Isothiazoles amino

Beckmann rearrangement, 6, 156 Isothiazole, 3-alkoxy-tautomerism, 6, 145 Isothiazole, alkyl-bromination, 5, 58 Isothiazole, 3-alkyl-5-amino-synthesis, 6, 166 Isothiazole, alkylthio-mass spectra, 6, 142 Isothiazole, amino-azo dyes from, 1, 330 tautomerism, 6, 157 Isothiazole, 3-amino-synthesis, 5, 135 tautomerism, 6, 146 Isothiazole, 4-amino-azo dyes from, 6, 175 diazotization, 6, 158 methylation, 5, 95 quaternization, 6, 158 reactions... 

Thieno[2,3-6]indoles synthesis, 4, 1074 Thieno[2,3-d]isothiazole, amino-synthesis, 6, 1016... 

Substituted isoxazoles, pyrazoles and isothiazoles can exist in two tautomeric forms (139, 140 Z = 0, N or S Table 37). Amino compounds exist as such as expected, and so do the hydroxy compounds under most conditions. The stability of the OH forms of these 3-hydroxy-l,2-azoles is explained by the weakened basicity of the ring nitrogen atom in the 2-position due to the adjacent heteroatom at the 1-position and the oxygen substituent at the 3-position. This concentration of electron-withdrawing groups near the basic nitrogen atom causes these compounds to exist mainly in the OH form. 

Isothiazoles with electron-releasing substituents such as amino, hydroxy, or alkoxy in the 3- or 5-position are brominated in high yield in the 4-position. Alkylisothiazoles give lower yields, but 3-methylisothiazole-5-carboxylic acid has been brominated in 76% yield (72AHC(14)1). Again, thiazoles with an electron-releasing substituent in the 2- or 4-position are brominated at the 5-position (79HC(34-1)5). 

Numerous examples of N—S bond formation using oxidative conditions have been described in the literature. A convenient synthesis of isothiazoles involves the direct oxidation of -y-iminothiols and numerous variations have been studied (see Chapter 4.17), The oxidation of the amidine (248) to give the 3-aminoisothiazole (249) illustrates the reaction scheme (65AHC(4)107, 72AHC(14)1), which has been extended to the synthetically useful 5-amino-4-cyano-3-methylisothiazole (251) obtained by oxidation of (250) with hydrogen peroxide (75JHC883). 

The exoeyelie earbonyl group of isothiazol-3-ones absorbs in the region 1610-1660 em <7lJHC59l). 2-Methylisothiazol-3-one itself has the C=0 and C=C bands at 1660 and 1629 em respeetively, in CCI4 solution <64TL1477). The low earbonyl frequeney is due in part to eontributions from the resonanee form (20b). The earbonyl frequeney inereases in sulfoxides (1660-1730 em ) and 1,1-dioxides (1690-1740 em ) where sueh forms are not favourable. Sulfoxides (1060-1190 em ) and sulfones (1330-1360 and 1150-1190 em ) absorb in the regions expeeted (e.g. saeeharin, 1353 and 1162 em ), but resonanee forms related to (13) eause a reduetion of the frequeney of the asymmetrie SO2 vibration to near 1280 em (70CB3166). A similar situation arises in 3-amino-1,2-benzisothiazole 1-oxides. 

One of the best methods of synthesis of isothiazoles is by direct oxidation of y- iminothiols (169) or their tautomers. The reaction is capable of many ramifications and is represented by the general equation shown in Scheme 27. The substituents represent a wide range of groups. Thus, iminothioamides (169 R = NH2) are oxidized to give 3-alkyl-5-aminoisothiazoles (170 = NH2), amidines (169 R = NH2) produce 3-amino compounds,... 

There are many references in the patent literature to azo dyes prepared from 4- and 5-aminoisothiazoles, 3-, 5- and 7-amino-1,2-benzisothiazoles, and their quaternized derivatives. These are particularly useful in the dyeing of synthetic fibres. Isothiazole compounds have also been suggested for other industrial purposes, such as corrosion inhibitors, fireproofing agents, additives in rubber vulcanization, photographic chemicals and fluorescent whiteners in detergents. 

Isothiazole, 5-acetamido-3-alkyl-nitrosation, 5, 59 6, 148 Isothiazole, 5-acetyl-thiosemicarbazone biological activity, 6, 175 Isothiazole, 4-acetyl-5-amino-3-bromo-synthesis, 6, 166 Isothiazole, 4-acetyl-3-methyl-oxime... 

Isothiazole, 5-amino-4-cyano-3-methyI-synthesis, 5, 135 Isothiazole, 5-amino-3-methyI-reactions... 

Naphtho[2,3-h]indolizine-6,l 1-dione, 1, 337 Naphthoisocoumarin synthesis, 3, 831, 832 Naphtho[l,2-c]isothiazole, 3-amino-synthesis, 5, 136 2-Naphthol, l-(2-thiazolylazo)-analytical uses, 6, 328 Naphtholactam, 1, 326 Naphtholactone dyes, 1, 326... 

Amino-isothiazole 5,5-dioxides with different substituents on C-5 could be obtained with various original methodologies already cited (Section II, B, 2). 

Azido-2-formylbenzo[b]-thiophene 613 is thiated and cyclized by 601 and HCl to give benzothieno[3,2-c]isothiazole 614 in 50% yield whereas 613 is reduced on treatment with 601, in the absence of HCl, to give 3-amino-2-formyl-ben-zo[b]thiophene 615 this reacts with excess 601 and HCl to give 3-amino-2-thiofor-myl-benzo[b] thiophene 616 [156] (Scheme 5.50). 

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