A series of highly fluorinated bicyclo [2.2. 0]-5-hexen-2-ones (3) and their hydrates (4) have been prepared in two steps from hexafluoro Dewar benzene (1). Photolysis of exo-3H- pentafluorobicyclo [2.2. 01-5-hexen-2-0ne (3d) at low pressure in the vapor phase gave 1H- pentafluorocyclopentadiene (€ 9, but in solution the principal product was pentafluorophenol (9). Under Favorskii conditions, exo-3-bromo-and exo-3-chloropentafluorobicyclo-[2.2. 0]- ...
