Progress in Selective Hydrogenation: Reactivity Trends in PdAu Heterogeneous Catalysts & Developing Chiral Building Blocks for New Homogeneous Catalysts

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2017-05
Authors
Chinen, Amy
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Cain, Matthew
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Chemistry
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University of Hawaii at Manoa
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Abstract
Selective hydrogenation is an essential method for converting cheap starting materials into more valuable chemical building blocks. Whether regioselectivity or diastereoselectivity is desired, catalysts are often employed to aid in this transformation. This work explores possibilities for finetuning both homogeneous and heterogeneous catalysts. Previously, bimetallic PdAu catalysts were used to enable the conversion of biologically produced 4-hydroxycoumarin (4HC) to pharmaceutically relevant coumarin and dihydroxycoumarin (DHC), but the subtleties of catalyst preparation and the effect of Pd loading were not known. Part I focuses on identifying reactivity trends resulting from variations in PdAu catalysts. Several PdAu catalysts with varying Pd:Au ratios were prepared by controlled surface reactions (CSR) or incipient wetness impregnation (IWI). Using high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GCMS), we determined the effects of the preparation method and Pd loading on reactivity, selectivity, and resistance to deactivation for the selective hydrogenation of 4HC to DHC. Part II aims to develop chiral building blocks for C1-symmetric, P-stereogenic ligands that will be used in the asymmetric hydrogenation of heavily functionalized substrates. To date, a new diastereoselective method of adding RO-H across a P=P double bond was identified and a new sterically dominating R group was generated. The results were analyzed by nuclear magnetic resonance (NMR) spectroscopy.
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selective hydrogenation, heterogeneous catalysis, biorenewable chemicals, asymmetric hydrogenation, homogeneous catalysis, P-stereogenic ligands
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34 pages
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