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Convenient Approach (convenient + approach)
Selected AbstractsHighly Enantioselective Catalytic Alkynylation of Ketones , A Convenient Approach to Optically Active Propargylic AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2006Gui Lu Abstract The development of highly enantioselective catalysts involving Cu(OTf)2 and chiral camphorsulfonamides for the alkynylation of ketone is described. The influences of Lewis acids, reaction conditions and chiral ligands on the outcome of the reaction are discussed. The best enantioselectivity (up to 97,% ee) was obtained in the alkynylation of 2,-chloroacetophenone. The scope of the reaction is also examined. [source] ChemInform Abstract: A Convenient Approach to Acyclic Unsaturated Amino Acids via Ring-Closing Metathesis.CHEMINFORM, Issue 38 2010Hani Mutlak A. Hassan Abstract An efficient synthesis of conformationally restricted cis- and trans-unsaturated amino acids (III) and (V) via lactams (II) or macrolactam (IV) is described. [source] ChemInform Abstract: Bismuth Nitrate Promoted Fischer Indole Synthesis: A Simple and Convenient Approach for the Synthesis of Alkyl Indoles.CHEMINFORM, Issue 31 2009Aralihalli Sudhakara Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Hetero-Diels,Alder Reaction of Propenenitriles with Enol Ethers: A Convenient Approach to Functionalized 3,4-Dihydro-2H-pyrans.CHEMINFORM, Issue 37 2008Aleksandra Palasz Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Convenient Approach to Tetrahydro-quinolizin-4-ones by Sequential Addition of Lithium Allyldibutylmagnesate to N-Allylpyridin-2-ones and Ring-Closing Metathesis Reactions.CHEMINFORM, Issue 1 2007Jacek G. Sosnicki Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A Convenient Approach to the Synthesis of Fused Acetal Derivatives by Tetrabutylammonium Peroxydisulfate-Mediated Oxidative Cycloaddition of 1,3-Dicarbonyl Compounds to Cyclic Enol Ethers: A Rebuttal.CHEMINFORM, Issue 25 2004Vidyadhar Jadhav Abstract For Abstract see ChemInform Abstract in Full Text. [source] An Efficient and Convenient Approach to the Synthesis of Benzopyrans by a Three-Component Coupling of One-Pot Reaction.CHEMINFORM, Issue 8 2004Tong-Shou Jin Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A Convenient Approach to Synthesis of 1,2,3-Triazole-4-carbothioamides.CHEMINFORM, Issue 30 2001T. V. Glukhareva Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Novel and Convenient Approach to Synthesis of AZT/d4T H-phosphonatesCHINESE JOURNAL OF CHEMISTRY, Issue 3 2004Chang-Xue Lin Abstract A convenient, efficient and general method has been developed for synthesis of H-phosphonate mono and diesters of AZT and d4T through one-pot reaction of phosphonic acid with AZT or d4T and different alcohols using pivaloyl chloride as condensing agent under mild conditions. [source] Role of Echocardiography in Percutaneous Occlusion of the Left Atrial AppendageECHOCARDIOGRAPHY, Issue 4 2007Mráz M.D. Percutaneous occlusion of the left atrial appendage (LAA) is a modern alternative for the treatment of patients with atrial fibrillation (AF) and with a high risk of stroke who are not eligible for long-term anticoagulation therapy. Echocardiography plays a significant role in selecting patients, guiding the procedure, and in the postprocedural follow-up. Objectives and methods: To test the role of transesophagoeal echocardiography (TEE) and intracardiac echocardiography (ICE) in facilitating and shortening the procedure. Results: ICE represents a more convenient approach in patients who are not under generally anesthesia and helps to facilitate transseptal puncture. On the other hand, TEE, having the ability to rotate the image plane, helps to better determine the position of the occluder. Conclusions: Echocardiographic guidance of this procedure is essential. Which approach will be preferred will depend on the development of these two methods. [source] Imaging genetics and development: Challenges and promisesHUMAN BRAIN MAPPING, Issue 6 2010B.J. Casey Abstract Excitement with the publication of the human genome has served as catalyst for scientists to uncover the functions of specific genes. The main avenues for understanding gene function have been in behavioral genetics on one end and on the other end, molecular mouse models. Attempts to bridge these approaches have used brain imaging to conveniently link anatomical abnormalities seen in knockout/transgenic mouse models and abnormal patterns of brain activity seen in humans. Although a convenient approach, this article provides examples of challenges for imaging genetics, its application to developmental questions, and promises for future directions. Attempts to link genes, brain, and behavior using behavioral genetics, imaging genetics, and mouse models of behavior are described. Each of these approaches alone, provide limited information on gene function in complex human behavior, but together, they are forming bridges between animal models and human psychiatric disorders. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Regioselective Palladium(0)-Catalyzed Cross-Coupling Reactions and Metal-Halide Exchange Reactions of Tetrabromothiophene: Optimization, Scope and LimitationsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009ng Thanh Tùng Abstract The Suzuki reaction of tetrabromothiophene with arylboronic acids provides a regioselective approach to various 5-aryl-2,3,4-tribromothiophenes, symmetrical 2,5-diaryl-3,4-dibromothiophenes, and tetraarylthiophenes. Unsymmetrical 2,5-diaryl-3,4-dibromothiophenes are prepared by Suzuki reaction of 5-aryl-2,3,4-tribromothiophenes. Tetraarylthiophenes containing two different types of aryl groups are obtained by Suzuki reactions of 2,5-diaryl-3,4-dibromothiophenes. During the optimization of the conditions of each individual reaction, the solvent, the catalyst and the temperature play an important role. In several cases, classical conditions [use of tetrakis(triphenylphosphane)palladium(0), Pd(PPh3)4, as the catalyst] gave excellent yields. The yields of those transformations which failed or proceeded sluggishly could be significantly improved by application of a new biarylmonophosphine ligand developed by Buchwald and co-workers. Regioselective metal-halide exchange reactions of tetrabromothiophene provide a convenient approach to various 2,5-disubstituted 3,4-dibromothiophenes. 5-Alkyl-2-trimethylsilyl-3,4-dibromothiophenes could be prepared in one pot by sequential addition of trimethylchlorosilane and alkyl bromides. The reaction of tetrabromothiophene with methyl chloroformate and subsequent Suzuki reactions afforded 3,4-diaryl-2,5-bis(methoxycarbonyl)thiophenes. [source] Biodegradation kinetics of benzene, methyl tert -butyl ether, and toluene as a substrate under various substrate concentrationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2007Chi-Wen Lin Abstract Owing to the complexity of conventional methods and shortcomings in determining kinetic parameters, a convenient approach using the nonlinear regression analysis of Monod or Haldane type nonlinear equations is presented. This method has been proven to provide accurate estimates of kinetic parameters. The major work in this study consisted of the testing of aromatic compound-degrading cultures in batch experiments for the biodegradation of benzene, methyl tert -butyl ether (MTBE), and toluene. Additionally, batch growth data of three pure cultures (i.e., Pseudomonas aeruginosa YAMT421, Ralstonia sp. YABE411 and Pseudomonas sp. YATO411) isolated from an industrial petrochemical wastewater treatment plant under aerobic conditions were assessed with the nonlinear regression technique and with a trial-and-error procedure to determine the kinetic parameters. The growth rates of MTBE-, benzene-, and toluene-degrading cultures on MTBE, benzene, and toluene were significant. Monod's model was a good fit for MTBE, benzene and toluene at low substrate concentrations. In contrast, Haldane's equation fitted well in substrate inhibition concentration. Monod and Haldane's expressions were found to describe the results of these experiments well, with fitting values higher than 98%. The kinetic parameters, including a maximum specific growth rate (µm), a half-saturation constant (Ks), and an inhibition constant (Ki), were given. Copyright © 2007 Society of Chemical Industry [source] A simple and convenient approach for evaluation of the parameters of ligand,receptor interaction.JOURNAL OF MOLECULAR RECOGNITION, Issue 2 2008Receptor blocking index, its application Abstract A new approach for determination of the parameters for ligand-receptor interaction, which is based on so-called dilution coordinates, was developed earlier. Equations that allow evaluation of not only the affinity of ligand-receptor interaction but also of the amount of free (or occupied by corresponding ligand) receptors were suggested. The most important advantage of this approach as compared with well-known methods is the ability to determine the binding parameters for ligand-receptor interaction even for the cases in which ligand and receptor are already present in a mixture and separation of counterparts from each other is technically difficult or even impossible. Due to this reason, the proposed approach can be especially useful for studying interactions between highly-labile biological receptors and corresponding ligands as found in vivo. In the present paper I continue to consider how to determine the binding parameters for a given ligand-receptor interaction if the value of receptor blocking index is determined experimentally. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simple method for determination of five terpenoids from different parts of Tripterygium wilfordii and its preparations by HPLC coupled with evaporative light scattering detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Xiao-Ling Luo Abstract By optimizing the extraction, separation, and analytical conditions, a reliable and accurate high-performance liquid chromatography method coupled with evaporative light scattering detection (ELSD) was developed for simultaneous determination of five terpenoids, i. e., triptolide, tripchlorolide, demethylzelastral, wilforlide B, and wilforlide A, in root, stem, leaves, root bark, twig, and root without bark of Tripterygium wilfordii Hook. f and six of its herbal preparations. This approach would thus provide a more accurate and general method for evaluating the quality of the herb and its preparations. Separation of these five terpenoids was achieved on a ZORBAX Eclipse XDB-C8 column with gradient elution using water and acetonitrile as solvents, both containing 0.05% formic acid, at a temperature of 30°C and a flow rate of 0.8 mL/min. The drift tube temperature of ELSD was set at 100°C, and the nitrogen flow rate at 1.5 L/min. Good linear relationships were obtained with correlation coefficients for the analytes exceeding 0.992, and the LOD and LOQ were less than 0.149 ,g and 0.297 ,g on column, respectively. Intra-day and inter-day precision of the analytes were less than 1.25% and 5.97%, respectively, and the average recovery rates obtained were in the range of 95.9 ± 3.7% to 100.4 ± 5.0% for all terpenoids with RSDs below 4.99%. Quantitative analysis of the five terpenoids in different parts of Tripterygium wilfordii and its six preparations showed that the contents of the terpenoids varied significantly. The tender root contained higher concentrations of triptolide, tripchlorolide, demethylzelastral, and wilforlide B than any other part of the herb. Correspondingly, the root bark contained the greatest concentration of wilforlide A, and the stem and twig came in second and third. This suggested that we could infer whether the medicinal materials were absolute roots without bark or not from the comparative contents of these terpenoids in the tablets in view of the fact that only the roots without bark are the valid officinal part of the plant. This method and the quantitation results obtained can provide a scientific and general as well as simple and convenient approach for the product manufacturers to set up quality control standards and for informing the public about the quality and safety of the preparations. [source] ChemInform Abstract: Copper-Catalyzed Direct Amination of ortho-Functionalized Haloarenes with Sodium Azides as the Amino Source.CHEMINFORM, Issue 40 2010Haibo Zhao Abstract The method provides a mild and convenient approach to 2-aminobenzoic acids, 2-aminobenzamides, and N-(2-aminophenyl)amides which can smoothly be converted into benzoxazinones, quinazolinones, and benzimidazoles. [source] Oligosubstituted Pyrroles Directly from Substituted Methyl Isocyanides and AcetylenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2009Alexander Abstract The formal cycloaddition of ,-metallated methyl isocyanides 1 onto the triple bond of electron-deficient acetylenes 2 represents a direct and convenient approach to oligosubstituted pyrroles 3. The scope and limitations of this reaction (24 examples, 25,97,% yield) are reported along with an optimization of the reaction conditions and a rationalization of the mechanism. In addition, a related newly developed CuI -mediated synthesis of 2,3-disubstituted pyrroles by the reaction of copper acetylides derived from unactivated terminal alkynes with substituted methyl isocyanides is described (11,examples, 5,88,%yield). [source] Capillary electrophoresis as a probe of enantiospecific interactions between photoactive transition metal complexes and DNAELECTROPHORESIS, Issue 15 2003James P. Schaeper Abstract Recently, we have demonstrated the capacity to separate chiral transition metal (TM) complexes of the type [M(diimine)3]n+ using CE buffers containing chiral tartrate salts. In separate work, several chromium(III)- tris -diimine complexes in particular have been shown to bind enantioselectively with calf-thymus (CT) DNA, and a qualitative assessment of the relative strength and enantiospecificity of this interaction is of significant interest in the characterization of these complexes as potential DNA photocleavage agents. Here, we describe two convenient approaches to investigate such binding behavior using chiral CE. For complexes with lower DNA affinities exhibiting primarily surface binding, DNA itself is used as the chiral resolving agent in the electrophoretic buffer. In this approach, resolution of the TM complexes into their , and , isomers is achieved with the isomer eluting later exhibiting superior binding affinity toward DNA. For more strongly bound TM complexes containing ligands known to intercalate with DNA, the [Cr(diimine)3]3+ complexes are preincubated with oligonucleotide and subsequently enantiomerically resolved in a dibenzoyl- L -tartrate buffer system that facilitates analysis of the unbound TM species only. Differences in isomer binding affinity are distinguished by the relative peak areas of the ,- and ,-isomers, and relative binding strengths of different complexes can be inferred from comparison of the total amount of unbound complex at equivalent DNA/TM ratios. [source] Renaissance in chiroptical spectroscopic methods for molecular structure determinationTHE CHEMICAL RECORD, Issue 2 2007Prasad L. Polavarapu Abstract Two of the chiroptical spectroscopic methods, namely optical rotatory dispersion (ORD) and electronic circular dichroism (ECD), have been around for several decades. But their use in determining the absolute configuration and predominant conformation is gaining renewed interest with the availability of quantum mechanical methods for predicting ORD and ECD. Two other methods, namely vibrational circular dichroism (VCD) and vibrational Raman optical activity (VROA), are relatively new and offer convenient approaches for deducing the structural information in chiral molecules. With the availability of quantum mechanical programs for predicting VCD and VROA, these methods have attracted numerous new researchers to this area. This review summarizes the latest developments in these four areas and provides examples where more than one method has been used to confirm the information obtained from individual methods. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 125,136; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20117 [source] | |||||||||||||||||||||||||