Tandem inter-/intra-Diels-Alder cycloadditions of 2-pyrones for the efficient synthesis of novel tetracycles

Abstract

Utilizing our previously reported regioselective Stille coupling reactions of 3,5-dibromo-2-pyrone, we prepared 5-(Z)- and (E)-alkenyl-3-bromo-2-pyrones, each of which has a latent diene group being realized upon initial cycloaddition reactions. When heating with ?, ?-dienes, both 5-(Z)- and (E)-alkenyl-3-bromo-2-pyrones underwent two consecutive Diels-Alder cycloadditions to highly functionalized, structurally novel tetracyclic lactones in good yields.