V. A. Roznyatovskii

Mechanisms and kinetics of the elementotropic rearrangements of tetrahydro-4,4,8,8-tetramethyl-4,8-disila-sym-indacene

The dynamic stereochemistry of silatropic rearrangements of tetrahydro-4,4,8,8-tetra-methyl-4,8-disila-sym-indacene (dimer of 6,6-dimethyl-6-silafulvene), which exists in solution as an equilibrium mixture of two interconverting isomers, was studied. The mechanisms and complete kinetic scheme of rearrangements were established using1H,13C, and29Si 2D quantitative EXSY NMR spectroscopy. It was found that the interconversion and degenerate rearrangements of the observed isomers proceedvia two concurrent pathways due to the formation of different intermediates. The activation parameters of the rearrangements were determined by means of total lineshape analysis of dynamic NMR (DNMR) spectra.

Photochemical reactions of 9-trimethylstannylanthracene in various solvents

Abstract9-Trimethylstannylanthracene (1) was synthesized and its photolysis by 365-nm light was studied. In aprotic solvents, the dimerization of 1 involves positions 9 and 10 and yields a head-to-tail dimer. The main route of the photolysis of 1 in alcohols is the cleavage of the C-Sn bond with the formation of anthracene. The quantum yields of the photoreaction and the lifetimes and quantum yields of 1 fluorescence were determined.

Chemically induced magnetic isotope effect on the tin nuclei during the photolysis of (1-fluorenyl)trimethyltin

A magnetic isotope effect on the 117Sn and 119Sn nuclei, accompanied by the fractionation of magnetic and nonmagnetic tin isotopes, was observed during the photolysis of (9-fluorenyl)trimethyltin. The magnetic and nonmagnetic isotopes were accumulated, respectively, in the initial compound and a photolysis product (hexamethyldistannane).

UNUSUAL BEHAVIOR OF 2-CYCLOPENTADIENYL-1,3-DIOXAPHOSPHOLANE

Abstract It has been found that 2-cyclopentadienyl-1,3-dioxaphospholane (2) and 2-cyclopentadienyl-1,3-dioxaphosphorinane (3) demonstrate different fluxional behavior. While 3 represents a mixture of three isomers 3a-c, 2 exists in only the allylic form 2a. The relative stability, molecular structure and the fast rate of [1,5]-phosphotropic shifts in 2a indicate that the efficiency of σ-π-conjugation is increased with a decrease in the O-P-O angle in dialkyl esters of cyclopentadienylphosphorous acids.