Substrate Controlled Synthesis of Benzisoxazole and Benzisothiazole Derivatives via PhI(OAc)2‑Mediated Oxidation Followed by Intramolecular Oxidative O–N/S–N Bond Formation

A phenyliodine­(III) diacetate (PIDA)-mediated, highly efficient and tandem approach for the synthesis of aryldiazenylisoxazolo­(isothiazolo)­arenes from simple 2-amino-N′-arylbenzohydrazides has been developed. The reaction proceeds via formation of (E)-(2-aminoaryl)­(aryldiazenyl)­methanone as the key intermediate, followed by intramolecular oxidative O–N/S–N bond formation in one pot at room temperature. The quiet different reactivity of the substrate is due to the formation of a diazo intermediate which encounters a nucleophilic attack by carbonyl oxygen on the electrophilic amine to produce isoxazole products, as compared to the previous reports,, in which an N-acylnitrenium ion intermediate is intramolecularly trapped by an amine group.