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Iridium-Catalyzed Asymmetric Hydrogenation of Furan Derivatives and Thiophene 1,1-Dioxides

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EUR 33,20

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Iridium-Catalyzed Asymmetric Hydrogenation of Furan Derivatives and Thiophene 1,1-Dioxides

Larissa Pauli (Autor)

Vorschau

Inhaltsverzeichnis, PDF (88 KB)
Leseprobe, PDF (400 KB)

ISBN-13 (Printausgabe) 9783954048519
ISBN-13 (E-Book) 9783736948518
Sprache Englisch
Seitenanzahl 178
Umschlagkaschierung matt
Auflage 1. Aufl.
Erscheinungsort Göttingen
Promotionsort Basel
Erscheinungsdatum 08.12.2014
Allgemeine Einordnung Dissertation
Fachbereiche Chemie
Organische Chemie
Schlagwörter asymmetric catalysis, furans, benzofurans, thiophene 1,1-dioxides, iridium, N,P ligands, hydrogenation
Beschreibung

The main focus of the research presented in this dissertation was to broaden the substrate scope of the iridium-catalyzed asymmetric hydrogenation of heterocyclic compounds. In view of the fact that a widely applicable hydrogenation system for the reduction of structurally diverse furans and benzofurans is to date not available, a thorough investigation of furan, benzofuran and thiophene 1,1-dioxide derivatives was carried out. Mono- and disubstituted furan derivatives were synthesized and submitted to iridium-catalyzed hydrogenation reactions. While 3-substituted furans were reduced using a catalyst based on a cyclopentane-annulated bicyclic pyridine-phosphine ligand with high enantiomeric excess (95–99% ee) and conversion (83–99%), 2-substituted counterparts proved to be less reactive (80–97% conv., 65–82% ee) with the same catalyst. Asymmetric hydrogenation of 2,4-disubstituted furans proved to be challenging for several reasons, not least because of the problem of controlling the cis/trans selectivity. Surprisingly, in the iridium-catalyzed hydrogenation of 3-substituted benzofurans only one catalyst, based on the cyclohexane-annulated pyridine-phosphinite ligand, showed high activity and enantioselectivity (75–89% conv., 91–92% ee), whereas the five-membered ring analog suffered from moderate activity and enantioselectivity. In contrast, the 2-alkyl substituted benzofurans gave superior results (99% conv., 97–99% ee). Disubstituted thiophene 1,1-dioxides were also investigated in the iridium-catalyzed asymmetric hydrogenation. The hydrogenation of 3,4 disubstituted thiophene 1,1 dioxides using a catalyst based on a cyclopentane-annulated bicyclic pyridine-phosphine ligand gave inferior results to those obtained with their 2,5 disubstituted counterparts.