Photocatalyzed oxidative cleavage of alkenes using CO2 as an oxygen donor.
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| Title: | Photocatalyzed oxidative cleavage of alkenes using CO |
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| Authors: | Qin, Yuman (AUTHOR), Ren, Peng (AUTHOR), Hu, Jun (AUTHOR), Pradhan, Suman (AUTHOR), Vuong, Thanh Huyen (AUTHOR), He, Xiufang (AUTHOR), Alluhaibi, Lulu (AUTHOR), Rockstroh, Nils (AUTHOR), Monti, Susanna (AUTHOR), Barcaro, Giovanni (AUTHOR), Jaworski, Aleksander (AUTHOR), Kuśtrowski, Piotr (AUTHOR), Rabeah, Jabor (AUTHOR), Hohenberger, Daniel (AUTHOR), Bagnich, Sergey (AUTHOR), Köhler, Anna (AUTHOR), Breu, Josef (AUTHOR), Vilé, Gianvito (AUTHOR), Beller, Matthias (AUTHOR), Das, Shoubhik (AUTHOR) |
| Source: | Science. 6/4/2026, Vol. 392 Issue 6802, p1-10. 10p. |
| Subjects: | Carbon oxides, Iron catalysts, Organic synthesis, Intermediates (Chemistry), Photocatalysis, Photocatalytic oxidation, Sustainable chemistry, Alkenes |
| Abstract: | Oxidative cleavage of carbon-carbon double bonds often requires hazardous reagents and demanding conditions. In this study, we report a photocatalytic oxidative cleavage of alkenes using benign carbon dioxide (CO2) as an oxygen donor, producing ketones or carboxylic acids at atmospheric pressure and room temperature. A robust iron-based heterogeneous photocatalyst facilitates oxygen transfer to form an epoxide intermediate that subsequently undergoes ring opening and carbon-carbon bond cleavage to yield the oxidative products with high selectivity. Comprehensive mechanistic studies combine time-resolved spectroscopy, isotope labeling, and in situ spectroscopic analyses with advanced quantum mechanical simulations. These results uncover fundamental principles of oxygen transfer from CO2 under photocatalytic conditions, offering a sustainable platform for light-driven oxidative transformations. Editor's summary: Slicing through carbon-carbon double bonds is a job for strong oxidants. Typical reagents include ozone and high-valent metal oxides. Carbon dioxide is essentially the thermodynamic opposite of those oxidants and conventionally reacts at the carbon rather than either oxygen. Remarkably, Qin et al. nonetheless found that a heterogeneous iron photocatalyst can break alkenes into ketones and acids using the oxygen from carbon dioxide. Hydrogen donation by chloroform assists the process, which appears to occur through an epoxide intermediate. —Jake S. Yeston INTRODUCTION: Photocatalytic oxidative cleavage of carbon–carbon double bonds to generate oxygenated products is an important class of reactions in organic synthesis. Conventional methods typically rely on stoichiometric oxidants or molecular oxygen, leading to excessive waste generation and safety concerns that are associated with the high oxidizing power or flammability of these reagents. By contrast, carbon dioxide (CO2), an abundant and oxygen-rich feedstock, represents an attractive alternative for a safer, more sustainable oxidation strategy. However, the exceptionally strong C=O bonds of CO2 (bond dissociation energy ≈ 179 kcal mol−1) severely limit its activation, and reported examples generally require harsh conditions. As a result, photocatalytic oxidative C=C bond cleavage using CO2 under mild conditions remains largely unexplored. RATIONALE: We hypothesized that an iron-based heterogeneous photocatalyst supported on modified carbon nitride could promote CO2 activation through chemisorption, inducing a distortion of CO2 from its linear geometry to a bent configuration. This structural perturbation substantially lowers the energetic barrier for C=O bond cleavage of CO2 under photocatalytic conditions. Coupled with a proton-assisted electron-transfer pathway, this strategy enables CO2 activation at room temperature and atmospheric pressure. During this process, Fe-bound oxygen species generated upon CO2 activation act as reactive oxidants, transferring oxygen to alkene C=C bonds coordinated to the Fe centers to form epoxide intermediates. Subsequent ring opening affords diol intermediates, which then undergo C–C bond extension and cleavage. A final oxidation step yields the corresponding ketones or carboxylic acids. RESULTS: Systematic reaction-condition screening identified CHCl3 as an effective proton source. Under the optimized conditions, 45 substrates, including activated alkene, unactivated alkene, and complex alkenes, were efficiently converted to corresponding ketone or carboxylic acid by using CO2 as the sole oxygen donor. Notably, high compatibility was observed for functional groups that are typically sensitive to strong oxidative conditions, including aldehydes, hydroxyl groups, and alkynes. Isotopic labeling experiments using C18O2 demonstrated that the oxygen atoms incorporated into the products originated from CO2. Intermediate-capture studies, combined with in situ diffuse reflectance infrared Fourier transform spectroscopy, revealed a stepwise pathway involving epoxide and diol intermediates before C–C bond cleavage. Extensive characterization of fresh and recycled photocatalysts by STEM, solid-state NMR, XPS, XRD, FTIR, in situ EPR, and x-ray absorption spectroscopy showed minimal structural changes, confirming the robustness of the catalyst. Advanced quantum mechanical simulations further supported the proposed reaction pathway and thermodynamic feasibility. CONCLUSION: This study establishes a robust heterogeneous photocatalytic platform for oxidative C=C bond cleavage using CO2 as the sole oxygen source under mild conditions, providing a practical alternative to traditional oxidative cleavage methods. By integrating CO2 activation and iron-centered oxygen transfer, the approach overcomes the intrinsic thermodynamic stability of CO2 and transforms it from a one-carbon (C1) feedstock into an active oxygen source, opening potential opportunities for sustainable photocatalytic oxidation reactions and CO2 utilization in organic synthesis. [ABSTRACT FROM AUTHOR] |
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| Database: | Psychology and Behavioral Sciences Collection |
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| Abstract: | Oxidative cleavage of carbon-carbon double bonds often requires hazardous reagents and demanding conditions. In this study, we report a photocatalytic oxidative cleavage of alkenes using benign carbon dioxide (CO2) as an oxygen donor, producing ketones or carboxylic acids at atmospheric pressure and room temperature. A robust iron-based heterogeneous photocatalyst facilitates oxygen transfer to form an epoxide intermediate that subsequently undergoes ring opening and carbon-carbon bond cleavage to yield the oxidative products with high selectivity. Comprehensive mechanistic studies combine time-resolved spectroscopy, isotope labeling, and in situ spectroscopic analyses with advanced quantum mechanical simulations. These results uncover fundamental principles of oxygen transfer from CO2 under photocatalytic conditions, offering a sustainable platform for light-driven oxidative transformations. Editor's summary: Slicing through carbon-carbon double bonds is a job for strong oxidants. Typical reagents include ozone and high-valent metal oxides. Carbon dioxide is essentially the thermodynamic opposite of those oxidants and conventionally reacts at the carbon rather than either oxygen. Remarkably, Qin et al. nonetheless found that a heterogeneous iron photocatalyst can break alkenes into ketones and acids using the oxygen from carbon dioxide. Hydrogen donation by chloroform assists the process, which appears to occur through an epoxide intermediate. —Jake S. Yeston INTRODUCTION: Photocatalytic oxidative cleavage of carbon–carbon double bonds to generate oxygenated products is an important class of reactions in organic synthesis. Conventional methods typically rely on stoichiometric oxidants or molecular oxygen, leading to excessive waste generation and safety concerns that are associated with the high oxidizing power or flammability of these reagents. By contrast, carbon dioxide (CO2), an abundant and oxygen-rich feedstock, represents an attractive alternative for a safer, more sustainable oxidation strategy. However, the exceptionally strong C=O bonds of CO2 (bond dissociation energy ≈ 179 kcal mol−1) severely limit its activation, and reported examples generally require harsh conditions. As a result, photocatalytic oxidative C=C bond cleavage using CO2 under mild conditions remains largely unexplored. RATIONALE: We hypothesized that an iron-based heterogeneous photocatalyst supported on modified carbon nitride could promote CO2 activation through chemisorption, inducing a distortion of CO2 from its linear geometry to a bent configuration. This structural perturbation substantially lowers the energetic barrier for C=O bond cleavage of CO2 under photocatalytic conditions. Coupled with a proton-assisted electron-transfer pathway, this strategy enables CO2 activation at room temperature and atmospheric pressure. During this process, Fe-bound oxygen species generated upon CO2 activation act as reactive oxidants, transferring oxygen to alkene C=C bonds coordinated to the Fe centers to form epoxide intermediates. Subsequent ring opening affords diol intermediates, which then undergo C–C bond extension and cleavage. A final oxidation step yields the corresponding ketones or carboxylic acids. RESULTS: Systematic reaction-condition screening identified CHCl3 as an effective proton source. Under the optimized conditions, 45 substrates, including activated alkene, unactivated alkene, and complex alkenes, were efficiently converted to corresponding ketone or carboxylic acid by using CO2 as the sole oxygen donor. Notably, high compatibility was observed for functional groups that are typically sensitive to strong oxidative conditions, including aldehydes, hydroxyl groups, and alkynes. Isotopic labeling experiments using C18O2 demonstrated that the oxygen atoms incorporated into the products originated from CO2. Intermediate-capture studies, combined with in situ diffuse reflectance infrared Fourier transform spectroscopy, revealed a stepwise pathway involving epoxide and diol intermediates before C–C bond cleavage. Extensive characterization of fresh and recycled photocatalysts by STEM, solid-state NMR, XPS, XRD, FTIR, in situ EPR, and x-ray absorption spectroscopy showed minimal structural changes, confirming the robustness of the catalyst. Advanced quantum mechanical simulations further supported the proposed reaction pathway and thermodynamic feasibility. CONCLUSION: This study establishes a robust heterogeneous photocatalytic platform for oxidative C=C bond cleavage using CO2 as the sole oxygen source under mild conditions, providing a practical alternative to traditional oxidative cleavage methods. By integrating CO2 activation and iron-centered oxygen transfer, the approach overcomes the intrinsic thermodynamic stability of CO2 and transforms it from a one-carbon (C1) feedstock into an active oxygen source, opening potential opportunities for sustainable photocatalytic oxidation reactions and CO2 utilization in organic synthesis. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00368075 |
| DOI: | 10.1126/science.aed6068 |
