2-(2-Sulfo-4-nitrostyryl)-5-aminobenzenesulfonic acid diazo, and 4-Hydroxynaphthalene-1-sulfonic acid coupling, and then in the presence of copper sulfate its into three thiazole structure of compounds, and the method will be reduced to amino Nitro. The product diazo, and 5-Amino-7-ehtoxy-2-naphthalenesulfonic acid coupling, again diazo, in alkaline conditions and 4-Hydroxy-7-(phenylamino)naphthalene-2-sulfonic acid coupling.
