An organocatalytic enantioselective alkylation of α,α-disubstituted aldehydes with 3-bromooxindoles is reported. Enantioenriched oxindoles with vicinal quaternary stereocenters are accessed by an asymmetric conjugate addition process of branched aldehydes with o-azaxylylene intermediates (indol-2-ones). Key to the success of highly diastereo- and enantioselective transformations is the combined use
报道了 α,α-二取代醛与 3-
溴氧
吲哚的有机催化对映选择性烷基化。通过支链醛与邻氮二
甲苯中间体(
吲哚-2-酮)的不对称共轭加成过程获得具有邻位季立体中心的对映体富集的羟
吲哚。高度非对映选择性和对映选择性转化成功的关键是联合使用源自螺
吡咯烷支架的三苯基甲
硅烷基保护的β-
氨基醇催化剂和
3,5-二硝基苯甲酸。这项研究还提出了醛烷基化形成连续四元立构中心的罕见例子。