Solid-State Regioselective Cyclization Initiated by the Electrophilic Attack on the Double Bond by N-Bromosuccinimide on Montmorillonite K-10 Clay Support under Microwave Irradiation.

Abstract 3‐Allyl‐4‐hydroxy‐coumarins and pyrones were regioselectively cyclized with N‐bromosuccinimide (NBS) on solid phase under microwave irradiation in excellent yield. NBS on montmorillonite K‐10 clay under microwave irradiation for expeditious solvent‐free regioselective cyclization has been used for the first time.