The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Fahmi Himo - One of the best experts on this subject based on the ideXlab platform.
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why is tetrazole formation by addition of azide to organic Nitriles catalyzed by zinc ii salts
Journal of the American Chemical Society, 2003Co-Authors: Fahmi Himo, Zachary Demko, Louis Noodleman, K. Barry SharplessAbstract:The mechanism by which zinc(II) catalyzes the union of an azide ion with organic Nitriles to form tetrazoles is investigated by means of density functional theory using the hybrid functional B3LYP. The calculations indicate that coordination of the nitrile to the zinc ion is the dominant factor affecting the catalysis; this coordination substantially lowers the barrier for nucleophilic attack by azide. Relative reaction rates of catalyzed and uncatalyzed tetrazole formation also provide experimental support for this conclusion.
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mechanisms of tetrazole formation by addition of azide to Nitriles
Journal of the American Chemical Society, 2002Co-Authors: Fahmi Himo, Zachary Demko, Barry K SharplessAbstract:It is well-known that azide salts can engage Nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.
Zachary Demko - One of the best experts on this subject based on the ideXlab platform.
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why is tetrazole formation by addition of azide to organic Nitriles catalyzed by zinc ii salts
Journal of the American Chemical Society, 2003Co-Authors: Fahmi Himo, Zachary Demko, Louis Noodleman, K. Barry SharplessAbstract:The mechanism by which zinc(II) catalyzes the union of an azide ion with organic Nitriles to form tetrazoles is investigated by means of density functional theory using the hybrid functional B3LYP. The calculations indicate that coordination of the nitrile to the zinc ion is the dominant factor affecting the catalysis; this coordination substantially lowers the barrier for nucleophilic attack by azide. Relative reaction rates of catalyzed and uncatalyzed tetrazole formation also provide experimental support for this conclusion.
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mechanisms of tetrazole formation by addition of azide to Nitriles
Journal of the American Chemical Society, 2002Co-Authors: Fahmi Himo, Zachary Demko, Barry K SharplessAbstract:It is well-known that azide salts can engage Nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.
Virender Kumar - One of the best experts on this subject based on the ideXlab platform.
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Nitrile Metabolizing Enzymes in Biocatalysis and Biotransformation
Applied Biochemistry and Biotechnology, 2018Co-Authors: Tek Chand Bhalla, Vijay Kumar, Virender Kumar, Neerja ThakurAbstract:Nitrile metabolizing enzymes, i.e., aldoxime dehydratase, hydroxynitrile lyase, nitrilase, nitrile hydratase, and amidase, are the key catalysts in carbon nitrogen triple bond anabolism and catabolism. Over the past several years, these enzymes have drawn considerable attention as prominent biocatalysts in academia and industries because of their wide applications. Research on various aspects of these biocatalysts, i.e., sources, screening, function, purification, molecular cloning, structure, and mechanisms, has been conducted, and bioprocesses at various scales have been designed for the synthesis of myriads of useful compounds. This review is focused on the potential of nitrile metabolizing enzymes in the production of commercially important fine chemicals such as Nitriles, carboxylic acids, and amides. A number of opportunities and challenges of nitrile metabolizing enzymes in bioprocess development for the production of bulk and fine chemicals are discussed.
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Enzymes of aldoxime–nitrile pathway for organic synthesis
Reviews in Environmental Science and Bio Technology, 2018Co-Authors: Tek Chand Bhalla, Vijay Kumar, Virender KumarAbstract:Aldoxime–nitrile pathway is one of the important routes of carbon and nitrogen metabolism in many life forms and a key interface for plant–microbe interactions. This pathway starts with transformation of amino acids to aldoximes, which are converted to Nitriles and the later are ultimately hydrolyzed to acids and ammonia. Understanding and engineering of the enzymes involved in this pathway viz. cytochrome P450/CYP79, aldoxime dehydratase, nitrilase, nitrile hydratase, amidase and hydroxynitrile lyase, presents unprecedented opportunities in biocatalysis and green chemistry. Co-expressing these enzymes in prokaryotic and eukaryotic microbial hosts and tailoring their properties i.e. activity, specificity, stability and enantioselectivity may lead to develop sustainable bioprocesses for the synthesis of industrially important Nitriles, amides and acids.
Barry K Sharpless - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of tetrazole formation by addition of azide to Nitriles
Journal of the American Chemical Society, 2002Co-Authors: Fahmi Himo, Zachary Demko, Barry K SharplessAbstract:It is well-known that azide salts can engage Nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.
K. Barry Sharpless - One of the best experts on this subject based on the ideXlab platform.
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why is tetrazole formation by addition of azide to organic Nitriles catalyzed by zinc ii salts
Journal of the American Chemical Society, 2003Co-Authors: Fahmi Himo, Zachary Demko, Louis Noodleman, K. Barry SharplessAbstract:The mechanism by which zinc(II) catalyzes the union of an azide ion with organic Nitriles to form tetrazoles is investigated by means of density functional theory using the hybrid functional B3LYP. The calculations indicate that coordination of the nitrile to the zinc ion is the dominant factor affecting the catalysis; this coordination substantially lowers the barrier for nucleophilic attack by azide. Relative reaction rates of catalyzed and uncatalyzed tetrazole formation also provide experimental support for this conclusion.
