Thiazolone 4-methyl

When unsubstituted, C-5 reacts with electrophilic reagents. Thus phosphorus pentachloride chlorinates the ring (36, 235). A hydroxy group in the 2-position activates the ring towards this reaction. 4-Methylthiazole does not react with bromine in chloroform (201, 236), whereas under the same conditions the 2-hydroxy analog reacts (55. 237-239. 557). Activation of C-5 works also for sulfonation (201. 236), nitration (201. 236. 237), Friede 1-Crafts reactions (201, 236, 237, 240-242), and acylation (243). However, iodination fails (201. 236). and the Gatterman or Reimer-Tieman reactions yield only small amounts of 4-methyl-5-carboxy-A-4-thiazoline-2-one. Recent kinetic investigations show that 2-thiazolones are nitrated via a free base mechanism. A 2-oxo substituent increases the rate of nitration at the 5-position by a factor of 9 log... 

From these results it appears that the 5-position of thiazole is two to three more reactive than the 4-position, that methylation in the 2-position enhances the rate of nitration by a factor of 15 in the 5-position and of 8 in the 4-position, that this last factor is 10 and 14 for 2-Et and 2-t-Bu groups, respectively. Asato (374) and Dou (375) arrived at the same figure for the orientation of the nitration of 2-methyl and 2-propylthiazole Asato used nitronium fluoroborate and the dinitrogen tetroxide-boron trifluoride complex at room temperature, and Dou used sulfonitric acid at 70°C (Table T54). About the same proportion of 4-and 5-isomers was obtained in the nitration of 2-methoxythiazole by Friedmann (376). Recently, Katritzky et al. (377) presented the first kinetic studies of electrophilic substitution in thiazoles the nitration of thiazoles and thiazolones (Table 1-55). The reaction was followed spec-trophotometrically and performed at different acidities by varying the... 

NMR spectra of nonlinear optical materials containing nitrobenzothiazole chromophores [785-787], 2-methylamino-5-nitrobenzothiazole [788], 7-alkyl-4-nitrobenzothiazoles [789], 2-chloromethyl-6-nitrobenzothiazole and its sulfonylalky-lation products [790], 2,7-disubstituted 4-nitrobenzothiazole used as antibacterial agents [791], 2-alkyl-5- and 2-alkyl-6-nitrobenzothiazole [792,793], 2-methylmercapto-5-and 2-methylmercapto-6-nitrobenzothiazole [794], l-(P-hydroxyethyl)-6-nitrobenzo-thiazolones-2 [795], 3-methyl- and 4-nitro-6-trifluoromethylbenzothiazolinethiones [796], 2-ethyl-3-methyl-6-nitrobenzothiazolium iodide and tosylate [797], copper(II) complex of N-2-(4-methylphenylsulfamoyl)-6-nitrobenzothiazole [214], and other nitrobenzothiazoles [798-802] have been measured. 

Methyl-4phenyl thiazolon<(2) aiusyliden hydrazon 27 II254. 

MetEyl.thiazolon-(2) 27 1 265, II206. C,H,oN(0) 3-Oxy-3-methyl-butan-trioarbon s4nre-(1.1.2)-dinitril-(1.2)(7) 3 II371. 

CuHnNjSi 4-Methyl-thiazolon-(2).anUiuothiO formyllmid 87 II 206 vgl. die folgende Verbmdung.. ... 

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