Author : Samantha Alizabeth Michelle Smith
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (133 download)
Book Synopsis Asymmetric Hydrogenation Using Catalysts Based on Abundant Metals by : Samantha Alizabeth Michelle Smith
Download or read book Asymmetric Hydrogenation Using Catalysts Based on Abundant Metals written by Samantha Alizabeth Michelle Smith and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of chiral catalysts for hydrogenation chemistry is a field forever continuing as there are always improvements to be made, either in activity, selectivity, or cost and toxicity of catalysts. This dissertation focuses on the design and synthesis of new base-metal catalysts with the intention to improve the activity and selectivity of asymmetric hydrogenation reactions. This was approached with the following goals in mind: the improvement of syntheses of current catalysts to reduce the cost or to decrease the harshness of catalytic conditions required, the variation of phosphine donors for insight into the mechanism and to use such data to assist in the future rational design of new catalysts, and the use of other less-used abundant first row transition metals to explore the limits of such metals in hydrogenation chemistry. Each of the chapters discussed, with the exception of Chapter 1, describes the findings of new catalysts which were synthesized following one or more of the goals outlined and how they differ from previously reported related complexes, both fundamentally in their molecular structures as well as their activity and selectivity in the asymmetric hydrogenation of ketones. New asymmetric transfer hydrogenation catalysts were synthesized following our previous reports with a series of phosphorus donors. This resulted in an increase in enantioselectivity of the product alcohols at the cost of lower activity. An improvement of synthesis and variation of donors for pincer iron catalysts applied in the asymmetric pressure hydrogenation of ketones resulted in an increase in enantioselectivity; however slightly higher pressures of H2 gas were required for complete conversion (10 vs 5 bar). Manganese analogues of the previously mentioned pincer complexes were discovered to be active in the asymmetric pressure hydrogenation of ketones. These complexes required higher pressures and temperatures than their iron counterparts, but we did see an improvement of catalytic results when comparing to other manganese hydrogenation catalysts recently reported since our catalysts operate at lower temperatures, pressures, and shorter reaction times. An iron complex bearing a new chiral, bidentate, and protic NHC-PPh2 ligand was synthesized for the asymmetric transfer hydrogenation of acetophenone. This complex requires UV-irradiation for catalysis.
