[3+1+1] Annulation Reaction of Benzo‐1,2‐Quinones, Aldehydes and Hydroxylamine Hydrochloride: Access to Benzoxazoles with Inorganic Nitrogen Source

A synthesis of benzoxazoles with an inorganic nitrogen source is reported. By employing large‐tonnage industrial feedstock inorganic hydroxylamine hydrochloride as the nitrogen source, its [3+1+1] annulation reaction with benzo‐1,2‐quinones and aldehydes delivers various useful benzoxazoles in high yields. Preliminary mechanistic studies prove that the quinone oxime rather than the aldehyde oxime is the reaction intermediate.