Cyclopropene chemistry. Part 1. Preparation and some reactions of 3,3-dichloro-1,2-bistrifluoromethyl- and 1,3-dichloro-2,3-bistrifluoromethyl-cyclopropene

Abstract

Both the title compounds may be obtained from the reaction of dichlorocarbene [generated by thermal decomposition of trifluoro(trichloromethyl)silane] with hexafluorobut-2-yne; the 3,3-dichloro-compound is isomerised to the 1,3-dichloro-isomer by heat, light, or chemical catalysis, but conditions are described for the preparation of either pure cyclopropene. Treatment of either isomer with antimony pentafluoride gives solutions containing the chlorobistrifluoromethylcyclopropenium ion. Both isomers undergo free-radical addition of halogens, but the slow reaction of the 1,3-dichloro-compound with trifluoromethyl radicals gives a mixture of products. Diels–Alder reactions of both cyclopropenes with cyclopentadiene or with furan are described, and the 3,3-dichloro-compound gives a high yield of ‘ene’-reaction products with (E)-but-2-ene.