Rhodium-Catalyzed Asymmetric Arylation/Defluorination of 1‑(Trifluoromethyl)alkenes Forming Enantioenriched 1,1-Difluoroalkenes

The reaction of 1-(trifluoromethyl)­alkenes (CF₃CH=CHR) with arylboroxines (ArBO)₃ in the presence of a chiral diene-rhodium catalyst gave high yields of chiral 1,1-difluoroalkenes (CF₂=CHC*HArR) with high enantioselectivity (≥95% ee). The reaction is assumed to proceed through β-fluoride elimination of a β,β,β-trifluoroalkylrhodium intermediate that is generated by arylrhodation of the 1-(trifluoromethyl)­alkene.