Catalytic C–F activation via cationic group IV metallocenes

• Catalytic C–F bond activation by cationic group IV metallocenes.
• In-situ FTIR analysis of the defluorination reactions.
• Mechanistic conclusions from FTIR traces and product compositions.

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.

The conversion of TFP and the aromatic solvent by either TIBA, TIBA + borate, or TIBA + borate + metallocene proceeds at different max. rates. The speed of the reaction is represented by the image of a snail (very slow), a turtle (slow) and a cheetah (fast).Figure optionsDownload as PowerPoint slide