Catalytic Hydration Of Alkenes And Alkynes

Author : Wing-Kei Chan
Publisher : Open Dissertation Press
ISBN 13 : 9781361426296
Total Pages : pages
Book Rating : 4.4/5 (262 download)

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Download or read book Oxidation of Alkenes and Alkynes Catalyzed by a Cyclodextrin-Modified Ketoester and Metalloporphyrins written by Wing-Kei Chan and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Oxidation of Alkenes and Alkynes Catalyzed by a Cyclodextrin-modified Ketoester and Metalloporphyrins" by Wing-kei, Chan, 陳永基, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled OXIDATION OF ALKENES AND ALKYNES CATALYZED BY A CYCLODEXTRIN-MODIFIED KETOESTER AND METALLOPORPHYRINS Submitted by Chan Wing Kei for the degree of Doctor of Philosophy at The University of Hong Kong in December 2005 Selective oxidation of alkenes and alkynes has been achieved using two classes of catalysts. The first one is cyclodextrin-modified ketoester (1b), which is an organocatalyst prepared by covalent attachment of a reactive ketone moiety to β-cyclodextrin. Treatment of 1b with Oxone as a terminal oxidant in situ generates a cyclodextrin dioxirane, which is able to effect stereoselective alkene epoxidation via inclusion complex formation in aqueous medium. The 1b-catalyzed (S)-α-terpineol epoxidations gave terpineol oxides in high yields, and the stereoselectivities (i.e., cis-: trans-epoxide ratio) decreased from 2.5: 1 to 1: 1.2 with increasing steric bulkiness of the terpenes. This steric-dependent stereoselectivity can be understood on the basis of different binding geometries of the 1b / terpene inclusion complexes according to H NMR titration and 2D ROESY experiments. Enantioselective epoxidation of styrenes has also been achieved with 1b as catalyst (20 - 50 mol%), and up to 40% ee was obtained. The second class of catalysts is metalloporphyrins. Highly diastereoselective epoxidations of allylic substituted alkenes including allylic alcohols, esters, and amines have been achieved using sterically bulky [Mn(2,6-ClTPP)Cl] and [Ru(2,6-Cl TPP)CO] [2,6-Cl TPP = meso-tetrakis(2,6-dichlorophenyl)porphyrin] as 2 2 catalysts. For cycloalkenes, trans-epoxides could be obtained in good yields (up to 99%) with up to >99: 1 trans-selectivity. For acyclic alkenes, up to 9: 1 erythro-selectivities for terminal allylic alkenes were achieved. It should be noted that such trans- and erythro-selectivities are the highest ones ever achieved in the literature. The synthetic utilities of this epoxidation method has been highlighted in stereoselective synthesis of key synthetic intermediates of anti-HIV drugs. Using [Mn(2,6-Cl TPP)Cl] as catalyst and Oxone as an oxidant, highly efficient and selective epoxidation reactions of steroids in high yields (up to 99%) with up to 30: 1 β-selectivity (TON up to 830) was achieved. The first example of catalytic epoxidation of flavones (92% isolated yield) (TON up to 620) has been attained using [Mn(F -TPP)Cl] [F -TPP = tetrakis(pentafluorophenyl)porphyrin] as catalyst. 20 20 The manganese porphyrin-catalyzed epoxidation method has been applied to stereoselective synthesis of β-acetylenosaccharides. A novel method for oxidative synthesis of amides from coupling of alkynes and amines using [Mn(2,6-Cl TPP)Cl] catalyst has been developed. A series of amides has been obtained in high yields (up to 96%) in aqueous medium. This method has been successfully applied to site-selective modification of peptides, which was characterized by MALDI-TOF and LC-MS/MS mass spectrometric analysis. DOI: 10.5353/th_b3670959 Subjects: Alkenes - Oxidation Alkynes - Oxidation Catalysis Porphyrins Esters