Catalytic Oxidations with Molecular Oxygen
Palladium Catalyzed Aerobic Oxidation
- Developing catalytic aerobic oxidation methods, including reactions of alcohols, alkenes, and aliphatic and aromatic C–H bonds
- Mechanistic understanding of catalytic mechanisms, elucidating the basis for ligand-promoted catalytic turnover with O2 as the oxidant
- Characterizing fundamental Pd-O2 reactivity, including structural characterization of Pd-peroxo and hydroperoxo complexes
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Key References
Review Articles:
Campbell, A. N.; Stahl, S. S. Overcoming the “Oxidant Problem”: Strategies to Use O2 as the Oxidant in Organometallic C-H Oxidation Reactions Catalyzed by Pd (and Cu). Acc. Chem. Res. 2012, 45, 851-863. DOI:10.1021/ar2002045
Wang, D.; Weinstein, A. B.; White, P. B.; Stahl, S. S. Ligand-Promoted Palladium-Catalyzed Aerobic Oxidation Reactions. Chem. Rev. 2018, 118, 2636-2679. DOI:10.1021/acs.chemrev.7b00334
Representative Publications:
Izawa, Y.; Pun, D.; Stahl, S. S. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science 2011, 333, 209-213. DOI:10.1126/science.1204183
Jaworski, J. N.; Kozack, C. V.; Tereniak, S. J.; Knapp, S. M. M.; Landis, C. R.; Miller, J. T.; Stahl, S. S. Operando Spectroscopic and Kinetic Characterization of Aerobic Allylic C–H Acetoxylation Catalyzed by Pd(OAc)2/4,5-Diazafluoren-9-one. J. Am. Chem. Soc. 2019, 141, 10462-10474. DOI:10.1021/jacs.9b04699
Salazar, C. A.; Gair, J. J.; Flesch, K. N.; Guzei, I. A.; Lewis, J. C.; Stahl, S. S. Catalytic Behavior of Mono-N-Protected Amino Acid Ligands in Ligand-Accelerated C-H Activation by Palladium(II). Angew. Chem. Int. Ed. 2020, 59, 10873-10877. doi: 10.1002/anie.202002484
Bruns, D. L.; Musaev, D. G.; Stahl, S. S. Can Donor Ligands Make Pd(OAc)2 a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria. J. Am. Chem. Soc. 2020, 142, 19678–19688. DOI: 10.1021/jacs.0c09464
Salazar, C. A.; Flesch, K. N.; Haines, B. E.; Zhou, P. S.; Musaev, D. G.; Stahl, S. S. Tailored Quinones Support High-Turnover Pd Catalysts for Oxidative C–H Arylation with O2. Science 2020, 370, 1454–1460. DOI: 10.1126/science.abd1085.
Copper Catalyzed Aerobic Oxidation
- How do catalysts that undergo one-electron redox chemistry mediate two-electron oxidation reactions with a four-electron oxidant (O2)?
- Establishing principles to distinguish between single-electron-transfer (SET) and organometallic oxidation pathways, including the demonstration of organocopper(III) intermediates
- Developing and characterizing oxidative N–N coupling reactions
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Key References
Representative Publications:
McCann, S. D.; Lumb, J.-P.; Arndtsen, B. A.; Stahl, S. S. Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst. ACS Cent. Sci. 2017, 3, 314-321. DOI:10.1021/acscentsci.7b00022
Ryan, M. C.; Martinelli, J. R.; Stahl, S. S. Cu-Catalyzed Aerobic Oxidative N–N Coupling of Carbazoles and Diarylamines Including Selective Cross-Coupling. J. Am. Chem. Soc. 2018, 140, 9074-9077. DOI:10.1021/jacs.8b05245
Ryan, M. C.; Whitmire, L. D.; McCann, S. D.; Stahl, S. S. Copper/TEMPO Redox Redux: Analysis of PCET Oxidation of TEMPOH by Copper(II) and the Reaction of TEMPO with Copper(I). Inorg. Chem. 2019, 58, 10194-10200. DOI: 10.1021/acs.inorgchem.9b01326
Ryan, M. C.; Kim, Y.-J.; Gerken, J. B.; Wang, F.; Aristov, M. M.; Martinelli, J. R.; Stahl, S. S. Mechanistic Insights into Copper-Catalyzed Aerobic Oxidative Coupling of N–N Bonds. Chem. Sci. 2020, 11, 1170-1175. DOI: 10.1039/C9SC04305E
Wang, F.; Gerken, J. B.; Bates, D. M.; Kim, Y. J.; Stahl, S. S. Electrochemical Strategy for Hydrazine Synthesis: Development and Overpotential Analysis of Methods for Oxidative N–N Coupling of an Ammonia Surrogate. J. Am. Chem. Soc. 2020, 142, 12349–12356. DOI: 10.1021/jacs.0c04626
Liu, W.; Twilton, J.; Wei, B.; Lee, M.; Hopkins, M. N.; Bacsa, J.; Stahl, S. S.; Davies, H. M. L. Copper-Catalyzed Oxidation of Hydrazones to Diazo Compounds Using Oxygen as the Terminal Oxidant. ACS Catal. 2021, 11, 2676-2683. DOI: 10.1021/acscatal.1c00264
Organic (Co)Catalysts for Aerobic Oxidation
- Developing Cu/aminoxyl catalysts for selective aerobic alcohol oxidation
- Establishing mechanisms of redox cooperativity between redox-active organic co-catalysts (aminoxyls, quinones) with transition metals (Cu, Co)
- Developing biomimetic quinones as catalysts for selective aerobic oxidation and oxidative coupling of amines
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Key References
Representative Publications:
Ryland, B. L.; Stahl, S. S. Practical Aerobic Oxidations of Alcohols and Amines with Homogeneous Copper/TEMPO and Related Catalyst Systems. Angew. Chem. Int. Ed. 2014, 53, 8824-8838. DOI:10.1002/anie.201403110.
Zultanski, S. L.; Zhao, J.; Stahl, S. S. Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines. J. Am. Chem. Soc. 2016, 138, 6416–6419. DOI:10.1021/jacs.6b03931
Piszel, P. E.; Vasilopoulos, A.; Stahl, S. S. Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines using Aerobic Copper/Nitroxyl Catalysis. Angew. Chem. Int. Ed. 2019, 131, 12211-12215. DOI: 10.1002/anie.20190613
Heterogeneous Catalytic Aerobic Oxidation
- Developing new heterogeneous catalysts for organic chemical synthesis
- Synthesizing and characterizing M-N-C, single-atom catalysts for chemical synthesis applications
- Characterizing the mechanism of liquid-phase heterogeneous aerobic oxidation catalysts
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Key References
Representative Publications:
Mannel, D. S.; Ahmed, M. S.; Root, T. W.; Stahl, S. S. Discovery of Multicomponent Heterogeneous Catalysts via Admixture Screening: PdBiTe Catalysts for Aerobic Oxidative Esterification of Primary Alcohols. J. Am. Chem. Soc. 2017, 139, 1690-1698. DOI:10.1021/jacs.6b12722
Ahmed, M. S.; Mannel, D. S.; Root, T. W.; Stahl, S. S. Aerobic Oxidation of Diverse Primary Alcohols to Carboxylic Acids with a Heterogeneous Pd-Bi-Te/C (PBT/C) Catalyst. Org. Process Res. Dev. 2017, 21, 1388-1393. DOI:10.1021/acs.oprd.7b00223
Catalytic Radical C‒H Oxidation and Cross-Coupling
- Developing new methods for chemo-, regio-, and stereoselective functionalization of C(sp3)‒H bonds
- Utilizing radical-relay strategies to achieve benzylic C(sp3)‒H functionalization and cross-coupling
- Controlling the selectivity of radical and non-radical C‒H oxidation methods for medicinal chemistry
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Key References
Representative Publications:
Zhang, W.; Wang, F.; McCann, S. C.; Wang, D.; Chen, P.; Stahl, S. S.; Liu, G. Enantioselective Cyanation of Benzylic C-H Bonds via Copper-Catalyzed Radical Relay. Science 2016, 353, 1014-10158. DOI:10.1126/science.aaf7783
Vasilopoulos, A.; Zultanski, S. L.; Stahl, S. S. Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes. J. Am. Chem. Soc. 2017, 139, 7705-7708. DOI:10.1021/jacs.7b03387
Hu, H.; Chen, S. J.; Mandal, M.; Pratik, S. M.; Buss, J. A.; Krska, S. W.; Cramer, C. J.; Stahl, S. S. Copper-Catalyzed Benzylic C-H Coupling with Alcohols via Radical Relay Enabled by Redox Buffering. Nat. Catal. 2020, 3, 358-367. DOI:10.1038/s41929-020-0425-1
Suh, S.-E.; Chen, S.-J.; Mandal, M.; Guzei, I. A.; Cramer, C. J.; Stahl, S. S. Site-Selective Copper-Catalyzed Azidation of Benzylic C–H Bonds. J. Am. Chem. Soc. 2020, 142, 11388–11393. DOI: 10.1021/jacs.0c05362
Vasilopoulos, A.; Golden, D. L.; Buss, J. A.; Stahl, S. S. Copper-Catalyzed C–H Fluorination/Functionalization Sequence Enabling Benzylic C–H Cross Coupling with Diverse Nucleophiles. Org. Lett. 2020, 22, 5753-5757. DOI: 10.1021/acs.orglett.0c02238
Buss, J. A.; Vasilopoulos, A.; Golden, D. L.; Stahl, S. S. Copper-Catalyzed Functionalization of Benzylic C–H Bonds with N-Fluorobenzenesulfonimide: Switch from C–N to C–F Bond Formation Promoted by a Redox Buffer and Brønsted Base. Org. Lett. 2020, 22, 5749-5752. DOI: 10.1021/acs.orglett.0c02239
Catalytic Methods for Biomass Conversion and Valorization
- Using a two-step oxidation/depolymerization sequence for conversion of lignin into aromatic monomers
- Demonstrating selective aerobic and electrochemical oxidation methods for oxidative deconstruction of lignin and illustrating how this reactivity contributes to acid-promoted cleavage of the lignin polymer
- Developing oxidative catalytic fractionation methods for direct convertion of biomass into high-quality sugar and aromatic streams
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Key References
Representative Publications:
Rahimi, A.; Ulbrich, A.; Coon, J. J.; Stahl S. S. Formic-acid-induced depolymerization of oxidized lignin to aromatics. Nature 2014, 515, 249–252. DOI:10.1038/nature13867
Das, A.; Rahimi, A.; Ulbrich, A.; Alherech, M.; Motagamwala, A. H.; Bhalla, A.; da Costa Sousa, L.; Balan, V.; Dumesic, J. A.; Hegg, E. L.; Dale, B. E.; Ralph, J.; Coon, J. J.; Stahl, S. S. Lignin Conversion to Low-Molecular-Weight Aromatics via an Aerobic Oxidation-Hydrolysis Sequence: Comparison of Different Lignin Sources. ACS Sustainable Chem. Eng. 2018, 6, 3367-3374. DOI:10.1021/acssuschemeng.7b03541
Perez, J. M.; Kontur, W. S.; Alherech, M.; Coplien, J.; Karlen, S. D.; Stahl, S. S.; Donohue, T. J.; Noguera, D. R. Funneling aromatic products of chemically depolymerized lignin into 2-pyrone-4-6-dicarboxylic acid with Novosphingobium aromaticivorans. Green Chem. 2019, 21, 1340-1350. DOI: 10.1039/C8GC03504K
Rafiee, M.; Alherech, M.; Karlen, S. D.; Stahl, S. S. Electrochemical Aminoxyl-Mediated Oxidation of Primary Alcohols in Lignin to Carboxylic Acids: Polymer Modification and Depolymerization. J. Am. Chem. Soc. 2019, 141, 15266-15276. DOI:10.1021/jacs.9b07243
Electrocatalysis and Electrochemical Organic Synthesis
- Using electron-proton-transfer mediators to lower overpotential in electrochemical oxidations and to expand their scope and utility for pharmaceutical synthesis
- Developing HAT and hydride-transfer mediators to enable electrochemical C‒H functionalization
- Utilizing scalable flow processes for suitable electrochemical synthesis
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Key References
Review Articles:
Nutting, J. E.; Rafiee, M.; Stahl, S. S. Tetramethylpiperidine N-Oxyl (TEMPO), Phthalimide N-Oxyl (PINO), and Related N-Oxyl Species: Electrochemical Properties and Their Use in Electrocatalytic Reactions. Chem. Rev. 2018, 118, 4834-4885. DOI:10.1021/acs.chemrev.7b00763
Wang, F.; Stahl, S. S. Electrochemical Oxidation of Organic Molecules at Lower Overpotential: Accessing Broader Functional Group Compatibility with Electron-Proton Transfer Mediators. Acc. Chem. Res. 2020, 53, 561-574. DOI: 10.1021/acs.accounts.9b00544
Representative Publications:
Wang, F.; Rafiee, M.; Stahl, S. S. Electrochemical Functional-Group-Tolerant Shono-Type Oxidation of Cyclic Carbamates Enabled by Aminoxyl Mediators. Angew. Chem. Int. Ed. 2018, 57, 6686-6690. DOI:10.1002/anie.201803539
Rafiee, M.; Wang, F.; Hruszkewycz, D. P.; Stahl, S. S. N-Hydroxyphthalimide-Mediated Electrochemical Iodination of Methylarenes and Comparison to Electron-Transfer-Initiated C–H Functionalization. J. Am. Chem. Soc. 2018, 140, 22-25. DOI:10.1021/jacs.7b09744
Lennox, A. J. J.; Goes, S. L.; Webster, M. P.; Koolman, H. F.; Djuric, S. W.; Stahl, S. S. Electrochemical Aminoxyl-Mediated α-Cyanation of Secondary Piperidines for Pharmaceutical Building Block Diversification. J. Am. Chem. Soc. 2018, 140, 11227-11231. DOI:10.1021/jacs.8b08145
Wang, F.; Gerken, J. B.; Bates, D. M.; Kim, Y. J.; Stahl, S. S. Electrochemical Strategy for Hydrazine Synthesis: Development and Overpotential Analysis of Methods for Oxidative N–N Coupling of an Ammonia Surrogate. J. Am. Chem. Soc. 2020, 142, 12349–12356. DOI: 10.1021/jacs.0c04626
Electrocatalysts and Electrochemical Energy Storage and Conversion
- Developing stable organic electron-proton transfer mediators for use in energy storage and conversion application
- Investigating molecular catalysts for low-overpotential O2 reduction to H2O2 and water
- Developing and characterizing heterogeneous catalysts for energy conversion applications
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Key References
Representative Publications:
Anson, C. W.; Ghosh, S.; Hammes-Schiffer, S.; Stahl, S. S. Co(salophen)-Catalyzed Aerobic Oxidation of p-Hydroquinone: Mechanism and Implications for Aerobic Oxidation Catalysis. J. Am. Chem. Soc. 2017, 138, 4186-4193. DOI:10.1021/jacs.6b00254
Preger, Y.; Gerken, J. B.; Biswas, S.; Anson, C. W.; Johnson, M. R.; Root, T. W.; Stahl, S. S. Quinone-Mediated Electrochemical O2 Reduction Accessing High Power Density with an Off-Electrode Co-N/C Catalyst. Joule 2018, 2, 2722-2731. DOI:10.1016/joule.2018.09.010
Gerken, J. B.; Stamoulis, A.; Suh, S.- E.; Fischer, N. D.; Kim, Y. J.; Guzei, I. A.; Stahl, S. S. Efficient Electrochemical Synthesis of Robust, Densely Functionalized Water Soluble Quinones. Chem. Commun. 2020, 56, 1199-1202. DOI:10.1039/C9CC08878D
Gerken, J. B.; Anson, C. W.; Preger, Y.; Symons, P. G.; Genders, J. D.; Qiu, Y.; Li, W.; Root, T. W.; Stahl, S. S. Comparison of Quinone‐Based Catholytes for Aqueous Redox Flow Batteries and Demonstration of Long‐Term Stability with Tetrasubstituted Quinones. Adv. Energy Mater. 2020, 10, 2000340. doi: 10.1002/aenm.202000340