Synthesis and spectral properties of azo dyes derived from 2-aminothiophenes and 2-aminothiazoles

A series of thienylazo and thiazolylazo disperse dyes has been prepared from their corresponding coupling components, 2-aminothiophenes and 2-aminothiazole. Depending on the various substituents present in the diazo component, absorption maxima varied from 437 to 534 nm in toluene. The spectroscopic properties of the azo dyes were examined with respect to the effects of 3- and 4-substituents present in the coupling component. Thus, the appropriate Hammett substituent constants could be related to the observed bathochromic shifts in the order CONH2<