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 12aH-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.