3- Imino-1,2-benzisothiazole

There are many related examples which are now known as the general Dimroth rearrangement. For example, 3-ethylamino-l,2-benzisothiazole (419) is in equilibrium in aqueous solution with the 2-ethyl-3-imino isomer (420) <72AHCf 14)43). Dimroth rearrangements are known in the 1,2,4-thiadiazole series (421- 422), and in the 1,3,4-thiadiazole series as products of reactions of halogeno-l,3,4-thiadiazoles see Section 4.02.3.9.1 <68AHC(9)165). For a similar example in the 1,2,3,4-thiatriazole series, see Section 4.02.3.1.9. 

From 3-amino 1,2-benzisothiazole 143, salts of 3-amino-1,2-benzisothiazole hydrochloride 144 were obtained by addition of hydrochloric acid followed by heating until equilibrium between the 3-imino-l,2-benzisothiazolium chloride 146 and 3-amino 147 was established. The equilibrium was affected by the solvent, pH and the nature of the substituents R and R2. The 3-nitrosamino benzisothiazole 145 could be easily converted in ether solution with hydrochloric acid at room temperature into hydrochlorides 144 (69CB1961, Scheme 49). 

A-Aryl 3-chloro-l,2-benzisothiazolium chlorides 109 were converted with thio-acetic acid to 3-aryl-imino-l,2-benzdithioles 332. In contrast, N-alkyl salts 109 reacted to form 2-alkyl-l,2-benzisothiazol-3(2//)-thiones 161, which are in equilibrium with 332 (67CB2435, Scheme 110). 

The ammonolysis of 2-substituted 3-chloro-l,2-benzisothiazolium chlorides (146) yields, instead of the expected 3-imino-l,2-benzisothiazolines (151), the isomeric 3-amino-l,2-benzisothiazoles (150). The structures of these compounds were confirmed by their spectral properties, and their isomerization was studied in detail. In suitable solvents, the hydrochlorides (152) of 3-amino-l,2-benzisothiazoles (150) rearrange to the... 

Cl3H18N2O2S, 3-Diisopropylamino-benzisothiazol-1,1-dioxide, 34B, 204 Cl3H18N2O2S2 f 2-(2,6-Dimethylphenyl)imino-3-mesyl-1,3-thiazine, 44B, 361... 

A general synthesis of 2-substituted l,2-benzisothiazolin-3-ones from 2-mer-captobenzoic acid involves esterification, halogenation to the sulphenyl halide, conversion into the sulphenamide, and cyclization with a strong base. The synthesis of 3-oxo-3/f-l,2-benzisothiazole 1-oxides by the action of hydrazoic acid on 2-sulphinylbenzoic acids has been extended (see Vol. 2, p. 579). 2-SuI-phinylbenzamides (48) react with hydrazoic acid in polyphosphoric acid to give 3-imino-3//-l,2-benzisothiazole 1-oxides (49) together with the related 5 functional derivatives of (49), and an unusual alkaline ring-scission to (50), were also described. ... 

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