Palladium-catalyzed [2+2] cycloaddition of allylic acetates and norbornene

Palladium-catalyzed reaction of norbornene with allyl acetate gave 3-methylenetricyclo[4.2.1.02,5]nonane 1 and 2-methylene-3-vinylnorbornane 2 in high yields. The substituents on allyl acetate strongly influenced the selectivity. In the reactions of 1- or 3-substituted allyl acetates, cycloadducts corresponding to 1 were obtained exclusively. Use of methallyl acetate gave solely a diene corresponding to 2.