Esters 2-methylbenzothiazole

The thioanilides of a -cyanomalonic ester (520), which exist preferentially in their enethiol form, are cyclized by bromine to benzothiazolines (521) which can be decarboxylated to the corresponding 2-methylbenzo thiazoles (522 Scheme 282) (69CB351). 2-Bromo- or 2-chloro-thioacetanilides (523) undergo an intramolecular displacement of halogen on treatment with sodium hydride in TV-methylpyrrolidone or sodium methoxide in DMF, to give a correspondingly substituted 2-methylbenzothiazole (522 Scheme 283) (76S730). 

We also were successful in applying the alkyl nitrate nitration to TT-deficient heterocyclic compounds such as 2- and 4-meth-ylpyridines, 4-methyl pyrimidine, and to ir-excessive heterocyclics such as 2-methylbenzoxazole and 2-methylbenzothiazole (15). Both sodium and potassium amides in liquid ammonia were found to be effective as bases. In the KNH2-JI.NH3 system optimum yields are obtained if the molar ratio of base to substrate to nitrate ester is 2.0 1.0 2.5. After allowing 2-3 minutes for anion formation the nitrate ester is added as rapidly as possible while maintaining the temperature below -33°. Next the ammonia is replaced with ether and the nitro salt filtered off and acidified with aqueous acetic acid. 

Trimethylsilyl-l-cyclopentene, 509-510 Trimethylsilyldehalogenation, 514 a-Trimethylsilyl esters, 515 2-Tiimethylsilylethanol, 510-511 /3-Trimethylsilylethyl chloroformate, 471 Trimethylsilylethyl esters, 510 a-Trimethylsilyl ketones, 246 Trimethylsilyllithium, 197,514 a-Trimethylsilyl-2-methylbenzothiazole,... 

Kiprianov (1957) studied the relative rates of formation of quaternary salts of 2-methylbenzothiazole with methyl iodide, methyl sulfate, and methyl esters of sulfonic acids and p-nitrosulfonic acids. He found that the reaction with methyl 2-nitrobenzenesulfonate was six times faster than that with Me2S04, while the methyl esters of the 2,3- and 2,4-dinitrobenzenesulfonic acid reacted sixty times more rapidly than did Me2S04. Such esters afford a method for very mild alkylation of very weak bases (Kip>rianov Tolmachev 1957). 

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