Ni-catalyzed reductive macrocyclizations of ynals are reported. Disubstituted alkynes afford either endocyclic or exocyclic allylic alcohols depending on the ligand. Phosphine ligands favor the formation of endocyclic olefins, whereas N-heterocyclic carbene ligands favor the formation of exocyclic olefins. Terminal alkynes provide 1,2-disubstituted olefins with N-heterocyclic carbene ligands.

A new procedure for catalytic reductive coupling of aldehydes and alkynes has been developed. The procedure uses Ni(COD)2 with an imidazolium carbene ligand as the catalyst and triethylsilane as the reducing agent. A crossover deuterium-labeling experiment illustrated that variants involving trialkyl phosphines and imidazolium carbene ligands with a nickel catalyst proceed by different mechanisms.

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A new strategy for effecting cascade cyclization processes using nickel enolates has been developed. Nickel enolates may be cleanly generated by the oxidative cyclization of an enal and alkyne with Ni(0), and the resulting enolate may be functionalized by a variety of alkylation processes. Partially and fully intramolecular versions of the process allow the rapid synthesis of complex polycyclics from simple achiral, acyclic precursors.