CARBENE CHEMISTRY. PART 13 . PREPARATION OF SOME FLUOROALLENES BY A CARBENE ROUTE, AND THE REACTION OF ALLENES WITH HALOGENOCARBENES

Article abstract of DOI:10.1016/S0022-1139(00)85226-4

Fluoroallene and 1,3-difluoroallene are prepared in good overall yield by the addition of dichlorocarbene to vinyl fluoride and 1,2-difluoroethylene respectively, followed by pyrolysis of the dichlorocyclopropanes and treatment of the resulting dichloropropenes with zinc.Pyrolysis of 1,1-dichloro-2-fluorocyclopropane over zinc gives fluoroallene directly.The reaction of allene with 2,2,3-trifluoro-3-trifluoromethyloxiran at 180 deg C as a source of difluorocarbene gives both 1,1-difluoro-2-methylenecyclopropane and its rearrangement product 1-(difluoromethylene)cyclopropane, the latter reacting more readily with a second difluorocarbene to give 2,2,3,3-tetrafluorospiropentane.In an analogous way, fluoroallene reacts with dichlorocarbene, generated from trifluoro(trichloromethyl)silane at 140 deg C, to give E- and Z-1,1-dichloro-2-(fluoromethylene)cyclopropane, 1-(dichloromethylene)-2-fluorocyclopropane, and 2,2,3,3-tetrachloro-4-fluorospiropentane.