Isomerisation reaction of a gem-bis-trifluoromethyl olefin in a basic medium: a kinetic study

The rearrangement of 5-phenyl-1,1,1-trifluoro-2-(trifluoromethyl)pent-2-ene to 5-phenyl-1,1,1-trifluoro-2-(trifluoromethyl)pent-3-ene has been studied by 19F NMR in dimethylsulphoxide (DMSO). This isomerisation is catalysed by a base such as triethylamine. It is apparent that the olefin is more stable when the two trifluoromethyl groups are placed on a saturated carbon rather than on a vinylic carbon. In the isomerisation process, the part of triethylamine is to assist the intramolecular hydrogen transfer to give the more stable isomer.