Synthesis of the new chiral tridentate ligand bis(pyrid-2-ylethyl) menthylphosphine and its use in the palladium-catalyzed allylic alkylations

We describe the synthesis of a new asymmetric P,N,N′-tridentate ligand (bis(pyrid-2-ylethyl) menthylphosphine, BPEMP), containing two pyridyl rings and (1S,2R,5S)-menthylphosphino group. The ligand is obtained in five steps from natural abundant l-menthol. The coordination behavior of the ligand toward cationic (allylic)Pd(II) moiety and its first application in palladium-catalyzed asymmetric allylic alkylation are presented. Crystallographic and spectroscopic analyses reveal that [(η³-allylic)Pd(BPEMP)]⁺ complex forms only one isomer in the solid state as well as in solution.     

Synthesis and two-electron redox behavior of diazuleno[2,1-a:1,2-c]naphthalenes

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.     

A Closed-Form Relation for Dimension-Dependent Two-Electron Matrix Elements of the Interelectronic Distance

The evaluation of matrix elements of two electron atoms is fundamental for the study of the electronic properties of those systems. We add to this knowledge by presenting an explicit expression for the matrix elements of the inverse of the interelectronic distance of two-electron atoms in any spatial dimension D. The basis functions used are the D-dependent hydrogenic wavefunctions {1s ²,2p ²,3d ²,4f ²,5g ²,...,21y ²,...}, extending and including, in this way, the results of the previous basis set {1s ²,2p ²,3d ²,4f ²}. The methodology used does not employ Fourier integral transforms as in previous works but hypergeometric transformation formulas.     

Improved cross-axis synchronous flow-through coil planet centrifuge for performing counter-current chromatography. II. Studies on retention of stationary phase in short coils and preparative separations in multilayer coils

Performance of the apparatus was evaluated in terms of stationary phase retention, partition efficiency and sample loading capacity. Preliminary studies with short coils revealed high retention of the stationary phase under a proper combination of the head-tail elution and planetary motion. Preparative capability of the apparatus was successfully demonstrated on efficient multigram separations of 2,4-dinitrophenyl amino acids, indole auxins, and bacitracin in a pair of large multilayer coils with a total capacity of 1.5 l.     

Experimental observations of the hydrodynamic behavior of solvent systems in high-speed counter-current chromatography. II. Phase distribution diagrams for helical and spiral columns

Extensive studies have been performed on hydrodynamic distribution of two immiscible solvent phases in helical and spiral columns by means of coil planet centrifugation. Under the Scheme IV [see Fig. 1 in Y. Ito, J. Chromatogr., 301 (1984) 377] planetary motion, the two phases display unilateral distribution in the coil, i.e., one phase travels toward the head and the other phase toward the tail. This hydrodynamic trend is sensitively affected by various factors such as physical properties of the solvent system, helical diameter of the column, revolutional radius, etc. Phase distribution diagrams obtained from a set of conventional two-phase solvent systems under various experimental conditions provide extremely useful information for both basic hydrodynamic studies and practical application in high-speed counter-current chromatography.     

Synthesis and characterization of flavylium salts having three types color depending on recrystallization conditions

Three types of flavylium salts (FVs, yellow, green and red) have been synthesized and the colors depended on recrystallization conditions. The existence of these color states was confirmed by diffuse reflectance spectra. The spectra were almost the same as the absorption spectra in ethanol solution. The molecular state of FVs in crystals will be the same as that in solutions. The crystal colors of the FVs are controlled by the recrystallization conditions.     

Studies on antiallergic agents. I. Synthesis and antiallergic activity of novel pyrazine derivatives.

Various pyrazine derivatives were synthesized and their antiallergic activity was examined. The inhibitory activity on allergic histamine release of the compounds bearing a 5-tetrazolyl group was more potent than that of the corresponding carboxyl derivatives. The introduction of -CONH- or -NHCO- between the pyrazine ring and the 5-tetrazolyl group as a spacer greatly enhanced the activity. N-(1H-Tetrazol-5-yl)-2-pyrazinecarboxamide (I-3) was estimated to exhibit nearly the same potency as disodium cromoglycate (DSCG). The structure-activity relationship among various derivatives modified by introducing some substituents onto the 3-, 5- or 6-position of the pyrazine ring of I-3 was investigated. The activity remained unchanged or was reduced when such substituents as methyl, chloro, methoxy, methylamino and dimethylamino were introduced at the 3- or 5-position. In contrast, 6-substitution with various alkylamino groups more or less increased the activity. Among them, the 6-dimethylamino (I-17c) and 6-(1-pyrrolidinyl) (I-34) derivative were proved to be most potent. The IC50 values (concentration which produces 50% inhibition of the allergic histamine release) of I-17c and I-34 were determined to be 4.7 x 10(-10) and 4.6 x 10(-10) M, respectively. These two compounds produced a potent inhibitory activity on passive cutaneous anaphylaxis (PCA) in rat, not only by the intravenous route (ED50 = 0.0096 mg/kg for both compounds) but also by the oral route (ED50 = 0.19 and 0.18 mg/kg, respectively). On the other hand, when the pyrazine ring of some representative compounds was replaced with a pyridine ring, the inhibitory activity on histamine release was significantly reduced.     

Cu/TiO2-NiO上光促表面催化CO2和H2O合成CH3OH反应规律

采用溶胶-凝胶法制备了n(电子型)-p(空穴型) 复合半导体材料0.5％Cu/TiO2-2.0％NiO (w),利用X射线衍射(XRD)、透射电镜(TEM)、红外光谱(IR)、紫外-可见光漫反射(UV-Vis)、程序升温脱附(TPD)技术对材料结构、吸光性能、化学吸附性能进行了表征,研究了该材料对CO2和H2O合成CH3OH的光促表面催化反应(PSSR)规律.结果表明,所制备材料能够明显促进目的反应,室温条件下即有CH3OH生成.在200 ℃下,由于光-表面-热的协同效应,CO2转化率得以提高,且CH3OH的选择性达到87.5％ .根据实验结果,得出CO2在材料表面的卧式吸附态为CH3OH的前驱物,并对PSSR机理进行了讨论.     

SPECIFIC PHOTOCOUPLING OF 5-BROMOURIDINE TO TRYPTOPHAN IN AQUEOUS FROZEN SOLUTION§

Abstract —5-Bromouridine (BrUd) photochemically reacted with l -tryptophan (trp) only in aqueous frozen solution giving rise to 2-[1,2,3,4-tetrahydro-1-(β-d -ribofuranosyl)-2,4-dioxo-5-pyrimidinyl]-l -tryptophan ( 1a ). Under similar conditions irradiation of 5-bromouracil (BrU) and trp gave the corresponding coupled product 2. Addition of acetone, potassium carbonate or sodium chloride to the frozen system completely inhibited the photocoupling reaction. These photocoupling reactions are suggested to proceed via mixed aggregate formation between trp and BrUd (or BrU) in frozen aqueous solution. Stacking interactions in these aggregates are characterized by an efficient quenching of trp fluorescence by BrUd. Under the same conditions other amino acids such as phenylalanine, tyrosine, histidine and lysine did not react with BrUd, indicating that the photocoupling of BrUd (or BrU) is specific for trp.     

Copolymerization of 1,6-anhydro-ß-D-galactopyranose and 1,6-anhydro-ß-D-mannopyranose derivatives

1,6-Anhydro-2,3,4-tri-O-(p-methylbenzyl)-ß-D -galactopyranose (TXGal,M₁) has been copolymerized with 1,6-anhydro-2,3,4-tri-O-benzyl-ß-D -mannopyranose (TBMan,M₂), the products characterized by NMR, specific rotation, and viscosity, and the reactivity ratios calculated. The reactivity ratios r₁ = 0.37 ± 0.15 and r₂ = 38 ± 4 indicate that the anhydromannose derivative is about 100 times as reactive as that of anhydrogalactose. A comparison of glucose, mannose, and galactose copolymerizations suggests that the reactivity differences of the three propagating cations are comparatively small and the reactivity differences of the monomers large. This result is consistent with a mechanism proposed earlier. Methyl substitution on the aromatic rings of the p-xylyl groups inhibits the initiation process significantly relative to benzyl, but propagation only slightly.