Vladimir V. Bagrov

Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO2

Binary and ternary acrylonitrile (AN) copolymers with methyl acrylate (MA) and either itaconic acid (IA, 1) or IA derivatives (monomethyl itaconate (2), monoethyl itaconate (3), IA monoamide (4), IA mono-n-octylamide (5)) were prepared in CO2. The obtained copolymers have good morphological and molecular weight characteristics. They demonstrate broad heat evolution during thermal cyclisation according to DSC measurements; therefore, they may be used to produce carbon fibres. The polymer yield per reaction volume is 2 to 3 times higher relative to that produced in solution (in DMSO or DMF) or an aqueous suspension.

Controlled ring-opening polymerisation of cyclic phosphates, phosphonates and phosphoramidates catalysed by heteroleptic BHT-alkoxy magnesium complexes

We report here that the heteroleptic BHT-Mg(OR) complex, i.e. [(BHT)Mg(OBn)(THF)]2 (Mg3), represents an effective and versatile ring-opening polymerisation (ROP) catalyst for several cyclic ethylene phosphate monomers (CEPMs), such as ethylene phosphates with methoxy- (MeOEP, 1), isopropoxy- (iPrOEP, 2), and tert-butoxy- (tBuOEP, 3) substituents, N,N-diethyl ethylene phosphoramidate (Me2NEP, 4) as well as ethyl (EtPPn, 5) and tert-butyl (tBuPPn, 6) ethylene phosphonates. Mg3 retains its catalytic activity over a broad temperature range from −50 to 100 °C and efficiently carries out the fast and controlled polymerisation of CEPMs with sterically unhindered alkoxy groups with less than 1% chain branching even at near-complete conversion. Compared with ROP catalysed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), Mg3 performs much better in the polymerisation of CEPMs with bulky groups and of monomers sensitive to strong nucleophiles, such as tBuOEP.

Cyclopentadienes Annelated with Five-membered Heterocycles: Methods of Synthesis, Heteroorganic Derivatives, and Synthetic Precursors. (Review)

The review is devoted to cyclopentadienes annelated with five-membered heterocycles (furan, pyrrole, thiophene, and their benzo analogs) (hetarenocyclopentadienes), their heteroorganic derivatives, and the synthetic precursors (hetarenocyclopentanones).

New cysteine-modifying reagents: Efficiency of derivatization and influence on the signals of the protonated molecules of disulfide-containing peptides in matrix-assisted laser desorption/ionization mass spectrometry

Mass spectrometric de novo sequencing of skin secretion peptides from genus Rana is complicated because of C-terminal disulfide cycles present in their structure. Brevinin-1E and brevinin-2Ec from the skin secretion of the Marsh Frog R. ridibunda were used for a comparative study of six N-phenylmaleimide derivatives as new alkylating agents for cysteine thiol moieties. The paper describes the synthesis and confirmation of the structures of the obtained compounds. A procedure was developed for modifying thiol groups with the proposed reagents. Alkylation efficiency and the effect on the peak intensity in matrix-assisted laser desorption/ionization (MALDI) spectra were investigated. The best results were obtained for 2,4- and 2,5-dimethylphenylmaleimides. Additionally tested iodoacetic acid was shown to be a powerful modifier of thiol groups, while its excess notably increases the intensities of the peaks of protonated molecules in the MALDI mass spectra of both peptides.

Synthesis and study of the mutagenic activity of di(indeno[2,1-b]indolyl)- and di(indeno[2,1-b]pyrrolyl)methanes and -dimethylsilanes

Dihetaryldimethylsilanes and dihetarylmethanes containing indeno[2,1-b]indolyl and indeno[2,1-b]pyrrolyl fragments were synthesized. Their mutagenic activity was tested according to Ames with standard test strains Salmonella typhimurium TA 1537, TA 98, and TA 100.

Synthesis of bis-cyclopentadienyl compounds with a 9,9-fluorenylidene bridge. Crystal and molecular structure of [μ-9,9-Flu(η5-Cp)2]ZrCl2

An efficient synthetic approach to 9,9-bis(cyclopentadienyl)fluorenes was developed. The two correspondingansa-zirconocenes were synthesized. The structure of one of these compounds was established by X-ray diffraction analysis.

A study of the morphology of acrylonitrile-methylacrylateitaconic acid/itaconic acid derivative copolymers synthesized in a supercritical carbon dioxide medium

Ternary copolymers of acrylonitrile with methylacrylate, itaconic acid (IA), and its derivatives, namely, monomethyl ester (MME), monoethyl ester (MEE), monoamide, and mono-n-octylamide, were synthesized in a supercritical carbon dioxide medium. The morphology of the synthesized copolymers was studied by scanning electron microscopy. Copolymers with IA, MME, and MEE were obtained in the form of regularly shaped particles of nearly 1 μm in size without the addition of stabilizers.

Steric and electronic factors in the promoting activity of diphosphine ligands in cyclohexene hydrocarbomethoxylation catalyzed by palladium acetate

Cyclohexene hydrocarbomethoxylation catalyzed by Pd(OAc)2-p-toluenesulfonic acid-diphosphine systems has been investigated for a wide range of diphosphine structures and concentrations. The factors controlling the activity of the palladium-containing catalysts include the hydrocarbon moiety of the ligand and the mutual arrangement of the phosphine groups. A comparison between the promoting effects of monophosphine and diphosphine ligands has demonstrated that bridged trans-diphosphines are more efficient in kinetic and concentration terms (TOF and P/Pd ratio, respectively). In particular, the promoting activity of diphosphines is one order of magnitude higher than that of triphenylphosphine, and this effect is attained at 8–65 times lower P/Pd ratios. It is discussed how the catalytic properties of the systems depend on the chelate effect and on the geometric compatibility between the diphosphine structure and the arrangement of vacant s and d orbitals of the palladium center.