Transition-metal-catalyzed C-C bond formation has become ubiquitous in organic synthesis. The role of cobalt as a transition-metal catalyst for organic reactions has long been confined to cyclisation reactions, eg. [2+2+2] cyclisations or Pauson-Khand reaction. However, in the last few decades, a new type of reactivity was discovered for cobalt salts, in carbon-carbon bond forming reactions. Our group used in particular cobalt for a variety of reactions, from arylzinc bromides synthesis to direct reductive cross-coupling reactions.<br/>Although various strategies involving stoichiometric organometallic species are efficient and have been described for many years, versatile metal-catalyzed reductive cross-coupling reactions have recently appeared as an alternative to create operationally simple C-C bonds. Different metals such as Pd and mainly Ni have been used as catalyst. However, Cobalt salts also allow the reductive cross-couplings between two electrophiles and present the advantage to be cheaper and more environmentally friendly. In such reactions, a catalytic cobalt organometallic reagent is generated under mild conditions thanks to Co/Mn or Co/Zn association.<br/>In this presentation, several Co-catalyzed reductive cross-coupling reactions will be presented in order to form various C-C bonds from either alkyl, vinyl, (hetero)aryl or allyl compounds. A broad scope of functionalized substrates was employed under mild conditions affording moderate to excellent yields. Depending on the nature of starting materials, the reactions seem to involve either a radical species (especially with alkyl compounds) or not.

Cobalt: A versatile catalyst to promote reductive cross-coupling reactions

254th National Meeting (2017)

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