Isothiazole, 3-aryl-5-methyl-, reaction

Recently, Schulze and coworkers synthesised a group of (2-aryl-4,5-diphenyl)isothiazol-3-ylidenes (see Figure 6.11) by deprotonation of the respective isothiazolium perchlorates with Bu OK as base [37], The compounds are yellow solids that dimerise readily and show typical carbene reactions like insertion into NH bonds. The tendency to dimerise follows the known electronic properties of substituents on the phenyl ring on nitrogen (< -methyl [Pg.317]

Diamino-3-methylisothiazole (178) (R = Me) on reaction with diethoxymethyi acetate gives a low yield of 3-methylimidazo[4,5-rf]isothiazole (179) (R = Me, R = H). The diamines (178) (R = H, Me) readily cyclize with thiocarbonyldimidazole to yield after methylation the 5-methyl-thioimidazo[4,5-f/]isothiazoles (179) (R = H, Me R = MeS) <93JHC1379>. Nonaqueous diazo-tization converts methyl 4-amino-3-arylisothiazolecarboxylates to the desamino and halo compounds (180) (X = H, Cl, Br, I). When the aryl group is 3-methoxyphenyl the isothiazole[4,3-... 

Reaction of 2-alkyl/aryl isothiazol-3(2//)-thiones 90 with various alkyl-halogenides gave the 3-iS -alkyl-substituted isothiazolium salts 25a,91 in good-to-very-good yields (70BSF3076, 73CJC3081, 93JHC929, Scheme 29). Several isothiazolium iodides 25a,91a-n, perchlorate 25a and chlorides 91o-v were also synthesized. The structure of 2-methyl-5-aryl-isothiazolium chloride 91q, isolated in 60% yield, was confirmed by X-ray analysis. The S-alkylated isothiazolium salts 25a,91 with yields and references are represented in Table 5. 

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