Direct Synthesis of Pyrrolo[1,2-α]quinoxalines via Iron-Catalyzed Transfer Hydrogenation between 1-(2-Nitrophenyl)pyrroles and Alcohols

Herein, we describe novel iron-catalyzed transfer hydrogenation between alcohols and 1-(2-nitrophenyl)pyrroles for the synthesis of pyrrolo[1,2-α]quinoxalines. The tricarbonyl (η⁴-cyclopentadienone) iron complex catalyzed the oxidation of alcohols and the reduction of nitroarenes, and the corresponding aldehydes and aniline were generated in situ. The resulting Pictet-Spengler-type annulation/oxidation completed the quinoxaline structure formation. The protocol tolerated various kinds of functional groups and provided 29 samples of 4-substituted pyrrolo[1,2-α]quinoxalines. The developed method was also applied for the synthesis of additional polyheterocycles.