Cyclisation with hydrazine and its derivatives. Part V. Condensation products of arylhydrazines with biphenyl-2,2′-dicarbaldehyde and related carbonyl compounds

Biphenyl-2,2′-dicarbaldehyde and phenylhydrazine (2 mol. equiv.) give the bisphenylhydrazone, but equimolar proportions give trans-9,10-dihydro-10-phenylazophenanthren-9-ol (Va), resulting from cyclisation of the monophenylhydrazone. Similar cyclic products are obtained from the dialdehyde with tolyl-, halogenophenyl-, and methyl-hydrazines, but o- or p-nitrophenylhydrazine gives the monoarylhydrazine (III), 2,2′-Diacetylbiphenyl gives mono- and bis-phenylhydrazones. The arylazo-compounds (V) are readily dehydrated to the corresponding 9-arylazophenanthrenes (VI) and they are oxidised by manganese dioxide to the corresponding 10-arylazophenanthren-9-ols (VII), which are also obtained by reaction of the arylhydrazines with 9,10-phenanthraquinone or by acidic treatment of arylhydrazones of 2′-formylbiphenyl-2-carboxylic acid. The mononitrophenylhydrazones (III) gave phenanthrene derivatives of type (VI) with acid but readily gave those of type (VII) with alkali.