E. A. Kantor

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.

Fragmentation of substituted 2-sila-1,3-dioxacycloalkanes under electron impact

The mass spectrometric dissociation of 2-sila-1,3-dioxacycloalkanes takes place mainly with loss of the substituent from position 2 of the heterocycle. The fragment formed here eliminates the molecular of carbonyl compounds or alkenes.

Homolytic telomerization of vinyltrimethylsilane with 5,5-dimethyl-1,3-dioxane

The homolytic telomerization of vinyltrimethylsilane by 5,5-dimethyl-1,3-dioxane follows three principal routes, with the formation of 2- and 4-substituted 5,5-dimethyl-1, 3-dioxanes and a formate ester. The rings in the reaction products (2-trimethylsilylethyl- and 4-trimethylsilylethyl-5,5-dimethyl-1,3-dioxane) exist in the chair conformation. The substituants in the 2- and 4-positions of the dioxane ring occupy equatorial positions.

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.

RECYCLIZATION OF 4,4,5‐TRIMETHYL‐1,3‐DIOXANE BY CARBONYL COMPOUNDS

Im Unterschied zu den 4,4-Dimethyl- und 4-Methyl-4-phenyldioxanen bildet die Titelverbindung (I) mit den Aldehyden (II) nur die 2-substituierten 3,6-Dihydropyrane (III).