Theoretical investigation of the role of formaldehyde dimers in the Prins reaction

Some features of adding a formaldehyde dimer to alkenes by the Prins reaction with the formation of oxygen-containing heterocycles are studied at the MP2(fc)/6-31G(d) computational level. The structure of the transition states and key intermediates are established, and thermochemical reaction parameters are determined. It is shown that this interaction in the gas phase or nonpolar media with the formation of 1,3-dioxanes is a single-stage pseudo synchronous syn-addition. Alkyl substituents at the double bond reduce activation energy. It is revealed that the hydrogenated pyrans formation by the Prins reaction is possible not only with the participation of formaldehyde monomers, but with its oligomers either. However, the activation energy of this reaction is higher than that of 1,3-dioxane formation.