Functionalization of Living Polymers via Ethoxysilane Based Compounds: Synthesis and Interaction with Silica Particles

To optimize the reaction of ω-carbanionic styrene or butadiene/styrene polymers with ethoxysilane based compounds, the influence of several experimental parameters on the orientation of the functionalization reaction and its yield was examined. The resulting end-functionalized polymers were systematically investigated by SEC, ¹H NMR and elementary analysis. The orientation of the reaction was found to be directly depending on the chemical nature of the chain end and / or on the type of additive (ethers, LiCl). Best results were obtained with tetraethoxysilane, provided the functionalization is conducted around 5°C, and the active chain end of isoprenyl type. These reactions were extended to bifunctional polymers, the reaction product of butyllithium with m-diisopropenylbenzene being used as an initiator. The efficiency of this initiator for the synthesis of well-defined bifunctionalized polydienes almost quantitatively fitted with three alkoxy functions at both chain ends was demonstrated. Some preliminary results on the mechanical properties of mixtures of functionalized polymers with silica were mentioned.     

X-ray microscopy of track membranes and biological objects in the soft-and hard-wavelength ranges

The methods used to obtain X-ray images of track membranes and various biological objects in the soft (20 nm) and hard (0.2–0.02 nm) wavelength ranges have been considered. In the range of soft X-rays, the images were obtained in a Schwarzshild microscope. In the spectral range of hard X-ray radiation, various methods were used including the use of Fresnel zone plates, asymmetric reflecting crystals, X-ray microradiography and microtomography.     

Specific heat of the elpasolite Pb2MgWO6

The specific heat of Pb₂MgWO₆ has been measured in the temperature interval 83–370 K. An anomaly in the specific heat associated with the phase transition at T ₀=312.8K has been discovered. The thermodynamic parameters of the structural phase transition Fm3m-Pmcn have been determined. Fiz. Tverd. Tela (St. Petersburg) 41, 1686–1688 (September 1999)     

Direct alkenylation of non-aromatic enamides via palladium-catalyzed oxidative coupling: Synthetic developments and applications

Direct C(3) alkenylation of non-aromatic enamides through palladium(II)-catalyzed Fujiwara–Moritani cross-coupling was developed. The reaction scope includes a range of cyclic enamides as well as activated alkenes. The utility of this methodology is illustrated by the synthesis of octa- or tetrahydroquinoline cores obtained from conjugated enamides via Diels–Alder cycloaddition.     

HETEROCYCLIC SULFUR COMPOUNDS LXXXIV: 3-Alkoxy-1,2-dithio-isocoumarins and 3-Alkylthio-1,2-dithio-isocoumarins

Abstract

Reaction of phosphorus pentasulfide with alkyl hydrogen homophthalates or dialkyl homophthalates gives a mixture of 3-alkoxy-1,2-dithio-isocoumarins and of 3-alkylthio-1,2-dithio-isocoumarins; some of these compounds resulting from a migration of an alkoxy or of an alkylthio group.

Oxidation of these dithio-isocoumarins into 2-thio-isocoumarins has been performed either by potassium permanganate or by benzonitrile N-oxide.     

A Simple and Efficient Synthesis of 2-Substituted 3-Diethylphosphono 5-Methylfurans

An efficient carbanionic synthesis of the phosphonic dicarbonylated compounds 2 was achieved and used as key intermediates in the synthesis of the phosphonic furans 4 by acid-induced Paal-Knorr cyclization reaction.