Cyclopropane chemistry. Part III. Thermal decomposition of some halogenopolyfluorocyclopropanes

Abstract

Thermal decomposition of pentafluoro-, perfluoro(methyl)-, 1,1-dichlorotrifluoro(trifluoromethyl)-, bromopentafluoro-, iodopentafluoro-, 1,2-dichlorotetrafluoro-, 1-chloro-1,2,2,3-tetrafluoro-, and 1,1,2-trifluoro-2-trifluoromethyl-cyclopropane, at temperatures in the range 170–250° in glass vessels, is described. The first three compounds decompose exclusively via the elimination of difluorocarbene, the last undergoes exclusive rearrangement to an olefin, and the remainder display both types of behaviour. The cyclopropanes were prepared from the appropriate olefins and either difluorotristrifluoromethylphosphorane or trifluoro(trichloromethyl)silane, or by reduction of a dichlorocyclopropane with tributyltin hydride. Application of this last method to 1,2-dichloro-tetrafluorocyclopropane gave cis- and trans-1,1,2,3-tetrafluorocyclopropane; the preparation of 3-chloro-1,1,2-trifluoro-2-trifluoromethylcyclopropane from 1,1-dichlorotrifluoro(trifluoromethyl)cyclopropane is also described.