Photochemistry of halogenocarbon compounds. Part II. Valence isomers from fluorinated pyridazines

Abstract

para-Bonded species are obtained by irradiation (at 254 or 300 nm) of perfluoroalkylpyridazines under flow conditions. Perfluoro-1,2-diazabicyclo[2.2.0]hexa-2,5-diene derivatives have been isolated in some cases; these are converted into perfluoro-2,5-diazabicyclo[2.2.0]hexa-2,5-diene derivatives by photo- or thermal reactions or in a process catalysed by firebrick. The para-bonded species have also been converted into the corresponding pyrazines; this establishes a new process for 1,3-shifts in an aromatic system. Perfluoro-1,4-diethyl-2,5-diazabicyclo[2.2.0]hexa-2,5-diene is remarkably stable to heat, and t values of this and other valence isomers are discussed.