Polyfluoroarenes. Part XV. Diazo-oxides and related compounds

Abstract

Pentafluoronitrobenzene reacts with potassium hydroxide in t-butyl alcohol to give mainly tetrafluoro-2-and tetra-fluoro-4-nitrophenol, with traces of trifluoro-4-nitroresorcinol. Reduction of each of the major products with tin and hydrochloric acid gives the corresponding aminophenol, which yields 1-diazotetrafluorobenzene 2-oxide or 1-diazotetrafluorobenzene 4-oxide on treatment with sodium nitrite in aqueous 70% sulphuric acid. Photochemical or thermal decomposition of the 1,2-diazo-oxide in benzene gives 2,3,4,5-tetrafluoro-6-hydroxybiphenyl, and thermal decomposition of the 1,2-diazo-oxide in benzonitrile, acetonitrile, or phenyl isothiocyanate yields 4,5,6,7-tetrafluoro-2-phenylbenzoxazole, 4,5,6,7-tetrafluoro-2-methylbenzoxazole, or 4,5,6,7-tetrafluoro-2-phen-ylimino-1,3-benzoxathiole, respectively. The benzoxazoles may also be obtained from 2-aminotetrafluorophenol and benzoyl chloride or acetic anhydride.