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Selective Preparation (selective + preparation)
Selected AbstractsHighly Selective Preparation of a Chiral Quaternary Allyl Aryl Piperidinedione by Palladium-Catalyzed Asymmetric Allylation Under Solid,Liquid Phase-Transfer CatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2007Audrey Nowicki Abstract The combination of a chiral palladium catalyst and a solid,liquid phase-transfer catalyst provides an effective method for the chemo- and enantioselective preparation of the chiral quaternary center of an allyl aryl piperidinedione. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Hydroxy Derivatives of Diamantane, Triamantane, and [121]Tetramantane: Selective Preparation of Bis-Apical Derivatives,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 28 2007Natalie A. Fokina Abstract Functionalizations of diamantane, triamantane, and tetramantane with electrophilic reagents (Br2, nitric acid) lead to various apical and medial disubstituted products that were separated and characterized individually. The highly desirable and otherwise inaccessible thermodynamically more stable apical bis-derivatives were obtained with high preparative yields through acid catalyzed isomerizations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Selective Preparation of Diamondoid Fluorides[1]ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Hartmut Schwertfeger Abstract The selective fluorination of diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane bromides and alcohols was achieved by using the fluorinating agents silver fluoride (AgF) and diethylaminosulfur trifluoride (DAST). Various mono-, di-, tri- and even tetrafluorinated diamondoid derivatives were prepared and characterized. We were also able to prepare the amino fluoro and the fluoro alcohol derivatives of diamantane from the corresponding monoprotected diamondoid diols. These reactions can be carried out in a highly selective manner and proceed without isomerizations. The fluorinated, unequally disubstituted derivatives are valuable compounds for the exploration of electronic, pharmacological, and material properties of functionalized diamondoids. [source] Selective Preparation of 3,4,5-Trinitro-1H- Pyrazole: A Stable All-Carbon-Nitrated AreneANGEWANDTE CHEMIE, Issue 18 2010Grégoire Hervé Dr. Pernitriert: 3,4,5-Trinitro-1H- pyrazol (TNP, siehe Bild) ist das unerwartete Produkt der Nitrierung von 3,5-Dinitropyrazol mit einem starken Elektrophil, das aus 20,30,% Oleum und Salpeteräure entsteht. TNP ist bemerkenswert stabil, weil die Ringstruktur erhalten bleibt und die Konformation der Nitrogruppe an C4 die Acidität des Materials in Grenzen hält. [source] ChemInform Abstract: Synthesis and Use of Achiral Oxazolidine-2-thiones in Selective Preparation of trans 2,5-Disubstituted Tetrahydrofurans.CHEMINFORM, Issue 20 2009Gael Jalce 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] Highly Selective Preparation of Allenic and Homopropargylic Hydrazides Through Regiospecific Addition of Propargyltrichlorosilane and Allenyltrichlorosilane to Various Types of N-Acylhydrazones.CHEMINFORM, Issue 24 2006Uwe Schneider 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 Phosphorimidate Rearrangement for the Facile and Selective Preparation of Allylic Amines.CHEMINFORM, Issue 36 2004Bin Chen Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Highly Selective Preparation of 2-(Hydroxymethyl)vinylphosphonates by Insertion of Ketones into Zirconacycle Phosphonates.CHEMINFORM, Issue 18 2002Abed Al Aziz Quntar 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] Selective preparation of poly(p -oxybenzoyl) by using fractional polycondensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006Kunio Kimura Abstract Selective preparation of poly(p -oxybenzoyl) (POB) in the copolymerization system of p -acetoxybenzoic acid (p -ABA) and m -acetoxybenzoic acid (m -ABA) was examined by using reaction-induced crystallization of oligomers. Polymer crystals mainly composed of p -oxybenzoyl moiety were precipitated when the content of m -ABA in the feed was 30 mol %. The formation of the polymer crystals was attributed to both the reactivity of monomer and the phase-separation behavior of oligomer. Reactivity of p -ABA was twice higher than that of m -ABA, and thereby, the homo-oligomers of p -oxybenzoyl moiety were more rapidly formed in solution than do co-oligomers at the early stage in polymerization. They were selectively precipitated by crystallization to form crystals because of low miscibility. Co-oligomers containing m -oxybenzoyl moiety were also formed in solution, but they were unable to be phase-separated because of higher miscibility. Further polycondensation occurred between oligomers in the precipitated crystals, leading to the formation of POB. This polymerization proceeded with selecting certain monomers by crystallization and afforded a new methodology for fractional polycondensation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2732,2743, 2006 [source] Double Wall Carbon Nanotubes with an Inner Diameter of 0.4 nmCHEMICAL VAPOR DEPOSITION, Issue 3 2003L. Ci Selective preparation of double wall carbon nanotubes (DWCNTs) is achieved by a floating iron catalyst CVD method with sufur promotion. SEM shows that the product consists of entangled nanotubes. HRTEM and Raman scattering have revealed that the smallest inner diameter of as-grown carbon nanotubes is 0.4 nm (see Figure). The smallest diameter is found to be produced at the low carbon partial pressure with low sulfur content. [source] Recent Applications of Palladium-Catalyzed Coupling Reactions in the Pharmaceutical, Agrochemical, and Fine Chemical IndustriesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Christian Torborg Abstract Palladium-catalyzed coupling reactions have become a central tool for the synthesis of biologically active compounds both in academia and industry. Most of these transformations make use of easily available substrates and allow for a shorter and more selective preparation of substituted arenes and heteroarenes compared to non-catalytic pathways. Notably, molecular-defined palladium catalysts offer high chemoselectivity and broad functional group tolerance. Considering these advantages, it is not surprising that several palladium-catalyzed coupling reactions have been implemented in the last decade into the industrial manufacture of pharmaceuticals and fine chemicals. In this review different examples from 2001,2008 are highlighted, which have been performed at least on a kilogram scale in the chemical and pharmaceutical industries. [source] Mutation of bacterium Vibrio gazogenes for selective preparation of colorantsBIOTECHNOLOGY PROGRESS, Issue 2 2010Farzaneh Alihosseini Abstract A novel marine bacterium strain effectively produced prodiginine type pigments. These colorants could dye wool, silk and synthetic fabrics such as polyester and polyacrylic and also show antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria on the dyed products. Methyl nitrosoguanidine was used as a mutation agent to increase the genetic diversity and the production yield of the bacteria of the family of Vibrio gazogenes. The analysis of the mutated samples showed that two new main colorants as well as three previously found ones were produced. Liquid chromatography electro spray ionization mass spectrometry (LC-ESI-MS) and nuclear magnetic resonance (NMR) spectroscopic techniques were used to elucidate the structures of the newly produced colorants. Mass measurements revealed that the colorants C1, C2, C3, C4 have molecular masses of 321, 323, 351, and 295 Da. One unstable colorant C5 with molecular mass of 309 Da was detected as well. The mutated bacteria strains increased the yield of pigment production by about 81% and produced prodigiosin in 97% purity. The antibiotic activities of pure colorants are discussed as well. Based on their bio-activity and excellent dyeing capabilities, these colorants could be employed in cosmetic and textile industries. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | |||||||||||||