Lewis Acid Promoted Single C–F Bond Activation of the CF3 Group: SN1′‐Type 3,3‐Difluoroallylation of Arenes with 2‐Trifluoromethyl‐1‐alkenes

Activation of the sp3 C−F bond in 2‐trifluoromethyl‐1‐alkenes was accomplished through treatment with a Lewis acid. In the presence of an equimolar amount of EtAlCl2, the (trifluoromethyl)alkenes readily underwent an SN1′‐type reaction with arenes through a Friedel–Crafts‐type mechanism via elimination of a fluoride ion to afford 3,3‐difluoroallylated arenes in good yields. This selective activation of one C−F bond of the CF3 group provides a synthetic method for accessing biologically and synthetically important 1,1‐difluoro‐1‐alkenes. A clean break: C−F bond activation in 2‐trifluoromethyl‐1‐alkenes was accomplished through treatment with a Lewis acid. In the presence of EtAlCl2, the (trifluoromethyl)alkenes readily undergo elimination of a F− ion and SN1′‐type reaction with arenes through a Friedel–Crafts‐type mechanism to give 3,3‐difluoroallylated arenes in good yields. This selective activation of just one sp3 C−F bond of the CF3 group provides facile access to 1,1‐difluoro‐1‐alkenes.