2-Methylbenzo -thiazole

The rate of the base-catalysed condensation of carbonyl compounds with alkyl groups activated by Jt-deficient aromatic systems is enhanced by the addition of quaternary ammonium salts. For example, 2-methylbenzoxazole, 2-methylbenzo-thiazole and 4-nitrotoluene react with a range of substituted benzaldehydes to produce the corresponding 2-styryl derivatives (62-80%) at room temperature over 1 -2 hours [61, 62]. The intermediate alcohol can also be isolated after a short reaction time. 

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). 

In the middle of the 1950s, Knott reported the synthesis of dyesmffs based on benzothiazole derivatives. Alkylation of Al-methylbenzo-l,3-thiazole-2-thione with a-bromoacetophenone and deprotonation of the resulting thiocarbonylium salt 5 yielded, after spontaneous desulfurization of the intermediate thiirane (7), the alkylidene derivative 8 (18) (Scheme 5.1). In order to rationalize the reaction, thiocarbonyl ylide 6 was proposed as the precursor of thiirane 7. To the best of our... 

Phenols and primary, secondary, and tertiary aromatic amines with free ortho- and/or /wra-positions react readily with thiocyanogen, (SCN)2. SCN enters the position para to the OH or NR2 group, or, if that is occupied, into the orfAtf-position.11,12 In the later case subsequent ring closure may be easy.14,760 For instance, / -toluidine gives 6-methylbenzo[A]thiazole-2-amine, and etyhl / -aminobenzoate gives ethyl 2-aminobenzo[Z ]thiazole-6-carboxylate. 

A range of secondary A-alkylanilines undergo oxidative olefination with 2-alkyl-quinoline, 4-methylquinoline, 1-methylisoquinoline, 2-methylquinoxaline, 2-methyl-quinazoline, 2-methylbenzo[fiG-thiazole, acetophenone, and malononitrile in DMF to form structurally diverse polysubstituted alkenes in moderate to excellent yields with excellent E Z >99 1 selectivity with the use of 2,3-dichloro-5,6-dicyano-l,4-benzoquinone as the oxidant. Mechanistically, the oxidative olefination reaction proceeds through amine oxidation followed by imine olefination." ii... 

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