Author : Sang Van
Publisher :
ISBN 13 :
Total Pages : 384 pages
Book Rating : 4.:/5 (318 download)
Book Synopsis The Search for Catalysts Using the Cooperativity of Transition Metals and Heterocyclic Ligands by : Sang Van
Download or read book The Search for Catalysts Using the Cooperativity of Transition Metals and Heterocyclic Ligands written by Sang Van and published by . This book was released on 2002 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of new and efficient catalysts plays an important role in chemical research. The inspiration for finding new catalysts includes long-term benefits such as (a) efficient, atom-economical reactions; (b) chemoselective reactions under mild conditions, obviating the need for protection and deprotection of functional groups; and (c) reduction of chemical waste in the production of fine chemicals for pharmaceuticals. For these purposes, artificial enzyme mimics are exploited. In the preparation of such catalysts, a promising approach is to translate the principles of enzyme catalysis for the design of new catalytic materials. In this research, we used design features of the cooperativity of Lewis acid transition metals and heterocyclic ligands designed to provide hydrogen bond donor (A) and acceptor (B), inspired by Nature's enzymes, to catalyze reactions of polar molecules such as water, alcohols, or amines with organic molecules.* To synthesize our catalysts, we envisioned anchoring a transition metal to a heterocycle which features a reasonably acidic N-H group (A). In this research, we prepared 10 pyrazole ligands and 35 of their complexes, 15 of which were analyzed by X-ray diffraction. Furthermore, isoelectronic and isosteric complexes incapable of donating or accepting hydrogen bond(s) were also synthesized to determine the relationship between hydrogen-bond donating properties and catalytic efficiency. All the complexes were characterized by NMR spectroscopy, IR spectroscopy, and elemental analysis. Part of our studies to date have focused on the hydrolysis of unactivated amide bonds, thought to be a more difficult challenge than similar reactions of phosphate diesters. We also focused on the use of hydrogen-donating-group-assisted in catalysis of chemoselective hydrogenation of imines. We also used bifunctional catalysts to catalyze regio- and stereoselective dimerization of terminal alkynes, and hydrogen transfer hydrogenation of aldehydes, ketones, and imines. The catalysts can also catalyze cyclization and coupling reactions of alkynols. Significantly, these catalytic processes involve both C-C and C-O bond formation with diastereo- and regioselectivity. These results are fruitful because we have opened another field of catalysis using the combined effects of hydrogen-bond donating ligands and Lewis acidic transition metals. *Please refer to dissertation for diagrams.
