Cyclisations with hydrazine and its derivatives. Part IV. 9-Arylazophenanthrenes and related reduction products from reactions of biphenyl-2,2′-dicarbaldehyde with arylhydrazines

9-Arylazophenanthrenes are the main end products (yields up to ca. 90%) from condensation and cyclisation reactions in organic solvents between biphenyl-2,2′-dicarbaldehyde and arylhydrazines. 9-Phenylazophenanthrene, thus obtained with phenylhydrazine, is converted by various reducing agents into 9-phenanthrylamine or into N-9-phenanthryl-N′-phenylhydrazine, which readily rearranges to give dibenzo[a,c]carbazole or 10-(o-aminophenyl)-9-phenanthrylamine. Reductants for 9-phenylazophenanthrene include phenylhydrazine; use of this leads mainly to the dibenzocarbazole, which consequently may be a by-product in preparations of the azo-compound.