A pathway to synthesize 2-methylbenzothiazole derivatives via a hydrogen sulfide promoted tandem reaction of calcium carbide and 2-iodoaniline

Abstract

Benzothiazoles, a significant class of nitrogen- and sulfur-containing heterocyclic compounds, are widely utilized in the fields of pesticides and pharmaceuticals. In this study, a novel method for synthesizing 2-methylbenzothiazole derivatives was developed through a multicomponent tandem reaction of 2-iodoaniline, CaC₂ and H₂S. It was found that H₂S reacts with CaC₂ to form a pivotal intermediate, ethanethial, which subsequently reacts with 2-iodoaniline to synthesize diverse 2-methylbenzothiazole derivatives in moderate to good yields with excellent functional group compatibility. Additionally, the reductive properties of H₂S facilitate the direct transformation of nitro compounds into their corresponding amino derivatives, significantly broadening the substrate scope and enhancing the versatility of this strategy. Importantly, H₂S serves three critical roles: depolymerizing CaC₂, substituting iodine atoms as a sulfur source, and reducing nitro groups as a reducing reagent. This synthetic method not only provides a practical and efficient pathway for converting CaC₂ and H₂S gases into 2-methylbenzothiazole derivatives but also highlights the broad applicability of this innovative strategy in organic synthesis.