Intramolecular nitrene insertions into aromatic and heteroaromatic rings. Part 8. Flash vacuum pyrolysis of 2-azidobenzylpyridines

Abstract

Flash vacuum pyrolysis of 2-azidobenzylpyridines (9)–(11) at temperatures from 350 to 700 °C gave mixtures of benzonaphthyridines and their dihydro derivatives as major products. The 3-pyridyl derivative (10) also gave 2-(3-cyanoprop-1-enyl)indole (19). Benzonaphthyridines were also obtained by pyrolysis of 2-aminophenyl(x-pyridyl)methanols (4), (5), and (6), [the 2-pyridyl derivative (4) also gave 2-aminobenzaldehyde and pyridine]. Treatment of the azides (9)–(11) with aluminium chloride gave the corresponding 2-amino-5-chlorobenzylpyridines (21)–(23). The mechanism of the reaction is discussed.