A powerful o-quinone dimethide strategy for intermolecular Diels-Alder cycloadditions

Conrotatory thermal fragmentation of trans-1,2-disilyloxybenzocyclobutenes generates o-quinone dimethides at remarkably low temperatures. Smooth stere oselective Diels-Alder cycloaddition with a range of dienophiles provides h ydronaphthalene derivatives in excellent yield. Direct oxidative desilylati on of the adducts affords the corresponding naphthoquinones. Substitution o f the benzene nucleus with an electron-releasing methoxyl group directs the cycloaddition to give good control of regioselectivity in the expected dir ection. A short synthesis of the aglycon of the anticancer antibiotic idaru bicin is presented.