Biphenylenes. Part XXIII. Synthesis of octafluorobiphenylene and its conversion into heptafluoro-1-and heptafluoro-2-methoxybiphenylene

Abstract

Octafluorobiphenylene has been prepared by the pyrolysis of tetrafluorophthalic anhydride at 750°/0.6 ± 0.1 mm. Reaction of the biphenylene with sodium methoxide gave mixtures containing mono- and polymethoxypoly-fluorobiphenylenes. Treatment of the biphenylene with potassium hydroxide followed by diazomethane gave heptafluoro-1- and heptafluoro-2-methoxybiphenylene. The structure of the latter (and hence of the former) was shown by a detailed ¹⁹F n.m.r. study. The orientations of both isomers are confirmed by the ¹H n.m.r. spectra. The ¹⁹F n.m.r. spectrum of octafluorobiphenylene is discussed.