Patent GB-598986-A (GB)
Title: Improvements in or relating to the manufacture of azo dyestuffs
Filed: 1945-07-13
Abstract: Intermediates for azo dyestuffs are prepared by condensing an ester of an acylacetic acid with a 5-aminobenzothiazole derivative containing an alkyl, alkoxy or alkylthio group in the 2-position. The azo dyestuffs may be formed in substance or on the fibre.  The following examples are given: (1) 2-Nitro-4-acetylamino-chloro-benzene is converted to 2,21 - dinitro - 4,41 - diacetylamino - diphenyl disulphide by treatment with sodium polysulphide, reduced to 4-acetylamino-2-aminothiophenol with iron and acetic acid, acetylated, boiled with hydrochloric acid, neutralized with ammonia to separate out the 5-amino-2-methylbenzothiazole, and condensed with acetoacetic ester in boiling chlorobenzene; (2) the 4-acetylamino-2-aminothiophenol obtained as in (1) is condensed with urea, made alkaline with aqueous caustic soda, and the 5-acetylamino-2-oxybenzothiazole precipitated by adding acid. This is dissolved in aqueous alkali and methylated with dimethyl sulphate, saponified, and the 5-amino-2-methoxybenzothiazole formed condensed with acetoacetic ester as in (1).  (3) 2-Nitro - 4 - acetylamino - chlorobenzene is treated with sodium polysulphide and carbon disulphide to produce 5 - acetylamino - 2 - mercaptobenzothiazole which is methylated by means of dimethyl sulphate and saponified to yield 5-amino-2-methylmercapto-benzothiazole.  This is then condensed with acetoacetic ester in the presence of chlorobenzene.  (4) 1-Chloro-2-nitro - 4 - acetylamino - 5 - methoxybenzene is converted in similar manner into 2,21-dinitro-4,41-diacetylamino - 5,51 - dimethoxy - diphenyldisulphide, 5 - methoxy - 4 - acetylamino - 2 - aminothiophenol, 6 - methoxy - 5 - amino - 2 - methylbenzothiazole, 6 - methoxy - 5 - acetoacetylamino - 2 - methylbenzothiazole, 6 - methoxy - 5 - acetylamino - 2 - oxybenzothiazole, 2,6 - dimethoxy - 5 - acetylamino benzothiazole, 2,6 - dimethoxy - 5 - amino benzothiazole, 2,6 - dimethoxy - 5 - acetoacetylaminobenzothiazole, 6 - methoxy - 5 - acetylamino - 2 - ethoxybenzothiazole, 6 - methoxy - 5 - amino - 2 - ethoxybenzothiazole, 6 - methoxy - 5 - acetoacetylamino - 2 - ethoxybenzothiazole, 6 - methoxy - 5 - acetylamino - 2 - mercaptobenzothiazole, 6 - methoxy - 5 - acetylamino - 2 - methyl - thiobenzothiazole, 6 - methoxy - 5 - amino - 2 - methyl - thiobenzothiazole and 6 - methoxy - 5 - acetoacetylamino - 2 - methyl - thiobenzothiazole.  (5) In a similar manner a series of 6-methyl derivatives is obtained from 5 - chloro - 4 - nitro - 2 - acetylaminotoluene.  (6) 6 - Methoxy - 5 - acetoacetyl - amino - 2 - methylbenzothiazole is mixed with a diazoamino compound of diazotized 5 - nitro - o - toluidine with oxyethylanthranilic sulphonic acid, pasted in turkey red oil and caustic soda, thickened with starch and gum tragacanth, and printed on to cotton tissue which is then steamed.  (7) A cotton tissue is printed with a thickened mixture of 6 - methyl - 5 - acetoacetylamino - 2 - methylthiobenzothiazole and the diazoamino compound from diazotized 4 - chloro - o - toluidine and sarcosine.  There may also be used the diazoamino compound obtained from 5-chloro-o-toluidine and sarcosine, p - chloro - o - aminoanisol and sarcosine, and 5-nitro-o-toluidine and oxyethylanthranilic-5-sulphonic acid.  Other amines specified are the nitrosamines, 2,5-dichloro-aniline, m-chloraniline, and o-nitrotoluidine.