I. V. Vakulin

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.

A theoretical investigation of the reaction mechanism for hydrogenated furan formation under Prins reaction conditions in trifluoroacetic acid medium

The formation mechanism of hydrogenated furans by coupling between terminal alkenes and aldehydes in trifluoroacetic acid medium were investigated by ab initio calculations, the main attention was focused on the study of the rate controlling step. Two possible mechanisms for this reaction involving unsaturated alkoxycarbenium ions or dioxolenium ions as a key intermediate were considered. It was shown that the mechanism of formation of 3-alkylsubstituted hydrogenated furans in trifluoroacetic acid under Prins reaction conditions preferably includes recyclization of 3-(2-hydroxyethyl)-1-trifluoromethyl-2,5-dioxolenium ions.

Intramolecular photoinduced electron transfer of fluorescent probes based on 1,8-naphthalimide and aniline derivatives

The effect of conformation and electronic structure of fluorescent probes based on 1,8-naphthalimide and aniline derivatives (4-methoxyaniline and N,N-dimethyl-p-phenylenediamine) on the intramolecular photoinduced electron transfer (PET) was investigated by density functional theory calculations (B3LYP/6-31G (d, p)). We established restricted rotation around spacer bonds of the model compounds and their protonated and oxidized forms do not block the convergence of the nitrogen atoms involved in the electron transfer at a distance of ~3Å, which is adequately for PET. Computed values of protonation free energy for the gas-phase (ΔG298 r) show that the investigated fluorescent probes are predominantly protonated on the nitrogen atoms of the donor moiety. Electron population and localization of the frontier orbitals (LUMO, HOMO, HOMO-1) on the donor and acceptor moieties are transformed under protonation and one-electron oxidation of fluorescent probes. The results show that appearance or disappearance of the PET can be predicted by the energy difference between the frontier orbitals and the nature of their location of donor and acceptor moieties, which is in agreement with the PET theory and observed experimental data.