PALLADIUM-CATALYZED CROSS-COUPLING OF BETA-(METHANESULFONYL)OXY ENONES WITH ORGANOSTANNANES

beta-(Methanesulfonyl)oxy enones, derived from 1,3-diones, cross-couple with vinylstannanes in 50-80% yields when a substoichiometric amount of Pd(PPh3)4 and stoichiometric lithium bromide are used. Phenyltributylstannane affords low yields of cross-coupled product. Tetrabutyltin, tributyltin hydride, and ethynyltributyltin do not couple under the reaction conditions. The reaction is proposed to involve in situ formation of the beta-bromo enone, oxidative addition to the Pd(0) catalyst, transmetalation, and reductive elimination to afford cross-coupled products. The analogous enol phosphates undergo coupling in low yields, the major product resulting from regeneration of the 1,3-dione.