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Choi H, Ham WS, van Bonn P, Zhang J, Kim D, Chang S. Mechanistic Approach Toward the C4-Selective Amination of Pyridines via Nucleophilic Substitution of Hydrogen. Angew Chem Int Ed Engl 2024; 63:e202401388. [PMID: 38589725 DOI: 10.1002/anie.202401388] [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: 01/19/2024] [Revised: 03/25/2024] [Accepted: 04/08/2024] [Indexed: 04/10/2024]
Abstract
The development of site-selective functionalization of N-heteroarenes is highly desirable in streamlined synthesis. In this context, direct amination of pyridines stands as an important synthetic methodology, with particular emphasis on accessing 4-aminopyridines, a versatile pharmacophore in medicinal chemistry. Herein, we report a reaction manifold for the C4-selective amination of pyridines by employing nucleophilic substitution of hydrogen (SNH). Through 4-pyridyl pyridinium salt intermediates, 4-aminopyridine products are obtained in reaction with aqueous ammonia without intermediate isolation. The notable regioselectivity was achieved by the electronic tuning of the external pyridine reagents along with the maximization of polarizability in the proton elimination stage. Further mechanistic investigations provided a guiding principle for the selective C-H pyridination of additional N-heteroarenes, presenting a strategic avenue for installation of diverse functional groups.
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Affiliation(s)
- Hoonchul Choi
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, South Korea
| | - Won Seok Ham
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, South Korea
| | - Pit van Bonn
- Institute of Organic Chemistry, RWTH Aachen University, Aachen, 52074, Germany
| | - Jianbo Zhang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, South Korea
| | - Dongwook Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, South Korea
| | - Sukbok Chang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, South Korea
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Corbin DA, Cremer C, Newell BS, Patureau FW, Miyake G, Puffer KO. Effects of the Chalcogenide Identity in N‐Aryl Phenochalcogenazine Photoredox Catalysts. ChemCatChem 2022; 14:e202200485. [PMID: 36245968 PMCID: PMC9541587 DOI: 10.1002/cctc.202200485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/06/2022] [Indexed: 11/06/2022]
Abstract
Phenochalcogenazines such as phenoxazines and phenothiazines have been widely employed as photoredox catalysts (PCs) in small molecule and polymer synthesis. However, the effect of the chalcogenide in these catalysts has not been fully investigated. In this work, a series of four phenochalcogenazines is synthesized to understand how the chalcogenide impacts catalyst properties and performance. Increasing the size of the chalcogenide is found to distort the PC structure, ultimately impacting the properties of each PC. For example, larger chalcogenides destabilize the PC radical cation, possibly resulting in catalyst degradation. In addition, PCs with larger chalcogenides experience increased reorganization during electron transfer, leading to slower electron transfer. Ultimately, catalyst performance is evaluated in organocatalyzed atom transfer radical polymerization and a photooxidation reaction for C(sp2)−N coupling. Results from these experiments highlight that a balance of PC properties is most beneficial for catalysis, including a long‐lived excited state, a stable radical cation, and a low reorganization energy.
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Affiliation(s)
| | - Christopher Cremer
- RWTH Aachen University: Rheinisch-Westfalische Technische Hochschule Aachen Institute of Organic Chemistry GERMANY
| | - Brian S. Newell
- Colorado State University Analytical Resources Core UNITED STATES
| | - Frederic W. Patureau
- RWTH Aachen University: Rheinisch-Westfalische Technische Hochschule Aachen Instit GERMANY
| | - Garret Miyake
- Colorado State University Chemistry and Biochemistry 301 W. Pitkin Street215 UCB80523United States 80523 Fort Collins UNITED STATES
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Purtsas A, Rosenkranz M, Dmitrieva E, Kataeva O, Knölker HJ. Iron-Catalyzed Oxidative C-O and C-N Coupling Reactions Using Air as Sole Oxidant. Chemistry 2022; 28:e202104292. [PMID: 35179270 PMCID: PMC9314016 DOI: 10.1002/chem.202104292] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Indexed: 01/31/2023]
Abstract
We describe the oxygenation of tertiary arylamines, and the amination of tertiary arylamines and phenols. The key step of these coupling reactions is an iron‐catalyzed oxidative C−O or C−N bond formation which generally provides the corresponding products in high yields and with excellent regioselectivity. The transformations are accomplished using hexadecafluorophthalocyanine−iron(II) (FePcF16) as catalyst in the presence of an acid or a base additive and require only ambient air as sole oxidant.
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Affiliation(s)
- Alexander Purtsas
- Fakultät Chemie, Technische Universität Dresden, Bergstraße 66, 01069, Dresden, Germany
| | - Marco Rosenkranz
- Center of Spectroelectrochemistry, Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Helmholtzstraße 20, 01069, Dresden, Germany
| | - Evgenia Dmitrieva
- Center of Spectroelectrochemistry, Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Helmholtzstraße 20, 01069, Dresden, Germany
| | - Olga Kataeva
- A. E. Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov Str. 8, Kazan, 420088, Russia
| | - Hans-Joachim Knölker
- Fakultät Chemie, Technische Universität Dresden, Bergstraße 66, 01069, Dresden, Germany
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