Organofluorine chemistry: principles and commercial applications

Abstract

A new stable equivalent of the trifluoromethyl anion has been synthesized from fluoroform. It reacts with nonenolizable carbonyl compounds such as the Ruppert's reagent. The number of new organofluorine compounds appearing every year 1 is steadily growing because of the unique properties of these products. 2 Among them, trifluoromethyl-substituted molecules are of huge interest for different applications. 3 At present, many reliable methods are available to introduce a CF 3 moiety into organic substrates 4 but the nucleophilic strategy is one of the most popular. Nevertheless, the very unstable-CF 3 anion must be stabilized, for example, by dispersing the negative charge into remote orbitals in order to avoid its dissociation into fluoride anion and difluorocarbene (Scheme 1). Presently, the commercial Ruppert's reagent (CF 3 SiMe 3) is the best tool that fulfills this requirement. Under fluoride activation, it behaves as a-CF 3 equivalent, even at lower temperature. 5 However, its synthesis is rather tricky and starts from CF 3 Br which is now banned for environmental reasons. These reasons prompt us to investigate new reagents for the nucleophilic trifluoromethylation. It has been previously shown that the deprotonation of fluoroform by a strong base in DMF leads to a-CF 3 anion which is stabilized by trapping with DMF. The resulting adduct is rather stable when formed in situ and can act as a-CF 3 reservoir (Scheme 2). 6,7 (1) Schofield, H.