Fluorinated Dialkyl Chloronium Salts: Synthesis and Reactivity for Fluoroalkylation and Hydride Abstraction.

A new concept for the synthesis of dialkyl chloronium cations [R-Cl-R] is described (R=CH, CHCF), that allows the formation of fluorinated derivatives. By utilizing the xenonium salt [XeOTeF][M(OTeF)] (M=Sb, n=6; M=Al, n=4) chlorine atoms of chloroalkanes or the deactivated chlorofluoroalkane CHClCF are oxidized and removed as ClOTeF leading to the isolation of the corresponding chloronium salt. Since the resulting highly electrophilic cation [Cl(CHCF)] is able to alkylate weak nucleophiles, this compound can be utilized for the introduction of a fluorinated alkyl group to those. In addition, the fluorinated alkyl chloronium cation displays a high hydride ion affinity, enabling the activation of linear hydrocarbons by hydride abstraction even at low temperatures ultimately leading to the formation of branched carbocations.