Reaction of vinyl epoxides with palladium-switchable bisnucleophiles: Synthesis of carbocycles

The selective activation of substrates I, potential bisnucleophiles, was ac hieved by using different palladium catalysts. The synthetic potential of t his strategy has been demonstrated in the regiodivergent synthesis of carbo cycles from substrates of type I, bearing malonate-type pronucleophiles and an alkenyl stannane, with vinyl epoxides. A selective palladium-catalyzed reaction of I with the vinyl epoxide gives rise to an allylic alcohol, whic h, after activation as a carbonate, led to the cyclization product by a sec ond palladium-catalyzed reaction. The transmetalation process is favored wi th palladium catalysts without phosphines or arsines as the ligands. On the other hand, the use of palladium complexes with PPh3 as the ligand inhibit s the transmetalation pathway and promotes the nucleophilic attack of the m alonate-type anions on the intermediate (eta (3)-allyl)palladium complexes.