Regioselective Synthesis of α,α-Difluorocyclopentanone Derivatives: Domino Nickel-Catalyzed Difluorocyclopropanation/Ring-Expansion Sequence of Silyl Dienol 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.

Platinum-catalyzed nucleophilic addition of vinylsilanes at the beta-position.

In the presence of catalytic amounts of PtCl(2) and metal iodides, beta-substituted vinylsilanes reacted with aldehydes at the beta-position to give allyl silyl ethers. The Pt-catalyzed addition to aromatic aldehydes proceeded efficiently in the presence of LiI. The combined use of PtCl(2) and MnI(2) was found to be effective in addition to aliphatic aldehydes.