Mechanistic investigation of alkene difluorocarbenation catalyzed by hypervalent organobismuth complexes

Mechanism of olefin difluorocarbenation catalyzed by hypervalent organobismuth complex, discovered recently by our research group, has been investigated.[1] Difluorocarbene, the active electrophilic reagent, is generated together with bismuth fluoride complex from bismuth trifluoromethyl complex by an α-elimination process. This reaction is reversible and highly endergonic, favoring the starting bismuth trifluoromethyl complex and disfavoring formation of difluorocarbene, which is generated only in a minimal concentration. However, the low concentration of difluorocarbene prevents side reactions, e.g., difluorocarbene dimerization, and leads to a high efficiency toward the TMSCF3, a stoichiometric source of difluorocarbene. The mechanism is supported by in silico and mechanistic experiments.