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Enantio- and Regioselective Hydrogenation of Minimally and Densely Decorated Unsaturated Carbocycles
Stockholm University, Faculty of Science, Department of Organic Chemistry.ORCID iD: 0000-0002-4465-6795
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Several cyclic prochiral olefins were successfully hydrogenated (>99 conv.,up to >99 % ee) using N,P-ligated iridium catalysts. Minimally functionalisedsubstrates (Class 1) were hydrogenated rapidly and in high ee, whichwas consistent with earlier reports. Substrates having functional groups(Class 2) and heterocycles (Class 3) attached to the unsaturated cycle, were43hydrogenated gradually over a period of time, however, high enantioselectivitywas still maintained (up to >99 % ee). This methodology is a highly practical,general and selective means of preparing chiral cyclohexanes.

National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-122417OAI: oai:DiVA.org:su-122417DiVA: diva2:866086
Available from: 2015-10-30 Created: 2015-10-30 Last updated: 2017-03-15Bibliographically approved
In thesis
1. Iridium Catalysed Asymmetric Hydrogenation of Olefins and Isomerisation of Allylic Alcohols
Open this publication in new window or tab >>Iridium Catalysed Asymmetric Hydrogenation of Olefins and Isomerisation of Allylic Alcohols
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work described in this thesis is focused on exploring the efficacy of asymmetric iridium catalysis in the hydrogenation of challenging substrates, including precursors to chiral sulfones and chiral cyclohexanes. Furthermore, iridium catalysis was used to isomerise allylic alcohols to aldehydes, and in a formal total synthesis of Aliskiren (a renin inhibitor). A large variety of unsaturated sulfones (cyclic, acyclic, vinylic, allylic and homoallylic) were prepared and screened in the iridium catalysed hydrogenation reaction using a series of previously developed N,P-ligated Ir-catalysts. The outcome was a highly enantioselective (>90% ee) protocol to prepare sulfones bearing chiral carbon scaffolds, sometimes having purely aliphatic substituents at the stereogenic centre. Furthermore, performing the Ramberg-Bäcklund reaction on the chiral products, under optimised conditions, produced cyclic and acyclic unsaturated derivatives without erosion of enantiomeric excess. This hydrogenation protocol was also successful in the hydrogenation of a number of cyclohexene-containing compounds. Minimally functionalised, functionalised and heterocycle-containing cyclohexenes were hydrogenated in up to 99% ee. Hitherto, both chiral sulfones and chiral cyclohexanes have been challenging targets for most catalytic asymmetric methodologies. Although the preparation of aldehydes and ketones by isomerisation of the corresponding allylic alcohol is well established, there has been limited success in the development of good enantioselective protocols. For the isomerisation of a number γ,γ-allylic alcohols to the corresponding chiral aldehydes, high enantioselectivities (up to >99% ee) and modest yields were achieved using an N,P-iridium catalyst. Noteworthy is the high selectivity obtained for isomerisation of and dialkyl γ,γ-allylic alcohols, which prior to this study had been difficult to isomerise in high enantioselectivity. Preparation of a key intermediate used in the synthesis of Aliskiren, a renin inhibitor drug was also accomplished. Using a convergent synthesis strategy, two allylic alcohol fragments were hydrogenated with high enantiomeric excess (>92% ee). These fragments were then joined using a Julia-Kocienski reaction, providing >95% geometry around the C=C bond, which was crucial for the subsequent steps in the synthesis.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2015. 53 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-122419 (URN)978-91-76492-79-6 (ISBN)
Public defence
2015-12-18, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16B, Stockholm, 10:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2015-11-26 Created: 2015-10-30 Last updated: 2015-11-25Bibliographically approved

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