Cationic Rhodium(I) Tetrafluoroborate-Catalyzed 　　　　　　　　Intramolecular Carbofluorination of Alkenes 　　　　　　　　　　via the Activation of a Carbon–Fluorine Bond in Acyl Fluorides

C–F bonds of acyl fluorides can be cleaved and added across teth-ered alkenes in the presence of a cationic rhodium(I) tetrafluorobo-rate catalyst. This 1,2-carbofluorination reaction offers a powerful method for the synthesis of tertiary alkyl fluoride derivatives with atom economy of 100%. Mechanistic studies indicate that the concerted action of a rhodium cation and a tetrafluoroborate anion is the key for the success of this catalytic cleavage and formation of C–F bonds in a controlled manner.