Synthesis of Carbolines via Microwave-Assisted Cadogan Reactions of Aryl-Nitropyridines

摘要

Suzuki-Miyaura-couplings to aryl-nitropyridines followed by Cadogan reactions is a straight-forward method for the synthesis of δ- and β-carbolines. Microwave irradiation of the nitrobiaryls in triethyl phosphite solutions conveniently gives moderate to very good yields of the carbolines. Reduction to the amines without cyclization occurs on certain substrates, and alkylation of the products is observed as a follow-up reaction. Instead of α-carbolines, naphthonitriles are generated by phosphite reduction and ring transformation.