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Epp, Konstantin, Bueken, Bart, Hofmann, Benjamin J. 
ORCID: https://orcid.org/0000-0001-6408-3472, Cokoja, Mirza, Hemmer, Karina, De Vos, Dirk and Fischer, Roland A.
(2019)
Network topology and cavity confinement-controlled diastereoselectivity in cyclopropanation reactions catalyzed by porphyrin-based MOFs.
Catalysis Science & Technology, 9 (22).
pp. 6452-6459.
ISSN 2044-4753
Abstract
In this work, we show that the stereoselectivity of a reaction can be controlled by directing groups of substrates, by network topology and by local cavity confinement of metal-organic framework (MOF) catalysts. We applied the porphyrin-based PCN-224(Rh), which contains no stereocenters in the cyclopropanation reaction using ethyl diazoacetate (EDA) as carbene source. When styrene and other non-coordinating olefins are used as substrates, high activity, but no diastereoselectivity is observed. Interestingly, conversion of 4-amino- and 4-hydroxystyrene substrates occurs with high diastereomeric ratios (dr) of up to 23 : 1 (trans : cis). We attribute this to local pore confinement effects as a result of substrate coordination to neighboring Rh-centers, which position the olefin with respect to the active site, causing a break of local symmetry of the coordinated substrate. The effect of local pore confinement was improved by using PCN-222(Rh) as catalyst, which is a structural analog of PCN-224(Rh) with characteristic Kagomé topology featuring shorter Rh-Rh distances. A remarkable dr of 42 : 1 (trans : cis) was observed for 4-aminostyrene. In this case, the length of the substrate corresponds to the average distance between two neighboring Rh centers within the pores of PCN-222(Rh), which drastically boosts the diastereoselectivity. This work showcases how diastereomeric control can be achieved by favorable substrate-catalyst interactions and thoughtful adjustment of confined reaction space using porphyrin-based MOFs, in which stereocenters are inherently absent.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | catalysis ,/dk/atira/pure/subjectarea/asjc/1500/1503 |
| Faculty \ School: | Faculty of Science > School of Chemistry (former - to 2024) |
| Related URLs: | |
| Depositing User: | LivePure Connector |
| Date Deposited: | 17 Jul 2021 00:12 |
| Last Modified: | 25 Sep 2024 15:42 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/80631 |
| DOI: | 10.1039/c9cy00893d |
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