Study of Hydrazone-Hydrazoimine Tautomerism in α-Azo-6-ketomethylphenanthridines

AB Azo-coupling of a series of 6-ketomethylphenanthridines products was performed starting from 6-ketomethylphenanthridines and benzene diazonium chloride. The products were characterised using 1H, 13C and 15N NMR, IR,UV and MS spectroscopic methods. The hydrazoimine forms were the only tautomer present in chloroform solution. Two rotamers were detected in chloroform solutions of the compounds studied. Analysis of the NMR data shows that the ratio of rotamers depends on electron-donating and electron-withdrawing properties of the substituent present in the benzene ring