Perfluoroalkyl derivatives of nitrogen. Part XXVI. The preparation and rearrangement of polyfluorovinylamines and of trifluoromethyl trifluorovinyl ether

Abstract

The flow pyrolysis of perfluoro-(1-dimethylamino-2-methoxycyclobutane) at 600°, low pressure (1–2 mm.), and a contact time of ca. 1 sec. gives perfluoro-(NN-dimethylvinylamine)(76%), perfluoro-2-azapent-2-ene (21%), trifluoromethyl trifluorovinyl ether (22%), and pentafluoropropionyl fluoride (54%). Similar pyrolysis of perfluoro-(1,2-bisdimethylaminocyclobutane) also gives the first two compounds (78 and 17%, respectively). The pyrolysis of bi(perfluoro-2-methoxycyclobutyl) gives more complex products, which include tetrafluoroethylene, perfluorocyclobutene, perfluoro-1,3-butadiene, trifluoromethyl trifluorovinyl ether, and pentafluoropropionyl fluoride. Pyrolysis of perfluoro-(NN-dimethylvinylamine) or of trifluoromethyl trifluorovinyl ether gives perfluoro-2-azapent-2-ene (55%) and pentafluoropropionyl fluoride (67%), respectively. The rearrangement of the vinylamine probably occurs by two mechanisms (mainly intramolecular and partly radical), since pyrolysis with a large excess of toluene gives the rearranged azapentene in lower yield (46%) and fluoroform (31%). The vinylamines (CF₃)₂N·CF:CF₂, (CF₃)₂N·CF:CHF, (CF₃)₂N·CH:CF₂, (CF₃)₂N·CBr:CF₂, and (CF₃)₂N·CF:CFCl are formed in high yield (generally >90%), from the reactions of suitable olefins with N-bromobistrifluoromethylamine followed by dehydrohalogenation or dehalogenation reactions. Pyrolysis of the chlorovinylamine (CF₃)₂N·CF:CFCl gives the rearrangement product CF₃·N:CF·CFCl·CF₃(51%) and chlorotrifluoromethane.

Irradiation of perfluoro-(NN-dimethylvinylamine) with hydrogen bromide gives the 1:1 adduct (CF₃)₂N·CHF·CF₂Br (99%), which indicates exclusive initial radical addition to the CF₂ group of the vinylamine.