Synthesis of 4-Aryl Pyrrolo[1,2-α]quinoxalines <i>via</i> Iron-Catalyzed Oxidative Coupling from an Unactivated Methyl Arene

Abstract

Herein, we describe the direct synthesis of pyrrolo[1,2-α]quinoxaline <i>via</i> oxidative coupling between methyl arene and 1-(2-aminophenyl) pyrroles. Oxidation of the benzylic carbon of the methyl arene was achieved by di-<i>t</i>-butyl peroxide in the presence of an iron catalyst, followed by conversion to an activated aldehyde <i>in situ</i>. Oxygen played a crucial role in the oxidation process to accelerate benzaldehyde formation. Subsequent Pictet-Spengler-type annulation completed the quinoxaline structure. The protocol tolerated various kinds of functional groups and provided 22 4-aryl pyrrolo[1,2-α]quinoxalines when various methyl arene derivatives were used. The developed method proceeded in air, and all catalysts, reagents, and solvents were easily accessible.