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.

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. [ABSTRACT FROM AUTHOR]