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Dimer involvement and origin of crossover in nickel-catalyzed aldehyde-alkyne reductive couplings.

ABSTRACT: The mechanism of nickel(0)-catalyzed reductive coupling of aldehydes and alkynes has been studied. Extensive double-labeling crossover studies have been conducted. While previous studies illustrated that phosphine- and N-heterocyclic carbene-derived catalysts exhibited differing behavior, the origin of these effects has now been evaluated in detail. Many variables, including ligand class, sterics of the ligand and alkyne, temperature, and ring size being formed in intramolecular versions, all influence the extent of crossover observed. A computational evaluation of these effects suggests that dimerization of a key metallacyclic intermediate provides the origin of crossover. Protocols that proceed with crossover are typically less efficient than those without crossover given the thermodynamic stability and low reactivity of the dimeric metallacycles involved in crossover pathways.

SUBMITTER: Haynes MT

PROVIDER: S-EPMC4277774 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Dimer involvement and origin of crossover in nickel-catalyzed aldehyde-alkyne reductive couplings.

Haynes M Taylor MT Liu Peng P Baxter Ryan D RD Nett Alex J AJ Houk K N KN Montgomery John J

Journal of the American Chemical Society 20141203 50

The mechanism of nickel(0)-catalyzed reductive coupling of aldehydes and alkynes has been studied. Extensive double-labeling crossover studies have been conducted. While previous studies illustrated that phosphine- and N-heterocyclic carbene-derived catalysts exhibited differing behavior, the origin of these effects has now been evaluated in detail. Many variables, including ligand class, sterics of the ligand and alkyne, temperature, and ring size being formed in intramolecular versions, all in ...[more]

PMID: 25401337

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