Study of hydrazone-Hydrazoimine tautomerism in α-Azo-6-ketomethylphenanthridines

Abstract

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 1 H, 13 C and 15 N 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.

Synthesis and Spectroscopic Properties of New Azo Dyes Derived from 3-Ethylthio-5-cyanomethyl-4-phenyl-1,2,4-triazole

“…The 1 H-NMR spectrum revealed a similar pattern as observed for 3B and 3C (see Experimental). Also, the spectrum do not show any more signals around 4.5 ppm which is usually reported for the methine proton of azo form 5A of the annulated similar compounds [46]. In addition, the 13 C-NMR spectrum of this product in CDCl 3 showed signals in accordance with the mixture of two tautomers, hydrazone form 5B and azo-enamine form 5C .…”