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Cobalt-Catalyzed Reductive Coupling of Saturated Alkyl Halides with Activated Alkenes

2005; American Chemical Society; Volume: 71; Issue: 2 Linguagem: Inglês

10.1021/jo052065w

1520-6904

Paritosh Shukla, Yun‐Chu Hsu, Chien‐Hong Cheng,

Asymmetric Hydrogenation and Catalysis

An efficient cobalt-catalyzed reductive coupling reaction of alkyl halides with electron-withdrawing alkenes (CH2CR1EWG, EWG = electron-withdrawing group) in the presence of water and zinc powder in acetonitrile to give the corresponding Michael-type addition product (RCH2CR1EWG) was described. The methodology is versatile such that unactivated primary, secondary, and tertiary alkyl bromides and iodides and various conjugated alkenes including acrylates, acrylonitrile, methyl vinyl ketone, and vinyl sulfone all successfully participate in this coupling reaction. For the alkyl halides used in the reaction, the iodides generally gave better yields compared to those of the corresponding bromides. It is a unique method employing CoI2dppe, zinc, and alkyl halides, affording conjugate addition products in high yields. Mechanistically, the reaction appears to follow an oxidative addition driven route rather than the previously reported radical route.