Synthesis of fully unsaturated monocyclic 1,2,5-triazepines from 4-azidopyridazines.

Abstract

Photolysis of the 3-methoxy-4-azidopyridazines (1) in the presence of a base such as methoxide ion and diethylamine resulted in ringexpansion to form the corresponding unstable 1H-1, 2, 5-triazepines (3 and 1), which were tautomerized to the relatively stable 4H-isomers 5 and 6 by further treatment with sodium methoxide. Treatment of the 1H-triazepines (3 and 4) with acetyl chloride in pyridine gave the stable 1-acetyl-1H-1, 2, 5-triazepines (7 and 8). The products 5-8 are the first examples of isolated 1, 2, 5-triazepines.