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.

Two for the price of one: The formation of two C(sp3)C(sp3) bonds can be achieved in a single operation by sequential cyclization and cross‐coupling of alkyl zinc bromides with iodoalkanes containing an alkene group (see scheme). The reaction is catalyzed by [Ni(py)4Cl2] in the presence of tridentate nitrogen ligands, shows a high functional‐group compatibility, and seems to follow a radical mechanism.

Gekuppelt unter Cyclisierung: Zwei C(sp3)‐C(sp3)‐Verknüpfungen gelingen in einer Stufe durch eine Folge aus Cyclisierung und Kreuzkupplung von Alkylzinkbromiden und Iodalkanen mit Alkengruppe (siehe Schema). Die Reaktion wird durch [Ni(py)4Cl2] in Gegenwart dreizähniger Stickstoffliganden katalysiert, sie ist mit vielen funktionellen Gruppen kompatibel und scheint radikalisch zu verlaufen.

Optimal conditions for a general Ni-catalysed Negishi cross-coupling of alkyl zinc halides with aryl, heteroaryl and alkenyl halides have been determined. These conditions allow the reaction to take place smoothly, with low catalyst loading, and in the presence of a wide variety of functional groups to afford products in good yields at room temperature. DFT studies on the mechanism support the occurrence of a catalytic cycle involving transmetalation of the alkyl zinc halide to Ni(I) followed by oxidative addition of the haloarene and C-C reductive elimination.

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