From energy to electron transfer photocatalysis (PenT → PET): oxidative cyclobutane cleavage alters the product composition

Photocatalytic [2+2]-cycloadditions between cyclic enones and electron-rich cyclic enol ethers are initiated by triplet-triplet energy transfer from an excited iridium photocatalyst to the enone acceptor. The composition of the resulting cycloadduct mixture shows a surprising time dependency of the...

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Bibliographic Details
Published in:Chemical communications (Cambridge, England) England), 2022-11, Vol.58 (93), p.12999-132
Main Authors: Lefarth, Jens, Haseloer, Alexander, Kletsch, Lukas, Klein, Axel, Neudörfl, Jörg, Griesbeck, Axel G
Format: Article
Language:English
Subjects:
Composition
Cyclobutane
Cyclobutanes
Electron transfer
Electron Transport
Electrons
Energy transfer
Ethers
Iridium
Isomerization
Oxidative Stress
Photocatalysis
Positron-Emission Tomography
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Summary:Photocatalytic [2+2]-cycloadditions between cyclic enones and electron-rich cyclic enol ethers are initiated by triplet-triplet energy transfer from an excited iridium photocatalyst to the enone acceptor. The composition of the resulting cycloadduct mixture shows a surprising time dependency of the cyclobutane stereoisomeric ratio which indicates that the products are not photostable under the reaction conditions. The isomerisation of the cycloadducts 3 by a photoinduced redox process points to a switch from triplet energy transfer (PenT) to photoinduced electron transfer (PET) catalysis. Photocatalytic [2+2]-cycloadditions between enones and electron-rich enol ethers are initiated by triplet-triplet energy transfer. In a consecutive step, photoinduced electron transfer leads to oxidative isomerization of the cyclobutane products.
ISSN:1359-7345
1364-548X
1364-548X
DOI:10.1039/d2cc04693h