2.1- Benzisothiazole 7- nitro

Fig. 1. HeterocycHc amines usedia azo dyes, (a) 2-Amino-6-nitrohenzothiazo1e [6285-57-0], (b) 3-amiao-5-nitro-2,l-benzisothiazole [14346-19-1], (c) 3-amiQo-4JT-l,2,4-triazole [65312-61 -0], (d) 5-amiQo-l,2,4-thiadiazole [7552-07-0, (e) 4,4 -diamiQo-2,2 -biphenylsulfone [6259-19-4], (f)...

Couplers which form scarlet dyes with 4-nitroani1ine and red dyes with 2-amiQO-6-nitrobenzothiazole yield blue dyes with 3-amiQo-5-nitro-2,l-benzisothiazole [14346-19-1]. 

Nitration of 1,2-benzisothiazole gives equal quantities of the 5- and 7-nitro compounds (72AHC(14)43> (see Section 4.02.3.2), as also do the 3-methyl (71JCS(C)3994, 80JCR(2)197> and... 

Nitro-1,2-benzisothiazoles are readily reduced to the amines (72AHC(14)43, 80JCR(S)197), as is 6-nitrosaccharin (69JHC745). When 5-nitro-2,l-benzisothiazole is treated with hydroxyl-amine, it is aminated at the 4-position (80JHC537). 

Cyanoacetyl-5-nitro-l,2-benzisothiazole loses carbon dioxide on heating to give the 3-cyanomethyl compound (79JCR(S)395). 3-Hydroxyisothiazole gives 3-chloroisothiazole on... 

Other heterocycles which have received attention include the aminoisothiazoles and the 3-amino-2,l-benzisothiazoles. The former compounds give rise to bluish-red dyes or reddish-blue dyes if substituted by a nitro group but they have been of little commercial interest. However, dyes derived from 3-amino-6-nitro-2,l-benzisothiazole (69MI11200), such as structure (50), are blue to greenish-blue and have achieved commercial status. Dyes... 

Amino-5-nitro-2,l-benzisothiazole is manufactured by thiolysis of 2-amino-5-nitrobenzonitrile and oxidative ring closure. With aniline coupling components, shades from navy to greenish blue are obtainable (e.g., 28 and 29). 

Ricci and co-workers28 found that nitrogen of 1,2-benzisothiazole (1) with potassium nitrate and sulfuric acid at 0° afforded a mixture of the 5-nitro compound (28) and the 7-nitro derivative (29). The... 

Gabriel and co-workers96,97 first prepared 2,1-benzisothiazole ( thioanthranil ) (2) in the 1890 s. Reduction of o-nitro-a-tolene-thiolcarbamate (63) or o-nitro-a-toluenethiol (64) with stannous chloride and hydrochloric acid yielded a crystalline solid which, on... 

The thiol (64) also yields 2,1-benzisothiazole on treatment with concentrated potassium hydroxide solution 2 in this case most of the thiol is oxidized to the disulfide (65) and the yield of product (2) is low.98 It was later found that o-nitro-a-toluenethiolacetic acid (66) undergoes a similar reaction with sodium hydroxide solution the yield of product (2) is however very small (less than 10%).99... 

The introduction of substituents into the position 3 does not change the reaction course [165, 167-169], 4-Amino-7-nitrobenzisothiazole in the sulfuric-nitric mixture forms 5,7-dinitro derivative in low yield [170], 4-Chloro-7-nitro-l,2-benzisothiazole was obtained as a result of the nitration of 4-chloro-l,2-benzisothiazole [171,172], 5-Hydroxy-l,2-benzothiazole is nitrated to the position 4, and in case of 5-hydroxy-4,6-dibromo-l,2-benzisothiazole a substitutive nitration to form 5-hydroxy-6-bromo-4-nitro isomer occurs [173],... 

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