Highly efficient rhodium/monodentate phosphoramidite catalyst and its application in the enantioselective hydrogenation of enamides and alpha-dehydroamino acid derivatives

An easily prepared and highly efficient monodentate phosphoramidite ligand derived from BINOL, (S)-2,2'-O,O-(1,1'-binaphthyl)-dioxo-N,N-diethylphospholidine, was examined in the hydrogenation of both enamides and alpha-dehydroamino acid derivatives. The catalyst provided remarkably high enantioselectivities (up to 99.6% ee for enamides and >99.9% ee for alpha-dehydroamino acid derivatives).     

高效石墨浮选剂的合成

高效石墨浮选剂的合成金婵，薛玉，汪进，刘欣荣，秦英海（哈尔滨工业大学应用化学系哈尔滨１５０００１）（大庆石化总公司大庆）关键词石墨，浮选剂，合成，混合烃由于石墨具有良好的力学性能、导电、高熔点等性质，广泛用于原子能、宇航和民用工业。隐晶质石墨属于微晶...     

Photo-stabilising action of metal chelates in polypropylene—Part IV: Influence of metal stearates in an exchange mechanism

The effect of calcium and nickel stearates on the photo-stabilising action and photo-decomposition of one calcium and two nickel metal chelates in polypropylene has been examined using infra-red and ultraviolet derivative spectroscopy. Whereas the presence of calcium stearate antagonises the photo-stabilising action of one nickel chelate, Irgastab 2002, it strongly synergises with the other, Cyasorb UV 1084. The presence of nickel stearate synergises with the calcium chelate, Irganox 1425, in unprocessed polymer whereas, in processed polymer, it exhibits antagonism. Rates of photo-decomposition of the metal chelates are also affected by metal stearates. The data suggests that, with these nickel chelates, there might be some degree of metal exchange with certain metal stearates.     

Carbon-13 spin-lattice relaxation studies of the effect of water on ion-selective electrode membranes

(13)C spin-lattice relaxation studies on bis(2-ethylhexyl) adipate (DOA) plasticized poly(vinylchloride) (PVC) membranes are reported for plasticization levels ranging from 25 to 100 wt% plasticizer. The interaction between DOA and PVC molecules in these membranes appears to involve an entrapment of the plasticizer molecule within the polymer matrix. This is based on the constancy of the characteristic segmental motions of the plasticizer chains throughout the concentration range studied. The segmental mobility of the plasticizer component is modified by water absorption in the membrane. The pattern of characteristic segmental motions of the plasticizer is altered, the effect depending on the amount of added salt in the membrane. The results show water has a weak influence on the microviscosity of the membrane matrix.     

Stoichiometric and catalytic oxidations of alkanes and alcohols mediated by highly oxidizing ruthenium-Oxo complexes bearing 6, 6'-dichloro-2,2'-bipyridine

The ruthenium(II) complex cis-[Ru(6, 6'-Cl(2)bpy)(2)(OH(2))(2)](CF(3)SO(3))(2) (1) is a robust catalyst for C-H bond oxidations of hydrocarbons, including linear alkanes, using tert-butyl hydroperoxide (TBHP) as terminal oxidant. Alcohols can be oxidized by the "1 + TBHP" protocol to the corresponding aldehydes/ketones with high product yields at ambient temperature. Oxidation of 1 with Ce(IV) in aqueous solution affords cis-[Ru(VI)(6, 6'-Cl(2)bpy)(2)O(2)](2+), which is isolated as a green/yellow perchlorate salt (2). Complex 2 is a powerful stoichiometric oxidant for cycloalkane oxidations under mild conditions. Oxidation of cis-decalin is highly stereoretentive; cis-decalinol is obtained in high yield, and formation of trans-decalinol is not observed. Mechanistic studies showing a large primary kinetic isotope effect suggest a hydrogen-atom abstraction pathway. The relative reactivities of cycloalkanes toward oxidation by 2 have been examined through competitive experiments, and comparisons with Gif-type processes are presented.     

Octahedral cobalt(III) complexes of the chloropentammine type. XVII. Association and reaction of some halogenopentamminecobalt(III) and halogenopentamminechromium(III) cations with hydroxide in aqueous dioxan

The replacement, by hydroxide ion, of the coordinated halide from some halogenopentamminecobalt(III) and -Chromium(III) cations in aqueous dioxan has been studied over a range of alkali concentrations up to 0.1 M. With excess of hydroxide ion at constant ionic strength, pseudo first-order rate constants were obtained. The results support a pre-equilibrium association of complex and hydroxide ions in these media, but do not provide distinction as to whether the resulting ion-pair subsequently reacts by direct exchange or by proton removal. The extents of ion association are found to be greater for the cobalt(III) than for the chromium(III) system, increasing with the amount of dioxin in the solvent mixture.     

Forces between a Rigid Probe Particle and a Liquid Interface

The effect of disjoining pressure between a rigid spherical probe particle (attached to an AFM cantilever) and a liquid interface (e.g., oil/water or air/water) is treated in an analytic manner to describe the total force F exerted on the probe as a function of the distance X of the probe from the rigid substrate (AFM stage) on which the liquid interface resides. Two cases (i) a flat interface under gravity and (ii) a drop whose size is sufficiently small that gravity can be neglected have been examined. A simple numerical algorithm is given for computing F(X) (the AFM observable) from a given form for the disjoining pressure. Numerical results are displayed for electrostatic probe/interface interactions which reveal the linear compliance regime experimentally observed in AFM experiments on these systems. The slope of the linear compliance regime is shown to be a function of the properties of the interface (capillary length, particle radius, drop size, contact angle of drop on rigid substrate etc.). Copyright 2001 Academic Press.     

Novel Chiral Aminophosphine Ligand:Synthesis and Application in Saymmetric Catalytic Hydrogenation Reaction

A new chiral aminophosphine ligand 6,6′-dimethoxy-2,2′-bis(diphenylphosphinoamino)biphenyl(DMBDPPABP) was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its dervatives.The effects of solvent and reaction temperature on enantioselectivity were also studied.     

Preparation and characterization of self-assembled nanoparticles based on glycol chitosan bearing adriamycin

An anthracycline drug, adriamycin, was chemically conjugated onto the backbone of glycol chitosan via an acid-labile cis-aconityl linkage. The physicochemical characteristics of the glycol chitosan–adriamycin (GC–ADR) conjugates were investigated by dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. The GC–ADR conjugates were capable of forming nano-sized self-aggregates in an aqueous medium, when the adriamycin content in the conjugate was in the range of 2.0–5.0 wt.%. The self-aggregates were spherical in shape, and had mean diameters of 238–304 nm, depending on the adriamycin content. The critical aggregation concentrations of the conjugates, estimated by the fluorescence quenching method, were as low as 1.0–2.5×10⁻² mg/ml. The size of self-aggregates was not affected by the polymer concentration in the range from 50 to 2,000 μg/ml, and was maintained up to 8 days in phosphate-buffered saline (pH 7.4), indicating high colloidal stability. The release of adriamycin from self-aggregates was significantly dependent on the pH of the medium due to the cis-aconityl linkage; e.g., the amount of adriamycin released for 4 days was 7.3±0.3% at pH 7, whereas it was 29.3±1.9% at pH 4. The cell viability results demonstrated that free adriamycin shows more potent cytotoxicity than the conjugates, primarily attributed to the sustained release of adriamycin from self-aggregates. In conclusion, the self-aggregates, formed by GC–ADR conjugates, might be useful for the site-specific delivery of adriamycin in a sustained manner.     

Ruthenium‐catalyzed synthesis of quinolines via reductive heteroannulation of nitroarenes with 3‐amino‐1‐propanols

Nitroarenes are reductively cyclized with 3‐amino‐1‐propanols in dioxane/H₂O in the presence of a ruthenium catalyst and tin(II) chloride dihydrate together with isopropanol to afford the corresponding quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from 3‐amino‐1‐propanols to anilines, N‐alkylation of anilines by 3‐anilino‐1‐propanols and heteroannulation of 1,3‐dianilinopropanes is proposed.