Cobalt-Catalyzed Reductive Coupling of Activated Alkenes with Alkynes

摘要

Cobalt complex/Zn systems effectively catalyze the reductive coupling of activated alkenes with alkynes in the presence of water to give substituted alkenes with very high regio- and stereoselectivity in excellent yields. While the intermolecular reaction of acrylates, acrylonitriles, and vinyl sulfones with alkynes takes place in the presence of CoL_2(PPh_3)_2/Zn, the reaction of enones and enals with alkynes requires the use of the Col2(dppe)/Zn/Znl_2 system. The intramolecular reductive coupling of activated alkenes (enones, enals, acrylates, and acrylonitriles) with alkynes also works efficiently. Further a variety of cyclic lactones and lactams were prepared using this methodology. Possible mechanistic pathways are proposed based on a deuterium-labeling experiment carried out in the presence of D_2O.