An efficient, general synthesis of 2-substituted 3,6-dihydropyrrolo[3,2-e]indoles involving one-pot Sonogashira coupling and cyclisation

摘要

A number of 2-substituted 3,6-dihydropyrrolo-[3,2-e]indoles were synthesised efficiently by the reaction of 4-iodo-1 -(phenylsulfonyl)-5-(trifluoroacetamido)indole with terminal acetylenes in the presence of a palladium(O) catalyst and a copper(I) co-catalyst. The reaction involved one-pot Sonogashira coupling/heteroannulation, the first one of its kind in the synthesis of the title compounds. The required amido-iodoindole was prepared smoothly from 5-nitroindole by successive N-protection, reduction of the nitroarene, iodination of the resulting aminoarene and N-trifluoroacetylation.