Defluoroalkylation of sp3 C-F Bonds of Industrially Relevant Hydrofluoroolefins

A simple, one-pot procedure is reported for the selective defluoroalkylation of trifluoromethyl alkene derivatives with aldehydes and ketones. The reaction sequence allows construction of a new C-C bond in a highly selective manner from a single sp(3) C-F bond of a CF3 group in the presence of sp(2) C-F bonds. The scope incorporates industrially relevant fluorocarbons including HFO-1234yf and HFO-1234ze. No catalyst, additives or transition metals are required, rather the methodology relies on a recently developed boron reagent. Remarkably, the boron site of this reagent plays a dual role in the reaction sequence, being nucleophilic at boron in the C-F cleavage step (S(N)2') but electrophilic at boron en route to the carbon-carbon bond-forming step (S(E)2'). The duplicitous behaviour is underpinned by a hydrogen atom migration from boron to the carbon atom of a carbene ligand.