L. F. Lapuka

Ring inversion in 5,5-disubstituted 1,3-dioxanes

The conformational mobility was studied by dynamic PMR and the free energies of activation of the conformational transitions of 5,5-bis(chloromethyl)-, 5,5-bis(iodomethyl)- and 2,3-pentamethylene-bis-5,5-bis(chloromethyl)-1,3-dioxanes were determined.

Three-dimensional structures of dihydropyrans

The three-dimensional structures of alkyl- and aryldihydropyrans were studied by means of PMR spectroscopy. It is shown that the investigated compounds exist primarily in the half-chair conformation.

Synthesis and three-dimensional structure of 5,5-disubstituted 2-alkoxy-1,3-dioxanes

It was established by PMR spectroscopy that a chair conformation with an axial orientation of the alkoxy substituent is the primary conformation for 5,5-disubstituted (and unsubstituted) 2-alkoxy-1,3-dioxanes. As compared with alkyl-1,3-dioxanes, 2-alkoxy-1,3-dioxanes are characterized by reversal of the chemical shifts of the axial and equatorial protons attached to C4, and C6.

Molecular complexes of chloroform with methyl-substituted 1,3-dioxanes

The 1H NMR method was used to study the relative electron donor capacity of a number of methyl-substituted 1,3-dioxanes in complex formation with chloroform. The spectral and thermodynamic parameters of 1∶1 H-complexes were determined. The values of the chemical shifts from the hydrogen bond in the complexes vary in correlation with the charges on the oxygen atoms of the investigated bases, calculated by the CNDO/2 method.

Three-dimensional structure of 2-dimethylamino-1,3-dioxacyclanes

It was established by 1H NMR spectroscopy that a chair conformation with an equatorial orientation of the dimethylamino group is the preferred conformation for methyl and 5,5-spiro derivatives of 2-dimethylamino-1,3-dioxanes.