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Biomimetic Hydrogen Bonding Catalysis of Imine Exchange for Rapid Equilibration of Dynamic Systems
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Olof Ramström)ORCID iD: 0000-0001-5298-4310
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Olof Ramström)
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Olof Ramström)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, for example in the preparation of dynamic systems for a wide variety of applications. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors, such as thioureas and squaramides, can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.

Keywords [en]
Dynamic Chemistry, Imine Exchange, Hydrogen Bonding Catalysis, Dynamic Systems, Solid-Supported Catalyst
National Category
Organic Chemistry
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-199717OAI: oai:DiVA.org:kth-199717DiVA, id: diva2:1065404
Funder
Swedish Research Council
Note

QC 20170116

Available from: 2017-01-16 Created: 2017-01-16 Last updated: 2017-01-16Bibliographically approved
In thesis
1. Catalysis in Dynamic Systems: Control within Molecular Reaction Networks
Open this publication in new window or tab >>Catalysis in Dynamic Systems: Control within Molecular Reaction Networks
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Life as we know it is based on complex networks of biochemical reactions that constantly interact within large dynamic systems. The field of systems chemistry uses chemical models to study how reaction networks – and thereby life – function on a molecular level. This thesis focuses on different aspects of catalysis in dynamic systems of interconnected reversible reactions. Using the reversible imine bond as the primary tool, such dynamic systems have both been used for catalyst screening and to achieve emergent systemic behavior.

First, constitutional dynamic chemistry was used to discover catalysts within large mixtures. A method based on dynamic deconvolution was used to identify a bifunctional organocatalyst for the Morita-Baylis-Hillman (MBH) reaction from a mixture of 16 candidates. A second method involved amplification of an organometallic intermediate from a dynamic system and was used to discover directing group/metal combinations for C-H functionalization of aldehydes.

Subsequently, the consequences of integrating the catalyst itself into a dynamic system were investigated. Here, dynamic covalent catalysts formed reaction networks with programmable systemic properties. Using the MBH reaction and dynamic imine exchange, catalysts capable of self-resolution, feedback regulation and error-correction were constructed.

Finally, selective catalyst systems for activation of new reversible covalent behavior for imines were developed. H-bond catalysis was used to facilitate imine exchange under mild conditions, and transamination was introduced as a dynamic covalent linkage that could change the directionality of the imine bond.

The research in this thesis should both be applicable for catalyst discovery within synthetic organic chemistry, for understanding connectivity in chemical and biological systems as well as for studies of the origin of life on earth and the evolution of simple molecules into advanced systems with emergent functionality.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan, 2017. p. 90
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:7
Keywords
systems chemistry, dynamic covalent chemistry, catalyst screening, reaction networks, organocatalysis, imine exchange, combinatorial chemistry, dynamic systemic resolution, feedback, error-correction, Morita-Baylis-Hillman reaction, C-H activation, H-bond catalysis, transamination
National Category
Organic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-199708 (URN)978-91-7729-255-5 (ISBN)
Public defence
2017-02-17, F3, Lindstedtsvägen 26, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20170216

Available from: 2017-01-16 Created: 2017-01-15 Last updated: 2017-01-27Bibliographically approved

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Schaufelberger, FredrikRamström, Olof

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