Hexafluoroisopropanol (HFIP)-Promoted Hydrodifluoroalkylation of Furans and Vinyl Ethers Using Difluorinated Silyl Enol Ethers for the Synthesis of gem-Difluorinated Ethers

A hexafluoroisopropanol (HFIP)-promoted hydrodifluoroalkylation of furans and vinyl ethers with difluorinated silyl enol ethers has been developed. Because of the inherent electron richer nature of furans and the poor nucleophilicity of difluorinated silyl enol ethers, the employment of simple furans as the substrates for nucleophilic dearomatization without a metal or stoichiometric chemical oxidizing reagent is challenging, especially considering the rearomatization driving force and ring fragmentation of the furan ring system. This protocol exploits the formation of oxocarbenium intermediate from furans using HFIP as a proton source to allow the nucleophilic addition of difluorinated silyl enol ethers, which provides an efficient synthetic strategy to install a gem-difluorinated group into heterocycles.