Photolysis of pyridyl azides in the presence of methoxide ions: Formation of fully unsaturated 1,3- and 1,4-diazepines.

Photolysis of 4-azidopyridines (1) in the presence of methoxide ions resulted in ring-expansion to give the 6H-1, 4-diazepines (4). Treatment of the diazepine (4a) with benzoyl chloride afforded the 1-benzoyl-1H-1, 4-diazepine (5), whose structure was confirmed by some thermal reactions. Upon irradiation under similar conditions, 3-azidopyridines (10) gave the 5H-1, 3-diazepines (13), but no 1, 4-diazepines could be obtained. Treatment of the diazepines (13) with benzoyl chloride resulted in the formation of the 5-benzoylamino-2-methoxypyridines (16), presumably via the 1-benzoyl-1H-1, 3-diazepines (14).