Theoretical Studies on the Mechanism of the Cycloaddition Reaction between Thioketene and Thioformaldehyde

Ab initio HF/6 - 31G* and density functional theory (DFT) B3LYP/6 - 31 + + G* * have been used to study the mechanism of the cycloaddition reaction between thioketene and thioformaldehyde. These two reactions that give different four-membered heterocyclic products; both proceed via a two-step mechanism involving a zwitterionic intermediate. Both processes proceed easily, but reaction (1) is more favorable. In addition, Bader type electron density topological analysis was used to study the electronic structures of stationary points for reactions (1) and (2) .