Enantioselective synthesis of (-)-roccellaric acid

[reaction in text] A new strategy for the synthesis of anti-4,5-disubstituted gamma-butyrolactones starting from inexpensive furan-2-carboxylic methyl ester was developed. By applying this methodology, the enantioselective synthesis of (-)-roccellaric acid ((-)-17) was accomplished using a copper(I)-catalyzed asymmetric cyclopropanation, a tin(IV)-catalyzed retroaldol/lactonization sequence of cyclopropanols, and a ruthenium-catalyzed intermolecular metathesis reaction as key steps.     

Solvent-free synthesis of 1-amidoalkyl-2-naphthols using magnetic nanoparticle-supported 2-(((4-(1-iminoethyl)phenyl)imino)methyl)phenol Cu (II) or Zn (II) Schiff base complexes

Two magnetic nanoparticle-supported 2-(((4-(1-iminoethyl)phenyl)imino)methyl)phenols were successfully synthesized, characterized, and applied in the one-pot three-component reaction of substituted benzaldehydes, 2-naphthol, and amides for synthesis of 1-amidoalkyl-2-naphthols. These three-component processes occurred under solvent-free reaction conditions at 80 °C. The magnetically recoverable supported Schiff base metal catalysts can be reused several times in the model reaction. The synthesized catalysts are also easily separated from the reaction mixture by applying an external magnet. This procedure offers the advantages of simple, operational procedure as well as no use of hazardous organic solvents.

     

CuCl-K(2)CO(3)-catalyzed highly selective borylcupration of internal alkynes - ligand effect

An efficient and practical copper-catalyzed highly regio- and stereoselective borylcupration of internal alkynes with bis(pinacolato)diboron using a catalytic amount of K(2)CO(3) as base producing Z-alkenylboron compounds has been demonstrated by applying the ligand effect: commercially available electron-rich tris(p-methoxyphenyl) phosphine ensures a smooth and efficient reaction. Functionalized alkynes, such as propargylic alcohols and derivatives as well as N-propargyl tosylamide, may also be used with excellent selectivity.     

Improvement on Simultaneous Determination of Cr(III) and Cr(VI) by Capillary Electrophoresis and Chemiluminescence Detection

Chromiumexistsindifferentoxidationstatesingroundwater,industrialwastewater,seawater,andsoilofourenvironment1,2.Chromium(III)isanessentialtraceelementforhumans,requiredforthemaintenanceofnormalglucose,cholesterol,andfattyacidmetabolism.Ontheotherhand,watersolublechromium(VI),intheformCr2O72-orCrO42-,ishighlyirritatingandtoxictohumansandanimals3.Itsacutetoxiceffectsincludeanimmediatecardiovascularshockandlatereffectsonkidney,liver,andblood-formingorgans.Therefore,itisnecessaryforriskassessme…     

Ultrafast Xanthate-Mediated Photoiniferter Polymerization-Induced Self-Assembly (PISA)

Polymerization-induced self-assembly (PISA) is a powerful technique for preparing block copolymer nanostructures. Recently, efforts have been focused on applying photochemistry to promote PISA due to the mild reaction conditions, low cost, and spatiotemporal control that light confers. Despite these advantages, chain-end degradation and long reaction times can mar the efficacy of this process. Herein, we demonstrate the use of ultrafast photoiniferter PISA to produce polymeric nanostructures. By exploiting the rapid photolysis of xanthates, near-quantitative monomer conversion can be achieved within five minutes to prepare micelles, worms, and vesicles at various core-chain lengths, concentrations, or molar compositions.     

Hydrothermal Synthesis and Structure Analysis of Indium Vanadate （InVO4）

1 INTRODUCTION Indium vanadate is a kind of vanadate compounds. There are two crystal phase structures, metastable monocline structure and stable orthogonal structure. Orel, B.[1] and his partners have discovered that V of tetrahedron VO4 has very sensitive energy gap band. Through XPS study of orthogonal InVO4, it is found that its band gap is shorter than those of InNbO4 and InTaO4, and its band-gap energy is 2.0 eV[4]. Ortho- gonal InVO4 can act during the range from short- wav…     

Systematic and in situ energy dispersive X-ray diffraction investigations on the formation of lanthanide phosphonatobutanesulfonates: Ln(O(3)P-C(4)H(8)-SO(3))(H(2)O) (Ln = La-Gd)

Using the flexible linker H(2)O(3)P-C(4)H(8)-SO(3)H (H(3)L) and rare earth ions Ln(3+) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) we were able to synthesize the new isostructural inorganic organic hybrid compounds Ln(O(3)P-C(4)H(8)-SO(3))(H(2)O). High-throughput experiments were employed to study the influence of the molar ratios Ln:H(3)L and pH on the product formation. The crystal structure of the compounds Sm(O(3)P-C(4)H(8)-SO(3))(H(2)O) (1) and Pr(O(3)P-C(4)H(8)-SO(3))(H(2)O) (2) were determined by single crystal diffraction. The structures are built up from chains of edge-sharing LnO(8)-polyhedra that are connected by the phosphonate and sulfonate groups into layers. These layers are linked by the -(CH(2))(4)- group to form a three-dimensional framework. The synthesis of compound 1 was scaled up in a conventional oven as well as in a microwave reactor system. A modification of a microwave reactor system allowed its integration into the beamline F3 at HASYLAB, DESY, Hamburg. The crystallization was investigated in situ by means of energy dispersive X-ray diffraction using conventional as well as microwave heating methods applying temperatures varying from 110 to 150 °C. The formation of Sm(O(3)P-C(4)H(8)-SO(3))(H(2)O) takes place in two steps. In the first step a crystalline intermediate was observed, which transforms completely into compound 1. The method by Sharp and Hancock was used to determine the rate constants, reaction exponents, and the Arrhenius activation energy for both reaction steps. Comparing both heating methods, microwave heating leads to fully crystallized reaction product after shorter reaction times, but neither the temperature nor the heating method has significant influence on the induction time.     

Unique Nafion-Os(bpy)3~(2 ) Modified Electrodes

TheelectrodesmodifiedwithaNafionfilmcontainingredoxcenters(mediators)formanattractivegroupofchemicallymodifiedelectrodesbecauseoftheirflexibilityinelectrocatalysisandotherinterestingproperties.Inmostcasesreportedintheliterature,arecastNafionfilmwasfirstcoatedonthesubstrateelectrodeandtheelectrodewasthendippedinasolutionofthemediatortobestudied(thetwostepmethod).Ansonandcoworkersl'2reportedstrikingeffectsofthemediatorconcentrationinthecoatingandthehydrationextentofthecoatingbeforedippingonthecy…     

Magnesium hydroperoxyacetate (MHPA) and magnesium dihydroperoxide (MDHP): New antibacterial agents for fibrous substrates

Water-dispersable products have been prepared from the reaction of magnesium acetate tetrahydrate with hydrogen peroxide at mole ratios of 1 : 2 to 1 : 40 to produce compositions with active oxygen or peroxide contents of 1–30%. The products are believed to be stoichiometric mixtures of HOO Mg OAc and HOO Mg OOH that vary in composition with the molar ratios used. These new compounds are hydrolytically stable at ambient temperatures for extended periods (at least 60 days) and thermally stable below 300°C. Pad-cure processes are described for applying the above reaction products as a dispersion in water or aqueous hydrogen peroxide or as a foam in aqueous hydrogen peroxide to impart antibacterial activity to celulosics, synthetic fibers and fiber blends. The textiles are treated with dispersions or foam containing 10–17% of the reaction products derived from mole ratios of 1 : 2 to 1 : 40 magnesium acetate tetrahydrate: hydrogen peroxide. On subsequent heating for 2–4 min at 120–150°C, washing and drying, the modified textiles contain durably bound active oxygen or peroxide (0.1–1.7%) that has activity against representative gram-positive and gramnegative bacteria for up to 50 launderings.     

A gas-phase crossed-beam study of OH produced in the radical-radical reaction of O((3)P) with iso-propyl radical (CH3)2CH

The gas-phase radical-radical reaction dynamics of ground-state atomic oxygen [O((3)P)] with iso-propyl radicals, (CH(3))(2)CH, were investigated by applying a combination of high-resolution laser-induced fluorescence spectroscopy in a crossed-beam configuration and ab initio calculations. The nascent distributions of OH (X(2)Π: υ' = 0) from the major reaction channel O((3)P) + (CH(3))(2)CH → C(3)H(6) (propene) + OH showed substantial internal excitations with a bimodal feature of low- and high-N' components with neither spin-orbit nor Λ-doublet propensities. Unlike previous kinetic results, proposed to proceed only through the direct H-atom abstraction process, on the basis of the population analysis and comparison with the statistical theory, the title reaction can be described in terms of two competing mechanisms at the molecular level: direct abstraction process and indirect short-lived addition-complex-forming process with a ratio of 1.25?:?1.     

Predictable and site-selective functionalization of poly(hetero)arene compounds by palladium catalysis

The challenge of achieving selective and predictable functionalizations at C-H bonds with complex poly(hetero)aromatic substrates was addressed by two different approaches. Site-selectivity can be obtained by applying various reaction conditions that are (hetero)arene specific to substrates that contain indoles, pyridine N-oxide, and polyfluorinated benzenes. An experimental classification of electron-rich heteroarenes based on their reactivity toward palladium-catalyzed C-H functionalization was established, the result of which correlated well with the order of reactivity predicted by the DFT-calculated concerted metalation-deprotonation (CMD) pathway. Model substrates containing two reactive heteroarenes were then reacted under general reaction conditions to demonstrate the applicability this reactivity chart in predicting the regioselectivity of the palladium-catalyzed direct arylation and benzylation reactions.     

Thermodynamic stability and reactivity of silylated bis(oxy)iminium ions

Silylation of various nitronates with trialkylsilyl triflates was investigated by applying NMR techniques. In several cases, a flexible nitronate-bis(oxy)iminium ion (as an ion pair with triflate as counterion) equlibrium was found, and its thermodynamic parameters were determined. Elevation of temperature or dilution shifts this equilibrium toward the reactants. Activation parameters for the C,C-coupling reaction of silylated bis(oxy)iminium ions with a series of reference nucleophiles were determined. Estimated electrophilicity of bis(oxy)iminium ions allows one to count on C,C-coupling when partner nucleophilicity is N > 4.     

Flow Injection Chemiluminescence Method for Nalbuphine Hydrochloride in Pharmaceutical Formulations Using Tris(2,2'-bipyridyl)ruthenium(II) Chloride-diperiodatocuprate(III) Reaction

Asensitive and selective method employing chemiluminescence(CL) coupled with flow injection(FI) is reported for nalbuphine hydrochloride(NAL) assay in pharmaceutical formulations. The enhancement effect of NAL on the CL reaction between tris(2,2'-bipyridyl)ruthenium(II) chloride-diperiodatocuprate(III) {Ru[(bpy)₃]²⁺-Cu(III) complex} in acidic medium is used as analytical measurement. The optimal conditions of the CL reaction were sulfuric acid 1.0×10^-3 mol/L, Ru[(bpy)₃]²⁺ 7.5×10^-5 mol/L, Cu(III)/Ag(III) complexes 4.0×10^-4/5.0×10^-4 mol/L, sample loop volume of 120 μL and flow rate of 2.5 mL/min. The sensitivities of the method in terms of detection(S/N=3) and quantification(S/N=10) limits are 5×10^-4 and 0.001 ppm(1 ppm=1 mg/L), respectively. The linear response of the instrument in the form of CL intensity with respect to NAL concentration is over the range 0.001-15.0 ppm(R²=0.9999) with relative standard deviation from 0.8% to 3.2% and injection throughput of 120 injection/h. The applications of the method include the quantitative analysis of NAL in pharmaceutical injection samples. Variations and the average results of the proposed method are not signi-ficantly different from the results of a reported method by applying F- and paired student t-test. The most likely CL reaction mechanism is written in accordance with spectrophotometric and CL studies.     

An easy approach to optically active alpha-amino phosphonic acid derivatives by chiral Zn(II)-catalyzed enantioselective amination of phosphonates

A catalytic direct enantioselective electrophilic amination of beta-keto phosphonates has been developed applying chiral bisoxazoline-zinc(II) complexes as the catalyst. The reaction proceeds well for both acyclic and cyclic substrates in high yields and with up to 98% ee using azodicarboxylates as the nitrogen source. The scope of the reaction is, for example, the further transformation to optically active beta-hydroxy-alpha-amino phosphonates with very high stereoselection.     

Behavior of 3,6-Bis(vinylsulfonyl)-1,2,4,5-tetrafluorobenzene in Homolytic Addition of Dialkyl Phosphites

Reaction of 3,6-bis(vinylsulfonyl)-1,2,4,5-tetrafluorobenzene with dialkyl phosphites at thermal initiation (70°C) gives rise to 3,6-bis(dialkoxyphosphonoethylsulfonyl)-1,2,4,5-tetrafluorobenzenes in up to 45% yield. The formation of diethoxyphosphonyl radicals in the course of the reaction was observed with the use of ESR method applying spin trapping by 2-methyl-2-nitrosopropane. The use as initiator of the azo-bis-isobutyronitrile increased the yield of diadducts to 60%.     

Ball milling: a green mechanochemical approach for synthesis of Ni (II), Co (II) and Cu (II) complexes

A series of Ni (II), Co (II) and Cu (II) complexes were synthesized with excellent yields via a one‐pot ball milling chelation reaction of those metals and β‐diketone. The process offers numerous advantages, such as better yield, short reaction time and mild reaction conditions. The computational studying was estimated to approve the geometry of the isolated solid compounds by applying density functional theory. The synthesized compounds were interpreted by using various spectroscopic techniques [infrared (IR), ¹H‐NMR, ¹³C‐NMR, UV–visible, electron spin resonance (ESR) and mass spectrometry] together with some physical studies (molar conductance and magnetic susceptibility). The outcomes data displayed that the (HD¹), (HD²) and (HD³) acted as neutral and/or mononegative bidentate ligands. The ESR as well as electronic spectra suggested the octahedral configuration for all isolated complexes, expect [Cu (HD2)(OAc)2]·2H₂O has square planar structure. Also, the in vitro antimicrobial assay was done by using the well diffusion method for HD¹, HD², HD³ and their complexes.     

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres supported palladium complex as an efficient catalyst for Heck reaction

<正>Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres synthesized by suspension polymerization were used as supports for palladium catalyst.The results showed the novel magnetic catalyst can promote Heck reaction of aryl halides with acrylic acid efficiently without an inert atmosphere.In addition,the novel catalyst can be conveniently recovered by applying an external magnet and reused at least five times without significant loss of its activity.     

Bisphenol-A polycarbonate–poly(butylene terephthalate) transesterification. II. Structure analysis of the reaction products by IR and 1H and 13C NMR

The structure of the four-component copolyester resulting from the exchange reaction between molten bisphenol-A polycarbonate and poly(butylene terephthalate) is analyzed as a function of the reaction time by infrared and nuclear magnetic resonance spectroscopy. By applying a statistical method developed earlier, the mean chain length of the various sequences as well as the degree of randomness is computed. The exchange reaction leads initially to the formation of a block copolyester with reduced solubility. As the reaction proceeds, a soluble random copolycondensate is progressively formed.     

Synthesis and characterization of chiral 1,2-diamines from 5-oxo-pyrrolidine-(S)-2-carboxylic acid

Unsymmetrical chiral secondary vicinal diamines were synthesized by applying a modified three-step reaction. The key step in this sequence is a primary amine mediated ring opening reaction of a diastereomeric oxazolidinone derivative. A possible mechanism for this step is described.