Studies on Diazepines. XXVIII. Syntheses of 5H-1, 3-Diazepines and 2H-1, 4-Diazepines from 3-Azidopyridines

Abstract

Photolysis of 2-unsubstituted (5a-f) and 2, 4-disubstituted (5k, l) 3-azidopyridines in the presence of sodium methoxide resulted in ring expansion to give the 4-methoxy-5H-1, 3-diazepines (8 and 18), presumably via the azirine intermediates 6 and 17 derived from the initially formed singlet 3-pyridylnitrenes by cyclization at the 2-position of the pyridine ring. On the other hand, in the photolysis of 2-substituted 3-azidopyridines (5g-j), the cyclization of the nitrenes occurred predominantly at the vacant 4-position giving rise to the 3-methoxy-2H-1, 4-diazepines (13).