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A new Imidazole-Containing Imidazolidinone Catalyst for Organocatalyzed Asymmetric Conjugate Addition of Nitroalkanes to Aldehydes
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
2007 (English)In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, no 4-5, 740-748 p.Article in journal (Refereed) Published
Abstract [en]

Herein we report a new organocatalyst for the asymmetric Michael addition of nitroalkanes to α,β-unsaturated aldehydes. This catalyst incorporates a basic imidazole group in addition to the secondary amine responsible for activation of the α,β-unsaturated carbonyl compounds via iminium ion formation. The new organocatalyst is capable of catalyzing the enantioselective carbon-carbon bond formation with a high degree of enantiocontrol providing products in enantiomeric excesses of up to 92% and yields of up to to 91 %. These results constitute the best results so far reported for organocatalyzed Michael additions of nitroalkanes to α,β-unsaturated aldehydes, and provide proof of principle that organocatalysts incorporating two internal basic moieties may find broad application in organocatalyzed Michael additions.

Place, publisher, year, edition, pages
2007. Vol. 349, no 4-5, 740-748 p.
Keyword [en]
α, β-unsaturated aldehydes, Asymmetric catalysis, C-C coupling, Iminium ion activation, Michael addition, Organocatalysis
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95939DOI: 10.1002/adsc.200600316ISI: 000245379400035OAI: oai:DiVA.org:uu-95939DiVA: diva2:170326
Available from: 2007-05-11 Created: 2007-05-11 Last updated: 2011-02-08Bibliographically approved
In thesis
1. Towards Rational Design of Asymmetric Catalyst for Organometallic and Organocatalytic Reactions
Open this publication in new window or tab >>Towards Rational Design of Asymmetric Catalyst for Organometallic and Organocatalytic Reactions
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with synthetically modified chiral molecules and their application in asymmetric catalysis. The first part of the thesis describes the use of commercially available chiral diamine ligands in the iridium catalyzed transfer hydrogenation of aromatic ketones. The chiral diamine ligands were mixed with an appropriate transition-metal complex, which after addition of suitable base provided a chiral transition metal complex capable of reducing a range of different aromatic ketones in high yields and enantioselectivities. The developed methodology constitutes a cost effective and readily available procedure for transfer hydrogenation reactions. The following chapters in the thesis are completely devoted to rational design of small organic molecules acting as catalyst in various organocatalytic transformations. Organocatalytic methodology, represent a new and complementary approach to asymmetric organic synthesis, as compared to e.g. transition metal based methodology. Advantages of this methodology typically include mild and less stringent reaction conditions. This, in combination with the lack of toxic transition metal by-products, makes the process more environmentally benign; the organocatalytic methodology, therefore represent a promising approach towards implementation of green chemistry in organic synthesis. Despite this promise, typical drawbacks of the current methodology are long reaction times and the need for high catalyst loadings. Thus, a large demand exists for enhancing reactivity and increasing selectivity in organocatalytic reactions. The present thesis describes several efforts where we have tried to rationally design improved catalysts for various enantioselective organocata-lytic reactions. First, a structurally modified L-proline, incorporating a 1H-tetrazolic acid, was synthesized and evaluated in the direct asymmetric organocatalytic aldol reaction. As shown in Paper II, the catalyst displayed very high reactivity and subsequent studies were initiated in order to rationalize the reactivity enhancement (Paper III). Delightfully, the design principle of a 1H-tetrazolic acid as replacement for a carboxylic acid has since been widely used in the community, including our own efforts in organocatalytic asymmetric cyclopropanations (Paper V)and Diels-Alder reactions (Paper VII). Novel catalysts, including other functionalizations, were also designed for organocatalytic asymmetric addition of nitroalkanes to α,β-unsaturated aldehydes (Paper IV) and for cyclopropanations (Paper VI).

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2007. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 313
Keyword
Organocatalysis, Transition Metal Complex, Asymmetric, Aldol Reaction, Cyclopropanation, Diels-Alder, Reduction, Conjugate Addition
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-7905 (URN)978-91-554-6905-4 (ISBN)
Public defence
2007-06-02, B41, BMC, Husargatan 3, Uppsala, 10:15
Opponent
Supervisors
Available from: 2007-05-11 Created: 2007-05-11Bibliographically approved

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