High performance liquid chromatography equipped with a cathodic detector and column-switching device as a high-throughput method for a phosphatase assay with p-nitrophenyl phosphate

A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarin compounds from the Chinese medicinal plant Peucedanum decursivum (Miq.) Maxim (Zihuaqianhu in Chinese) was successfully established by using light petroleum-ethyl acetate-methanol-water (5:5:7:4, v/v) as the two-phase solvent system. The upper phase of light petroleum-ethyl acetate-methanol-water (5:5:7:4, v/v) was used as the stationary phase of HSCCC. Nodakenetin (2.8 mg), 6.1 mg of Pd-C-IV, 7.3 mg of Pd-D-V, 4.7 mg of ostruthin, 7.8 mg of decursidin and 11.2 mg of decursitin C with the purity of 88.3%, 98.0%, 94.2%, 97.1%, 97.8% and 98.4%, respectively, were separated successfully in one-step separation from 150 mg of crude sample from P. decursivum (Miq.) Maxim. After purified by HSCCC again with light petroleum-ethyl acetate-methanol-water (5:5:4:5, v/v) as the two-phase solvent system, the purity of (I) can reach 99.4%. The structures of all the compounds were identified by 1H NMR and 13C NMR.     

Aerobic oxidation of 1,3,5-triisopropylbenzene using N-hydroxyphthalimide (NHPI) as key catalyst

The first systematic study on the aerobic oxidation of 1,3,5-triisopropylbenzene was examined by the use of N-hydroxyphthalimide (NHPI) as a key catalyst. It was found that 1,3,5-triisopropylbenzene was efficiently oxidized with O₂ in the presence of a catalytic amount of NHPI and azobisisobutyronitrile (AIBN) at 75 °C. Upon treatment of the resulting products with sulfuric acid followed by acetic anhydride led to 5-acetoxy-1,3-diisopropylbenzene and 3,5-diacetoxy-1-isopropylbenzene as major products and a small amount of 1,3,5-triacetoxybenzene. When t-butylperoxypivalate (BPP) was employed as a radical initiator, the oxidation could be achieved in good yield even at 50 °C. This oxidation provides a facile method for preparing phenol derivatives bearing an isopropyl moiety, which can be used as pharmaceutical starting materials.     

Thermogravimetry as a screening tool for the estimation of the vapor pressures of pure compounds

A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more accurate techniques for vapor pressure assessment.     

General synthesis of sugar-pendant 1,3-propanediamines containing a C-glycoside linkage

A straightforward route to C-glycoside linked sugar-pendant 1,3-propanediamines is described. The three-step preparation procedure involves (1) C-glycosylation of an OH-protected α-glycosyl halide with malononitrile, (2) catalytic hydrogenation of the nitriles to amines, and (3) deprotection of acetyl groups via acid-catalyzed hydrolysis. In the case of the galactose derivative, excess sodiomalononitrile promotes the second addition of a carbanion in the first step. The β-anomeric configuration was confirmed by X-ray crystallography of the glycosylated intermediates. This method demonstrates a general method to access a new class of carbohydrate-pendant C-glycoside chelators.     

Molecular metamagnet [Ni(4ImNNH)(2)(NO(3))(2)] (4ImNNH = 4-imidazolyl nitronyl nitroxide) and the related compounds showing supramolecular H-bonding interactions

A new chelating radical ligand 4ImNNH (2-(4-imidazolyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide) was prepared, and complexation with divalent transition metal salts gave complexes, [M(4ImNNH)(2)X(2)], which showed intermolecular ferromagnetic interaction in high probability (7 out of 10 paramagnetic compounds investigated here). The nitrate complexes (X = NO(3); M = Mn (1), Co (2), Ni (3), Cu (4)) crystallize isomorphously in monoclinic space group P2(1)/a. The equatorial positions are occupied with two 4ImNNH chelates and the nitrate oxygen atoms are located at the axial positions. Magnetic measurements revealed that the intramolecular exchange couplings in 1, 2, and 4 were antiferromagnetic, while that in 3 was ferromagnetic with 2J/k(B) = +85 K, where the spin Hamiltonian is defined as H = -2J(S(1).S(2) + S(2).S(3)) based on the molecular structures determined as the linear radical-metal-radical triads. The intramolecular ferromagnetic interaction in 3 is interpreted in terms of orthogonality between the radical pi and metal dsigma orbitals. Compounds 1-3 exhibited intermolecular ferromagnetic interaction ascribable to a two-dimensional hydrogen bond network parallel to the crystallographic ab plane. Complex 3 became an antiferromagnet below 3.4 K and exhibited a metamagnetic transition on applying a magnetic field of 5.5 kOe at 1.8 K. The complexes prepared from metal halides, [M(4ImNNH)(2)X(2)] (X = Cl, Br; M = Mn, Co, Ni, Cu), showed intramolecular antiferromagnetic interactions, which are successfully analyzed based on the radical-metal-radical system. The crystal structures determined here on 1-4, [Mn(4ImNNH)(2)Cl(2)], and [Cu(4ImNNH)(2)Br(2)] always have intermolecular hydrogen bonds of H(imidazole).X(axial ligand)-M, where X = NO(3), Cl, Br. This interaction seems to play an important role in molecular packing and presumably also in magnetic coupling.     

Hydroformylation of Olefins Catalyzed by Rhodium Trichloride Anchored on Ti-HMS

Rhodium trichloride supported on Ti-hexagonal mesoporous silica (Ti-HMS), via a bipyridyl group, is an efficient catalyst for the hydroformylation of olefins at 120 °C and 40.8 atm of CO/H₂ (CO/H₂=2/1). The catalyst is selective leading to high ratios of linear or branched aldehydes from functionalized olefins, and high activity in the case of propene which gave a turnover frequency of 6209 mol/mol(Rh)/h.     

The role of salt on cellulose dissolution in ethylene diamine/salt solvent systems

Ethylene diamine (EDA)/salt solvent systems can dissolve cellulose without any pretreatment. A comparison of the electrical conductivity of different salts in EDA was made at 25 °C, and conductivity decreased in the order of KSCN>KI>NaSCN at the same molar concentration. Among the salts tested, potassium thiocyanate (KSCN) was capable of dissolving both high molecular weight (DP>1000) and low molecular weight (DP = 210) cellulose, and this was confirmed by polarized light microscopy. ³⁹K and ¹⁴N NMR experiments were conducted at 70 °C as a function of cellobiose concentration with EDA/KSCN as the solvent. The results showed that the K⁺ ion interacts with cellobiose more than the SCN⁻ ion does. Recovered cellulose was studied by infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). Changes in the FTIR absorption bands at 1,430 and 1,317 cm⁻¹ were associated with a change in the conformation of the C-6CH₂OH group. The changes in positions and/or intensities of absorption bands at 2,900, 1,163, and 8,97cm⁻¹ were related to the breaking of hydrogen bonds in cellulose. X-ray diffraction studies revealed that cellulose, recovered by precipitating cellulose solutions with water, underwent a polymorphic transformation from cellulose I to cellulose II.     

Preparation of high molecular weight polyurethane particles by nonaqueous emulsion polyaddition

A versatile nonaqueous emulsion polyaddition process for the one-step fabrication of spherical polyurethane nanoparticles is presented. Three different emulsion systems were used consisting of N,N′-dimethylformamide (DMF) dispersed in n-hexane, acetonitrile dispersed in cyclohexane, and acetonitrile dispersed in tetradecane. After successful stabilization of the emulsion systems by using a poly(isoprene)-poly(methylmethacrylate) block copolymer, the fabrication of the polyurethanes was carried out within the dispersed polar phase. The polyurethane particles showed average diameters as small as 35 nm. Additionally, infrared (IR) characterization revealed that the formation of any urea, which decreases the mechanical properties of the polyurethanes, was prevented during the polyaddition. This was attributed to the anhydrous reaction conditions. Gel permeation chromatography (GPC) analysis demonstrated the average molecular weights (M _n) of the polyurethanes to be as high as 16,500 g/mol, corresponding to conversions of 0.98. Comparable molecular weights and conversions have not previously been achieved without the formation of urea.     

The synthesis and characterization of a new (<Emphasis Type="Italic">E,E</Emphasis>)-dioxime containing 13-membered dithiadiazamacrocyclic moieties and its mononuclear complexes

A new (E,E)-dioxime, (6Z,7Z)-15,16-dihydro-14H-dibenzo[b,h][1,10,4, 7]dithiadiazacyclotride-cine-6,7(5H,8H)-dionedioxime (H ₂ L) has been synthesized by reacting cyanogen-di-N-oxide (2) with 2,2′-[propane-1,3-diylbis(thio)]dianiline (1). Mononuclear complexes (4) and (5) of this ligand have been synthesized by reacting the vic-dioxime (H₂L) with NiCl₂ · 6H₂O and CoCl₂ · 6H₂O, respectively. The BF ₂ ⁺ capped Ni(II) and Co(III) complexes (6) and (7) of the dioxime have been synthesized from (4) and (5). The new compounds were characterized by a combination of elemental analysis, ¹H- and ¹³C-n.m.r, i.r. and m.s. spectral data.     

Polymer dispersions from catalytic polymerization in aqueous systems

By contrast to traditional free radical emulsion polymerization, catalytic polymerization allows for polymer microstructure control. In terms of polymerizable monomers, both techniques are largely complementary. Since the beginning of this decade, an increasing number of reports on polyolefin, polybutadiene, polyalkenamer, polynorbornene, polyketone, and polyacetylene dispersions prepared by catalytic polymerization in disperse aqueous systems has appeared. This contribution reviews the preparation of these dispersions, their colloidal properties, particle formation mechanisms, particle morphologies, and polymer microstructures.