Process for preparing an azo compound from a 2-aminothiazole diazo component

#The present invention relates to an improved process for preparing thiazolazo compounds.

#Thiazolazo compounds from 2-aminothiazoles are used to a large extent as disperse and cationic dyestuffs as well as pharmaceutical products.

#The preparation of these compounds is effected in the way that 2-aminothiazoles are diazotized, coupled with suitable coupling components and the dyestuffs obtained are quarternized, if desired, or that 2-aminothiazoles are used as coupling components.

#The following Examples illustrate the invention. Parts and percentages are by weight unless stated otherwise.

#a. 22,8 Parts of thiourea were introduced into 120 parts by volume of glacial acetic acid. At 40.degree.-50.degree. C. 52.3 parts of a 45% aqueous chloroacetaldehyde solution were added dropwise to this suspension, stirring was continued for 2 hours at 40.degree.-50.degree. C. and the whole was cooled to 0.degree. C. Into this solution containing 2-amino-thiazole 72 parts of a 42.3% nitrosyl-sulfuric acid were introduced at 0.degree. to 5.degree. C., while stirring well, stirring was continued for 30 - 60 minutes with a constant excess of nitrile, and subsequently the excess of nitrite was destroyed with amidosulfonic acid. At 0.degree. to 20.degree. C. a solution of 53 parts of 3-methyl-phenylmorpholine in 60 parts by volume of glacial acetic acid was introduced into the yellow clear diazo solution, stirring was continued for 1 hour at 25.degree. C., and the reaction batch was poured onto 1500 parts of ice water. The pH-water was adjusted to 3 with aqueous sodium hydroxide solution. The precipitated crystalline dyestuff was suction-filtered and washed well with water. After drying at 60.degree. C., 66 parts of dyestuff of the formula ##STR5## was obtained, which is suitable for dyeing polyesters. b. 29 Parts of this dyestuff were dehydrated azeotropically with 300 parts by volume of toluene, then clarified with charcoal and kieselguhr. The filtrate was mixed with one part of magnesium oxide. While stirring, a solution consisting of 10 parts by volume of dimethyl sulfate and 25 parts by volume of toluene were added dropwise at 80.degree.- 90.degree. C. Stirring was continued for about 7 hours until the quarternation was finished at 80.degree.-90.degree. C. The crystalline dyestuff was suction-filtered and washed well with toluene.

#After drying 39 parts of dyestuff of the formula ##STR6## were obtained which dyed acid modified polyacrylnitrile fibres in brilliant violet shades having excellent coloristical fastness properties.