Facile Synthesis of Quinoxaline-2-thiol and Quinoxaline from α-Oxosulfines and o-Arylenediamines

Abstract A series of quinoxaline-2-thiols and quinoxalines were prepared in moderate to good yields from various phenacyl sulfoxides bearing 1-methyl-1H-tetrazole and o-arylenediamines. The proposed reaction mechanism involves generation of sulfines from the phenacyl sulfoxides bearing 1-methyl-1H-tetrazole through thermolysis elimination. Then, site-selective carbophilic addition of sulfines by o-arylenediamines, followed by elimination, intramolecular nucleophilic addition, and dehydration condensation. The current method provides a direct and simple strategy for the preparation of quinoxaline-2-thiols and quinoxalines.