Intramolecular azo coupling in a number of 1-substituted 2-aminobenzimidazoles

Diazotization of heterocyclic primary amines

“…Such reactions are not conclusive proofs for the primary nitrosoamine structures.598 It is also of interest that the compounds 33 gave positive Liebermann nitroso reactions while the materials 39 and 40 did not. Also in cases where some other heterocyclic amines have been diazotized in aqueous acetic acid or very dilute mineral acids, diazoamino compounds were formed, e.g., compounds 11,34 (also 48 below). These often separate as hydrates and are cleaved by concentrated hydrochloric acid to hydrazines and amines.…”