Diaquabis(2,5‐dihydroxybenzoato‐κO)bis(1,10‐phenanthroline‐κ2N,N′)strontium(II) bis(1,10‐phenanthroline) tetrahydrate

The title compound, [Sr(C₇H₅O₄)₂(C₁₂H₈N₂)₂(H₂O)₂]·2C₁₂H₈N₂·4H₂O, consists of an Sr^II complex, uncoordinated phenanthroline (phen) molecules and solvent water molecules. The Sr^II ion is located on a twofold axis and is coordinated by two phen ligands, two dihydroxybenzoate anions and two water molecules in a distorted tetragonal antiprismatic geometry. Partially overlapped arrangements exist between parallel coordinated and parallel uncoordinated phen rings; the face‐to‐face separations between the former (coordinated) and the latter (uncoordinated) rings are 3.436 (13) and 3.550 (14) Å, respectively. This difference suggests the effect of metal coordination on π–π stacking between phen rings.     

L-脯氨酸催化下甲基酮和1-芳基-2,2,2-三氟乙酮的不对称Aldol反应

Direct asymmetric aldol addition of methyl ketones to 2,2,2-trifluoro-1-phenylethanone and its ring-substituted derivatives was achieved using L-proline as a chiral promoter. Various optically active β-trifluoromethyl-β-hydroxy ketones were obtained in almost quantitative yields with moderate enantioselectivities up to 64 % ee.     

Electrical Conductance and Volumetric Studies in Aqueous Solutions of DL-Pyroglutamic Acid

Conductivity measurements of DL-pyroglutamic acid and sodium pyroglutamate in dilute aqueous solutions were performed in the 288.15–323.15 K temperature range. The limiting molar conductances of pyroglutamate anion, λ^o(pGlu⁻, T) and the dissociation constants of pyroglutamic acid, K(T) were derived from the Onsager, and the Quint and Viallard conductivity equations. Densities of aqueous solutions with molalities lower than 0.5 mol-kg⁻¹ were determined at 5 K intervals from T = 288.15 K to 333.15 K. Densities served to evaluate the apparent molar volumes, V_2,φ(m, T), the cubic expansion coefficients, α (m,T) and the changes of the isobaric heat capacities with respect to pressure, (∂ C_P/∂ P)_T,m. They were correlated qualitatively with the changes in the structure of water when pyroglumatic acid is dissolved in it.     

Efficient synthesis in three steps and spectral determination of methyl‐5‐[(o‐, m‐, and p‐substituted‐phenylthio]‐2‐benzimidazolecarbamates

The preparation and spectral properties often novel methyl 5‐[(o‐, m‐, and p‐substituted)‐phenylthio]‐2‐benzimidazolecarbamates with possible pharmacological activity as antihelmintics is described; by condensation and cyclization between 5‐methylthioures sulfate chloroformic acid methyl ester and 3,4‐diaminophenyl‐substituted‐phenylthio ether dissolved in ethanol. The structures of all final products were corroborated by ir; ¹H‐nmr, ¹³C‐nmr and ms.     

A new synthesis of 1,2,3,5‐tetrahydroimidazo[2,3‐b]‐[1,3]benzodiazocines

A new synthesis of 6‐carbomethoxy‐1,2,3,5‐tetrahydroirnidazo[2,3‐b][1,3]benzodiazocines 13 by the intramolecular cycloaddition reaction of methyl 2‐(1‐aziridinylmethyl)‐3‐(2‐ureidophenyl)propenoates 10 under Appel's dehydration conditions is described. The latter were readily obtained from 2‐nitrobenzalde‐hyde with methyl acrylate through the Baylis‐Hillman reaction.     

Energy Dissipation Processes of singlet‐excited 1‐Hydroxyfluorenone and its Hydrogen‐bonded Complex with N‐methylimidazole¶

Effects of solvent, pH and hydrogen bonding with N‐methylimidazole (MIm) on the photophysical properties of 1‐hydroxyfluorenone (1HOF) have been studied. Fluorescence lifetime, fluorescence quantum yield and triplet yield measurements demonstrated that intersystem crossing was the dominant process in apolar media and its rate constant significantly diminished with increasing solvent polarity. The acceleration of internal conversion in alcohols paralleled the strength of intermolecular hydrogen bonding. The faster energy dissipation from the singlet‐excited state in cyclohexane was attributed to intramolecular hydrogen bonding. The pK_a of 1HOF decreased from 10.06 to 5.0 on light absorption, and H₃O⁺ quenched the singletexcited molecules in a practically diffusion‐controlled reaction. On addition of MIm in toluene, dual fluorescence was observed, which was attributed to reversible formation of excited hydrogen‐bonded ion pair. Rate constants for the various deactivation pathways were derived from the combined analysis of the steady‐state and the time‐resolved fluorescence results.     

Insertion Reactions of Carbon Disulfide into Mg‐C and Mg‐N Bonds: Syntheses and Structural Determinations of Mg(S2CY)2(THF)n(Y=NEt2, NiPr2, iPr,Ph) and BrMg(S2CZ)(THF)3(Z=Ph,iPr)

The insertion reaction of CS₂ with Mg(NR₂)₂ (R= Et, ⁱPr), MgR′₂ (R′= Et, Ph) and R″MgBr (R″= ⁱPr, Ph) respectively lead solid products, Mg(S₂CNR₂)₂(THF)_n ( 1 : R= Et, n=2; 2 : R= ⁱPr, n=1), Mg(S₂C′R)₂(THF)₂ ( 3 : ′R= Et, 4 : ′R= Ph), BrMg(S₂C″R) (THF)₃ ( 5 : ″R= ⁱPr, 6 : ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with ¹H, ¹³C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X‐ray crystallography.     

Synthesis and in vitro degradation of poly(N‐vinyl‐2‐pyrrolidone)‐based graft copolymers for biomedical applications

This work is devoted to the design of a novel family of hydrosoluble biomaterials: poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐based graft copolymers. A synthesis route has been elaborated in which ω‐functionalized PVP is prepared via chain‐transfer radical polymerization, end‐group modified, and subsequently grafted onto a polyhydroxylated backbone, typically dextran or poly(vinyl alcohol). The resulting graft copolymer biomaterials are designed for use in various biomedical applications, particularly as materials with a stronger potential for plasma expansion than already existing products have. The graft copolymers are potentially degradable because the PVP grafts are connected to the polyol backbone via a hydrolytically labile carbonate or ester linkage. The degradation of the graft copolymers was performed in vitro over a period of 6 weeks. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3652–3661, 2002     

Synthesis and properties of amine‐containing poly(arylene ether sulfone) as an anion‐exchange matrix

Poly(arylene ether sulfone) (PSF), showing good thermal stability and excellent mechanical properties, was synthesized as an anion‐exchange matrix. It was synthesized by the condensation polymerization between bisphenol A and 4,4′‐dichlorodiphenylsulfone. 1°‐Amine‐containing poly(arylene ether sulfone) (1°‐APSF) was synthesized by the reduction reaction of a nitrated PSF. Then, it was transferred to 3°‐amine‐containing poly(arylene ether sulfone) (3°‐APSF) by the alkylation of the amine of 1°‐APSF. The properties of PSF, 1°‐APSF, and 3°‐APSF were investigated by Fourier transform infrared, ¹H NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The introduction of the 3°‐amine group into PSF increased the glass‐transition temperature but decreased thermooxidative stability. The ion‐exchange capacities of 1°‐APSF and 3°‐APSF were shown to be 2.24 and 2.86 mequiv/g, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4281–4287, 2002     

A scheme for the analysis of monazite and monazite concentrates

A scheme using ion-exchange methods is described for the analysis of monazites and monazite concentrates. The sample is opened up with concentrated sulphuric acid, and the resultant solution is applied to a column of Zeocarb 225 resin. After phosphate has been washed out, lead, aluminium, titanium, iron, uranium, calcium and magnesium are eluted with N hydrochloric acid and determined by specific, mainly spectrophotometric, methods. Rare earth elements are eluted with 3 N hydrochloric acid. Cerium is separated from the other rare earths by solvent extraction of its nitrate with methyl iso-butyl ketone; both groups are determined gravimetrically. Thorium is eluted from the ion-exchange resin with 3.6 N sulphuric acid and determined spectrophotometrically with thorin.The sulphuric acid-insoluble minerals are brought into solution by a double fusion method, and the determinations are carried out by a combination of ion-exchange and photometric procedures. Silica, phosphorus pentoxide, tin and chromium are determined by photometric methods, using separate portions of the sample.Lanthanum, yttrium and ytterbium are determined in a 1 M perchloric acid solution of the mixed rare earth oxides (less cerium) using flame photometry. Samarium, praseodymium and neodymium are determined by spectrophotometry.