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Catalytic Cyclooligomerization of Enones with Three Methylene Equivalents
- Farley, Conner M., Zhou, You-Yun, Banka, Nishit, Uyeda, Christopher
- Journal of the American Chemical Society 2018 v.140 no.40 pp. 12710-12714
- carbenes, catalysts, migratory behavior, nickel
- Cyclic structures are highly represented in organic molecules, motivating a wealth of catalytic methods targeting their synthesis. Among the various ring-forming processes, cyclooligomerization reactions possess several attractive features but require addressing a unique challenge associated with controlling ring-size selectivity. Here we describe the catalytic reductive cocyclooligomerization of an enone and three carbene equivalents to generate a cyclopentane, a process that constitutes a formal [2 + 1 + 1 + 1]-cycloaddition. The reaction is promoted by a (quinox)Ni catalyst and uses CH₂Cl₂/Zn as the C₁ component. Mechanistic studies are consistent with a metallacycle-based pathway, featuring sequential migratory insertions of multiple carbene equivalents to yield cycloalkanes larger than cyclopropanes.