Diversity-oriented synthesis of azo disperse dyes with improved fastness properties via employing Ugi four-component reaction

A novel approach has been established for accessing structurally diverse azo disperse dyes with improved fastness properties by employing an Ugi four-component reaction (Ugi-4CR). The process includes three steps: (1) Ugi-4CR of aniline, cyclohexyl isocyanide, formic acid , and an aromatic aldehyde; (2) selective hydrolysis of amide functionality in the Ugi product; and (3) coupling the hydrolysis product with an aryl diazonium salt. Employing Ugi-4CR herein had advantages over easily controlling the molecular weight/size of the dye. Six new azo disperse dyes were synthesized and their structures were fully characterized by 1 H NMR, 13 C NMR, MS, and FT-IR. It was found that the washing and sublimation fastness properties of the obtained azo disperse dyes on both poly (ethylene terephthalate) (PET) and nylon fibers were remarkably improved as compared with conventional C.I. Disperse Orange 3. The improved fastness properties should be attributed to the moderately increased molecular weight/size and the amide functionality introduced in Ugi-4CR.