Convenient synthesis of spiroindole derivatives via palladium-catalyzed cyclization of propargyl chlorides

Abstract

Herein, we report the palladium-catalyzed cyclization reactions of indoles bearing a propargyl chloride side chain at their 3-position. In the presence of an external nucleophile, such as a sulfonamide or malonate, indoles bearing a propargyl group at their 3-position gave fused tetracyclic spiroindolines preferentially. However, in the absence of an external nucleophile, the same substrates afforded spiroindoles. Our attempts to develop a catalytic asymmetric spirocyclization onto a propargylpalladium species are also presented in this paper.