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Hall MN, Lee M, Root TW, Davies HML, Stahl SS. Heterogeneous Fe-N-C Catalyst for Aerobic Dehydrogenation of Hydrazones to Diazo Compounds Used for Carbene Transfer. J Am Chem Soc 2024; 146:13741-13747. [PMID: 38717594 DOI: 10.1021/jacs.4c04430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Organic diazo compounds are versatile reagents in chemical synthesis and would benefit from improved synthetic accessibility, especially for larger scale applications. Here, we report a mild method for the synthesis of diazo compounds from hydrazones using a heterogeneous Fe-N-C catalyst, which has Fe ions dispersed within a graphitic nitrogen-doped carbon support. The reactions proceed readily at room temperature using O2 (1 atm) as the oxidant. Aryl diazoesters, ketones, and amides are accessible, in addition to less stable diaryl diazo compounds. Initial-rate data show that the Fe-N-C catalyst achieves faster rates than a heterogeneous Pt/C catalyst. The oxidative dehydrogenation of hydrazones may be performed in tandem with Rh-catalyzed enantioselective C-H insertion and cyclopropanation of alkenes, without requiring isolation of the diazo intermediate. This sequence is showcased by using a flow reactor for continuous synthesis of diazo compounds.
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Affiliation(s)
- Melissa N Hall
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Maizie Lee
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Thatcher W Root
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Huw M L Davies
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Shannon S Stahl
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Mu Y, Chen B, Zhang H, Fei M, Liu T, Mehta N, Wang DZ, Miller AJM, Diaconescu PL, Wang D. Highly Selective Electrochemical Baeyer-Villiger Oxidation through Oxygen Atom Transfer from Water. J Am Chem Soc 2024; 146:13438-13444. [PMID: 38687695 DOI: 10.1021/jacs.4c02601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The Baeyer-Villiger oxidation of ketones is a crucial oxygen atom transfer (OAT) process used for ester production. Traditionally, Baeyer-Villiger oxidation is accomplished by thermally oxidizing the OAT from stoichiometric peroxides, which are often difficult to handle. Electrochemical methods hold promise for breaking the limitation of using water as the oxygen atom source. Nevertheless, existing demonstrations of electrochemical Baeyer-Villiger oxidation face the challenges of low selectivity. We report in this study a strategy to overcome this challenge. By employing a well-known water oxidation catalyst, Fe2O3, we achieved nearly perfect selectivity for the electrochemical Baeyer-Villiger oxidation of cyclohexanone. Mechanistic studies suggest that it is essential to produce surface hydroperoxo intermediates (M-OOH, where M represents a metal center) that promote the nucleophilic attack on ketone substrates. By confining the reactions to the catalyst surfaces, competing reactions (e.g., dehydrogenation, carboxylic acid cation rearrangements, and hydroxylation) are greatly limited, thereby offering high selectivity. The surface-initiated nature of the reaction is confirmed by kinetic studies and spectroelectrochemical characterizations. This discovery adds nucleophilic oxidation to the toolbox of electrochemical organic synthesis.
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Affiliation(s)
- Yu Mu
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Boqiang Chen
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Hongna Zhang
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Muchun Fei
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Tianying Liu
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Neal Mehta
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - David Z Wang
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Alexander J M Miller
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Paula L Diaconescu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Dunwei Wang
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
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Czaikowski ME, Anferov SW, Anderson JS. Metal-ligand cooperativity in chemical electrosynthesis. CHEM CATALYSIS 2024; 4:100922. [PMID: 38799408 PMCID: PMC11115383 DOI: 10.1016/j.checat.2024.100922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Electrochemistry has been an increasingly useful tool for organic synthesis, as it can selectively generate reactive intermediates under mild conditions using an applied potential. Concurrently, synergistic activity of a metal and a ligand has been used in thermal catalysis and electrocatalytic renewable fuel generation for substrate selectivity and improved catalyst activity. Combining these synthetic strategies is an attractive approach for mild, selective, and sustainable electrosynthesis. This perspective discusses examples of metal-ligand synergistic catalysis in electrochemical applications in organic and organometallic synthesis. The range of reactions and ligand design principles illustrates many opportunities for further discovery in this area and the potential for far-reaching synthetic benefits.
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Affiliation(s)
- Maia E. Czaikowski
- Department of Chemistry, The University of Chicago, Chicago, IL 60627, USA
- These authors contributed equally
| | - Sophie W. Anferov
- Department of Chemistry, The University of Chicago, Chicago, IL 60627, USA
- These authors contributed equally
| | - John S. Anderson
- Department of Chemistry, The University of Chicago, Chicago, IL 60627, USA
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Hoque MA, Gerken JB, Stahl SS. Synthetic dioxygenase reactivity by pairing electrochemical oxygen reduction and water oxidation. Science 2024; 383:173-178. [PMID: 38207052 PMCID: PMC10902909 DOI: 10.1126/science.adk5097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Accepted: 12/04/2023] [Indexed: 01/13/2024]
Abstract
The reactivity of molecular oxygen is crucial to clean energy technologies and green chemical synthesis, but kinetic barriers complicate both applications. In synthesis, dioxygen should be able to undergo oxygen atom transfer to two organic molecules with perfect atom economy, but such reactivity is rare. Monooxygenase enzymes commonly reductively activate dioxygen by sacrificing one of the oxygen atoms to generate a more reactive oxidant. Here, we used a manganese-tetraphenylporphyrin catalyst to pair electrochemical oxygen reduction and water oxidation, generating a reactive manganese-oxo at both electrodes. This process supports dioxygen atom transfer to two thioether substrate molecules, generating two equivalents of sulfoxide with a single equivalent of dioxygen. This net dioxygenase reactivity consumes no electrons but uses electrochemical energy to overcome kinetic barriers.
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Affiliation(s)
- Md Asmaul Hoque
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - James B Gerken
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Shannon S Stahl
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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