A new insertion reaction of phenyl isocyanate

A new reaction of the insertion of phenyl isocyanate into the C-C bond of P-containing zwitterions based on 2-cyanoacrylates was found. A probable mechanism of this reaction has been discussed.The X-ray structural study of compound3b was carried out by Yu. T. Struchkov and O. V. Shishkin, and its results will be published separately.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 186–187, January, 1995.     

Solid phase insertion of diamines into peptide chains

Diamines derived from naturally occurring aminoacids were inserted into peptide chains by the reaction of the monophthaloyl diamines with amino acid 1-benzotriazolyl esters, bound through their amino functions onto trityl-type resins. The phthaloyl group was removed and peptide chains using N-Fmoc amino acids, were assembled on the liberated amino function. The peptidyl diamides obtained, were cleaved from the resins with ^tBu-side chain protection remaining intact, or fully deprotected.     

Insight into the reaction mechanism of sulfur chains adjustable polymer cathode for high-loading lithium-organosulfur batteries

Small molecules with adjustable sulfur atoms in the confined structure were acted as precursor for the synthesis of polymer cathodes for lithium-organosulfur batteries.Among them,poly(diallyl tetrasulfide)(PDATtS)delivered a high capacity of 700 mAh g^-1,stable capacity retention of 85%after 300 cycles,high areal capacity~4 m Ah cm^-2 for electrode with up to 10.3 mg cm^-2 loading.New insight into the reaction mechanism of PDATtS electrode that radicals arisen from the homolytic cleavage of S-S bond in PDATtS reacted with Li+to generate thiolates(RSLi)and insoluble lithium sulfides(Li₂S)or lithium disulfide(Li₂S₂)was clearly verified by in-situ UV/Vis spectroscopy,nuclear magnetic resonance(NMR)studies and density-functional theory(DFT)calculations.Therefore,based on the unique reaction mechanism,problems of rapid capacity fading due to the formation of soluble polysulfide intermediates and their serious shuttle effect in conventional lithium-sulfur(Li-S)batteries was totally avoided,realizing the dendrite-free lithium sulfur batteries.This study sets new trends for avenues of further research to advance Li-S battery technologies.     

Easy-dispersible poly(glycidyl phenyl ether)-functionalized graphene sheets obtained by reaction of "living" anionic polymer chains

Excellent dispersion of functionalized graphene (FG) sheets in polystyrene was achieved relying on the reaction of "living" poly(glycidyl phenyl ether) chains onto graphene sheets. The physical aging of polystyrene was substantially accelerated by the presence of FG sheets at low filler content, retaining film transparency and increasing the electrical conductivity.     

A novel reaction of cyclic ketene acetals with phenyl isocyanate through zwitterion

A novel reaction of cyclic ketene acetals with phenyl isocyanate through zwitterion was found to yield the corresponding spiro compounds in good yields.     

Preparation and characterization of novel cyanate ester/epoxy resin microspheres

A novel kind of cyanate ester (CE)/epoxy resin microspheres have been synthesized using the polymerization technology of cyanate ester and epoxy resin in anhydrous ethanol media; surfactant sodium dodecylbenzene sulfonate was used as an emulsifier, and imidazole was used as catalyst or curing agent. The morphologies, chemical structures, and thermal properties of microspheres were investigated by Fourier transform infrared spectroscopy, scanning electron microscope, laser scanning confocal fluorescence microscopy, optical microscope, differential scanning calorimeter, and thermogravimetric analyzer, respectively. The effects of process parameters such as the amount of imidazole and the weight ratio of epoxy resin to CE on the size and morphology of microsphere were discussed. Results indicate that the reactivity and surface morphology of microsphere can be adjusted by the amount of imidazole and the weight ratio of epoxy resin to CE. The prepared microsphere shows excellent thermal stability and good reactivity.     

Facile insertion reaction of arynes into carbon-carbon sigma-bonds

The carbon-carbon sigma-bond of various beta-dicarbonyl compounds was found to add to the triple bond of arynes under extremely mild conditions, leading to direct introduction of different carbon functional groups into the aromatic skeletons.     

Investigation into Sonogashira reaction on 5-iodo-1-(phenyl/p-halophenyl)imidazole-4-carbonitrile compounds

Investigation into Sonogashira reaction on 5-iodo-1-(phenyl/p-halophenyl)imidazole-4-carbonitrile compounds had been developed by introducing an iodo atom at the C-5 position of the imidazole ring of 5-amino-1-(phenyl/p-halophenyl)imidazole-4-carbonitrile compounds. Specifically, 5-iodo-1-(4-iodophenyl)imidazole-4-carbonitrile compound had shown double Sonogashira coupling reactions with two differently substituted iodine along with the formation of two other compounds where an unusual coupling product with self-aggregation property was obtained. In other cases, monocoupling had been observed together with another compound where iodine atom present at C5 position of imidazole was replaced by hydrogen atom.     

Uncatalyzed insertion reaction of isocyanides into a carbon-sulfur bond

Tert-butylisocyanide and tert-octylisocyanide insert into the carbone-sulfur bond of activated sulfides 2 yielding thioimidates 5 which rearrange to enamines 6.     

Stereochemistry at titanium in the sulfur dioxide insertion reaction of titanocene compounds

The insertion reaction of SO₂ has been studied for the two diastereoisomeric forms of η⁵-C₅H₅-η⁵-C₅H₄ CHMePhTi(C₆F₅)CH₃. The reaction is regioselective and stereospecific. Arguments that it involves a retention at the titanium atom are given.     

Porous triazine polymer: A novel catalyst for the three-component reaction

A new porous triazine-based covalent organic polymer (Triazine-COP) was prepared through the Schiff-base condensation of 2,4,6-tris(4-formyl phenoxy)-1,3,5-triazine and 4,4′-oxydianiline, under sonication. The synthesized Triazine-COP with a high surface area was stable in water and other organic solvents. In the next step, Au (III) ions were immobilized on the nitrogen-rich Triazine-COP that on the reduction with NaBH₄ produced the heterogeneous catalyst of gold clusters in nanosize (Au-NCs@Triazine-COPs). It was applied as an efficient catalyst for the A³ coupling reaction of alkynes, aldehydes with and amines. Both electron-withdrawing/releasing groups produced the corresponding propargylamines with high yields. The high activity of the Au-NCs@Triazine-COPs in this reaction was because of the nanoporous structure of the support that enables the high dispersion and an unhindered open environment for the NCs. The catalyst was reused up to 7 times without significant loss in activity.     

Mechanical properties of polymer composites based on commercial epoxy vinyl ester resin and glass fiber

The effect of the addition of methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate (CoNaph) on the mechanical behavior of epoxy vinyl ester resin (EVER) laminates has been investigated by using a factorial experimental design, in which the MEKP and NaphCo contents were varied. Previous results showed that there is an interaction effect between the process variables analysed on the mechanical properties evaluated. It was also observed that the MEKP/CoNaph ratio affected the tensile behavior of the EVER/glass fiber composites.     

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.     

A novel coordination polymer containing both interdigitated 1D chains and interpenetrated 2D grids

A hydro(solvo)thermal reaction between zinc perchlorate and ethyl ester of a new pyridinecarboxylate bridging ligand of approximately 17.6 A in length yields a unique coordination polymer which contains both interdigitated infinite 1D chains and interpenetrated 2D rhombohedral grids [Zn(2.5)(L)(4)(mu(3)-OH)] x (H(2)O)(5), 1, where L is 3-[[4-(4-pyridylethenyl)phenyl]ethenyl]benzoate. The 1D chains contain mu(3)-bridged hydroxy groups and have a [Zn(4)(mu(3)-OH)(2)(L)(6)] stoichiometry, while the 2D grids have a Zn(L)(2) formula and diagonal distances of 31.7 and 25.2 A. Crystal data for 1: monoclinic space group P2/c, a = 15.686(2) A, b = 12.6103(16) A, c = 38.999(5) A, beta = 98.397(2) degrees, and Z = 4.     

Curing properties of novel curing agent based on phenyl bisthiourea for an epoxy resin system

Phenyl bisthioureas: 4,4′-(bisthiourea)diphenylmethane (DTM), 4,4′-(bisthiourea)diphenyl ether (DTE), and 4,4′-(bisthiourea)diphenyl sulfone (DTS) were synthesized and used as curing agents for the epoxy resin diglydicyl ether bisphenol A (DGEBA). Synthesized phenyl bisthioureas were characterized using FT-IR and ¹H-NMR analysis. For comparison studies the epoxy system was also cured using the conventional aromatic amine 4,4′-diaminodiphenyl ether (DDE). Curing kinetics of epoxy/amine system was studied by dynamic and isothermal differential scanning calorimeter (DSC). Curing kinetic was evaluated based on model-free kinetics (MFK) and ASTM E 698 model, and the activation energy was compared with DDE. Curing system of phenyl bisthiourea link (DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS) shows two exothermic peaks, while that of the conventional aromatic amines showed only a single peak. The initial exothermic peak is due to the primary nitrogen of the thiourea group, and the exotherm at higher temperature is due to the presence of thiourea groups. Glass transition temperature (T _g) of DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS cured resins were lowered by 323 K when compared to the widely used diaminodiphenyl ether (DDE) cured resin. Oxidation induction temperature measurement performed on DSC suggests that the DGEBA/DTM, DGEBA/DTE, and DGEBA/DTS system cured resins has better oxidative stability when compared to cured DGEBA/DDE resin system.     

The first example of magnesium carbenoid 1,3-CH insertion reaction: a novel method for synthesis of cyclopropanes from 1-chloroalkyl phenyl sulfoxides in high yields

Treatment of 1-chloroalkyl phenyl sulfoxides having a geminal methyl group or a geminal benzyl group at the 2-position in THF at −78 °C with isopropylmagnesium chloride gave magnesium carbenoids. Carbenoid 1,3-CH insertion reaction of the magnesium carbenoids took place instantaneously to afford cyclopropanes in high to quantitative yields.