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Regioselective Synthesis of α,α-Difluorocyclopentanone Derivatives: Domino Nickel-Catalyzed Difluorocyclopropanation/Ring-Expansion Sequence of Silyl Dienol Ethers
- Aono, Tatsuya, Sasagawa, Hisashi, Fuchibe, Kohei, Ichikawa, Junji
- Organic letters 2015 v.17 no.23 pp. 5736-5739
- chemical reactions, ketones, moieties, nickel, regioselectivity, silyl enol ethers
- Silyl dienol ethers prepared from α,β-unsaturated ketones underwent nickel-catalyzed difluorocyclopropanation of the electron-rich alkene moiety with trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate. The subsequent vinylcyclopropane–cyclopentene rearrangement afforded silyl 5,5-difluorocyclopent-1-en-1-yl ethers in good yields. The obtained five-membered silyl enol ethers were demonstrated to be versatile intermediates for the synthesis of di- and monofluorinated cyclopentanones and cyclopentenones. A nickel difluorocarbene complex is proposed as a key intermediate in the difluorocyclopropanation.