Catalyst-free reductive cyclization of bis(2-aminophenyl) disulfide with CO2 in the presence of BH3NH3 to synthesize 2-unsubstituted benzothiazole derivatives

Abstract

An efficient and catalyst-free methodology for the reductive cyclization of various disulfides using BH₃NH₃ as a reductant and CO₂ as a C1 resource was developed. The desired 2-unsubstituted benzothiazole derivatives were obtained in good to excellent yields. Moreover, mechanism investigation demonstrated that BH₃NH₃ played an important role in the formation of benzothiazole. As a reducing agent, BH₃NH₃ reduced CO₂ and cleaved the S–S bond of the disulfide efficiently. In addition, the N–H bond of the amino group was also activated by BH₃NH₃. 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 CO₂.