The photo-induced ring expansion of azido(methoxy)quinolines to methoxypyridoazepines

Abstract

The yields of 9-alkylamino-5H-pyrido[2,3-c]azepines from the photo-induced ring-expansion of 8-azidoquinoline in primary amines are increased significantly by the presence of a 6-methoxy group, which also for the first time induces ring-expansion of the azide in secondary amines. Optimum conditions have been found for the ring-expansion of 8-azidoquinoline in methanol–potassium methoxide to give 9-methoxy-5H-pyrido[2,3-c]azepine, and under the same conditions 8-azido-6-methoxy- and 6-azido-8-methoxy-quinoline ring-expand in excellent yield to the corresponding dimethoxypyridoazepines.