong Brønsted basicity of the iminophosphorane moiety of the catalyst provides the necessary activation of the alkyl thiol pro-nucleophile, while the two tert-leucine residues flanking a
描述了在温和条件下由双功能亚氨基正膦有机催化剂催化的烷基硫醇与未活化的 α-取代丙烯酸酯的高度对映选择性磺基-迈克尔加成反应。催化剂亚氨基正膦部分的强布朗斯台德碱性为烷基硫醇亲核试剂提供了必要的活化,而中央硫脲氢键供体侧翼的两个叔亮氨酸残基促进了瞬态烯醇中间体质子化过程中的高对映选择性. 该反应在烷基硫醇、酯部分和 α,β-不饱和酯的 α-取代基方面的范围很广,以优异的产率(高达 >99%)和对映选择性(高达到 96% ee),并且可以使用低至 0 的催化剂负载量进行十克放大。