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Design, Development and Mechanistic Study of Ruthenium-Based Catalysts for the Hydrogenation of Imides and Amides Open Access

Descriptions

Other title
Subject/Keyword
Imides
Amides
Hydrogenation
Ruthenium
Catalysis
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
John, Jeremy Michael
Supervisor and department
Bergens, Steven (Chemistry)
Examining committee member and department
Hall, Dennis (Chemistry)
de Klerk, Arno (Chemical and Materials Engineering)
Bergens, Steven (Chemistry)
Schafer, Laurel (Chemistry)
Buriak, Jillian (Chemistry)
Rivard, Eric (Chemistry)
Department
Department of Chemistry
Specialization

Date accepted
2013-12-13T11:04:37Z
Graduation date
2014-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Prior mechanistic studies demonstrate that trans-[RuH2((R)-BINAP)((R,R)-dpen)] is a remarkably active carbonyl reducing agent at low-temperatures in THF-d8. This dissertation describes the monohydrogenation of cyclic meso-imides using this catalyst and related complexes under mild conditions. Bicyclic meso-imides were chemo-, diastereo- and enantio-selectively desymmetrized to form chiral hydroxy lactams (90-99% conversion, 88-97% ee, dr >93:7, C=O/C=C selectivity >99%) with up to five stereogenic centers in one hydrogenation under the reported reaction conditions (0.1-1 mol% Ru, 0.9-9.9 mol% KOt-Bu under 50 atm H2 at 0-22 °C in 3-57 h). Compounds of academic and commercial interest were also synthesized from these hydroxy lactams. A detailed low-temperature investigation into the desymmetrization-hydrogenation reaction led to the discovery of a previously unobserved active pathway for carbonyl hydrogenation. Reaction intermediates resulting from the unexpected deprotonation and di-deprotonation respectively of the parent dihydrides i.e. trans-M[RuH2((R,R)-HN–CH(Ph)CH(Ph)NH2)((R)-BINAP)], where M = K+ or Li+, and trans-M2[RuH2((R,R)-HN–CH(Ph)CH(Ph)N–H)((R)-BINAP)] where M = Li+, were synthesized and characterized. The mono-deprotonated dihydrides were found to have unprecedented activity towards the hydrogenation of imide and amide carbonyls at low temperatures in THF-d8. The origins of the enantioselection for this reaction were also proposed using simple well-defined models based on current literature and the outcomes of this investigation. The hydrogenation of amides using trans-[RuH2((R)-BINAP)((R,R)-dpen)] and its variants is also described herein. In contrast to the high activity of trans-[RuH2((R)-BINAP)((R,R)-dpen)] towards ketones, imides (in the presence of base), and esters, the catalyst exhibited low to moderate activity towards amides. This difference in activity was attributed to thermal instability of the catalyst at high temperatures. By tethering the phosphine and amine units together, a robust pre-catalyst, [Ru(η3-C3H5)(Ph2P(CH2)2NH2)2]BF4 was prepared, which, when combined with NaOMe (Ru:NaOMe:Amide = 1:500:10,000), catalyzes the hydrogenation of amides with a TON up to 7120. The analogous base-free system comprising [Ru(η3-C3H5)(Ph2P(CH2)2NH2)2]BF4 and NaBH4 was also shown to be an efficient catalyst system for this reaction under reported conditions (0.1 mol% Ru, 0.2 mol% NaBH4 under 50 atm H2 at 100 °C in 24 h) in contrast to trans-[RuH(η1-BH4)((R)-BINAP)((R,R)-dpen)].
Language
English
DOI
doi:10.7939/R3PR7N29D
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
John, J. M.; Takebayashi, S.; Dabral, N.; Miskolzie, M.; Bergens, S. H. J. Am. Chem. Soc. 2013, 135, 8578-8584.John, J. M.; Bergens, S. H. Angew. Chem., Int. Ed. 2011, 50, 10377-10380.Takebayashi, S.; John, J. M.; Bergens, S. H. J. Am. Chem. Soc. 2010, 132, 12832-12834.

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