Synthesis of new 5-thiazolyl azo-disperse dyes for dyeing polyester fabrics

Diazotized aryl amines were coupled with 2-aminothiazoles 1 and 2 to give the corresponding thiazolylazo dyes 3 and 4, respectively. 2-Amino-5-arylazothiazoles 5 reacted with chloroacetyl chloride to afford the chloro-acetamide derivatives 6 which further reacted with 2-mercaptobenzothiazole to furnish a new series of 5-arylazothiazolyl dyes 7. The azo structure of the dyes (rather than the tautomeric hydrazo structure) was assessed by ab initio DFT calculations at the B3LYP/6-31G* level. These dyes were applied to polyester fabric as disperse dyes and their fastness properties were evaluated.