Convenient routes to pyrrolo[3,2-b]-, pyrrolo[3,2-c]-, and pyrrolo[2,3-c]-quinolines, and a study of the pyrolysis of 2-quinolylhydrazones

Abstract

A useful one-step synthesis of pyrrolo[3,2-b]quinoline (1) from 3-amino-2-methylquinoline and the preparations of derivatives of pyrrolo[3,2-c]-(12) and pyrrolo[2,3-c]-quinoline (21) are described. Pyrolysis of deoxybenzoin 2-quinolylhydrazone (26) is shown to give 2-aminoquinoline (31), 2,3-diphenylimidazo[1,2-a]quinoline (32), and tetraphenylpyrrole (36); butan-2-one 2-quinolylhydrazone (27) gives the aminoquinoline (31), 2,2′-azoquinoline (35), and what is probably an aminodiquinolylamine (33). The mechanisms of these pyrolyses are discussed.