Other Type B Syntheses

Other Type B Syntheses.—The prolonged interaction of 2-picoline with meta-substituted anilines in the presence of sulphur at 170 °C under Wiligerodt-Kindler conditions gives, apart from the thioanilides (18), only one of the two possible isomers, namely 5-substituted benzothiazoles (19), the structure of which was confirmed by their unequivocal synthesis from (20). In contrast, both isomers (19) and (21) are obtained by the oxidative cyclization of the thioanilides (18) by the modified Jacobson reaction the two reactions clearly occur by distinct mechanisms.  

5-AryIimino-4-methyl-l,2,3,4-thiatriazoles (22), obtainable by methylation of the parent heterocycles with diazomethane, undergo ring contraction at 120—130°C, with loss of nitrogen, to afford the corresponding benzothiazoles (23) in 50% yield.  

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Other Type B Syntheses.— The interaction of 2-picoline with 3-substituted anilines in the presence of sulphur under Willgerodt-Kindler conditions, reported... 

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