Selective Synthesis\nof Vinyl Sulfides or 2‑Methyl\nBenzothiazoles from Disulfides and CaC<sub>2</sub> Mediated by a Trisulfur\nRadical Anion

In\nthis report, we have established a novel and efficient method\nfor selectively synthesizing either vinyl sulfides or 2-methylbenzothiazoles\nfrom the reaction of CaC<sub>2</sub> and disulfides. The selective\nsynthesis of these two distinct products can be controlled by simply\nadjusting the amount of K<sub>2</sub>S. The underlying reaction mechanism\nhas been thoroughly investigated through control experiments, HRMS,\nand FTIR, which collectively support the pivotal role of a trisulfur\nradical anion. This radical species, generated in situ from K<sub>2</sub>S, is essential for the homolytic cleavage of the S–S\nbonds in a catalytic manner. Additionally, the trisulfur radical anion\nalso acts as an effective mediator for activating the vinyl group\nof 2-aminophenyl vinyl sulfides, facilitating the crucial intramolecular\ncyclization required to produce 2-methylbenzothiazoles. Moreover,\nCaC<sub>2</sub> not only serves as an acetylene source but also creates\nthe basic conditions essential for the selective formation of vinyl\nsulfides. This methodology demonstrates broad substrate compatibility\nand excellent functional group tolerance, significantly enhancing\nits practical utility in diverse synthetic applications.