Synthesis Of Benzothiazoles And Benzimidazoles Catalyzed By Br(?)nsted Acid

Benzothiazole and benzimidazole structural motifs are used as versatile and key synthetic intermediates in medicinal chemistry and agricultural chemistry due to their good antitumor, anticancer, and antimicrobial activities. As a member of this family,2-arylbenzothiazoles and 2-arylbenzimidazoles are very important building blocks of light-sensitive material having a good optical performance. Therefore, the development of novel synthetic method for synthesis of 2-aryl-benzothiazoles and 2-benzimidazoles is always desirable.In this paper, Bronsted acid-catalyzed cyclization reactions of 2-amino thiophenols with aromatic nitriles for synthesis of 2-arylbenzothiazoles and cyclization reactions of 2-amino anilines with aromatic nitriles for synthesis of 2-arylbenzimidazoles are described. The TfOH-catalyzed cyclization reaction proceeds smoothly in the absence of solvent at 120 ℃ for 14 h to afford 2-arylbenzothiazoles in high yields (up to 94%). However,2-arylbenzimidazoles was obtained in only 15% from reaction of 2-amino aniline with aromatic nitrile under same reaction conditions. This reaction has a broad prospect in industrial manufacture because of its good atom economy, simple operation, readily available of starting material.