Reactions of acetylenes with substituted 2<i>H</i>-thiopyran-2-thiones and their isoelectronic analogues: difficult choice of optimal route

The potential energy surfaces (PESs) for a number of reactions between substituted acetylenes and substituted 2<i>H</i>-thiopyran-2-thiones, as well as their isoelectronic analogues were studied by PCM/DFT/B3LYP/6-311++G(d,p) quantum chemical calculations. Theoretical studies have revealed the similarity of the PESs, which differ from each other only in their energetic characteristics. Similar reaction channels on these surfaces lead to different products through six similar minimum-energy pathways (MEPs). In the case of an excess of acetylene, the formation of 4-thiophene-substituted thiopyran derivatives is energetically preferred.