Remote Fluorination of α,β-Unsaturated Carbonyls via Silyl Dienol Ethers

We report a general, regioselective, and metal free γ-fluorination of α,β-unsaturated carbonyls via silyl dienol ethers that are readily prepared from simple ketones and aldehydes. The transformation displays broad scope including 27 cyclic and acyclic siloxydienes providing γ-fluoro compounds in 28-91 % yield. Notably, the reported conditions are also suitable for the synthesis of challenging tertiary fluorides. The regioselectivity of the reaction was studied on a series of acyclic siloxydienes and was observed to be sensitive to the conformational flexibility of the substrate. Diversification of the γ-fluorocarbonyls demonstrates the promise of fluorine as a stereocontrol element.