Synthesis of Benz[d]oxazolones Involving Concomitant Acetyl Migration from Oxygen to Nitrogen

Abstract

Heating of o-acetoxybenzoyl azides 6–10 in toluene leads to the Curtius reaction, which, when followed by closure of oxazolone ring with concomitant migration of acetyl group from oxygen to nitrogen, produces 3-acetoxybenz[d]oxazol-2(3H)-ones 11–15, which undergo hydrolysis with hot dilute hydrochloric acid to furnish benz[d]oxazol-2(3H)-ones 17–21. Thermal reaction of 2-hydroxy-5-nitrobenzoyl azide (22) in toluene finally yields a mixture of 5-nitrobenz[d]oxazol-2(3H)-one (20) and 5-nitrobenz[d]isoxazol-3(2H)-one (23).

Keywords:

• Benz[d]oxazolone
• concomitant migration
• 5-nitrobenz[d]isoxazolone
• o-acetoxybenzoyl azides
• O to N acetyl migration

ACKNOWLEDGMENTS

We thank A. Acharya and P. Ghosh for ¹H NMR and ¹³C NMR spectral measurements. One of the authors (S. G.) is thankful to the University Grants Commission, New Delhi, and the Council for Scientific and Industrial Research, New Delhi, for a research fellowship.