Application of Pyridinium 1,4-Zwitterionic Thiolates: Synthesis of Benzopyridothiazepines and Benzothiophenes

Pyridinium 1,4-zwitterionic thiolates, as a novel kind of sulfur-containing synthon, have been applied to the synthesis of 12a H -benzo[ f ]pyrido[1,2- d ][1,4]thiazepines and benzo[ b ]thiophenes. Benzopyridothiazepines were produced through a 1,5-dipolar cycloaddition reaction from pyridinium 1,4-zwitterionic thiolates with arynes, whereas benzothiophenes as side products were generated via a [3 + 2] cascade cyclization reaction. The [5 + 2] reaction mode of pyridinium 1,4-zwitterionic thiolates is disclosed for the first time.