Catalyst-free reductive cyclization of bis(2-aminophenyl) disulfide with CO in the presence of BHNH to synthesize 2-unsubstituted benzothiazole derivatives.

An efficient and catalyst-free methodology for the reductive cyclization of various disulfides using BHNH as a reductant and CO as a C1 resource was developed. The desired 2-unsubstituted benzothiazole derivatives were obtained in good to excellent yields. Moreover, mechanism investigation demonstrated that BHNH played an important role in the formation of benzothiazole. As a reducing agent, BHNH reduced CO and cleaved the S-S bond of the disulfide efficiently. In addition, the N-H bond of the amino group was also activated by BHNH. To the best of our knowledge, this is an unprecedented catalyst-free protocol for the synthesis of 2-unsubstituted benzothiazole from bis(2-aminophenyl) disulfide and CO.