Cyclopropanation of Strained Alkenes by Palladium-Catalyzed Reaction of 3-Trimethylsilyl- or 3-Pinacolatoboryl-1-arylallyl Acetates

The palladium-catalyzed cyclopropanation of strained alkenes with 3-trimethylsilyl- or 3-pinacolatoboryl-1-arylallyl acetate derivatives is described. This reaction gives cyclopropanation products in good to high yields with a single diastereomer, and the key step is likely to involve the formation of a palladacyclobutene complex from the a-trimethylsilyl- or a-pinacolatoboryl-s-allylpalladium complex.