Reaction of o-acylaminobenzazides with amines and hydrazines

Azides in general and 0-acylaminobenzazides 1, in particular, are unstable compounds that decompose easily. The decomposition product of 1 is dependent upon the medium of reaction. Decomposition in boiling benzene gives the urea derivative 2, while decomposition in hot acetic acid medium gives the benzimidazolone derivative 3. Both of latter compounds are formed via the formation of the isocyanate derivative 4, the primary decomposition product of the azide. The urea derivative 2 was reported to be formed by the reaction of the isocyanate derivative 4 with the amine formed when part of 4 was hydrolysed under the influence of moisture present in the reaction medium