Synthesis of Organosulfur Compounds. VIII. Cyclization Products from the Modified Willgerodt-Kindler Reaction

Abstract

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