Metal Carbene-Promoted Sequential Transformations for the Enantioselective Synthesis of Highly Functionalized Cycloheptadienes

A two-step, three-component coupling of an alkyne, enol ether, and vinyl diazoester was accomplished by use of successive metal carbene-catalyzed transformations. This efficient approach to cycloheptadienes is both diastereo- and enantioselective. Kinetic resolution was accomplished on dienol ethers bearing a racemic chiral center at the propargylic position. A model is offered which explains the observed selectivity and accounts for the reactivity difference between trans- and cis-dienol ethers.