A Sequential Transition Metal and Organocatalytic Approach to the Enantioselective Synthesis of C2-spiroindoline Systems

We report herein an organocatalyzed, enantioselective spirocyclization process for the construction of spiroindolines. This methodology creates a new avenue for the easy access to valuable C2-spiroindoline scaffolds bearing a quaternary stereocenter, via an aza-Michael addition reaction, wherein the acid additives play a role of dual functionality. The substrates for this key step were put together by an exo-selective, Pd-catalyzed gamma-arylation of silyldienol ethers of the corresponding cyclohexenones. A close alliance between a low catalyst loading and a sluggish reaction yields the spiroindolines in very good enantioselectivity.