Converting dipyrrinones to lactim ethers to fluorescent N,N′-difluoroboryl derivatives

A high-yield straightforward conversion of lactams to lactim ethers is shown by the conversion of (10H)-dipyrrin-1-ones to (11H)-dipyrrin-1-ol methyl and ethyl ethers in 90% yield from heating in neat trimethyl or triethyl phosphite at 160°C. Unlike the parent dipyrrinones, which form intermolecularly hydrogen-bonded dimers in CHCl₃, their lactim ethers are shown to be monomeric by vapor pressure osmometry. The latter react with boron trifluoride etherate to N,N′-bridged BF₂ derivatives that exhibit strong fluorescence (φ_F 0.6–0.8) near 535 nm. X-Ray crystal structures were obtained of the lactim ethyl ether of kryptopyrromethenone and the BF₂ derivative of the lactim ethyl ether 2,3-diethyl-7,8-dimethyl-(10H)-dipyrrin-1-one.     

“Ship-in-a-Bottle” Approach to Synthesize Ag@hm-SiO2 Yolk/Shell Nanospheres

An e ective protocol is presented for the synthesis of Ag@hm-SiO₂ yolk/shell nanostructures (YSNs) via a facile “ship-in-a-bottle” method. TEM observations show that the as-obtained Ag@hm-SiO₂ YSNs have a single silver core in the interior of hollow mesoporous silica (hm-SiO₂) nanospheres, in which the thickness of hm-SiO₂ outer shell is about 14 nm and the silver core has an average size of about 43 nm. And the content of silver in Ag@hm-SiO₂ YSNs is about 10.29% based on the inductively coupled plasma measurement. The as-synthesized Ag@hm-SiO₂ YSNs exhibited signi cantly enhanced catalytic performance compared with the pure Ag nanoparticles toward the reduction of 4-nitrophenol to 4-aminophenol in the presence of Na₄.     

Application of the addition of triorganozincates to N-(tert-butanesulfinyl)imines to the enantioselective synthesis of α-amino acids

Highly enantiomerically enriched N-protected α-amino acids can be easily prepared from optically pure N-(tert-butanesulfinyl)imines by a four-step sequence involving: diastereoselective addition of a triorganozincate to the imine, removal of the sulfinyl group, benzoylation of the nitrogen atom of the obtained primary amine and oxidation of one of the substituents on the carbon atom α to the nitrogen. Using the same configuration in the sulfinyl chiral auxiliary, amino acids with the (R) or the (S) configuration can be prepared by choosing the proper combination of imine and organozincate. α,α-Disubstituted α-amino esters with high optical purity can also be prepared by the diastereoselective addition of trialkylzincates to α-imino esters.     

LiBr/β-CD/IBX/H2O-DMSO: A new approach for one-pot biomimetic regioselective ring opening of chalcone epoxides to bromohydrins and conversion to 1,2,3-triketones

Highly regioselective ring cleavage of chalcone epoxides to bromohydrins has been carried out in good yields with LiBr in the presence of β-CD using DMSO-H₂O as solvent system. The ring-opened product, i.e., bromohydrin, was well adapted to IBX-mediated oxidation in such a fashion that the bromohydrins are transformed to their corresponding 1,2,3-triketones in moderate-to-good yields in one pot.     

Photodecarboxylative additions of N-protected α-amino acids to N-methylphthalimide

Photoreactions involving N,N-dimethylated α-amino acid salts and N-methylphthalimide are dominated by photoreduction and acetone trapping. Only, N-phenyl glycinate underwent photodecarboxylative addition in a moderate yield of 30%. In contrast, N-acylated α-amino acid salts readily gave addition products in fair to high yields of 20-95%. Comparison experiments with N,N-dimethylacetamide and amino-/amido-containing phthalimides revealed the origin of the crucial electron-transfer step and the reactivity order NR₃ »  ? RCONR₂ was established.     

A simple path to ambient temperature ionic H- superconductors

<正>Hydride ion (H^-) has high polarizability (α_H-=10.17?³) and high redox potential (H^-/H₂:-2.3 V), and therefore is an attractive energy carrier [1,2]. The H^- superconductors play a crucial role in the development of high-density energy storage and chemical conversion technologies [3].     

(p, ρ, T, x) properties for CO2/isobutane binary mixtures at T = (280 to 440) K and (3 to 200) MPa

The (p, ρ, T, x) properties for binary mixtures of CO₂ (volume fraction purity 0.99999) and isobutane (mole fraction purity 0.99988) {x₁ CO₂ + x₂ isobutane (x₁ = 0.2482, 0.4718, and 0.7506)} were measured in the compressed liquid phase using a metal-bellows variable volumometer. Measurements were conducted from T = (280 to 440) K and (3 to 200) MPa. The expanded uncertainties (k = 2) were estimated to be: temperature, <3 mK; pressure, 1.5 kPa (p ? 7 MPa), 0.06% (7 MPa < p ? 50 MPa), 0.1% (50 MPa < p ? 150 MPa), 0.2% (p > 150 MPa); density, 0.10%; and composition, 4.4 · 10⁻⁴. At >100 MPa and T = (280 or 440) K, the uncertainties in the density measurements increased to 0.14% and 0.22%, respectively. The data are compared with the available equation of state. The excess molar volumes, , of the mixtures were calculated and plotted as a function of temperature and pressure.     

A Hierarchical-Equation-of-Motion Based Semiclassical Approach to Quantum Dissipation?

We present a semiclassical (SC) approach for quantum dissipative dynamics, constructed on basis of the hierarchical-equation-of-motion (HEOM) formalism. The dynamical components considered in the developed SC-HEOM are wavepackets' phase-space moments of not only the primary reduced system density operator but also the auxiliary density operators (ADOs) of HEOM. It is a highly numerically efficient method, meanwhile taking into account the high-order effects of system-bath couplings. The SC-HEOM methodology is exemplified in this work on the hierarchical quantum master equation[J. Chem. Phys. 131 , 214111 (2009)] and numerically demonstrated on linear spectra of anharmonic oscillators.     

A modular approach to α,β-unsaturated N-aryl ketonitrones

A modular approach to α,β-unsaturated N-aryl ketonitrones has been developed. Specifically, condensation of anilines and enals followed by alkylation of the resulting α,β-unsaturated imines provided N-allyl anilines, which were subjected to oxidation with Oxone® to form α,β-unsaturated N-aryl ketonitrones. This modular approach is general and provides rapid access to diversely substituted α,β-unsaturated N-aryl ketonitrones with a single purification step in good yields.     

Regioselective addition of thiophenol to α,β-unsaturated N-acylbenzotriazoles

Regioselective addition of thiophenol to α,β-unsaturated N-acylbenzotriazoles has been achieved by controlling the conditions. Thus, three types of products, namely α,β-unsaturated thioesters, β-thiophenoxy substituted N-acylbenzotriazoles, and β-thiophenoxy substituted thioesters were selectively obtained in good to excellent yields.     

Synthetic approach to seco-tetracenomycin natural products saccharothrixone A–C

Design and development of first synthetic approach to the functionalized tetracyclic framework of structurally novel seco-tetracenomycin natural products saccharothrixones A–C has been reported. A thermal dehydro Diels-Alder reaction of an arenyne-alkyne unit has been utilized as the key synthetic step. This strategy has been extended for the generation of a small library of diversely functionalized tetracyclic systems of seco-tetracenomycins. An approach for the synthesis of poly-hydroxyl tetracyclic system has also been described. This report represents the first synthetic approach to the tetracenomycin natural products saccharothrixones A–C.     

Combined molecular dynamics and continuum solvent approaches (MM-PBSA/GBSA) to predict noscapinoid binding to γ-tubulin dimer

γ-tubulin plays crucial role in the nucleation and organization of microtubules during cell division. Recent studies have also indicated its role in the regulation of microtubule dynamics at the plus end of the microtubules. Moreover, γ-tubulin has been found to be over-expressed in many cancer types, such as carcinomas of the breast and glioblastoma multiforme. These studies have led to immense interest in the identification of chemical leads that might interact with γ-tubulin and disrupt its function in order to explore γ-tubulin as potential chemotherapeutic target. Recently a colchicine-interacting cavity was identified at the interface of γ-tubulin dimer that might also interact with other similar compounds. In the same direction we theoretically investigated binding of a class of compounds, noscapinoids (noscapine and its derivatives) at the interface of the γ-tubulin dimer. Molecular interaction of noscapine and two of its derivatives, amino-noscapine and bromo-noscapine, was investigated by molecular docking, molecular dynamics simulation and binding free energy calculation. All noscapinoids displayed stable interaction throughout simulation of 25 ns. The predictive binding free energy (ΔG_bind) indicates that noscapinoids bind strongly with the γ-tubulin dimer. However, bromo-noscapine showed the best binding affinity (ΔG_bind = –37.6 kcal/mol) followed by noscapine (ΔG_bind = –29.85 kcal/mol) and amino-noscapine (ΔG_bind = –23.99 kcal/mol) using the MM-PBSA method. Similarly using the MM-GBSA method, bromo-noscapine showed highest binding affinity (ΔG_bind = –43.64 kcal/mol) followed by amino-noscapine (ΔG_bind = –37.56 kcal/mol) and noscapine (ΔG_bind = –34.57 kcal/mol). The results thus generate compelling evidence that these noscapinoids may hold great potential for preclinical and clinical evaluation.     

In situ construction of ligand nano-network to integrin αvβ3 for angiogenesis inhibition

Angiogenesis occurs during the process of tumor growth, invasion and metastasis, and is essential for the survival of solid tumors. As an integrin significantly overexpressed in human tumor vascular endothelial cells, α_vβ₃ is a suitable targeting site for anti-angiogenesis of tumor. We designed and prepared a selfassembling peptide (SAP) with the ability to targeting α_vβ₃ and self-assembly. SAP formed nanoparticles in solution and transformed into nanofibrous network once specifically binding to integrin α_vβ₃ on the surface of human umbilical vein endothelial cells (HUVECs). The SAP network stably anchored on HUVECs over 24 h, which consequently resulted in high-efficient inhibition of vascularization. In vitro anti-angiogenesis experiment displayed that the inhibition rate of tube-formation reached 94.9%. In vivo anti-angiogenesis array based on chick chorioallantoic membrane (CAM) model exhibited that the SAP had an inhibition rate up to 63.1%. These results indicated the outstanding anti-angiogenic ability of SAP, potentially for tumor therapy.     

Kinetics of Methane Partial Oxidation to Syngas over a LiLaNiO/γ -Al2O3 Catalyst

The kinetic behavior of partial oxidation of methane to syngas over a LiLaNiO/γ -Al₂O₃ catalyst was investigated under steady-state conditions. Under kinetic control, syngas, to a large extent, is formed via a direct partial oxidation (DPO) scheme. CO and CO₂ are formed in parallel by oxidation reaction over the catalyst. The active sites in the kinetically controlled regime are different from those in the non-kinetic regime, thus the CO selectivity in the former may not increase with temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

Catalytic Oxidation of Dimethyl Ether to Hydrocarbons over SnO2/MgO and SnO2/CaO Catalysts

A novel reverse microemulsion method was used to prepare SnO2/MgO and SnO2/CaO catalysts. It was found that both the catalysts were active for the reaction of catalytic oxidation of dimethyl ether (DME) in the temperature range of 275 to 300℃. SnO2/CaO catalyst exhibits much higher activity than SnO2/MgO. On SnO2/CaO catalyst, DME conversion of 21.8% was obtained at 300℃, while selectivities to methyl formate (MF) and dimethoxyethane (DMET) of 19.1% and 59.0% respectively were obtained at 275℃.     

Heterogenization of [Ti(η-C5HMe4)Cl3] on to MCM-41 and organomodified MCM-41 to form epoxidation catalyst

This paper describes the heterogenization of a tetramethylmonocyclopentadienyl titanium (IV) trichloride complex, [Ti(η⁵-C₅HMe₄)Cl₃] onto mesoporous MCM-41. Its immobilization has been performed via a straightforward grafting process of the organometallic precursor in the pores of an MCM-41 host material and by reaction with previously organomodified MCM-41 material with a hydroxyl triazine based compound. Applying all-silica MCM-41 hosts, stable and heterogeneous liquid-phase epoxidation catalysts are obtained. Powder X-ray diffraction and nitrogen adsorption-desorption analysis indicated that the structural integrity of the support has been preserved during the titanium complex immobilization. These materials have been also extensively characterized using diffuse reflectance UV-vis, ¹³C and ²⁸Si MAS NMR and FT-IR spectroscopy. With these techniques the strong adsorption of the intact catalytic complex within an all-silica MCM-41 host is demonstrated. These materials have been tested as catalyst for the epoxidation of aliphatic and aromatic alkenes with TBHP as oxidant exhibiting a significant selectivity toward the epoxide with negligible leaching of titanium species. The conversion values are moderated, being the olefin trend reactivity 1-octene > cyclohexene > styrene.     

A Novel Catalyst CuCl/1,10-Phenanthroline/N-Methylimidazole for the Oxidative Carbonylation of Ethanol to Diethyl Carbonate

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Diastereocontrolled addition of organometallic reagents to S-chiral N-(tert-butanesulfinyl)-α-fluoroenimines

Grignard and organolithium reagents efficiently react with (S)-N-(tert-butanesulfinyl)-α-fluoroenimines to provide chiral allylamines in excellent yields and with diastereomeric ratios of up to 96:4. Acidic removal of the sulfinyl group and simple functional group transformations allow to get enantiopure fluoroolefin dipeptide mimics.     

Comments to EURACHEM/CITAC guide “Measurement uncertainty arising from sampling”

The EURACHEM/CITAC Guide “Measurement uncertainty arising from sampling” deals with the design and analysis of experiments for the evaluation of the sampling and analytical standard deviation when a defined sampling and analytical method is used for the determination of the concentration, expressed as mass fraction (mg/kg), of an analyte in a specified material. The Guide recommends reporting the relative expanded uncertainty and using it directly, i.e. it implicitly assumes that the standard deviation is proportional to the mass fraction even in case the experimental data do not support this assumption. Example A1 (and some of the other examples of the Guide) demonstrates that this can result in extreme levels of underestimation or overestimation of the uncertainty of measurement results. Hence, such recommendations should be avoided!