Nickel-catalysed Negishi cross-coupling reactions: scope and mechanisms

The Negishi cross-coupling of organozinc reagents is a valuable tool for the formation of C-C bonds in the presence of functional groups. Although this reaction is catalysed by Ni or Pd complexes, the latter have been much more developed. Nevertheless, Ni derivatives have become important in recent years, especially for their activity in the formation of alkyl-alkyl bonds. The mechanisms involved in Ni-catalysed reactions are different from the usual catalytic cycle involving oxidative addition-transmetalation-reductive elimination that is generally accepted for Pd-catalysed reactions. This tutorial review presents the more recent advances in Ni-catalysed Negishi cross-couplings for the formation of different kinds of C-C bonds and discusses their proposed reaction mechanisms.