CATALYTIC ACRYLOXYPALLADATION OF VINYLCYCLOALKANES AND EXO-METHYLENE CYCLOALKANES - MECHANISTIC INSIGHTS INTO THE COMPETITION BETWEEN ALLYLIC ACRYLOXYPALLADATION AND FORMATION OF ALPHA-METHYLENE-GAMMA-BUTYROLACTONES

Acryloxypalladation of exo-methylenecycloalkanes (three-, four-, five- and six-membered rings) and vinylcycloalkanes (three-, five- and six- membered rings) in the presence of the Pd(OAc)(2)/p-benzoyquinone/MnO2 catalytic system is reported. Except for the case of eso-methylenecyc lopropane, this reaction provides a rapid entry to the corresponding a lpha-methylene gamma-butyrolactone, which essentially results from a 1 ,2-Markovnikov acryloxypalladation addition on the double bond. The su bsequent insertion of the acrylate double bond into the carbon-palladi um bond is followed by a beta-elimination step. However, this reaction competes with the formation of intermediate pi-allyl complexes which yields the corresponding allylic acrylates. The ratio of butyrolactone s to allylic acrylates is dependent on ring size.