Convenient Synthesis of Benzothiazoles and Benzimidazoles through Bronsted Acid Catalyzed Cyclization of 2-Amino Thiophenols/Anilines with β-Diketones

Bronsted acid catalyzed cyclization reactions of 2-amino thiophenols/anilines with beta-diketones under oxidant-, metal-, and radiation-free conditions are described. Various 2-substituted benzothiazoles/benzimidazoles are obtained in satisfactory to excellent yields. Different groups such as methyl, chloro, nitro, and methoxy linked on benzene rings were tolerated under the optimized reaction conditions.