Copper-Catalyzed Synthesis of 2-Amino-benzothiazoles

Significance

The synthesis of N-substituted 2-aminobenzothiazoles by the copper(I)-catalyzed addition-cyclization reaction of 2-haloanilines and isothiocyanates is reported. The reaction is carried out under ligand-free conditions and the best results are obtained using CuI as a catalyst and K₂CO₃ as a base. The reaction proceeds well with electron-rich isothiocyanatobenzenes and in moderate yields with electron-deficient isothiocyanatobenzenes and benzoyl isothiocyanates. It is also successful with 2-bromoanilines and 2-bromo­pyridines. A mechanism involving a nucleophilic attack of the 2-haloaniline nitrogen onto the isothiocyanate followed by a ring closure under copper catalysis is proposed without evidence.