Palladium-catalyzed [3 + 2] cycloaddition reaction of vinylcyclopropanes with α,β-unsaturated esters or ketones

Reaction of vinylcyclopropanes having two electron-withdrawing groups with α,β-unsaturated esters or ketones in the presence of Pd2(dba)3.CHC13-1,2- bis(diphenylphosphino)ethane (dppe) or tributylphosphine catalyst gave vinyl- cyclopentanes in good yields.