Research and Application of Pyridinium 1,4-Zwitterionic Thiolates in Organic Synthesis

Pyridinium 1,4-zwitterionic thiolates are important sulfur- and nitrogen-containing synthons, in which the pyridine fragments can act as leaving groups, but also as electrophilic sites, constructing various types of sulfur- and nitrogen-heterocycles. Hence, pyridinium 1,4-zwitterionic thiolates have attracted much attention on the synthesis for N-containing and S-containing heterocyclic compounds in recent years. The progress of pyridinium 1,4-zwitterionic thiolates participated annulation via [3+m] and [5+m] modes is reviewed, their applications on constructing N- and S-heterocyclic rings are summarized, and their future prospects are discussed.