Catalytic C-F activation via cationic group IV metallocenes

The catalytic cleavage of sp³ C-F bonds of 3,3,3-trifluoropropene (TFP) can be performed using cationic group IV metallocenes and an excess of triisobutylaluminum. The isobutyl adduct 1,1-difluoro-5-methyl-hex-1-ene (DFMH) as well as 3,3-(difluoroallyl)aromates (DFAArs) are formed in different ratios, depending on reaction conditions. The Friedel-Crafts type reaction of TFP and the aromatic solvent represents a new catalytic route toward DFAArs with different substituents (especially electron donors), such as alkyl groups. In-situ FTIR and ¹⁹F NMR spectroscopy were used to gain closer insight into the different defluorination reactions. The influence of the central metal, the ligand structure, the aromatic solvent and the concentration of the reactants was investigated and mechanistic conclusions were drawn.