Cooperative N-heterocyclic carbene (NHC)–Lewis acid-mediated regioselective umpolung formal [3 + 2] annulations of alkynyl aldehydes with isatins
作者:Yu Zhang、Yingyan Lu、Weifang Tang、Tao Lu、Ding Du
DOI:10.1039/c4ob00145a
日期:——
A novel and regioselective umpolung synthesis of spirooxindoles has been developed by cooperative NHC–Lewis acid-mediated formal [3 + 2] annulations of alkynyl aldehydes with isatins. In most cases, the reactions proceeded via a3–d3 umpolung of alkynyl aldehydes resulting in spirooxindole butenolides. In a few cases, spirooxindole furan-3(2H)-ones were formed as the major products via an a1–d1 umpolung