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Tomczyk I, Kalek M. Electrochemical Dearomatizing Methoxylation of Phenols and Naphthols: Synthetic and Computational Studies. Chemistry 2024; 30:e202303916. [PMID: 38315289 DOI: 10.1002/chem.202303916] [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: 11/24/2023] [Revised: 02/05/2024] [Accepted: 02/05/2024] [Indexed: 02/07/2024]
Abstract
The electrochemical oxidative dearomatizing methoxylation of phenols and naphthols was developed. It provides an alternative route for the preparation of methoxycyclohexadienones, important and versatile synthetic intermediates, that eliminates the need for stoichiometric high-energy chemical oxidants and generates hydrogen as a sole by-product. The reaction proceeds in a simple constant current mode, in an undivided cell, and it employs standardized instrumentation. A collection of methoxycyclohexadienones derived from various 2,4,6-tri-substituted phenols and 1-substituted-2-naphthols was obtained in moderate to excellent yields. These include a complex derivative of estrone, as well as methoxylated dearomatized 1,1'-bi-2-naphthols (BINOLs). The mechanism of the reaction was subject to profound investigations using density functional theory calculations. In particular, the reactivity of two key intermediates, phenoxyl radical and phenoxenium ion, was carefully examined. The obtained results shed light on the pathway leading to the desired product and rationalize experimentally observed selectivities regarding a side benzylic methoxylation and the preference for the functionalization at the para over the ortho position. They also uncover the structure-selectivity relationship, inversely correlating the steric bulk of the substrate with its propensity to undergo the side-reaction. Moreover, the loss of stereochemical information from enantiopure BINOL substrates during the reaction is rationalized by the computations.
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Affiliation(s)
- Ireneusz Tomczyk
- Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097, Warsaw, Poland
| | - Marcin Kalek
- Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097, Warsaw, Poland
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2
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Stünkel T, Siebold K, Okumatsu D, Murata K, Ruyet L, Daniliuc CG, Gilmour R. para-Selective dearomatization of phenols by I(i)/I(iii) catalysis-based fluorination. Chem Sci 2023; 14:13574-13580. [PMID: 38033893 PMCID: PMC10685341 DOI: 10.1039/d3sc05952a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 11/08/2023] [Indexed: 12/02/2023] Open
Abstract
The regio- and enantio-selective dearomatization of phenols has been achieved by I(i)/I(iii) catalysis enabled fluorination. The process is highly para-selective, guiding the fluoride nucleophile to the distal C4 position of the substrate to generate fluorinated cyclohexadienones in an operationally simple manner. Extensive optimization has revealed key parameters that orchestrate enantioselectivity in this historically challenging transformation. A range of diversely substituted substrates are disclosed (20 examples, up to 92 : 8 e.r.) and the reaction displays efficiency that is competitive with the current state of the art in hydroxylation chemistry: this provides a preparative platform to enable OH to F bioisosterism to be explored. Finally, the utility of the products in accessing densely functionalized cyclic scaffolds with five contiguous stereocenters is disclosed together with crystallographic analyses to unveil fluorine-carbonyl non-covalent interactions.
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Affiliation(s)
- Timo Stünkel
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Kathrin Siebold
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Daichi Okumatsu
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Kazuki Murata
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Louise Ruyet
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Constantin G Daniliuc
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
| | - Ryan Gilmour
- Organisch-Chemisches Institut, Universität Münster Corrensstraße 36 48149 Münster Germany
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3
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Zheng H, Cai L, Pan M, Uyanik M, Ishihara K, Xue XS. Catalyst-Substrate Helical Character Matching Determines the Enantioselectivity in the Ishihara-Type Iodoarenes Catalyzed Asymmetric Kita-Dearomative Spirolactonization. J Am Chem Soc 2023; 145:7301-7312. [PMID: 36940192 DOI: 10.1021/jacs.2c13295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023]
Abstract
Catalyst design has traditionally focused on rigid structural elements to prevent conformational flexibility. Ishihara's elegant design of conformationally flexible C2-symmetric iodoarenes, a new class of privileged organocatalysts, for the catalytic asymmetric dearomatization (CADA) of naphthols is a notable exception. Despite the widespread use of the Ishihara catalysts for CADAs, the reaction mechanism remains the subject of debate, and the mode of asymmetric induction has not been well established. Here, we report an in-depth computational investigation of three possible mechanisms in the literature. Our results, however, reveal that this reaction is best rationalized by a fourth mechanism called "proton-transfer-coupled-dearomatization (PTCD)", which is predicted to be strongly favored over other competing pathways. The PTCD mechanism is consistent with a control experiment and further validated by applying it to rationalize the enantioselectivities. Oxidation of the flexible I(I) catalyst to catalytic active I(III) species induces a defined C2-symmetric helical chiral environment with a delicate balance between flexibility and rigidity. A match/mismatch effect between the active catalyst and the substrate's helical shape in the dearomatization transition states was observed. The helical shape match allows the active catalyst to adapt its conformation to maximize attractive noncovalent interactions, including I(III)···O halogen bond, N-H···O hydrogen bond, and π···π stacking, to stabilize the favored transition state. A stereochemical model capable of rationalizing the effect of catalyst structural variation on the enantioselectivities is developed. The present study enriches our understanding of how flexible catalysts achieve high stereoinduction and may serve as an inspiration for the future exploration of conformational flexibility for new catalyst designs.
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Affiliation(s)
- Hanliang Zheng
- Department of Chemistry, Zhejiang Normal University, 688 Yingbin Road, Jinhua 321004, China
| | - Liu Cai
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Ming Pan
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Muhammet Uyanik
- Graduate School of Engineering, Nagoya University Furocho, Chikusaku, Nagoya 464-8603, Japan
| | - Kazuaki Ishihara
- Graduate School of Engineering, Nagoya University Furocho, Chikusaku, Nagoya 464-8603, Japan
| | - Xiao-Song Xue
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.,School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, P. R. China
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4
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Juneau A, Lepage I, Sabbah SG, Winter AH, Frenette M. Mechanistic Insight into Phenol Dearomatization by Hypervalent Iodine: Direct Detection of a Phenoxenium Cation. J Org Chem 2022; 87:14274-14283. [PMID: 36215691 DOI: 10.1021/acs.joc.2c01765] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phenol dearomatization is one of several oxidation reactions enabled by hypervalent iodine reagents. However, the presence of a proposed free phenoxenium intermediate in phenol dearomatization is a matter of debate in the literature. Here, we report the unambiguous detection of a free phenoxenium intermediate in the reaction of an electron-rich phenol, 2,4,6-trimethoxyphenol, and (diacetoxyiodo)benzene using UV-vis and resonance Raman spectroscopies. In contrast, we predominantly detect single electron oxidation products of less electron-rich phenols or alkoxy-substituted aromatics in their reaction with (diacetoxyiodo)benzene using UV-vis and electron paramagnetic resonance (EPR) spectroscopies. We conclude that the often-postulated free phenoxenium intermediate, while possible with highly stabilizing substituents, is unlikely to be a general mechanistic pathway in the reaction of typical phenols with hypervalent iodine reagents. The polar solvent 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) or the use of more strongly oxidizing hypervalent iodine reagents, such as [bis(trifluoroacetoxy)iodo]benzene (PIFA) or [hydroxy(tosyloxy)iodo]benzene (HTIB), can help reduce the formation of radical byproducts and favors the formation of phenoxenium intermediates.
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Affiliation(s)
- Antoine Juneau
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Iannick Lepage
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Sami G Sabbah
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50010, United States
| | - Mathieu Frenette
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
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Scheiber N, Blaser G, Pferschy-Wenzig EM, Kaiser M, Mäser P, Presser A. Efficient Oxidative Dearomatisations of Substituted Phenols Using Hypervalent Iodine (III) Reagents and Antiprotozoal Evaluation of the Resulting Cyclohexadienones against T. b. rhodesiense and P. falciparum Strain NF54. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27196559. [PMID: 36235096 PMCID: PMC9573667 DOI: 10.3390/molecules27196559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/21/2022] [Accepted: 09/29/2022] [Indexed: 11/07/2022]
Abstract
Quinones and quinols are secondary metabolites of higher plants that are associated with many biological activities. The oxidative dearomatization of phenols induced by hypervalent iodine(III) reagents has proven to be a very useful synthetic approach for the preparation of these compounds, which are also widely used in organic synthesis and medicinal chemistry. Starting from several substituted phenols and naphthols, a series of cyclohexadienone and naphthoquinone derivatives were synthesized using different hypervalent iodine(III) reagents and evaluated for their in vitro antiprotozoal activity. Antiprotozoal activity was assessed against Plasmodium falciparum NF54 and Trypanosoma brucei rhodesiense STIB900. Cytotoxicity of all compounds towards L6 cells was evaluated and the respective selectivity indices (SI) were calculated. We found that benzyl naphthoquinone 5c was the most active and selective molecule against T. brucei rhodesiense (IC50 = 0.08 μM, SI = 275). Furthermore, the antiprotozoal assays revealed no specific effects. In addition, some key physicochemical parameters of the synthesised compounds were calculated.
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Affiliation(s)
- Nina Scheiber
- Institute of Pharmaceutical Sciences, Pharmaceutical Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
| | - Gregor Blaser
- Institute of Pharmaceutical Sciences, Pharmaceutical Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
| | - Eva-Maria Pferschy-Wenzig
- Institute of Pharmaceutical Sciences, Pharmacognosy, University of Graz, Beethovenstrasse 8, 8010 Graz, Austria
| | - Marcel Kaiser
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland
- Swiss Tropical and Public Health Institute, University of Basel, Petersplatz 1, 4001 Basel, Switzerland
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland
- Swiss Tropical and Public Health Institute, University of Basel, Petersplatz 1, 4001 Basel, Switzerland
| | - Armin Presser
- Institute of Pharmaceutical Sciences, Pharmaceutical Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
- Correspondence: ; Tel.: +43-316-380-5369
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Yadav G, Kumar S, Kumar D, Kataria R, Laroche C, Kerwin SM. Phenyliodine(III) diacetate-mediated dearomatization of 2-(2-hydroxyaryl)benzoxazoles and 2-(2-hydroxyaryl)benzothiazoles: Regio- and stereoselective synthesis of tetramethoxycyclohexenones and bicyclo[2.2.2]octenones. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.133520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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7
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Kraszewski K, Tomczyk I, Kalek M. Intermolecular enantioselective dearomatizing para-methoxylation of phenols using 2-iodoresorcinol/lactamide catalysts. Tetrahedron Lett 2022. [DOI: 10.1016/j.tetlet.2022.154127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Golub TP, Abazid AH, Nachtsheim BJ, Merten C. Structure Elucidation of
In Situ
Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD). Angew Chem Int Ed Engl 2022; 61:e202204624. [PMID: 35570718 PMCID: PMC10084129 DOI: 10.1002/anie.202204624] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Indexed: 12/23/2022]
Abstract
The structure of in situ generated chiral aryl-λ3 -iodanes obtained under oxidative reaction conditions was not yet observable with experimental techniques and their proposed structures are purely based on DFT calculations. Herein, we establish vibrational circular dichroism (VCD) spectroscopy as an experimental technique to verify DFT-calculated chiral iodane structures. Based on a chiral triazole-substituted iodoarene catalyst, we were able to elucidate a yet undescribed cationic chiral iodane as the most populated intermediate under oxidative conditions with a significant intramolecular N-I-interaction and no significant interactions with tosylate or m-chlorobenzoic acid as potential anionic ligands. Instead, aggregation of these substrates was found, which resulted in the formation of a non-coordinating anionic hydrogen bonded complex. The importance of VCD as a crucial experimental observable is further highlighted by the fact that our initial structural proposal, that was purely based on DFT calculations, could be falsified.
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Affiliation(s)
- Tino P. Golub
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Germany
| | - Ayham H. Abazid
- Universität Bremen Fachbereich 2—Biologie und Chemie, Institut für Organische und Analytische Chemie Germany
| | - Boris J. Nachtsheim
- Universität Bremen Fachbereich 2—Biologie und Chemie, Institut für Organische und Analytische Chemie Germany
| | - Christian Merten
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Germany
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Golub TP, Abazid AH, Nachtsheim BJ, Merten C. Strukturaufklärung eines chiralen
in situ
erzeugten hypervalentem Iod‐Komplex mittels VCD‐Spektroskopie. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Tino P. Golub
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Deutschland
| | - Ayham H. Abazid
- Universität Bremen Fachbereich 2 – Biologie und Chemie, Institut für Organische und Analytische Chemie (Deutschland)
| | - Boris J. Nachtsheim
- Universität Bremen Fachbereich 2 – Biologie und Chemie, Institut für Organische und Analytische Chemie (Deutschland)
| | - Christian Merten
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Deutschland
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10
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Tra BBJ, Abollé A, Coeffard V, Felpin FX. Flow Conditions‐Controlled Divergent Oxidative Cyclization of Reticuline‐type Alkaloids to Aporphine and Morphinandienone Natural Products. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | | | | | - Francois-Xavier Felpin
- Nantes University: Universite de Nantes UFR Sciences et Techniques, UMR CNRS 6230, CEISAM 2 Rue de la Houssiniere 44322 Nantes FRANCE
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11
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Aziz MN, Singh RP, Gout D, Lovely CJ. Dearomatizing spirocyclization of thioureas, ureas and guanidines. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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12
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Sarkar S, Ghosh MK, Kalek M. Synthesis of Pummerer’s ketone and its analogs by iodosobenzene-promoted oxidative phenolic coupling. Tetrahedron Lett 2020. [DOI: 10.1016/j.tetlet.2020.152459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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