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N‑Heterocyclic Carbene-Catalyzed Diastereoselective Vinylogous Michael Addition Reaction of γ‑Substituted Deconjugated Butenolides

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posted on 2015-12-18, 00:00 authored by Hao Guo, Fen Xing, Guang-Fen Du, Kuo-Wei Huang, Bin Dai, Lin He
An efficient N-heterocyclic carbene (NHC)-catalyzed vinylogous Michael addition of deconjugated butenolides was developed. In the presence of 5 mol % of the NHC catalyst, both γ-alkyl- and aryl-substituted deconjugated butenolides undergo vinylogous Michael addition with various α, β-unsaturated ketones, esters, or nitriles to afford γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary carbon centers in good to excellent yields with excellent diastereoselectivities. In this process, the free carbene is assumed to act as a strong Brønsted base to promote the conjugate addition.

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