Mechanism of the C=C Bond’s Migration in Allyl Phenyl Sulfide during Catalysis by Methanesulfonic Acid

The mechanism of the C=C bond’s migration in allyl phenyl sulfide in the presence of methanesulfonic acid is analyzed by quantum chemistry using the density functional theory in the B3PW91/6-31G** approximation. The reaction proceeds through the formation of 1-(phenylthio)prop-2-ylium and 2-methyl-1-phenylthiiranium. The calculations show the possibility of the protonation of allyl phenyl sulfide and deprotonation of the resulting cation to phenyl propenyl sulfide. The possibility of the opening of the thiiranium cation under the action of methyl sulfonate to form a complex of phenyl propenyl sulfide with methanesulfonic acid is also shown. Comparison of the results of calculations with and without a solvent shows that the energy profile of the reaction (ΔG 298 0 , and ΔE tot ZPE ) is practically preserved.