Studies on Regioselectivity of Nitration of Coumarins with Cerium(IV) Ammonium Nitrate: Solid-State Nitration of 6-Hydroxy-Coumarins on Montmorillonite K-10 Clay Support Under Microwave Irradiation

Abstract

6-Hydroxycoumarins and their O-methyl ethers were selectively nitrated in the carbocyclic ring even in the presence of activating 4-Me group in the 2-pyrone ring with cerium(IV) ammonium nitrate (CAN) in acetic acid and acetonitrile in acceptable-to-excellent yields. Acetonitrile was found to be a better solvent for regioselective nitration than acetic acid. Use of CAN on montmorillonite K-10 clay under microwave irradiation for expeditious solvent-free regioselective nitration has been revealed for the first time.

Acknowledgments

We sincerely thank RSIC, CDRI (Lucknow) for providing mass spectral data. We also thank CSIR, New Delhi for a research fellowship to one of us (PD). MD is thankful to the University of Kalyani for a research fellowship.