3- Amino-l,2-benzisothiazoles

Amino-l,2-benzisothiazole is cleaved by nitrous acid to give di-(o-cyanophenyl) disulfide (73SST(2)556). 

Bis-l,2-benzisothiazoline was prepared by Stolle and Merkle34 by treatment of 3-amino-l,2-benzisothiazole with nitrous acid. 

Amino-l,2-benzisothiazoles such as 54 have been claimed22 to possess antiinflammatory, analgesic, and hypotensive properties, while 3-dialkylamino-l,2-benzisothiazoles16 and 3-aryloxy- or 3-arylthio-l,2-benzisothiazoles (55)23 have useful antimycotic activity. 

The exocyclic carbonyl group of isothiazol-3-ones absorbs in the region 1610-1660 cm-1 (71JHC591). 2-Methylisothiazol-3-one itself has the C=0 and C=C bands at 1660 and 1629 cm-1, respectively, in CCLt solution (64TL1477). The low carbonyl frequency is due in part to contributions from the resonance form (20b). The carbonyl frequency increases in sulfoxides (1660-1730 cm-1) and 1,1-dioxides (1690-1740 cm-1) where such forms are not favourable. Sulfoxides (1060-1190 cm-1) and sulfones (1330-1360 and 1150-1190 cm-1) absorb in the regions expected (e.g. saccharin, 1353 and 1162 cm-1), but resonance forms related to (13) cause a reduction of the frequency of the asymmetric S02 vibration to near 1280 cm-1 (70CB3166). A similar situation arises in 3-amino-l,2-benzisothiazole 1-oxides. 

In amidines transamination is possible,especially useful for such purposes are imidoylimid-azolides, e.g. (341 equation 172). In some cases it is usefiil to prepare amidines by ring opening of suitable heterocycles, which can be achieved by treatment with amines or other nucleophilic (basic) compounds. Examples are the synthesis of amidines firom 1,3,5-oxadiazinium salts (342), 3-amino-l,2-benzisothiazoles (343), 2-ethoxycarbonyl-3,l-benzoxazin-4(4//) one (344), 1,2,5-oxa-diazolo[3,4]pyrimidine 1-oxides (pyrimidofuroxans 345) and l,2,4,6-thiatriazenium-5-olate 1,1-dioxides (345) as shown in Scheme 58. 

Amino-l,2-benzisothiazoles were prepared in satisfactory yield by reaction of 2,2 -dithiobis(benzonitrile) with various secondary amines followed by oxidation <978871>. This method was found to be superior to other methods of preparation, which had usually involved nucleophilic displacement of a 3-halobenzisothiazole as the last step. This reaction t)fpically gave moderate yields of aminobenzisothiazole due to the isothiazole s ring lability with nucleophiles. 

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... 

The action of diethyl ethoxymethylenemalonate on 3-amino-l,2-benzisothiazole 1,1-dioxide affords low yields of the 3-aminomethylene-malonate derivative (163), which is converted into (164) by the action of morpholine. The reaction may proceed by the addition of the base to the C=N bond, followed by elimination of diethyl aminomethylenemalonate. ... 

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