Studies on Organosulfur Compounds. IX. Selective Cyclization to Benzothiazole by the Reaction between 4-Picoline and meta-Substituted Anilines under the Modified Willgerodt-Kindler Reaction

Abstract

In order to clarify in more detail the cyclization of thioanilide to benzothiazole under the modified Willgerodt-Kindler reaction conditions, 4-picoline was heated with metasubstituted anilines (I) in the presence of sulfur and the reaction also gave thioanilides and one of the two possible benzothiazoles. The latter was proved to have the structure of 5-substituted 2-(4-pyridyl) benzothiazoles (III) by independent synthesis. On the other hand, the expected two isomeric benzothiazoles (III and IV) were obtained from the oxidative cyclization of thioanilides by the modified Jacobson reaction.