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 RF(CF3)CC
CF2(RF= CF3 or n-C3F7) react in the gas phase with difluoro- and dichlorocarbene to give methylenecyclopropanes RF(CF3)[graphic omitted]C
CX2(RF= 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.