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Shaashua O, Pollok D, Dyadyuk A, Shames AI, Waldvogel SR, Pappo D. Dynamic Thermodynamic Resolution of Racemic 1,1'-Binaphthyl-2,2'-diol (BINOL). Org Lett 2024; 26:2129-2134. [PMID: 38446080 DOI: 10.1021/acs.orglett.4c00520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
A dynamic thermodynamic resolution method for converting (R/S)-BINOL (1,1'-binaphthyl-2,2'-diol) into (R)-BINOL in 100% theoretical yield is reported. This technique involves mixing (R/S)-BINOL with N-benzyl cinchonidinium bromide (1 equiv) and a [Cu2(tmeda)2(μ-OH)2]Br2 (2.5 mol %) redox catalyst in acetonitrile. In the background of this process is the observation that the energy for atropoisomerization decreases significantly when an electron is removed from BINOL. Therefore, it is possible to convert both enantiomers into the thermodynamically favorable [N-benzyl cinchonidinium bromide·(R)-BINOL] adduct.
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Affiliation(s)
- Omer Shaashua
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Dennis Pollok
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Alina Dyadyuk
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Alexander I Shames
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Siegfried R Waldvogel
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Doron Pappo
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
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Pollok D, Großmann LM, Behrendt T, Opatz T, Waldvogel SR. A General Electro‐Synthesis Approach to Amaryllidaceae Alkaloids. Chemistry 2022; 28:e202201523. [PMID: 35662286 PMCID: PMC9543536 DOI: 10.1002/chem.202201523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Indexed: 11/28/2022]
Abstract
Amaryllidaceae alkaloids appeal to organic chemists with their attractive structures and their impressive antitumor and acetylcholinesterase inhibitory properties. We demonstrate a highly versatile access to this family of natural products. A general protocol with high yields in a sustainable electro‐organic key transformation on a metal‐free anode to spirodienones facilitates functionalization to the alkaloids. The biomimetic syntheses start with the readily available, inexpensive biogenic starting materials methyl gallate, O‐methyl tyramine, and vanillin derivatives. Through known dynamic resolutions, this technology provides access to both enantiomeric series of (epi‐)martidine, (epi‐)crinine, siculine, and galantamine, clinically prescribed for the treatment of Alzheimer's disease.
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Affiliation(s)
- Dennis Pollok
- Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
| | - Luca M. Großmann
- Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
| | - Torsten Behrendt
- Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
| | - Till Opatz
- Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
| | - Siegfried R. Waldvogel
- Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
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Häring AP, Pollok D, Strücker BR, Kilian V, Schneider J, Waldvogel SR. Beyond Kolbe and Hofer-Moest: Electrochemical Synthesis of Carboxylic Anhydrides from Carboxylic Acids. Chemistry 2022; 11:e202200059. [PMID: 35561027 PMCID: PMC9100815 DOI: 10.1002/open.202200059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 04/17/2022] [Indexed: 01/04/2023]
Abstract
Herein we report a conceptually new non-decarboxylative electrolysis of carboxylic acids to obtain their corresponding anhydrides as highly valuable reagents in organic synthesis. All carbon atoms of the starting material are preserved in the product in an overall redox-neutral reaction. In a broad substrate scope of carboxylic acids the anhydrides are generated with high selectivity, which demonstrates the versatility of the developed method. Beneficially, no dehydrating reagents are required in comparison to conventional methods and the synthesis is based on uncritical starting materials using graphite and stainless steel as very inexpensive and eco-friendly electrode materials.
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Affiliation(s)
- Andreas P Häring
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Dennis Pollok
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Benjamin R Strücker
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Vincent Kilian
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Johannes Schneider
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Siegfried R Waldvogel
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
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Abstract
The naturally occurring colchicine and allocolchicines in the meadow saffron are potentially active ingredients for cancer therapy. A concise protocol for the sustainable synthesis of allocolchicines using up to two electro-organic key transformations is demonstrated. This straightforward synthesis of N-acetylcolchinol methyl ether in a five-step protocol was adopted using protecting groups to enable access to N-acetylcolchinol and the phosphate derivative ZD6126.
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Affiliation(s)
- Dennis Pollok
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Florian U Rausch
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Sebastian B Beil
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Peter Franzmann
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Siegfried R Waldvogel
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
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Abstract
The use of electric current as a traceless activator and reagent is experiencing a renaissance. This sustainable synthetic method is evolving into a hot topic in contemporary organic chemistry. Since researchers with various scientific backgrounds are entering this interdisciplinary field, different parameters and methods are reported to describe the experiments. The variation in the reported parameters can lead to problems with the reproducibility of the reported electroorganic syntheses. As an example, parameters such as current density or electrode distance are in some cases more significant than often anticipated. This Minireview provides guidelines on reporting electrosynthetic data and dispels myths about this technique, thereby streamlining the experimental parameters to facilitate reproducibility.
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Affiliation(s)
- Sebastian B. Beil
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Dennis Pollok
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Siegfried R. Waldvogel
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
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Affiliation(s)
- Sebastian B. Beil
- Department Chemie Johannes Gutenberg-Universität Mainz Duesbergweg 10–14 55128 Mainz Deutschland
| | - Dennis Pollok
- Department Chemie Johannes Gutenberg-Universität Mainz Duesbergweg 10–14 55128 Mainz Deutschland
| | - Siegfried R. Waldvogel
- Department Chemie Johannes Gutenberg-Universität Mainz Duesbergweg 10–14 55128 Mainz Deutschland
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Abstract
The severe limitations of fossil fuels and finite resources influence the scientific community to reconsider chemical synthesis and establish sustainable techniques. Several promising methods have emerged, and electro-organic conversion has attracted particular attention from international academia and industry as an environmentally benign and cost-effective technique. The easy application, precise control, and safe conversion of substrates with intermediates only accessible by this method reveal novel pathways in synthetic organic chemistry. The popularity of electricity as a reagent is accompanied by the feasible conversion of bio-based feedstocks to limit the carbon footprint. Several milestones have been achieved in electro-organic conversion at rapid frequency, which have opened up various perspectives for forthcoming processes.
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Affiliation(s)
- Dennis Pollok
- Department of Chemistry, Johannes Gutenberg University Mainz Duesbergweg 10-14 55128 Mainz Germany www.aksw.uni-mainz.de
| | - Siegfried R Waldvogel
- Department of Chemistry, Johannes Gutenberg University Mainz Duesbergweg 10-14 55128 Mainz Germany www.aksw.uni-mainz.de
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Abstract
The importance of sustainable and green synthetic protocols for the synthesis of fine chemicals has rapidly increased during the last decades in an effort to reduce the use of fossil fuels and other finite resources. The replacement of common reagents by electricity provides a cost- and atom-efficient, environmentally friendly, and inherently safe access to novel synthetic routes. The selective formation of carbon-carbon bonds between two distinct substrates is a crucial tool in organic chemistry. This fundamental transformation enables access to a broad variety of complex molecular architectures. In particular, the aryl-aryl bond formation has high significance for the preparation of organic materials, drugs, and natural products. Besides well-known and well-established reductive- and oxidative-reagent-mediated or transition-metal-catalyzed coupling reactions, novel synthetic protocols have arisen, which require fewer steps than conventional synthetic approaches. Electroorganic conversions can be categorized according to the nature of the electron transfer processes occurring. Direct transformations at inert electrode materials are environmentally benign and cost-effective, whereas catalytic processes at active electrodes and mediated electrosynthesis using an additional soluble reagent can have beneficial properties in terms of selectivity and reactivity. In general, these conversions require challenging optimization of the reaction parameters and the appropriate cell design. Galvanostatic reactions enable fast conversions with a rather simple setup, whereas potentiostatic electrolysis may enhance selectivity. This Account discusses the development of seminal carbon-carbon bond formations over the past two decades, focusing on phenols leading to precursors for ligands in, e.g., hydroformylation reaction. A key element in the success of these electrochemical transformations is the application of electrochemically inert, non-nucleophilic, highly fluorinated alcohols such as 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), which exhibit a large potential window for transformations and enable selective cross-coupling reactions. This selectivity is based on the capability of HFIP to stabilize organic radicals. Inert, carbon-based and metal-free electrode materials like graphite or boron-doped diamond (BDD) open up novel electroorganic pathways. Furthermore, novel active electrode materials have been developed to enable intra- and intermolecular dehydrogenative coupling reactions of electron-rich aryls. The application of 2,2'-biphenol derivatives as ligand components for catalysts requires reactions to be carried out on larger scale. In order to achieve this, continuous flow transformations have been established to overcome the drawbacks of heat transfer, overconversion, and conductivity. Modular cell designs enable the transfer of a broad variety of electroorganic conversions into continuous processes. Recent results demonstrate the application of organic electrochemistry to natural product synthesis of the pharmaceutically relevant opiate alkaloids (-)-thebaine or (-)-oxycodone.
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Affiliation(s)
- Johannes L. Röckl
- Graduate School Materials Science in Mainz, Staudingerweg 9, 55128 Mainz, Germany
| | - Dennis Pollok
- Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Robert Franke
- Evonik Performance Materials GmbH, Paul-Baumann-Str. 1, 45772 Marl, Germany
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Universitätstraße 150, 44801 Bochum, Germany
| | - Siegfried R. Waldvogel
- Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
- Graduate School Materials Science in Mainz, Staudingerweg 9, 55128 Mainz, Germany
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Beil SB, Franzmann P, Müller T, Hielscher MM, Prenzel T, Pollok D, Beiser N, Schollmeyer D, Waldvogel SR. Investigations on isomerization and rearrangement of polycyclic arenes under oxidative conditions – Anodic versus reagent-mediated reactions. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.02.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Melchert HU, Pollok D, Pabel E, Rubach K, Stan HJ. Determination of tocopherols, tocopherolquinones and tocopherolhydroquinones by gas chromatography-mass spectrometry and preseparation with lipophilic gel chromatography. J Chromatogr A 2002; 976:215-20. [PMID: 12462612 DOI: 10.1016/s0021-9673(02)00941-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Lipophilic gel chromatography using Sephadex LH-20 helps in separating alpha-, beta- + -gamma, and delta-tocopherol and also in separation of their oxidation products e.g. the tocopherolquinones or other oxidation products. This preseparation can help to overcome analytical problems due to the complexity of synthesis mixtures of tocopherol oxidation procedures as well as in separation of complex physiological matrices. Determination of the preseparated tocopherols, tocopherolquinonesand tocopherolhydroquinones can then be achieved by means of GC-MS measurement of the free substances or their trimethylsilyl derivatives.
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Affiliation(s)
- H U Melchert
- Robert Koch-Institute, Bereich Tempelhof, General-Pape-Straase 62-66, D-12101 Berlin, Germany.
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