Oxidative Heteroannulation Route to Benzoxazoles and Benzimidazoles

Significance

Reported is a mild and facile approach to the synthesis of 2-arylbenzoxazoles, 2-arylbenzimidazoles, and 1,3,5-trisubstituted pyrazoles by iodine-mediated heteroaromatization of in situ generated Schiff bases and hydrazones which, in turn, are readily available from aniline and enone precursors. The scope appears to be restricted to aromatic aldehydes and arylenones. Complications of electrophilic iodination of electron-rich aryl aldehydes appear not to occur. Most products can be easily and directly purified by recrystallization. The procedure is appropriate for scale-up.