Regioselective Stille coupling reactions of 3,5-dibromo-2-pyrone with various aryl and vinyl stannanes

3,5-Dibromo-2-pyrone underwent facile regioselective Stille coupling reactions with aryl, heteroaryl and vinyl stannanes to produce various 3-substituted, 5-bromo-2-pyrones. Addition of a catalytic amount of Cul greatly increased the selectivity and chemical yield of the desired 3-aryl-5-bromo-2-pyrone. Second Stille Coupling reactions on the resulting 3-aryl-2-pyrones gave rise to a series of potentially useful 2-pyrones with two different functionalities at C3 and C5 position in good to excellent isolated yields. 2-Pyrones with pyridyl groups at C3 position can undergo Lewis acid catalyzed Diels-Alder cycloaddition reactions with benzyl vinyl ether. (C) 2002 Elsevier Science Ltd. All rights reserved.