Control of chemoselectivity by counteranions of cationic palladium complexes: a convenient enantioselective synthesis of dihydrocoumarins.

High chemoselectivity for the synthesis of two kinds of substituted coumarins controlled by the counteranions of the cationic palladium catalysts is described. The asymmetric version of the reaction for the synthesis of 3-alkylidene dihydrocoumarins is realized with high enantioselectivity.