Novel symmetrical and asymmetrical disaryl hydrazono sulphur-containing direct dyes as possible alternatives for benzidine-based dyestuffs

Two novel series of disaryl azo 2-(thiadiazin-2-yl)-1,2,4-benzothiadiazine-based direct dyes have been synthesized. The produced dyes, being accommodating solubilizing functions, are likely to undergo oxidation and/or hydrolysis to soluble metabolites thus ensure lack of carcinogenicity and in turn, might satisfy the basic requirements for a satisfactory replacement of the prohibited benzidine-based dyes.The assigned structures for the hitherto prepared dyes were confirmed on the basis of elemental analysis and spectral data and, whenever possible, by alternative synthetic routes. Moreover, the predominant tautomeric forms for these highly colored dyes were tested and discussed on the basis of different spectral investigations.