Reaction of silyl enol ethers with xenon difluoride in MeCN: Evidence for a nonclassical radical cation intermediate

The reactions of xenon difluoride in MeCN solution in Pyrex flasks with a series of TMS enol ethers have been investigated. The types of products formed are dependent on the structures of individual enol ethers, but under these conditions all products are consistent with a mechanism involving single electron transfer to un-ionized XeF2 giving a radical cation and subsequent formation of an alpha-fluoroketone, together with some ketone formation, The results suggest that if the radical cation is particularly stable, fluorodesilylation leads to radical formation, and solvent-derived products are then observed, Using other solvents, such as CFCl3 and C6F6, much more complex mixtures of products are obtained, and this is attributed to a different mode of reaction of xenon difluoride involving ionization to FXe+.