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Functionalized spirolactones by photoinduced dearomatization of biaryl compounds
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry. Dalian Institute of Chemical Physics (DICP), China .
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Number of Authors: 52019 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 10, no 12, p. 3681-3686Article in journal (Refereed) Published
Abstract [en]

The idea of using biaryl structures to generate synthetic building blocks such as spirolactones is attractive because biaryl structures are abundant in biomass waste streams. However, the inertness of aromatic rings of biaryls makes it challenging to transform them into functionalized structures. In this work, we developed photoinduced dearomatization of nonphenolic biaryl compounds to generate spirolactones. We demonstrate that dearomatization can be performed via either aerobic photocatalysis or anaerobic photooxidation to tolerate specific synthetic conditions. In both pathways, dearomatization is induced by electrophilic attack of the carboxyl radical. The resulting spirodiene radical is captured by either oxygen or water in aerobic and anaerobic systems, respectively, to generate the spirodienone. These methods represent novel routes to synthesize spirolactones from the biaryl motif.

Place, publisher, year, edition, pages
2019. Vol. 10, no 12, p. 3681-3686
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-168611DOI: 10.1039/c8sc05476bISI: 000463759100026PubMedID: 30996963OAI: oai:DiVA.org:su-168611DiVA, id: diva2:1315261
Available from: 2019-05-13 Created: 2019-05-13 Last updated: 2020-02-25Bibliographically approved
In thesis
1. Production and transformation of organic compounds from renewable feedstock: Catalytic approaches
Open this publication in new window or tab >>Production and transformation of organic compounds from renewable feedstock: Catalytic approaches
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on the development of strategies for lignocellulosic biomass valorization. The thesis consists of two parts.

The first part of the presented work is related to the catalytic fractionation of biomass (lignin-first approach) and the production of monomeric compounds from lignocellulose. In the first project (Chapter 2) we have established a process to study the transformations occurring during the catalytic organosolv pulping of wood in the presence of Pd/C. This was achieved by performing a fractionation under continuous-flow conditions. In the designed process, the pulping and the transition metal catalyzed reactions were separated in space and time. Thus, the role of the solvolysis and the transfer hydrogenation reactions were studied independently. We discovered that during the solvolysis of wood, a substantial amount of monomeric lignin fragments are released into the solution. The main role of the catalyst is to stabilize these monomers and prevent their repolymerization. Based on the obtained knowledge we developed a new version of the lignin-first approach (Chapter 3). In this process zeolites were used as shape-selective catalysts. We have demonstrated that by tuning the size of pores of the catalyst the undesirable bimolecular reactions can be minimized. Furthermore, the released monomers can be converted into stable products via transfer hydrogenation reactions.  

The second part is related to studies of dimeric and trimeric lignin model compounds. In Chapter 4, the reactivity of the dibenzodioxocin motif, which is considered a main branching point in the lignin structure has been investigated. We have designed a protocol for the catalytic reductive cleavage of lignin model compounds representing this motif, in the presence of Pd/C and benign hydride donors. The cleavage of the dibenzodioxocin structure results in the formation of dimeric biaryl compounds. Unlike monomers, the valorization of lignin-derived dimers is less studied. The last chapter is focused on the transformation of biaryls into highly functionalized synthetic building blocks. This was achieved via a visible light induced dearomative spirolactonization of biaryl carboxylic acids. The synthetic value of the obtained products was demonstrated by the conversion of the products into more complex structures.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2020. p. 70
Keywords
Lignin, biomass, lignin-first, catalytic fractionation, flow reactors, dibenzodioxocin, silanes, zeolites, visible light photocatalysis, dearomatization, spirolactones
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-179101 (URN)978-91-7911-028-4 (ISBN)978-91-7911-029-1 (ISBN)
Public defence
2020-05-27, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, 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 4: Manuscript.

Available from: 2020-05-04 Created: 2020-02-18 Last updated: 2020-05-25Bibliographically approved

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