Polyhalogeno-allenes and -acetylenes. Part 14. The reactions of perfluoro-1,2-dienes with dichloro- and difluoro-carbene, and a new route to 1,1-dichloroperfluoro-1,2-dienes

Abstract

Perfluoro-1,2-dienes R_F(CF₃)CCCF₂(R_F= CF₃ or n-C₃F₇) react in the gas phase with difluoro- and dichlorocarbene to give methylenecyclopropanes R_F(CF₃)[graphic omitted]CCX₂(R_F= CF₃, n-C₃F₇; X = F, Cl) in good yield by an addition–rearrangement sequence. Pyrolysis of 1-dichloromethylene-3,3-difluoro-2,2-bis(trifluoromethyl)cyclopropane results in extrusion of difluorocarbene and the formation of 1,1-dichloro-4,4,4-trifluoro-3-trifluoromethylbuta-1,2-diene in high yield. This new allene reacts readily with methanol and undergoes efficient Diels–Alder additions to the perfluoroalkyl-substituted double bond.