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Book Dissertation Abstracts International

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1984 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Cobalt Catalyzed Asymmetric Hydrogenation of Alkenes

Download or read book Cobalt Catalyzed Asymmetric Hydrogenation of Alkenes written by Hongyu Zhong and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal-catalyzed hydrogenation reactions represent one of the cornerstones in homogeneous catalysis. The asymmetric hydrogenation of unsaturated molecules is an atom-economical method for the synthesis of enantio-enriched compounds and is of particular interest to the pharmaceutical, agrochemical and fine chemical industries. Catalysts based on second- and third-row transition metals, including rhodium, iridium and ruthenium, have been intensively studied in the past five decades and applied widely in industries. Thorough mechanistic studies have been carried out, facilitating catalyst designs and process optimizations. There has been a growing interest in developing relatively Earth abundant, 3d transition metal hydrogenation catalysts based on manganese, iron, cobalt and nickel as alternatives to 4d and 5d transition metals owing to their reduced cost, uninterrupted supply chains and relatively lower toxicity. First-row metals have kinetically and thermodynamically accessible oxidation states separated by one-electrons, which offers opportunities for catalyst designs with new reaction mechanisms. Despite recent progress, the understandings of catalyst speciation upon in situ activation are still limited. Elucidating the coordination chemistry, oxidation states and spin states of active catalysts is of fundamental importance to inform catalyst designs and improve the catalytic performance of first-row metals.In this dissertation, the synthesis, characterization and mechanistic studies of a host of cobalt catalysts for the asymmetric hydrogenation of carbon?carbon double bonds will be introduced. In particular, cobalt catalysts supported by chiral bidentate phosphine ligands have been identified as a ?privileged? class of catalysts and will be the focus of this dissertation.The cobalt-catalyzed asymmetric hydrogenation affording the epilepsy medication, levetiracetam, has been developed and applied to a 200-gram, pilot scale hydrogenation. The unique stability and high activity of reduced cobalt catalysts in protic solvents represent major advances for first-row alkene hydrogenation catalysts. The reaction mechanisms of enamide asymmetric hydrogenation with the formally cobalt(0) catalysts were investigated by experimental and computational methods. The enantioselectivity originates from the different reactivity of a pair of diastereomeric bis(phosphine)cobalt(0)?enamide complexes with H2. The cobalt-catalyzed asymmetric hydrogenation of ?, ?-unsaturated carboxylic acids with unusual homolytic H2 cleavage has been achieved, affording chiral acid products including Naproxen, Flurbiprofen and an L-DOPA precursor. The reactions between bis(phosphine)cobalt(II) dialkyl precatalysts and alcohols have been investigated and the bis(phosphine)Co(II) alkoxide products remained catalytically active. A cobalt-promoted methanol dehydrogenation reaction was also studied. The long-sought-after cobalt analogs of Schrock-Osborn type rhodium catalysts have been synthesized and characterized. A cationic bis(phosphine)cobalt(I) arene catalyst was discovered to be highly active for the asymmetric hydrogenation affording the type 2 diabetes medication, Sitagliptin. The ligand substitution of bis(phosphine)cobalt(0)(diene) catalysts was investigated using kinetic methods establishing a dissociative substitution mechanism. Solid state parameters and electronic structure studies imply their alternative assignment as bis(phosphine)cobalt(II) metallacyclopropane, providing a rationale for the unique protic stability. A family of cobalt precatalysts supported by the bis(phosphine), (R,R)-BenzP*, has been synthesized and characterized. The magnetic properties of dimeric bis(phosphine)Co(I)monochloride precatalysts have also been elucidated.

Book Comprehensive Dissertation Index

Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1989 with total page 1116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Transient and Isotopic Tracing Kinetic Study on Supported Rhodium Catalysts in the CO Hydrogenation Reaction

Download or read book Transient and Isotopic Tracing Kinetic Study on Supported Rhodium Catalysts in the CO Hydrogenation Reaction written by Angelos Michael Efstathiou and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book American Doctoral Dissertations

Download or read book American Doctoral Dissertations written by and published by . This book was released on 1983 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Studies on Rhodium Catalyzed 5 2 Cocyclization Reactions

Download or read book Studies on Rhodium Catalyzed 5 2 Cocyclization Reactions written by Hermann Wegner and published by Cuvillier Verlag. This book was released on 2004 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book F T I R study of CO H2 reactions over rhodium catalysts

Download or read book F T I R study of CO H2 reactions over rhodium catalysts written by Mandy Wighton McQuire and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Intercalation of Rhodium Complex Catalyst in Layered Silicates

Download or read book Intercalation of Rhodium Complex Catalyst in Layered Silicates written by Rasik Haridas Raythatha and published by . This book was released on 1978 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: