title: Cobalt-catalyzed reductive coupling of activated alkenes with alkynes.
abstract: 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 CoI2(PPh3)2/Zn, the reaction of enones and enals with alkynes requires the use of the CoI2(dppe)/Zn/ZnI2 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 D2O.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.forename: Thiruvellore Thatai
authors.initials: TT
authors.lastname: Jayanth
authors.forename: Chun-Chih
authors.initials: CC
authors.lastname: Wang
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Cheng