An isomeric diamine undergoes reaction with NaNO ₂/ HCl at 0-5^ C to yield 1,5-dimethyl- 1H -benzotriazole as the major product. Identify the correct starting material.

Step-by-step solution

The formation of a substituted 1H -benzotriazole from a diamine involves the diazotization of a primary amine followed by intramolecular nucleophilic attack by an adjacent secondary amine. In the product 1,5-dimethyl- 1H -benzotriazole, the N1 atom bears a methyl group, indicating it originated from a secondary amine ( -NHCH ₃ ). The N3 atom originated from the primary amine ( -NH ₂ ) which was diazotized. Mapping the benzotriazole numbering back to the benzene ring: N1 is attached to the bridgehead carbon C7a. N3