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Selected Abstractstert -Butanesulfinylphosphines: Simple Chiral Ligands in Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to Electron-Deficient OlefinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Feng Lang Abstract An efficient rhodium complex catalyst system was developed by using a class of simple tert -butanesulfinylphosphines as bidentate ligands, which solely bear sulfur chirality and combine the advantages of both sulfoxide and phosphine ligands. Excellent activities (in 0.5 hour, up to 99% yield) and enantioselectivities (up to 98% ee) were displayed in Rh-catalyzed asymmetric 1,4-additions under mild conditions. [source] Mesoporous Silica Nanosphere-Supported Chiral Ruthenium Catalysts: Synthesis, Characterization, and Asymmetric Hydrogenation StudiesCHEMCATCHEM, Issue 3 2009David Abstract Chiral RuCl2,diphosphine,diamine complexes with a pendant siloxy group were synthesized and characterized by NMR spectroscopy and mass spectrometry. The Ru complexes were grafted onto three different types of mesoporous silica nanospheres (MSNs) through the siloxane linkage, and the resulting MSN-supported Ru catalysts were highly active for the asymmetric hydrogenation of aromatic ketones, to afford chiral secondary alcohols, and racemic arylaldehydes, to give chiral primary alcohols. Excellent activities and enantioselectivities were observed for these MSN-supported Ru catalysts owing to readily accessible and uniform catalytic sites within the large channels of MSNs (diameters of >2,nm) and short diffusion lengths for the organic compounds as a result of small nanoparticle sizes of less than 1,,m. This catalyst immobilization strategy with MSN supports should be amenable to the design of many highly active and enantioselective heterogeneous asymmetric catalysts. [source] New Indenylidene-Schiff Base-Ruthenium Complexes for Cross-Metathesis and Ring-Closing MetathesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Abstract We here report on the stability and catalytic activity of new indenylidene-Schiff base-ruthenium complexes 3a,f through representative cross-metathesis (CM) and ring-closing metathesis (RCM) reactions. Excellent activity of the new complexes was found for the two selected RCM reactions; prominent conversion was obtained compared to the commercial Hoveyda,Grubbs catalyst 2. Moreover, excellent results were obtained for a standard CM reaction. Higher conversions were achieved with one of the indenylidene catalysts compared with Hoveyda,Grubbs catalyst. Unexpectedly, an isomerization reaction was observed during the CM reaction of allylbenzene. To the best of our knowledge, isomerization reactions in this model CM reaction in closed systems have never been described using first generation catalysts, including the Hoveyda,Grubbs catalyst. The first model CM reactions as well as the RCM reactions have been monitored using 1H,NMR. The course of the CM reaction of 3-phenylprop-1-ene (8) and cis -1,4-diacetoxybut-2-ene (9) was monitored by GC. The isomerization reaction was studied by means of GC-mass spectrometry and in situ IR spectroscopy. All catalysts were structurally characterized by means of 1H, 13C, and 31P,NMR spectroscopy. [source] A Novel D2 -Symmetrical Chiral Tetraoxazoline Ligand for Highly Enantioselective Hydrosilylation of Aromatic KetonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Wei Jie Li Abstract A novel D2 -symmetrical chiral tetraoxazoline ligand was synthesized from 1,2,4,5-benzenetetracarboxylic acid and L -valinol via a one-pot reaction, and the asymmetric hydrosilylation of aromatic ketones was carried out in dichloromethane in the presence of 1.0,mol% of a bivalent copper ion catalyst with the tetraoxazoline to give optically active secondary alcohols. The chiral catalyst showed excellent activities and enantioselectivities in the hydrosilylation of aryl ketones with up to 99% ee. [source] Indenylidene-Ruthenium Complexes Bearing Saturated N-Heterocyclic Carbenes: Synthesis and Catalytic Investigation in Olefin Metathesis ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2008Stijn Monsaert Abstract The synthesis of complexes of the general formula Cl2Ru(SIMes)(L)(3-phenylinden-1-ylidene) (5, L = PCy3; 6, L = py; and 7, L = PPh3) from Cl2Ru(PR3)2(3-phenylinden-1-ylidene) (2a, R = Ph; 2b, R = Cy) is reported. This family of olefin metathesis catalysts was fully characterized (1H, 13C and 31P NMR spectroscopy and elemental analysis) and provided excellent activity in the ring-opening metathesis polymerization of 1,5-cyclooctadiene and the ring-closing metathesis of diethyl diallylmalonate. Comparison with the corresponding benzylidene-containing catalysts, 1a,c and 8b, established the decisive role of the carbene ligand on the procedure of the reaction and led to the observation of an unusual catalytic phenomenon, here called "self-inhibition".(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Direct Amide Synthesis from Alcohols and Amines by Phosphine-Free Ruthenium Catalyst SystemsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Subhash Chandra Ghosh Abstract Amides are synthesized directly from alcohols and amines in high yields using an in situ generated catalyst from easily available ruthenium complexes such as the (p -cymene)ruthenium dichloride dimer, [Ru(p -cymeme)Cl2]2, or the (benzene)ruthenium dichloride dimer, [Ru(benzene)Cl2]2, an N-heterocyclic carbene (NHC) ligand, and a nitrogen containing L-type ligand such as acetonitrile. The phosphine-free catalyst systems showed improved or comparable activity compared to previous phosphine-based catalytic systems. The in situ generated catalyst from [Ru(benzene)Cl2]2, an NHC ligand, and acetonitrile showed excellent activity toward reactions with cyclic secondary amines such as piperidine and morpholine. [source] Nanocrystalline Magnesium Oxide-Stabilized Palladium(0): An Efficient and Reusable Catalyst for Suzuki and Stille Cross-Coupling of Aryl HalidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005Kantam, M. Lakshmi Abstract A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stabilization of PdCl42, with nanocrystalline MgO followed by reduction. This ligand-free heterogeneous nanocrystalline MgO-stabilized nanopalladium [NAPMgPd(0)] catalyst using the basic MgO in place of basic ligands exhibits excellent activity in Suzuki and Stille cross-coupling of haloarenes (chloro, bromo and iodo) to afford the unsymmetrical biaryls. The catalyst is quantitatively recovered by simple filtration and reused for four cycles with almost consistent activity. [source] High-performance HTLcs-derived CuZnAl catalysts for hydrogen production via methanol steam reformingAICHE JOURNAL, Issue 5 2009Ying Tang Abstract A series of CuZnAl oxide-composite catalysts were prepared via decomposition of CuZnAl hydrotalcite-like compounds (HTLcs). The catalysts derived from CuZnAl HTLcs (Cu: 37%, Zn: 15%, Al: 48% mol; using metal nitrate or acetate precursors) at 600°C provided excellent activity and stability for the methanol steam reforming. CuZnAl HTLcs were almost decomposed completely at 600°C to form highly dispersed CuO with large specific surface area while forming CuAl2O4 spinel that played a key role in separating and stabilizing the nano-sized Cu and ZnO during the reaction. The CuZnAl catalyst prepared from metal acetates could highly convert H2O/MeOH (1.3/1, mol/mol) mixture into hydrogen with only ,0.05% CO at 250°C or ,0.005% at 210°C. It is evidenced that the former afforded stronger Cu-ZnO interaction, which might be the intrinsic reason for the significant promotion of catalyst selectivity. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Synthesis and Antibacterial Activity of Novel 4,- O -Carbamoyl Erythromycin-A DerivativesARCHIV DER PHARMAZIE, Issue 8 2010Yunkun Qi Abstract Novel 4,- O -carbamoyl erythromycin-A derivatives were designed, synthesized, and evaluated for their in-vitro antibacterial activities. All of the 4,- O -carbamoyl derivatives showed excellent activity against erythromycin-susceptible Staphylococcus aureus ATCC25923, Streptococcus pyogenes, and Streptococcus pneumoniae ATCC49619. Most of the 4,- O -arylalkylcarbamoyl derivatives displayed potent activity against erythromycin-resistant S. pneumoniae encoded by the mef gene and greatly improved activity against erythromycin-resistant S. pneumoniae encoded by the erm gene or the erm and mef genes. In particular, the 4,- O -arylalkyl derivatives 4c,4e and 4g were found to possess the most potent activity against all the tested erythromycin-susceptible strains, which were comparable to those of erythromycin, clarithromycin, or azithromycin. 4,- O -Arylalkyl derivatives 4e and 4g were the most effective against erythromycin-resistant S. pneumoniae encoded by the mef gene (0.25 and 0.25,µg/mL). 4,- O -Arylalkyl derivatives 4a and 4b exhibited significantly improved activity against erythromycin-resistant S. pneumoniae encoded by the erm gene. In contrast, the 4,- O -alkylcarbamoyl derivatives hardly showed improved activity against all the tested erythromycin-resistant strains. [source] Synthesis, in-vitro Antimicrobial and Cytotoxic Studies of Novel Azetidinone DerivativesARCHIV DER PHARMAZIE, Issue 4 2010Rangappa S. Keri Abstract Developing novel antimicrobial drugs is increasingly important in the modern pharmaceutical industry. A series of novel 3-chloro-4-[4-(2-oxo-2H -chromen-4-ylmethoxy)phenyl]-1-phenylazetidin-2-ones 5a,o have been synthesized from 4-bromomethylcoumarins 1a,e and 4-aryliminomethyl-phenols 3a,c. These compounds were screened for their in-vitro antibacterial activity against two Gram-positive (Staphylococcus aureus and Vancomycin resistant enteroccoccus) and two Gram-negative (Escherichia coli and Shigella dysentery) bacterial strains and antifungal activity against Aspergillus fumigatus, Candida albicans, and Penicillium. Results revealed that compounds 5c, 5f, 5h, 5j, and 5m showed excellent activity against a panel of microorganisms. The brine-shrimp bioassay was also carried out to study their in-vitro cytotoxic properties and two compounds, 5h and 5m, possessing LD50 = 7.154×10,4 M and 5.782×10,4 M, respectively, displayed potent cytotoxic activity against Artemia salina. The presence of a chlorine group in the coumarin moiety, its effect on their antibacterial, antifungal, and cytotoxic activities is discussed. All newly synthesized compounds were characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and MS. [source] Synthesis and In Vitro Antibacterial Activity of 7-(3-Alkoxyimino-4-methyl-4-methylaminopiperidin-1-yl)-fluoroquinolone DerivativesARCHIV DER PHARMAZIE, Issue 3 2010Yi-Bin Zhang Abstract A series of novel 7-(3-alkoxyimino-4-methyl-4-methylaminopiperidin-1-yl)fluoroquinolone derivatives were designed, synthesized, and characterized by 1H-NMR, MS, and HRMS. These fluoroquinolones were evaluated for their in-vitro antibacterial activity against representative Gram-positive and Gram-negative strains. Generally, all of the target compounds have considerable antibacterial activity against the tested forty strains, and exhibit exceptional potency in inhibiting the growth of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) ATCC33591 (MICs: 0.06 to 2 ,g/mL). In particular, compounds 14, 19, 28, and 29 are fourfold more potent than ciprofloxacin against MSSA 08-49. Compounds 23, 26, and 27 are twofold more potent than ciprofloxacin against MRSA ATCC33591 and MSSA ATCC29213. In addition, compound 14 exhibits excellent activity (MIC: 0.06 ,g/mL) against Acinetobactes calcoaceticus, which is two- to 16-fold more potent than the reference drugs gemifloxacin, levofloxacin, and ciprofloxacin. [source] Low pH dye decolorization with ascomycete Lamprospora wrightii laccaseBIOTECHNOLOGY JOURNAL, Issue 8 2010Kitti Mueangtoom Abstract In a screening of saprotrophic, ectomycorrhizal and plant pathogen ascomycetes a frequent occurrence of laccase was observed. Lamprospora wrightii, the best producing organism, was chosen to elucidate the properties of a laccase from a moss-associated, saprotrophic ascomycete. The expression of laccase by this bryophilic fungus could be increased by the addition of tomato juice or copper sulfate to the medium. The obtained volumetric activity after optimization was 420 U/mL in either shaking flask or bioreactor-based cultivations. The purified laccase has a molecular mass of 68 kDa and an isoelectric point of 3.4. Although of ascomycete origin, its catalytic properties are similar to typical basidiomycte laccases, and an excellent activity and stability was observed at low pH, which makes it suitable for bioremediation in acidic environments. As an example, the decolorization reactions of azo-, anthraquinone-, trimethylmethane- and indigoid dyes at pH 3.0 and 5.0 were investigated. All ten selected dyes were decolorized, five of them very efficiently. Depending on the dye, the decolorization was found to be a combination of two reactions, degradation of the chromophore and formation of polymerized products, which contributed to the overall process in a dye-specific pattern. [source] HER-2/neu expression as a predictor of response to neoadjuvant docetaxel in patients with operable breast carcinomaCANCER, Issue 11 2005Peter A. Learn M.D. Abstract BACKGROUND The use of biologic markers to predict response to neoadjuvant chemotherapy may permit tailoring regimens to achieve maximal tumor response. Taxanes have demonstrated excellent activity in breast carcinoma; however, tumor-specific factors that predict clinical response have not been characterized thoroughly. METHODS The authors performed a historic review evaluating the association of tumor prognostic factors and response to neoadjuvant cyclophosphamide and doxorubicin (AC) with or without docetaxel (D) (AC vs. AC+D) in 121 women who previously were enrolled in a Phase III, randomized, clinical trial. Using pretreatment biopsy materials, immunohistochemical studies were performed for estrogen receptor (ER), progesterone receptor (PR), HER-2/neu, p53, and Ki-67. Outcome variables were pathologic complete response (pCR) and positive clinical response (cPOS), which was defined as a , 50% regression in clinical tumor size prior to surgery. RESULTS In a multivariate analysis that controlled for tumor size and lymph node status, improved cPOS rates were observed with the addition of docetaxel in women with HER-2/neu -negative tumors (81% vs. 51%; P < 0.05), yielding an adjusted odds ratio of 3.5 (95% confidence interval, 1.2,13.0) in favor of docetaxel. Women who had HER-2/neu -negative tumors appeared to have a lower response rate with AC alone compared with women who had HER-2/neu -positive tumors (51% vs. 75%; P = 0.06), but response rates were matched when docetaxel was added (81% vs. 78%; P = 0.99). ER, PR, p53, and Ki-67 results were not associated significantly with response rates. CONCLUSIONS HER-2/neu status may predict improved clinical response rates from the addition of docetaxel to anthracycline-based neoadjuvant chemotherapy. Docetaxel may "rescue" the response in women who have HER-2/neu -negative tumors to match that observed in women who have HER-2/neu -positive tumors treated with AC alone. Cancer 2005. © 2005 American Cancer Society. [source] Active Site Ring-Opening of a Thiirane Moiety and Picomolar Inhibition of GelatinasesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2009Christopher Forbes (±)-2-[(4-Phenoxyphenylsulfonyl)methyl]thiirane 1 is a potent and selective mechanism-based inhibitor of the gelatinase sub-class of the zinc-dependent matrix metalloproteinase family. Inhibitor 1 has excellent activity in in vivo models of gelatinase-dependent disease. We demonstrate that the mechanism of inhibition is a rate-limiting gelatinase-catalyzed thiolate generation via deprotonation adjacent to the thiirane, with concomitant thiirane opening. A corollary to this mechanism is the prediction that thiol-containing structures, related to thiirane-opened 1, will possess potent matrix metalloproteinase inhibitory activity. This prediction was validated by the synthesis of the product of this enzyme-catalyzed reaction on 1, which exhibited a remarkable Ki of 530 pm against matrix metalloproteinase-2. Thiirane 1 acts as a caged thiol, unmasked selectively in the active sites of gelatinases. This mechanism is unprecedented in the substantial literature on inhibition of zinc-dependent hydrolases. [source] Preparation of Ni-Based Metal Monolithic Catalysts and a Study of Their Performance in Methane Reforming with CO2CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 6 2008Kai Wang Abstract A series of Ni/SBA-15/Al2O3/FeCrAl metal monolithic catalysts with Ni loadings varying between 3,% and 16,% were prepared, and their structure was characterized by various techniques. The catalytic activity of the catalyst for methane reforming with CO2 leading to synthesis gas was evaluated using a fixed-bed reactor. The results indicate good catalytic activity of the Ni/SBA-15/Al2O3/FeCrAl samples under the reaction conditions. The catalyst with a Ni loading of 8.0,% displays excellent activity and stability at 800,°C over 1400,h time on stream. After reaction, the hexagonal mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. Interactions between NiO, SBA-15, and the Al2O3/FeCrAl support modify the redox properties of the Ni/SBA-15/Al2O3/FeCrAl catalysts. [source] Heck Reactions Catalyzed by Palladium Complex Supported on 4-Aminopyridine ResinCHINESE JOURNAL OF CHEMISTRY, Issue 5 2009Xiangmei WU Abstract 4-Aminopyridine resin-immobilized palladium catalyst was prepared by a simple procedure, which exhibited excellent activity at low loading levels for the phosphine-free Heck vinylation of activated and non-activated aryl or heteroaryl substrates with olefins in air. This method has the advantage of environmental benignity, generality, simplicity and potential for recycling of the resin catalyst. [source] Novel Flower-Like Ag-SiO2 -MgO-Al2O3 Material: Preparation, Characterization and Catalytic Application in Methanol DehydrogenationCHINESE JOURNAL OF CHEMISTRY, Issue 6 2008Jing-Xia LI Abstract Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag-SiO2 -MgO-Al2O3 catalysts prepared by sol-gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al2O3 and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X-ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet-visible spectroscopy (UV-Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH3 -TPD), desorption of CO2 (CO2 -TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag-SiO2 - MgO-Al2O3 catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side-products is attributed to its unique flower-like structure with a surface area less than 1 m2/g, and the strong interactions between neutralized support and the nano-sized Ag particles as active centers. [source] | |||||||||||||