Conformational analysis of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes

Abstract

Study of conformational isomerization of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes using quantum-chemical HF/6-31G(d) and PBE/3z approximations showed that its route involves an equilibrium between the chair conformers with different orientation of substituent at C5 ring atom and proceeds through a transition state corresponding to the 2,5-twist conformation. Molecular dynamics method showed that at room temperature this conformation transforms into the equatorial or axial chair conformers through 1,4-twist or sofa forms. Based on the experimental and theoretical values of vicinal 1H NMR coupling constants we determined quantitative conformational composition of the molecules of these compounds and the values of ΔG0 of the conformational equilibrium.