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Wei W, Li C, Fan Y, Chen X, Zhao X, Qiao B, Jiang Z. Catalytic Asymmetric Redox-Neutral [3+2] Photocycloadditions of Cyclopropyl Ketones with Vinylazaarenes Enabled by Consecutive Photoinduced Electron Transfer. Angew Chem Int Ed Engl 2024; 63:e202406845. [PMID: 38687326 DOI: 10.1002/anie.202406845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 04/30/2024] [Accepted: 04/30/2024] [Indexed: 05/02/2024]
Abstract
Consecutive photoinduced electron transfer (ConPET) is a powerful and atom-economical protocol to overcome the limitations of the intrinsic redox potential of visible light-absorbing photosensitizers, thereby considerably improving the substrate and reaction types. Likely because such an exothermic single-electron transfer (SET) process usually does not require the aid of chiral catalysts, resulting in an inevitable racemic background reaction, notably, no enantioselective manifolds have been reported. Herein, we report on the viability of cooperative ConPET and chiral hydrogen-bonding catalysis for the [3+2] photocycloaddition of cyclopropyl ketones with vinylazaarenes. In addition to enabling the first use of olefins that preferentially interact with chiral catalysts, this catalysis platform paves the way for the efficient synthesis of pharmaceutically and synthetically important cyclopentyl ketones functionalized by azaarenes with high yields, ees and dr. The robust capacity of the method can be further highlighted by the low loading of the chiral catalyst (1.0 mol %), the good compatibility of both 2-azaarene and 3-pyridine-based olefins, and the successful concurrent construction of three stereocenters on cyclopentane rings involving an elusive but important all-carbon quaternary.
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Affiliation(s)
- Wenhui Wei
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Chunyang Li
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Yifan Fan
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Xiaowei Chen
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Xiaowei Zhao
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Baokun Qiao
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
| | - Zhiyong Jiang
- Henan Key Laboratory of Natural Medicine Innovation and Transformation, Henan University, Kaifeng, Henan, 475004, P. R. China
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan, 453007, P. R. China
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Li H, Wenger OS. Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202110491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Han Li
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Oliver S. Wenger
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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Li H, Wenger OS. Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis. Angew Chem Int Ed Engl 2021; 61:e202110491. [PMID: 34787359 PMCID: PMC9299816 DOI: 10.1002/anie.202110491] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/16/2021] [Indexed: 12/25/2022]
Abstract
The two‐electron reduced forms of perylene diimides (PDIs) are luminescent closed‐shell species whose photochemical properties seem underexplored. Our proof‐of‐concept study demonstrates that straightforward (single) excitation of PDI dianions with green photons provides an excited state that is similarly or more reducing than the much shorter‐lived excited states of PDI radical monoanions, which are typically accessible after biphotonic excitation with blue photons. Thermodynamically demanding photocatalytic reductive dehalogenations and reductive C−O bond cleavage reactions of lignin model compounds have been performed using sodium dithionite acts as a reductant, either in aqueous solution or in biphasic water–acetonitrile mixtures in the presence of a phase transfer reagent. Our work illustrates the concept of multi‐electron reduction of a photocatalyst by a sacrificial reagent prior to irradiation with low‐energy photons as a means of generating very reactive excited states.
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Affiliation(s)
- Han Li
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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Neumann S, Wenger OS, Kerzig C. Controlling Spin-Correlated Radical Pairs with Donor-Acceptor Dyads: A New Concept to Generate Reduced Metal Complexes for More Efficient Photocatalysis. Chemistry 2021; 27:4115-4123. [PMID: 33274791 PMCID: PMC7986886 DOI: 10.1002/chem.202004638] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/02/2020] [Indexed: 12/30/2022]
Abstract
One-electron reduced metal complexes derived from photoactive ruthenium or iridium complexes are important intermediates for substrate activation steps in photoredox catalysis and for the photocatalytic generation of solar fuels. However, owing to the heavy atom effect, direct photochemical pathways to these key intermediates suffer from intrinsic efficiency problems resulting from rapid geminate recombination of radical pairs within the so-called solvent cage. In this study, we prepared and investigated molecular dyads capable of producing reduced metal complexes via an indirect pathway relying on a sequence of energy and electron transfer processes between a Ru complex and a covalently connected anthracene moiety. Our test reaction to establish the proof-of-concept is the photochemical reduction of ruthenium(tris)bipyridine by the ascorbate dianion as sacrificial donor in aqueous solution. The photochemical key step in the Ru-anthracene dyads is the reduction of a purely organic (anthracene) triplet excited state by the ascorbate dianion, yielding a spin-correlated radical pair whose (unproductive) recombination is strongly spin-forbidden. By carrying out detailed laser flash photolysis investigations, we provide clear evidence for the indirect reduced metal complex generation mechanism and show that this pathway can outperform the conventional direct metal complex photoreduction. The further optimization of our approach involving relatively simple molecular dyads might result in novel photocatalysts that convert substrates with unprecedented quantum yields.
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Affiliation(s)
- Svenja Neumann
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Oliver S. Wenger
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Christoph Kerzig
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10—1455128MainzGermany
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