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.