Selective fluorination of (1R,3S)-(+)-camphoric acid with sulphur tetrafluoride. Preparation of fluorinated optically active derivatives of 1,2,2-trimethylcyclopentane

Abstract

Treatment of (1R,3S)-(+)-camphoric acid ( 1) with sulphur tetrafluoride at ambient temperature gives, in general, three products: 1,2,2-trimethyl-3-trifluoromethyl-1-cyclopentanoyl fluoride ( 2), 2,2,4,4-tetrafluoro-1,8,8-trimethyl-3-oxa-bicyclo[3.2.1] octane ( 3) and camphoroyl difluoride ( 4). The ratio of products strongly depends on the reaction time. Alkaline hydrolysis of ( 2) gives 1,2,2-trimethyl-3-trifluoromethyl-1-cyclopentanecarboxylic acid ( 5), quantitatively. All products exhibit optical activity.