Tatyana V. Strelkova

Synthesis and Characterization of Large Stereoregular Organosiloxane Cycles

The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of general formula [PhSi(OSiMe 3 )O] n ( n =6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligophenylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 ( n =6) and 4 ( n =12) have been characterized by NMR-spectroscopy method and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and configuration (the same as in the initial OPMS) during the trimethylsilylation. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed.

PROBLEMS OF SYNTHESIS OF TETRAHEDRAL ORGANOSILSESQUIOXANES. HYDROLYTIC CONDENSATION OF HEXAFUNCTIONAL BRANCHED ORGANOTETRASILOXANES

The hydrolytic condensation of methyltris(methyldichlorosiloxy)silane (1b), methyl(1a), and vinyltris(methyldiethoxysiloxy)silanes (1c) in dilute homogeneous solutions was studied. It was found by X-ray diffraction and1H NMR methods that, irrespective of reaction conditions, only octaorganooctasilsesquioxanes (T8), namely, octamethyloctasilsesquioxane and 1,4-divinylhexamethyloctasilsesquioxane, were obtained instead of the expected tetraorganotetrasilsesquioxanes (T4). These data suggest that the condensation processes involved in the hydrolysis of1a–c are predominantly intermolecular, and the molecules of the starting oligomers do not undergo rearrangements. Probably, the formation ofT4, whose molecules are built of four strained six-membered organosiloxane cycles, is less favorable thermodynamically than the formation of their homologs (T8) built of eightmembered organosiloxane cycles.

Synthesis of functionalized fluorine-containing trimethylsilylcarbodiimides

New functionalized polyfluorinated carbodiimides RFN=C=NSiMe3 were prepared by the reactions of bis(trimethylsilyl)carbodiimide with electrophilic reagents. The structures of the resulting compounds were confirmed by1H,13C,29Si,14N,15N, and17O NMR spectroscopy.

Reactions of imides with samarium(ii) iodide

The tendency of a series of imides and lactams to react with samarium(II) iodide was investigated. Under the action of Sml2 at ∼20 °C, one of the carbonyl groups ofN-phenylphthalimide was reduced to a CHOH or CH2 group depending on the molar ratio of the reagents and the order of their introduction into the reaction mixture. Both CO groups ofN-acetylcaprolactam are reduced with SmI2 under similar conditions, whereas the CO group of ε-caprolactam is not reduced by SmI2.

E,Z-Isomers of 3-ethoxy-4,4,4-trifluorobut-2-enenitrile and N-methylpyrrolidines derived from them

Abstract3-Ethoxy-4,4,4-trifluorobut-2-enenitrile was synthesized by the Wittig reaction of ethyl trifluoroacetate and (cyanomethylidene)triphenylphosphorane and was separated to individual E- and Z-isomers by rectification. Each isomer undergoes stereospecific 1,3-dipolar cycloaddition to N-methyl(methaniminio)-N-methylide generated in situ to give E- and Z-isomers of 4-cyano-3-ethoxy-3-trifluoromethyl-1-methylpyrrolidine.

A Study of the Polycondensation of (Tetrahydroxy)(Tetraaryl)Cyclotetrasiloxanes under Equilibrium and Non-Equilibrium Conditions in the Presence and Absence of Montmorillonite

Oligo- and polycyclosiloxanes were obtained by the polycondensation of (tetrahydroxy)(tetraaryl)cyclotetrasiloxanes in equilibrium and non-equilibrium conditions in the presence and absence of montmorillonite (MMT). Their composition and the structures of their components were investigated by infrared (IR) spectroscopy, 29Si nuclear magnetic resonance (NMR) spectroscopy, atmospheric pressure chemical ionization (APCI) mass spectrometry, powder X-ray diffraction (XRD), and gel-penetrating chromatography (GPC). Also, a comparison of polymers formed in the presence of MMT and via anionic polymerization was performed showing differences in their structures.

Some peculiarities of hydrosilylation of α,ω-divinyloligosilanes

The stability of Si-Si bonds in linear and cyclic permethyloligosilanes and in α,ω-divinyloligosilanes under conditions of hydrosilylation in the presence of the Speiers catalyst was studied. Polycarbosilanes containing silylene fragments in their backbone chains were prepared by the reaction of 1,4-bis(dimethylsilyl)benzene with α,ω-divinyloligosilanes. It was found that the structure of these polymers is disturbed due to the side reaction involving the cleavage of the Si-Si bond in vinyloligosilanes under the action of H2PtCl6.