Thermal reactions of hexafluoro-1,3-butadiene. Part I. Primary products and their thermal transformations

Article abstract of DOI:10.1016/S0022-1139(00)80417-0

Depending on the temperature, the thermal reactions of hexafluoro-1,3-butadiene include intra- and/or intermolecular cycloaddition and give hexafluorocyclobutene, <2+4>- and <2+2>-cycloadducts as primary products.The latter react with hexafluorobutadiene to give its trimers while the <2+2>-cycloadduct, being generated as two isomers, undergoes some thermal rearrangements in addition.Thus, cis-perfluorodivinylcyclobutane is isomerized at 150 deg C to perfluorotricyclo<4.2.0.0^2,5>- and -<3.3.0.0^2,6>octanes together with unstable, easily polymerized, cis,trans-perfluoro-1,5-cyclo-octadiene.The trans isomer is isomerized at 200 deg C to perfluorovinyl-4-cyclohexene and perfluorotricyclo<3.3.0.0^2,6>octane.Possible schemes for the formation of the latter are discussed.Racemic trans,trans-perfluoro-1,5-cyclo-octadiene is argued to be a precursor of perfluorotricyclo<3.3.0.0^2,6>octane in the isomerizations of both the cis- and trans-<2+2>-cycloadducts.