An eco-friendly Pictet–Spengler approach to pyrrolo- and indolo[1,2-a]quinoxalines using p-dodecylbenzenesulfonic acid as an efficient Brønsted acid catalyst

Abstract

A facile and environmentally benign Pictet–Spengler strategy for the synthesis of a series of biologically important pyrrolo- and indolo[1,2-a]quinoxalines has been developed by reacting 1-(2-aminophenyl)-pyrrole or 1-(2-aminophenyl)indoles with a wide range of aromatic aldehydes, acetophenones or isatins in ethanol at ambient temperature using p-dodecylbenzenesulfonic acid (p-DBSA) as an efficient Brønsted acid–surfactant combined catalyst. This methodology was found to be applicable to generate diverse quinoxaline derivatives in fairly good yields under mild reaction conditions.