A new method has been developed for constructing vicinal quaternary stereocenters with an oxindole–butanolide hybrid framework through asymmetric vinylogous addition of a siloxyfuran to an indol-2-one in the presence of a readily available N,N′-dioxide–Ni(OTf)2 complex catalyst. Various oxindole–lactones were obtained in up to 98% yield with >19:1 dr and 97% ee under mild reaction conditions. A possible
开发了一种新方法,通过在容易获得的N , N ' -二氧化物-Ni(OTf)存在下,将甲硅氧呋喃不对称插烯加成到吲哚-2-酮上,从而构建具有羟吲哚-丁内酯杂化骨架的邻位季立体中心2络合物催化剂。在温和的反应条件下,以 >19:1 dr 和 97% ee 获得了高达 98% 的收率和 97% ee 的各种羟吲哚内酯。提出了一种可能的过渡态模型来解释不对称感应的起源。
Regioselectivity of dimerisation of butenolides via captodative stabilised radicaloid intermediates
作者:Sharanjeet K. Bagal、Robert M. Adlington、Rohan A.B. Brown、Jack E. Baldwin
DOI:10.1016/j.tetlet.2005.04.125
日期:2005.7
The regioselective outcome observed during dimerisation of butenolides to dimeric structures via captodative stabilised radicaloids has been studied. The captodative stabilised radicaloids were generated by initial conversion of butenolides to chlorobutenolides via the corresponding hydroxybutenolides, followed by treatment with CoCl(PPh3)3.