Kinetically Controlled Stereoselective Access to Branched 1,3-Dienes by Ru-Catalyzed Remote Conjugative Isomerization

A Ru-catalyzed conjugative isomerization of remote alkenes that affords branched 1,3-dienes is described. These kinetic products are obtained in high yields, good levels of regiocontrol, and high stereoselectivity. A broad range of functional groups and heterocycles are compatible with the mild reaction conditions, and isomerization is sustained over long distances. Control experiments support a metal-hydride mechanism consisting of iterative migratory insertions/β-H eliminations, which is initiated preferentially at the terminal olefinic site. Two one-pot multimetallic selective catalytic sequences using [Ru/Cu] and [Ru/Rh] combinations have been developed to illustrate the synthetic potential of the process.