New versatile Pd-catalyzed alkylation of indoles via nucleophilic allylic subsitution: Controlling the regioselectivity

A systematic study addressed toward the optimization of the Pd-catalyzed alkylation of indoles by allylic carbonates is presented. The protocol uses a catalytic amount of [PdCl(pi-allyl)](2)/phosphine as a promoting agent, providing allylindoles in excellent yields. The regioselectivity of the reaction can be controlled by a proper choice of the base and the reaction media. The method proved to be effective also for intramolecular allylic alkylations of indolyl carbonates, providing a flexible route to fused indole alkaloids.