Super-Electron Donors:  Bis-pyridinylidene Formation by Base Treatment of Pyridinium Salts

Murphy, John A.; Garnier, Jean Marc; Park, Stuart R.; Schoenebeck, Franziska; Zhou, Sen; Turner, Angela

doi:10.1021/ol800134g

Cited by 107 publications

(113 citation statements)

References 18 publications

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“…In terms of the applications of these stronger electron donors, benzimidazole-derived 6 converts iodoarenes into aryl radicals, 15 while the stronger donors 7 and 8 reduce the same substrates to aryl anions. 12,14 Donors 7 and 8 are also able to reduce reducing power is significantly less than that of the strongest metals (e.g. the oxidation potential of Li, E 0 = 3.02 V) 20 and questions arise about whether a limit is being approached in the design of organic neutral donors.…”

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confidence: 99%

A novel neutral organic electron donor with record half-wave potential

2013

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This version is available at https://strathprints.strath.ac.uk/46029/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.Journal Name of one and two electrons respectively, also plays an important role in determining the strength of these electron donors. Table 1 compares the oxidation potentials of these compounds with the widely used sulfur-containing electron donor, tetrathiafulvalene (TTF).Among the nitrogen-containing electron-donors, TDAE (1) is the parent compound in the series and the standard by which the others can be judged. 7 Neither 1 nor its oxidized products is aromatic. Compound 2 could be considered anti-aromatic 8 if planar and so its oxidation through loss of two electrons might 30 expect to be strongly driven; however it is quite deformed from planarity and it contains two aromatic pyrrole rings -as a result it is not a strong reducing agent. Compound 3 9 is already aromatic and hence its oxidation does not benefit from aromatization as a driving force, and so it also is not a strong donor of electrons. In 35 contrast, donors 4-8 are all converted into aromatic products upon oxidation [10][11][12][13][14][15][16][17][18][19] and this adds to their strength as reducing agents. To illustrate the aromaticity that arises, the oxidation products of compound 8 are also shown in Figure 1. Loss of one electron leads to radical cation 13 featuring one pyridinium ring, 40 while loss of a second electron affords the aromatic disalt 14. In terms of the applications of these stronger electron donors, benzimidazole-derived 6 converts iodoarenes into aryl radicals, 15 while the stronger donors 7 and 8 reduce the same substrates to aryl anions.12,14 Donors 7 and 8 are also able to reduce 45 arenesulfonamides, 16 Weinreb amides 17 and acyloin derivatives. reducing power is significantly less than that of the strongest metals (e.g. the oxidation potential of Li, E 0 = 3.02 V) 20 and questions arise about whether a limit is bei...

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A novel neutral organic electron donor with record half-wave potential

2013

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“…Thed ocumented performance of OED-2 as ap owerful electron donor in organic synthesis [1,8] suggests that the initiation of the polymerization was induced by electron transfer. As previously stated, the reactivity of the monomers, which varied according to their reduction potential, and the restriction to highly polar aprotic solvents both support this hypothesis.Achange of color,a so bserved during the …”

Section: Angewandte Chemiementioning

confidence: 99%

“…In the presence of the bispyridinylidene OED-2 (10 mol %), [8] EMA was totally converted into the expected poly(ethyl methacrylate) (PEtMA) in less than 3min (Table 1, entry 5). Thew eightaverage molar mass (M w )a nd the number-average molar mass (M n )w ere 13 100 and 9900 gmol À1 ,r espectively,t hus indicating ad ispersity ()o f1 .33.…”

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Polymerization Initiated by Organic Electron Donors

et al. 2016

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Polymerization reactions with organic electron donors (OED) as initiators are presented herein. The metal-free polymerization of various activated alkene and cyclic ester monomers was performed in short reaction times, under mild conditions, with small amounts of organic reducing agents, and without the need for co-initiators or activation by photochemical, electrochemical, or other methods. Hence, OED initiators enabled the development of an efficient, rapid, room-temperature process that meets the technical standards expected for industrial processes, such as energy savings, cost-effectiveness and safety. Mechanistic investigations support an electron-transfer initiation pathway that leads to the reduction of the monomer.

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“…2 Electron donors based on alternate scaffolds, that are easier to prepare and offer similar, or even slightly increased, reducing power became available when Murphy described an elegant synthesis for amino-substituted bispyridinylidenes such as 4a (E 1/2 (DMF) = -1.24 V vs SCE). 7,11,12 Their facile preparation has led these DMAP-derived electron transfer agents to find applicability in the polymerization of various activated alkene and cyclic ester monomers, 13 as well as the ground-state or photoexcited reduction of a variety of substrates including aryl halides, 11 Weinreb amides, 14 acyloin derivatives, 15 arenesulfonamides, 11 triflates and triflamides, 16 as well as benzylic C-O, 17 C-N, 18 and C-C bonds. 19 Most commonly, these reactions involve the in situ generation of the air and moisture sensitive electron donors via the reaction of easily handled pyridinium ion precursors with a strong base.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, of the seven bis-pyridinylidene derivatives prepared by Murphy, 7 only 4a-4c have been spectroscopically characterized and only the propylene bridged derivatives 4a and 4b have been isolated (83 % and 71 % yield, respectively). 11,12 More recently, we have been able to isolate some iminophosphorano-substituted bispyridinylidenes, which are even more powerful reductants. 20,21 The availability of isolable reducing agents, free from by-products or excess base from their in situ generation, can be beneficial in increasing the utility of these reagents.…”

Section: Introductionmentioning

confidence: 99%

Facile preparation and isolation of neutral organic electron donors based on 4-dimethylaminopyridine

Martin

Dyker

2018

Can. J. Chem.

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A number of new neutral bis-2-(4-dimethylamino)pyridinylidene electron donors featuring N-akyl groups of varying lengths (propyl, butyl, hexyl, dodecyl) have been prepared from 4-dimethylaminopyridine by means of a simple two-step procedure. Each derivative could be isolated in high yield and could be stored indefinitely under inert atmosphere. The electron donors were chemically oxidized to the corresponding bipyridinium ions, and all compounds were characterized by NMR spectroscopy and cyclic voltammetry. As an emerging class of electron transfer agents, the availability of the isolated neutral bispyridinylidenes should be beneficial for cases that are incompatible with generating the electron donor in situ.

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Super-Electron Donors: Bis-pyridinylidene Formation by Base Treatment of Pyridinium Salts

Cited by 107 publications

References 18 publications

A novel neutral organic electron donor with record half-wave potential

A novel neutral organic electron donor with record half-wave potential

Polymerization Initiated by Organic Electron Donors

Facile preparation and isolation of neutral organic electron donors based on 4-dimethylaminopyridine

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