A nickel-catalyzed method for cyclizations of electron-deficient alkenes with tethered unsaturation in the presence of organozincs was developed. Considerable flexibility in the structure of each reactive component was observed. Enones, alkylidene malonates, unsaturated β-ketoesters, and nitroalkenes participated as the electron-deficient alkene; alkynes, enones, 1,3-dienes, and aldehydes participated as the tethered unsaturation; and a variety of sp2 and sp3-hybridized organozincs, including those that possess β-hydrogens, participated as the nucleophilic component. Substrate structure, organozinc structure, and ligand structure all played a significant role in determining product selectivities. Of particular synthetic significance was the opportunity to prepare either E or Z tri- or tetrasubstituted alkenes from a common alkyne. A discussion of probable mechanisms is provided.

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Substrates that possess an a,b-unsaturated carbonyl tethered to an alkyne have been utilized in a variety of nickel-catalyzed processes. Depending on ligand structure, reagent structure, reaction conditions, and workup conditions, several different monocyclic and bicyclic ring systems may be accessed from a common substrate. Evidence for a nickel metallacycle as a common intermediate is provided.