1
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Festa AA, Storozhenko OA, Voskressensky LG, Van der Eycken EV. Visible light-mediated halogenation of organic compounds. Chem Soc Rev 2023. [PMID: 37975853 DOI: 10.1039/d3cs00366c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
The use of visible light and photoredox catalysis emerged as a powerful and sustainable tool for organic synthesis, showing high value for distinctly different ways of bond creation. Halogenated compounds are the cornerstone of contemporary organic synthesis: it is almost impossible to develop a route towards a pharmaceutical reagent, agrochemical, natural product, etc. without the involvement of halogen-containing intermediates. Moreover, the halogenated derivatives as final products became indispensable for drug discovery and materials science. The idea of this review is to understand and summarise the impact of visible light-promoted chemistry on halogenation and halofunctionalisation reactions.
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Affiliation(s)
- Alexey A Festa
- Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya st. 6, Moscow, 117198, Russian Federation.
| | - Olga A Storozhenko
- Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya st. 6, Moscow, 117198, Russian Federation.
| | - Leonid G Voskressensky
- Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya st. 6, Moscow, 117198, Russian Federation.
| | - Erik V Van der Eycken
- Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya st. 6, Moscow, 117198, Russian Federation.
- Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, University of Leuven (KU Leuven), Celestijnenlaan 200F, B-3001, Leuven, Belgium
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2
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Lee TC, Tong Y, Fu WC. Advances in Continuous Flow Fluorination Reactions. Chem Asian J 2023; 18:e202300723. [PMID: 37707985 DOI: 10.1002/asia.202300723] [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: 08/17/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/16/2023]
Abstract
Fluorination reactions are important in constructing organofluorine motifs, which contribute to favorable biological properties in pharmaceuticals and agrochemicals. However, fluorination reagents and reactions are associated with various problems, such as their hazardous nature, high exothermicity, and poor selectivity and scalability. Continuous flow has emerged as a transformative technology to provide many advantages relative to batch syntheses. This review article summarizes recent continuous flow techniques that address the limitations and challenges of fluorination reactions. Approaches based on different flow techniques are discussed, including gas-liquid reactions, packed-bed reactors, in-line purifications, streamlined multistep synthesis, large-scale reactions well as flow photoredox- and electrocatalysis.
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Affiliation(s)
- Tsz Chun Lee
- Department of Chemistry, City University of Hong Kong, Tat Chee Ave, Kowloon, Hong Kong SAR, China
| | - Yi Tong
- Department of Chemistry, City University of Hong Kong, Tat Chee Ave, Kowloon, Hong Kong SAR, China
| | - Wai Chung Fu
- Department of Chemistry, City University of Hong Kong, Tat Chee Ave, Kowloon, Hong Kong SAR, China
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3
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Abstract
The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C-H functionalization approaches that make use of low energy photons as a controllable energy source. Compared to traditional late-stage functionalization strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- and chemoselectivities. Merging the compelling benefits of photocatalysis with the late-stage functionalization workflow offers a potentially unmatched arsenal to tackle drug development campaigns and beyond. This Review highlights the photocatalytic late-stage C-H functionalization strategies of small-molecule drugs, agrochemicals, and natural products, classified according to the targeted C-H bond and the newly formed one. Emphasis is devoted to identifying, describing, and comparing the main mechanistic scenarios. The Review draws a critical comparison between established ionic chemistry and photocatalyzed radical-based manifolds. The Review aims to establish the current state-of-the-art and illustrate the key unsolved challenges to be addressed in the future. The authors aim to introduce the general readership to the main approaches toward photocatalytic late-stage C-H functionalization, and specialist practitioners to the critical evaluation of the current methodologies, potential for improvement, and future uncharted directions.
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Affiliation(s)
- Peter Bellotti
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 36, 48149Münster, Germany
| | - Huan-Ming Huang
- School of Physical Science and Technology, ShanghaiTech University, 201210Shanghai, China
| | - Teresa Faber
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 36, 48149Münster, Germany
| | - Frank Glorius
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 36, 48149Münster, Germany
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4
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Yakubov S, Stockerl WJ, Tian X, Shahin A, Mandigma MJP, Gschwind RM, Barham JP. Benzoates as photosensitization catalysts and auxiliaries in efficient, practical, light-powered direct C(sp 3)-H fluorinations. Chem Sci 2022; 13:14041-14051. [PMID: 36540818 PMCID: PMC9728569 DOI: 10.1039/d2sc05735b] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 10/28/2022] [Indexed: 12/14/2023] Open
Abstract
Of the methods for direct fluorination of unactivated C(sp3)-H bonds, photosensitization of SelectFluor is a promising approach. Although many substrates can be activated with photosensitizing catalysts, issues remain that hamper fluorination of complex molecules. Alcohol- or amine-containing functional groups are not tolerated, fluorination regioselectivity follows factors endogenous to the substrate and cannot be influenced by the catalyst, and reactions are highly air-sensitive. We report that benzoyl groups serve as highly efficient photosensitizers which, in combination with SelectFluor, enable visible light-powered direct fluorination of unactivated C(sp3)-H bonds. Compared to previous photosensitizer architectures, the benzoyls have versatility to function both (i) as a photosensitizing catalyst for simple substrate fluorinations and (ii) as photosensitizing auxiliaries for complex molecule fluorinations that are easily installed and removed without compromising yield. Our auxiliary approach (i) substantially decreases the reaction's induction period, (ii) enables C(sp3)-H fluorination of many substrates that fail under catalytic conditions, (iii) increases kinetic reproducibility, and (iv) promotes reactions to higher yields, in shorter times, on multigram scales, and even under air. Observations and mechanistic studies suggest an intimate 'assembly' of auxiliary and SelectFluor prior/after photoexcitation. The auxiliary allows other EnT photochemistry under air. Examples show how auxiliary placement proximally directs regioselectivity, where previous methods are substrate-directed.
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Affiliation(s)
- Shahboz Yakubov
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
| | - Willibald J Stockerl
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
| | - Xianhai Tian
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
| | - Ahmed Shahin
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
- Chemistry Department, Faculty of Science, Benha University 13518 Benha Egypt
| | - Mark John P Mandigma
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
| | - Ruth M Gschwind
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
| | - Joshua P Barham
- Fakultät für Chemie und Pharmazie, Universität Regensburg 93040 Regensburg Germany
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5
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Harry SA, Xiang MR, Holt E, Zhu A, Ghorbani F, Patel D, Lectka T. Hydroxy-directed fluorination of remote unactivated C(sp 3)-H bonds: a new age of diastereoselective radical fluorination. Chem Sci 2022; 13:7007-7013. [PMID: 35774162 PMCID: PMC9200124 DOI: 10.1039/d2sc01907h] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 05/02/2022] [Indexed: 11/23/2022] Open
Abstract
We report a photochemically induced, hydroxy-directed fluorination that addresses the prevailing challenge of high diastereoselectivity in this burgeoning field. Numerous simple and complex motifs showcase a spectrum of regio- and stereochemical outcomes based on the configuration of the hydroxy group. Notable examples include a long-sought switch in the selectivity of the refractory sclareolide core, an override of benzylic fluorination, and a rare case of 3,3'-difluorination. Furthermore, calculations illuminate a low barrier transition state for fluorination, supporting our notion that alcohols are engaged in coordinated reagent direction. A hydrogen bonding interaction between the innate hydroxy directing group and fluorine is also highlighted for several substrates with 19F-1H HOESY experiments, calculations, and more.
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Affiliation(s)
- Stefan Andrew Harry
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Michael Richard Xiang
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Eric Holt
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Andrea Zhu
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Fereshte Ghorbani
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Dhaval Patel
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Baltimore MD 21218 USA
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6
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Capilato JN, Harry SA, Siegler MA, Lectka T. Spectroscopic and Crystallographic Characterization of the R 3 N + -C-H⋅⋅⋅X Interaction. Chemistry 2022; 28:e202103922. [PMID: 35133051 DOI: 10.1002/chem.202103922] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Indexed: 01/11/2023]
Abstract
As appreciation for nonclassical hydrogen bonds has progressively increased, so have efforts to characterize these interesting interactions. Whereas several kinds of C-H hydrogen bonds have been well-studied, much less is known about the R3 N+ -C-H⋅⋅⋅X variety. Herein, we present crystallographic and spectroscopic evidence for the existence of these interactions, with special relevance to Selectfluor chemistry. Of particular note is the propensity for Lewis bases to engage in nonclassical hydrogen bonding over halogen bonding with the electrophilic F atom of Selectfluor. Further, the first examples of 1 H NMR experiments detailing R3 N+ -C-H⋅⋅⋅X (X=O, N) hydrogen bonds are described.
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Affiliation(s)
- Joseph N Capilato
- Department of Chemistry, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Stefan A Harry
- Department of Chemistry, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
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7
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Buglioni L, Raymenants F, Slattery A, Zondag SDA, Noël T. Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry. Chem Rev 2022; 122:2752-2906. [PMID: 34375082 PMCID: PMC8796205 DOI: 10.1021/acs.chemrev.1c00332] [Citation(s) in RCA: 228] [Impact Index Per Article: 114.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Indexed: 02/08/2023]
Abstract
Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing a plethora of opportunities to synthetic organic chemists. However, performing a photochemical transformation can be quite a challenge because of various issues related to the delivery of photons. These challenges have barred the widespread adoption of photochemical steps in the chemical industry. However, in the past decade, several technological innovations have led to more reproducible, selective, and scalable photoinduced reactions. Herein, we provide a comprehensive overview of these exciting technological advances, including flow chemistry, high-throughput experimentation, reactor design and scale-up, and the combination of photo- and electro-chemistry.
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Affiliation(s)
- Laura Buglioni
- Micro
Flow Chemistry and Synthetic Methodology, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, Het Kranenveld, Bldg 14—Helix, 5600 MB, Eindhoven, The Netherlands
- Flow
Chemistry Group, van ’t Hoff Institute for Molecular Sciences
(HIMS), Universiteit van Amsterdam (UvA), Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Fabian Raymenants
- Flow
Chemistry Group, van ’t Hoff Institute for Molecular Sciences
(HIMS), Universiteit van Amsterdam (UvA), Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Aidan Slattery
- Flow
Chemistry Group, van ’t Hoff Institute for Molecular Sciences
(HIMS), Universiteit van Amsterdam (UvA), Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Stefan D. A. Zondag
- Flow
Chemistry Group, van ’t Hoff Institute for Molecular Sciences
(HIMS), Universiteit van Amsterdam (UvA), Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Timothy Noël
- Flow
Chemistry Group, van ’t Hoff Institute for Molecular Sciences
(HIMS), Universiteit van Amsterdam (UvA), Science Park 904, 1098 XH, Amsterdam, The Netherlands
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8
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Affiliation(s)
- Yen-Chu Lu
- Department of Chemistry, Rice University, 6500 Main St., Houston, Texas 77005, United States
| | - Julian G. West
- Department of Chemistry, Rice University, 6500 Main St., Houston, Texas 77005, United States
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9
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10
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Nobile E, Castanheiro T, Besset T. Radical-Promoted Distal C-H Functionalization of C(sp 3 ) Centers with Fluorinated Moieties. Angew Chem Int Ed Engl 2021; 60:12170-12191. [PMID: 32897632 DOI: 10.1002/anie.202009995] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/28/2020] [Indexed: 12/12/2022]
Abstract
Due to their unique properties, fluorinated scaffolds are pivotal compounds in pharmaceuticals, agrochemicals, and materials science. Over the last years, the development of versatile strategies for the selective synthesis of fluorinated molecules by direct C-H bond functionalization has attracted a lot of attention. In particular, the design of novel transformations based on a radical process was a bottleneck for distal C-H functionalization reactions, offering synthetic solutions for the selective introduction of fluorinated groups. This Minireview highlights the major contributions in this blossoming field. The development of new methodologies for the remote functionalization of aliphatic derivatives with various fluorinated groups based on a 1,5-hydrogen atom transfer process and a β-fragmentation reaction will be showcased and discussed.
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Affiliation(s)
- Enzo Nobile
- Normandie Univ, INSA Rouen, UNIROUEN, CNRS, COBRA (UMR 6014), 76000, Rouen, France
| | - Thomas Castanheiro
- Normandie Univ, INSA Rouen, UNIROUEN, CNRS, COBRA (UMR 6014), 76000, Rouen, France
| | - Tatiana Besset
- Normandie Univ, INSA Rouen, UNIROUEN, CNRS, COBRA (UMR 6014), 76000, Rouen, France
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11
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Nobile E, Castanheiro T, Besset T. Radical‐Promoted Distal C−H Functionalization of C(sp
3
) Centers with Fluorinated Moieties. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202009995] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Enzo Nobile
- Normandie Univ INSA Rouen UNIROUEN CNRS COBRA (UMR 6014) 76000 Rouen France
| | - Thomas Castanheiro
- Normandie Univ INSA Rouen UNIROUEN CNRS COBRA (UMR 6014) 76000 Rouen France
| | - Tatiana Besset
- Normandie Univ INSA Rouen UNIROUEN CNRS COBRA (UMR 6014) 76000 Rouen France
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12
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Capilato JN, Siegler MA, Rowshanpour R, Dudding T, Lectka T. Cooperative Noncovalent Interactions Lead to a Highly Diastereoselective Sulfonyl-Directed Fluorination of Steroidal α,β-Unsaturated Hydrazones. J Org Chem 2021; 86:1300-1307. [PMID: 33300794 DOI: 10.1021/acs.joc.0c02716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of steroidal α,β-unsaturated hydrazones is presented whose behavior and reactivity are governed by various types of weak C-H hydrogen bonds. Several interesting features in a representative X-ray crystal structure and 1H NMR spectrum are examined that provide evidence for a unique bifurcated intramolecular C-H interaction. Moreover, these steroid derivatives undergo functionalization in the form of a highly regio- and stereoselective fluorination; the sulfonyl oxygen atoms are proposed to direct the fluorinating reagent through C-H hydrogen bonds.
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Affiliation(s)
- Joseph N Capilato
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Rozhin Rowshanpour
- Department of Chemistry, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Travis Dudding
- Department of Chemistry, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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13
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Zhang F, Wang X, Zhou Y, Shi H, Feng Z, Ma J, Marek I. Remote Fluorination and Fluoroalkyl(thiol)ation Reactions. Chemistry 2020; 26:15378-15396. [DOI: 10.1002/chem.202003416] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Indexed: 12/22/2022]
Affiliation(s)
- Fa‐Guang Zhang
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Xue‐Qi Wang
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Yin Zhou
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Hong‐Song Shi
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Zhe Feng
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Jun‐An Ma
- Department of Chemistry Tianjin Key Laboratory of Molecular Optoelectronic Sciences Frontiers Science Center for Synthetic Biology (Ministry of Education), and Tianjin Collaborative Innovation Center of Chemical Science & Engineering Tianjin University Tianjin 300072 China
| | - Ilan Marek
- Schulich Faculty of Chemistry Technion-Israel Institute of Technology Haifa 3200009 Israel
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14
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Ghorbani F, Harry SA, Capilato JN, Pitts CR, Joram J, Peters GN, Tovar JD, Smajlagic I, Siegler MA, Dudding T, Lectka T. Carbonyl-Directed Aliphatic Fluorination: A Special Type of Hydrogen Atom Transfer Beats Out Norrish II. J Am Chem Soc 2020; 142:14710-14724. [PMID: 32786786 DOI: 10.1021/jacs.0c07004] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Recently, our group reported that enone and ketone functional groups, upon photoexcitation, can direct site-selective sp3 C-H fluorination in terpenoid derivatives. How this transformation actually occurred remained mysterious, as a significant number of mechanistic possibilities came to mind. Herein, we report a comprehensive study describing the reaction mechanism through kinetic studies, isotope-labeling experiments, 19F NMR, electrochemical studies, synthetic probes, and computational experiments. To our surprise, the mechanism suggests intermolecular hydrogen atom transfer (HAT) chemistry is at play, rather than classical Norrish hydrogen atom abstraction as initially conceived. What is more, we discovered a unique role for photopromoters such as benzil and related compounds that necessitates their chemical transformation through fluorination in order to be effective. Our findings provide documentation of an unusual form of directed HAT and are of crucial importance for defining the necessary parameters for the development of future methods.
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Affiliation(s)
- Fereshte Ghorbani
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Stefan Andrew Harry
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Joseph N Capilato
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Cody Ross Pitts
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Jacob Joram
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Garvin N Peters
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - John D Tovar
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Ivor Smajlagic
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Travis Dudding
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
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15
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Petzold D, Giedyk M, Chatterjee A, König B. A Retrosynthetic Approach for Photocatalysis. European J Org Chem 2020. [DOI: 10.1002/ejoc.201901421] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Daniel Petzold
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
| | - Maciej Giedyk
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01‐224 Warsaw Poland
| | - Anamitra Chatterjee
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
| | - Burkhard König
- Department of Organic Chemistry University of Regensburg Universitätsstraße 31 93053 Regensburg Germany
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16
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Capilato JN, Pitts CR, Rowshanpour R, Dudding T, Lectka T. Site-Selective Photochemical Fluorination of Ketals: Unanticipated Outcomes in Selectivity and Stability. J Org Chem 2020; 85:2855-2864. [PMID: 32031800 DOI: 10.1021/acs.joc.9b03047] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a method for the regioselective photochemical sp3 C-H fluorination of acetonide ketals that presents interesting problems in chemical reactivity. The question of why certain products of the reaction are stable while others are not is addressed, as is the question of why only select α-ethereal hydrogen atoms are targeted in the reaction. We demonstrate that the method can be employed to synthesize unprecedented fluorinated sugars and steroids, and it can also be applied toward the fluorination of carbamates. Though some substrates contain up to eight discrete α-ethereal C-H bonds, we observed site-selectivity in each case, prompting us to investigate potential transition states for the reaction. Finally, a remarkable regiochemical switch upon minor structural modification of a diketal is also analyzed.
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Affiliation(s)
- Joseph N Capilato
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Cody Ross Pitts
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Rozhin Rowshanpour
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON L2S 3A1, Canada
| | - Travis Dudding
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON L2S 3A1, Canada
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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17
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Di Filippo M, Bracken C, Baumann M. Continuous Flow Photochemistry for the Preparation of Bioactive Molecules. Molecules 2020; 25:molecules25020356. [PMID: 31952244 PMCID: PMC7024297 DOI: 10.3390/molecules25020356] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 01/09/2020] [Accepted: 01/10/2020] [Indexed: 12/21/2022] Open
Abstract
The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future.
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18
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Szpera R, Moseley DFJ, Smith LB, Sterling AJ, Gouverneur V. Fluorierung von C‐H‐Bindungen: Entwicklungen und Perspektiven. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201814457] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Robert Szpera
- Chemistry Research Laboratory Oxford University 12 Mansfield Road Oxford OX1 3TA Großbritannien
| | - Daniel F. J. Moseley
- Chemistry Research Laboratory Oxford University 12 Mansfield Road Oxford OX1 3TA Großbritannien
| | - Lewis B. Smith
- Chemistry Research Laboratory Oxford University 12 Mansfield Road Oxford OX1 3TA Großbritannien
| | - Alistair J. Sterling
- Chemistry Research Laboratory Oxford University 12 Mansfield Road Oxford OX1 3TA Großbritannien
| | - Véronique Gouverneur
- Chemistry Research Laboratory Oxford University 12 Mansfield Road Oxford OX1 3TA Großbritannien
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19
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Szpera R, Moseley DFJ, Smith LB, Sterling AJ, Gouverneur V. The Fluorination of C-H Bonds: Developments and Perspectives. Angew Chem Int Ed Engl 2019; 58:14824-14848. [PMID: 30759327 DOI: 10.1002/anie.201814457] [Citation(s) in RCA: 245] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Indexed: 12/16/2022]
Abstract
This Review summarizes advances in fluorination by C(sp2 )-H and C(sp3 )-H activation. Transition-metal-catalyzed approaches championed by palladium have allowed the installation of a fluorine substituent at C(sp2 ) and C(sp3 ) sites, exploiting the reactivity of high-oxidation-state transition-metal fluoride complexes combined with the use of directing groups (some transient) to control site and stereoselectivity. The large majority of known methods employ electrophilic fluorination reagents, but methods combining a nucleophilic fluoride source with an oxidant have appeared. External ligands have proven to be effective for C(sp3 )-H fluorination directed by weakly coordinating auxiliaries, thereby enabling control over reactivity. Methods relying on the formation of radical intermediates are complementary to transition-metal-catalyzed processes as they allow for undirected C(sp3 )-H fluorination. To date, radical C-H fluorinations mainly employ electrophilic N-F fluorination reagents but a unique MnIII -catalyzed oxidative C-H fluorination using fluoride has been developed. Overall, the field of late-stage nucleophilic C-H fluorination has progressed much more slowly, a state of play explaining why C-H 18 F-fluorination is still in its infancy.
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Affiliation(s)
- Robert Szpera
- Chemistry Research Laboratory, Oxford University, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Daniel F J Moseley
- Chemistry Research Laboratory, Oxford University, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Lewis B Smith
- Chemistry Research Laboratory, Oxford University, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Alistair J Sterling
- Chemistry Research Laboratory, Oxford University, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Véronique Gouverneur
- Chemistry Research Laboratory, Oxford University, 12 Mansfield Road, Oxford, OX1 3TA, UK
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20
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Tang L, Yang Z, Jiao J, Cui Y, Zou G, Zhou Q, Zhou Y, Rao W, Ma X. Chemoselective Mono- and Difluorination of 1,3-Dicarbonyl Compounds. J Org Chem 2019; 84:10449-10458. [PMID: 31335142 DOI: 10.1021/acs.joc.9b01808] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
By altering the amount of Selectfluor, the highly selective mono- and difluorination of 1,3-dicarbonyl compounds has been achieved, affording a variety of 2-fluoro- and 2,2-difluoro-1,3-dicarbonyl compounds in good to excellent yields. The reaction can be readily performed in aqueous media without any catalyst and base, which features practical and convenient fluorination. Importantly, a gram-scale reaction, transformation of 2-fluoro-1,3-diphenylpropane-1,3-dione to 4-fluoro-1,3,5-triphenyl-1H-pyrazole, and chlorination and bromination of 1,3-dicarbonyl compounds are realized to further exhibit its synthetic utility.
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Affiliation(s)
- Lin Tang
- Henan Key Laboratory of Utilization of Non-metallic Mineral in the Sourth of Henan , Xinyang 464000 , P. R. China
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21
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Capilato JN, Bume DD, Lee WH, Hoffenberg LES, Jokhai RT, Lectka T. Fluorofunctionalization of C═C Bonds with Selectfluor: Synthesis of β-Fluoropiperazines through a Substrate-Guided Reactivity Switch. J Org Chem 2018; 83:14234-14244. [PMID: 30418026 DOI: 10.1021/acs.joc.8b02429] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The halofunctionalization of alkene substrates remains an essential tool for synthetic chemists. Herein, we report regioselective ammoniofluorination of unactivated alkenes through photochemical means. A one-pot transformation of the ammonium fluoride products into pharmaceutically relevant β-fluoropiperazines is highlighted. Furthermore, a substrate-guided reactivity switch is observed: certain alkenes are shown to react with the same fluorinating reagent to instead give the less-substituted fluoride. We hope that the ammoniofluorination reaction will be of utility in the area of medicinal chemistry, where nitrogen and fluorine are among the most important heteroatoms.
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Affiliation(s)
- Joseph N Capilato
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Desta Doro Bume
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Wei Hao Lee
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Louis E S Hoffenberg
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Rayyan Trebonias Jokhai
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Thomas Lectka
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
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Bume DD, Harry SA, Lectka T, Pitts CR. Catalyzed and Promoted Aliphatic Fluorination. J Org Chem 2018; 83:8803-8814. [PMID: 29894188 DOI: 10.1021/acs.joc.8b00982] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the last six years, the direct functionalization of aliphatic C-H (and C-C) bonds through user-friendly, radical-based fluorination reactions has emerged as an exciting research area in fluorine chemistry. Considering the historical narratives about the challenges of developing practical radical fluorination in organic frameworks, notable advancements in controlling both reactivity and selectivity have been achieved during this time. As one of the participants in the field, herein, we a provide brief account of research efforts in our laboratory from the initial discovery of radical monofluorination on unactivated C-H bonds in 2012 to more useful strategies to install fluorine on biologically relevant molecules through directed fluorination methods. In addition, accompanying mechanistic studies that have helped guide reaction design are highlighted in context.
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Affiliation(s)
| | | | | | - Cody Ross Pitts
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir-Prelog-Weg 2 , 8093 Zürich , Switzerland
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