H2-Mediated Copper Catalyzed C–C Coupling Reactions – Selective Formation of Skipped Dienes

A simple copper(I)/N-heterocyclic carbene complex facilitates a H2-mediated C–C coupling reaction of internal alkynes and allylic chlorides. The catalytic protocol delivers the corresponding 1,4-dienes (skipped dienes) with high chemo-, regio- and stereoselectivity without any isomerization to the thermodynamically more stable 1,3-dienes or overreduction to the corre-sponding alkanes. The H2-mediated C–C coupling reaction allows for the exploitation “copper hydride catalysis” with H2 as terminal reducing agent and source of hydrides for forging of new C–C bonds. In this way, this approach gives rise to C–C bond forming reactions with a 3d metal without the need for a stoichiometric organometallic reducing agent.