Home About us Contact
|
Home About us Contact | ||
|
|
||
Valuable Compounds (valuable + compound)
Selected AbstractsKinetics and mechanism of the dehydration reaction of sarcosine to a bislactame through diacyclperoxide intermediate in strong acidic mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2009Homayoon Bahrami The influence of substitution on the amine functional group of glycine in the permanganic oxidation of such an ,-amino acid in moderately concentrated sulfuric acid medium has been investigated. Reaction products analysis has revealed that contrary to the usual ,-amino acid oxidation product, which is an aldehyde species, a valuable compound, namely 1,4-dimethylpiperazine-2,5-dione, has been obtained as the main product via a cheap, simple, efficient, and novel method. Sarcosine has been chosen as a substituted derivative of glycine, and the kinetics and mechanism of its permanganic oxidation have been investigated using a spectrophotometric technique. Conclusive evidence has proven delayed autocatalytic activity for Mn(II) in this reaction, analogous to some ,-amino acids. It has been revealed that such activity can show up when a certain concentration ratio of Mn(II) to sarcosine is built up in the medium, which we call the "critical ratio." The magnitude of the latter ratio depends on the sulfuric acid concentration. Considering the "delayed autocatalytic behavior" of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. The reaction shows first-order dependence on permanganate ions and sarcosine concentrations in both catalytic and noncatalytic pathways, and apparent first-order dependence on Mn2+ ions in catalytic pathways. The correspondence of pseudo-order rate constants of the catalytic and noncatalytic pathways to Arrhenius and Eyring laws has verified "critical ratio" as well as "delayed autocatalytic behavior" concepts. The activation parameters associated with both pathways have been computed and discussed. Mechanisms for both catalytic and noncatalytic routes involving radical intermediates as well as a product having a diketopiperazine skeleton have been reported for the first time. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 689,703, 2009 [source] Palladium-Catalyzed Aerobic Oxidation of Naturally Occurring Allylbenzenes as a Route to Valuable Fragrance and Pharmaceutical CompoundsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Luciana Abstract A palladium-catalyzed, aerobic oxidation of naturally occurring allylbenzenes, i.e., eugenol, methyleugenol, safrole, and estragole, in dimethylacetamide/water solutions under mild conditions has been developed, in which palladium(II) chloride is used in the absence of co-catalysts or special stabilizing ligands as the sole and recyclable catalyst. Methyl ketones that are important for the flavour and pharmaceutical industries have been obtained in good to excellent yields with low catalyst loadings (1,2,mol%) and high average turnover frequencies. This simple catalytic method represents an ecologically benign and economically attractive route to industrially valuable compounds starting from renewable substrates easily available from essential oils. [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] Water in Stereoselective Organocatalytic ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Michelangelo Gruttadauria Abstract In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess (reaction medium), are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented. [source] Helical Chiral Pyridine N -Oxides: A New Family of Asymmetric CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2009Jinshui Chen Dr. Abstract Optically active chiral alkyl chlorides are valuable compounds because of their bioactivity and versatile synthetic utility. Accordingly, the ring opening of epoxides with a chloride nucleophile stands as an important goal in asymmetric catalysis. We describe herein recent advances in the design and development of chiral pyridine N -oxide catalysts for the enantioselective synthesis of chlorohydrins. [source] | ||||||||||