A Concise Protocol for the Synthesis of 2-Alkenylindoles through [4+1] Annulation of Aminobenzyl Phosphonium Salts with Acrylaldehydes

Abstract

A [4+1] annulation protocol is developed for the synthesis of various 2-alkenylindole derivatives starting from aminobenzyl phosphonium salts and cinnamaldehydes. In this process, the reaction proceeds efficiently without the usage of any metal catalysts or base, which is featured with easily available starting materials, broad substrate scope, excellent yields and simple reaction conditions.