Polyhalogenoaromatic compounds. Part VI. Nucleophilic reactions of polyfluoronaphthalenes, NN-disubstituted aminopolyfluoronaphthalene N-oxides, and NN-disubstituted aminopentafluorobenzene N-oxides
Nucleophilic substitution of octafluoronaphthalene by various secondary amines to give 2-mono- and 2,6-di-(NN-disubstituted amino) fluoronaphthalenes is described. Oxidation of the NN-disubstituted 2-aminoheptafluoronaphthalenes to the corresponding N-oxides was readily brought about with performic acid. These N-oxides react with secondary amines (1 mol.) to give, after deoxygenation, 1,2- and 2,3-di-(NN-disubstituted amino)-hexafluoronaphthalenes and with an excess of nucleophile to give 1,2,3-tri-(NN-disubstituted amino)pentafluoronaphthalenes. Hydrazine causes defluorination and deoxygenation of the N-oxides; a mechanism for this reaction is advanced. The products were assigned structures on the basis of their 19F n.m.r. spectra. Reaction of N-pentafluorophenylpiperidine N-oxide with hydrazine likewise results in monodefluorination and deoxygenation as well as cyclisation to a benzimidazole.