From C1 to C3 : Copper-Catalyzed gem-Bis(trifluoromethyl)olefination of α-Diazo Esters with TMSCF3.

A Cu-catalyzed gem-bis(trifluoromethyl)olefination of α-diazo esters, using TMSCF3 as the only fluorocarbon source, has been developed and provides an exquisite method to access gem-bis(trifluoromethyl)alkenes. This unprecedented olefination process involves a carbene migratory insertion into "CuCF3 " to generate the α-CF3 -substituted organocopper species, which then undergoes β-fluoride elimination and two consecutive addition-elimination processes to give the desired products. The key to this efficient one-pot C1 -to-C3 synthetic protocol lies in the controllable double (over single and triple) trifluoromethylations of the gem-difluoroalkene intermediates.