Pd-catalyzed oxidative carbonylation of sulfurated substrates: Theoretical mechanistic outcomes

Abstract

In the present study, a detailed computational investigation has been carried out on the recently reported PdI2/KI-catalyzed conversion of 1-(methylthio)-3-yn-2-ols to thiophene-3-carboxylate esters, using 2-methyl-1-(methylthio)oct-3-yn-2-ol as the model substrate. On the basis of a number of mechanistic hypotheses that were taken into account, outcomes on the energetic feasibility of the generally-accepted reaction scheme for this process have been provided. The current investigation indeed dissects the role of each species coming into play during the reaction, in each step of the mechanism. In detail, the contribution of co-catalytic KI for the demethylation of the S-containing nucleophilic agent, concertedly to the 5-endo-dig mechanism, from the early stage of the reaction has been highlighted, as well as the role of transient dimethyl ether cation for the dehydration step and that of the solvent methanol molecules for the formation/energy stabilization of the product. The calculated barriers are in good agreement with available experimental data.