Catalytic Enantioselective Transannular Morita-Baylis-Hillman Reaction.

Catalytic and enantioselective approaches to transannular reactions are very limited and mostly are based on chiral Lewis acid catalyzed pericyclic reactions. In this report, we present an efficient and straightforward methodology to access bicyclic carbo- and heterocyclic scaffolds combining different ring sizes through transannular Morita-Baylis-Hillman reaction catalyzed by a chiral enantiopure bifunctional phosphine. The reaction is remarkably wide in scope and enables the use of a variety of medium and large size ketoenone substrates leading to the final products in high yields and providing excellent stereocontrol in the formation of a quaternary stereogenic center at the ring fusion. Moreover, its potential as a general tool in organic synthesis has been highlighted through the accomplishment of the first enantioselective total synthesis of (-)-γ-gurjunene, a sesquiterpene natural product.