A direct entry to polycyclic quinoxaline derivatives via I2-DMSO mediated oxidative decarboxylation of α-amino acids and the subsequent Pictet–Spengler cyclization reaction

Abstract

A facile and highly efficient iodine-promoted strategy has been delineated for the synthesis of indolo and pyrrolo[1,2-a]quinoxaline derivatives via an oxidative Pictet–Spengler type amino cyclo-annulation reaction using ∝-amino acids as aldehyde surrogates. The concomitant benzylic oxidation and the compatibility of different starting materials under standard conditions made the current method versatile. The salient features of the protocol such as readily available starting materials, inexpensive promoters, environmental benignity, broad substrate scope, scalability, and good to excellent yield make the method more attractive to practitioners of organic synthesis.