EP2438214B1 - Method for anodic cross-dehydrodimerization of arenes - Google Patents

Method for anodic cross-dehydrodimerization of arenes Download PDF

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Publication number
EP2438214B1
EP2438214B1 EP10724436.0A EP10724436A EP2438214B1 EP 2438214 B1 EP2438214 B1 EP 2438214B1 EP 10724436 A EP10724436 A EP 10724436A EP 2438214 B1 EP2438214 B1 EP 2438214B1
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process according
group
arenes
electrolysis
mediators
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EP2438214A1 (en
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Andreas Fischer
Itamar Michael Malkowsky
Florian Stecker
Siegfried R. Waldvogel
Axel Kirste
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BASF SE
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/29—Coupling reactions

Definitions

  • the invention relates to a process for the preparation of biaryls, which is carried out by anodic cross-dehydrodimerization of substituted phenols with arenes in the presence of partially and / or perfluorinated mediators and a conductive salt.
  • the oxidative cross-coupling of arenes is a highly topical field of research and is characterized by (a) LJ Goossen, G. Deng, Guojun, LM Levy, in Science 2006, 313, 662 ; by DR Stuart, K. Fagnou, in Science 2007, 316, 1172 ; by Jean, J. Cantat, D. Birard, D. Bouchu, S. Canesi, in Org. Lett. 2007, 9, 2553 ; by R. Li, L. Jiang, W. Lu, in Organometallics 2006, 25, 5973 ; by A. Timothy, NR Dwight, DC Dagmara, J. Ryan, D. Brenton, in Org. Lett. 2007, 9, 3137 and by KL Hull, MS Sanford, in J. Am. Chem. Soc. 2007, 129, 11904 been described.
  • electrochemical processes have not been described in this context, despite numerous potential advantages.
  • the general strategy of oxidative cross-coupling of arenes utilizes the reactivity of a reagent with a component (A) of the coupling partners (A and B) to form an intermediate (I).
  • the entry into the reaction cascade on the first component (A) either by special neighboring groups, which allows the insertion of a strong oxidizing metal ion such as Pd 2+ in a C-H bond.
  • the subsequent cross-coupling usually uses halogen-substituted reactant (B).
  • the specific reactivity of indoles and fluorinated arenes towards transition metals can also be used for such a transformation.
  • hypervalent iodine compounds such as PIFA (phenyliodine bis (trifluoroacetate) and derivatives, upon activation with a Lewis acid, can coordinate to a ⁇ system, thus initiating the reaction sequence by electron transfer T.
  • PIFA phenyliodine bis (trifluoroacetate) and derivatives
  • Oxidative cross-coupling reactions of phenols with anilines or other electron-rich aromatic moieties can, in a few cases, be achieved either by certain Lewis acid additives such as by G. Satori, R. Maggi, F. Bigi, A. Arienti, G. Casnati, in Tetrahedron, 1992, 43, 9483 is described or achieved by prior co-crystallization. In the latter example, there is a preorganization via hydrogen bonding as it is by M. Smrcina, S. Vyskocil, AB Abbott, P. Kocovsky, J. Org. Chem. 1994, 59, 2156 ; by K. Ding, Q. Xu, Y. Wang, J. Liu, Z. Yu, B.
  • the object of the present invention is to provide a process which enables the anodic cross-dehydrodimerization of substituted aryl alcohols with arenes without having to use expensive catalysts and compounds having specific leaving groups and without generating toxic waste products.
  • This object is achieved by a process for the preparation of biaryls, wherein substituted aryl alcohols in which the OH group of the imbedded aryl alcohols is bonded directly to the aromatic, in the presence of partially and / or perfluorinated mediators and at least one conductive salt with arenes anodically to form the cross-coupling products are dehydrodimerized.
  • the process according to the invention is advantageous if the substituted aryl alcohols used can be mono- or binuclear.
  • the process of the invention is advantageous if the substituted arenes used can be mononuclear or binuclear.
  • the process according to the invention is advantageous if the dimerization takes place ortho to the alcohol group of the aryl alcohol.
  • the process according to the invention is advantageous if the mediators used are partially and / or perfluorinated alcohols and / or acids.
  • the process according to the invention is advantageous if 1,1,1,3,3,3-hexafluoroisopropanol and / or trifluoroacetic acid are used as mediators.
  • the process according to the invention is advantageous if the conductive salts used are those which are selected from the group of alkali, alkaline earth metal, tetra (C 1 to C 6 alkyl) ammonium salts.
  • the counterions of the conducting salts are selected from the group consisting of sulfate, hydrogensulfate, alkyl sulfates, aryl sulfates, halides, phosphates, carbonates, alkyl phosphates, alkyl carbonates, nitrate, alcoholates, tetrafluoroborate, hexafluorophosphate and perchlorate.
  • the process according to the invention is advantageous if no further solvent is used for the electrolysis.
  • the inventive method wherein a diamond anode and a nickel cathode are used.
  • the method according to the invention is advantageous if the diamond electrode is a boron-doped diamond electrode.
  • the process according to the invention is advantageous if a flow cell is used for the electrolysis.
  • the process according to the invention is advantageous when current densities of 1 to 1000 mA / cm 2 are used.
  • the process according to the invention is advantageous if the electrolysis is carried out at temperatures in the range from -20 to 100 ° C. and atmospheric pressure.
  • the process according to the invention is advantageous if 4-methylguajacol is used as the aryl alcohol.
  • aryl alcohol is understood as meaning aromatic alcohols in which the hydroxyl group is bonded directly to the aromatic nucleus.
  • the aromatic which is based on the aryl alcohol, may be mononuclear or polynuclear.
  • the aromatic is preferably mononuclear (phenol derivatives) according to formula I or binuclear (naphthol derivatives) according to formula II of III, in particular mononuclear.
  • An sp 2 -hybridized ring carbon atom of the aromatic, which is the basis of the aryl alcohol, can also be replaced by a nitrogen atom (pyridine, quinoline or isoquinoline derivative).
  • the aryl alcohols may also carry further substituents R1 to R7.
  • substituents R 1 to R 7 are independently selected from the group of C 1 -C 10 -alkyl groups, halogens, hydroxy, C 1 -C 10 -alkoxy groups, alkylene or arylene radicals interrupted by oxygen or sulfur, C 1 -C 10 -alkoxycarboxyl , Amino, nitrile, nitro and C 1 -C 10 alkoxycarbamoyl.
  • the substituents R 1 to R 7 are preferably selected from the group of methyl, ethyl, n-propyl, isopropyl, n-butyl, trifluoromethyl, fluorine, chlorine, bromine, iodine, hydroxy, methoxy, ethoxy, methylene, ethylene, propylene, isopropylene, Benzylidene, amino, nitrile, nitro.
  • the substituents R1 to R7 are particularly preferably selected from the group of methyl, methoxy, methylene, ethylene, trifluoromethyl, fluorine and bromine. Very particular preference is given to 4-alkyl- and 2,4-dialkyl-substituted phenols.
  • Suitable substrates for the electrodimerization according to the present invention are in principle all arenes, provided that they are capable of cross-dehydrodimerization because of their spatial structure and steric requirements.
  • Arene in the context of the present invention is understood as meaning aromatic carbon compounds and heteroaromatics. Preference is given in this connection to carbon compounds and heteroaromatics of the general formula IV to VIII.
  • the aromate on which the arene is based can be mononuclear or polynuclear.
  • the aromatic is preferably mononuclear (benzene derivatives) or binuclear (naphthalene derivatives), in particular mononuclear.
  • the arenes can also carry further substituents.
  • Preferred arenes are those of the formula IV to VIII.
  • An sp 2 -hybridized ring carbon atom of the arenes Moreover, according to formulas IV and V, it may be replaced by a nitrogen atom (pyridine, quinoline or isoquinoline derivative
  • R8 to R 37 which are independently selected from the group of C 1 -C 10 alkyl groups, halogens, hydroxy, C 1 -C 10 alkoxy, interrupted by oxygen or sulfur alkylene or arylene radicals, C 1 -C 10- Alkoxycarboxyl-, amino, nitrile, nitro and C 1 -C 10 alkoxycarbamoyl radicals.
  • the substituents are preferably selected from the group of methyl, ethyl, n-propyl, isopropyl, n-butyl, trifluoromethyl, fluorine, chlorine, bromine, iodine, hydroxyl, methoxy, ethoxy, methylene, ethylene, propylene, isopropylene, benzylidene, amino , Nitrile, nitro.
  • the substituents are particularly preferably selected from the group of methyl, methoxy, methylene, ethylene, trifluoromethyl, fluorine and bromine.
  • the preparation of the biaryl is carried out electrochemically, wherein the corresponding aryl alcohol is anodized.
  • the process according to the invention is referred to below as electrodimerization. It has surprisingly been found that the biaryls are produced selectively and in high yield by the method according to the invention using mediators. It has furthermore been found that undivided cell structures and solvent-free methods can be used by the method according to the invention.
  • the processing and recovery of the desired biaryle is very simple.
  • the electrolyte solution is worked up by general separation methods. For this purpose, the electrolyte solution is generally first distilled and recovered the individual compounds in the form of different fractions separately. Further purification can be carried out, for example, by crystallization, distillation, sublimation or chromatographic.
  • a diamond electrode is used. These diamond electrodes are formed by applying one or more diamond layers to a substrate.
  • Possible support materials are niobium, silicon, tungsten, titanium, silicon carbide, tantalum, graphite or ceramic supports such as titanium suboxide.
  • a support of niobium, titanium or silicon is preferred for the process according to the invention, very particular preference is given to a support of niobium.
  • Electrodes selected from the group of iron, steel, stainless steel, nickel, noble metals such as platinum, graphite, carbon materials such as the diamond electrodes are used for the process according to the invention.
  • Suitable anode materials are, for example, noble metals such as platinum or metal oxides such as ruthenium or chromium oxide or mixed oxides of the type RuO x TiO x and diamond electrodes.
  • a diamond electrode which is also doped with further elements is preferred. Boron and nitrogen are preferred as doping elements.
  • BDD electrode boron-doped diamond electrode
  • the cathode material is selected from the group of iron, steel, stainless steel, nickel, precious metals such as platinum, graphite, carbon, glassy carbon materials and diamond electrodes.
  • the cathode is selected from the group of nickel, steel and stainless steel.
  • the cathode is particularly preferably made of nickel.
  • Partially and / or perfluorinated alcohols and / or acids preferably perfluorinated alcohols and carboxylic acids, very particularly preferably 1,1,1,3,3,3-hexafluoroisopropanol or trifluoroacetic acid, are used as mediators in the process according to the invention.
  • the electrolysis is carried out in the usual, known in the art electrolysis cells.
  • Suitable electrolysis cells are known to the person skilled in the art. Preferably, one works continuously in undivided flow cells or discontinuously in beaker cells.
  • Particularly suitable are bipolar switched capillary gap cells or plate stack cells, in which the electrodes are designed as plates and are arranged plane-parallel as in Ullmann's Encyclopaedia of Industrial Chemistry, Electrochemistry, 1999 electronic release, Sixth Edition, Wiley-VCH Weinheim (doi: 10.1002 / 14356007.a09_183.pub2) and in Electrochemistry, Chapter 3.5. special cell designs and Chapter 5, Organic Electrochemistry, Subchapter 5.4.3.2 Cell Design is described.
  • the current densities at which the process is carried out are generally 1 to 1000, preferably 5 to 100 mA / cm 2 .
  • the temperatures are usually -20 to 100 ° C, preferably 10 to 60 ° C. In general, working at atmospheric pressure. Higher pressures are preferably used when operating at higher temperatures to avoid boiling of the co-solvents or mediators.
  • the aryl alcohol compound and the arene are dissolved in a suitable solvent.
  • suitable solvents known to the person skilled in the art, preferably solvents from the group of polar protic and polar aprotic solvents, are suitable.
  • the aryl alcohol compound itself serves as a solvent and reagent.
  • polar aprotic solvents include nitriles, amides, carbonates, ethers, ureas, chlorinated hydrocarbons.
  • particularly preferred polar aprotic solvents include acetonitrile, dimethylformamide, dimethyl sulfoxide, propylene carbonate and dichloromethane.
  • polar protic solvents include alcohols, carboxylic acids and amides.
  • particularly preferred polar protic solvents include methanol, ethanol, propanol, butanol, pentanol and hexanol. These may also be partially or completely halogenated, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) or trifluoroacetic acid (TFA).
  • HFIP 1,1,1,3,3,3-hexafluoroisopropanol
  • TFA trifluoroacetic acid
  • the electrolysis solution is added to customary cosolvents.
  • these are the inert solvents customary in organic chemistry with a high oxidation potential. Examples include its dimethyl carbonate, propylene carbonate, tetrahydrofuran, dimethoxyethane, acetonitrile or dimethylformamide.
  • Conducting salts which are contained in the electrolysis solution are generally alkali metal, alkaline earth metal, tetra (C 1 - to C 6 -alkyl) ammonium, preferably tri (C 1 - to C 6 -alkyl) -methylammonium salts .
  • Suitable counterions are sulfates, hydrogen sulfates, alkyl sulfates, aryl sulfates, halides, phosphates, carbonates, alkyl phosphates, alkyl carbonates, nitrate, alcoholates, tetrafluoroborate, hexafluorophosphate or perchlorate.
  • the acids derived from the abovementioned anions are suitable as conductive salts.
  • MTBS methyltributylammonium methylsulfates
  • MTES methyltriethylammonium methylsulfate
  • TABF tetrabutylammonium, tetrafluoroborate
  • Example 1 Anodic oxidation of 4-methyl guaiacol and substituted benzenes at a BDD anode with hexafluoroisopropanol
  • an electrolysis cell attached via a flange to a BDD-coated silicon plate and connected as an anode, the electrolyte consisting of substituted benzene and 4-methyl guaiacol in a molar ratio of 10: 1 according to Table 1, 0.68 g Methyltriethylammoniummethylsulfat (MTES) and 30 mL hexafluoroisopropanol presented.
  • MTES Methyltriethylammoniummethylsulfat
  • the cathode used is a nickel mesh which is immersed in the electrolyte at a distance of 1 cm from the BDD anode.
  • the cell is heated in a sand bath (50 ° C).
  • the electrolysis is carried out under galvanostatic control and a current density of 4.7 mA / cm 2 .
  • the reaction is stopped after reaching the set charge limit (1 F per mole of 4-methylguajacol).
  • the cooled reaction mixture is transferred with about 20 mL of toluene in a flask from which toluene and the fluorinated solvent used are almost completely removed on a rotary evaporator. Excess starting materials can be recovered by short path distillation at reduced pressure. By column chromatographic purification of the distillation residue on silica gel 60 and subsequent washing with a little cold n-heptane, the product can be isolated as a colorless, crystalline solid.

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Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Biarylen, wobei durch anodischen Kreuz-Dehydrodimerisierung von substituierten Phenolen mit Arenen in Gegenwart von teil- und/oder perfluorierten Mediatoren und einem Leitsalz gearbeitet wird.The invention relates to a process for the preparation of biaryls, which is carried out by anodic cross-dehydrodimerization of substituted phenols with arenes in the presence of partially and / or perfluorinated mediators and a conductive salt.

Die oxidative Kreuzkupplung von Arenen stellt ein hochaktuelles Forschungsfeld dar und ist von (a) L. J. Goossen, G. Deng, Guojun, L. M. Levy, in Science 2006, 313, 662 ; von D. R. Stuart, K. Fagnou, in Science 2007, 316, 1172 ; von A. Jean, J. Cantat, D. Birard, D. Bouchu, S. Canesi, in Org. Lett. 2007, 9, 2553 ; von R. Li, L. Jiang, W. Lu, in Organometallics 2006, 25, 5973 ; von A. Timothy, N. R. Dwight, D. C. Dagmara, J. Ryan, D. Brenton, in Org. Lett. 2007, 9, 3137 und von K. L. Hull, M. S. Sanford, in J. Am. Chem. Soc. 2007, 129, 11904 beschrieben worden. Elektrochemische Verfahren sind jedoch in diesem Zusammenhang trotz zahlreicher potentieller Vorteile bisher nicht beschrieben.The oxidative cross-coupling of arenes is a highly topical field of research and is characterized by (a) LJ Goossen, G. Deng, Guojun, LM Levy, in Science 2006, 313, 662 ; by DR Stuart, K. Fagnou, in Science 2007, 316, 1172 ; by Jean, J. Cantat, D. Birard, D. Bouchu, S. Canesi, in Org. Lett. 2007, 9, 2553 ; by R. Li, L. Jiang, W. Lu, in Organometallics 2006, 25, 5973 ; by A. Timothy, NR Dwight, DC Dagmara, J. Ryan, D. Brenton, in Org. Lett. 2007, 9, 3137 and by KL Hull, MS Sanford, in J. Am. Chem. Soc. 2007, 129, 11904 been described. However, electrochemical processes have not been described in this context, despite numerous potential advantages.

Die generelle Strategie der oxidativen Kreuzkupplung von Arenen nutzt die Reaktivität eines Reagenzes mit einer Komponente (A) der Kupplungspartner (A und B) unter Bildung eines Intermediats (I). Im Folgeschritt kommt es zum Angriff an die andere Komponente (B) durch das erzeugte Intermediat (I). Bisher wurde der Eintritt in die Reaktionskaskade an der ersten Komponente (A) entweder durch spezielle Nachbargruppen, welche den Einschub eines stark oxidierend wirkenden Metallions wie Pd2+ in eine CH-Bindung ermöglicht. Die nachfolgende Kreuzkupplung bedient sich meist Halogensubstituierter Reaktionspartner (B). Auch die spezifische Reaktivität von Indolen und fluorierten Arenen gegenüber Übergangsmetallen kann für eine solche Transformation genutzt werden. Im Gegensatz dazu können hypervalente lodverbindungen, wie PIFA (Phenyliodinebis(trifluoroacetate) und Derivate, nach Aktivierung mit einer Lewis-Säure an ein π-System koordinieren und so durch Elektronentransfer die Reaktionssequenz einleiten wie es von T. Dohi, Motoki Ito, K. Morimoto, M. Iwata,Y. Kita, in Angew. Chem. 2008, 120, 1321 ; und in Angew. Chem. Int. Ed. 2008, 47, 3787 beschrieben ist. Nachteilig für beide Ansätze ist, dass jeweils nur ein sehr eingeschränktes Substratspektrum umgesetzt werden kann und bei der Transformation relativ viel und meist auch toxischer Abfall generiert wird. Zusätzlich zeichnen sich die Reagenzien durch einen hohen Preis aus.The general strategy of oxidative cross-coupling of arenes utilizes the reactivity of a reagent with a component (A) of the coupling partners (A and B) to form an intermediate (I). In the following step, attack on the other component (B) by the generated intermediate (I). So far, the entry into the reaction cascade on the first component (A) either by special neighboring groups, which allows the insertion of a strong oxidizing metal ion such as Pd 2+ in a C-H bond. The subsequent cross-coupling usually uses halogen-substituted reactant (B). The specific reactivity of indoles and fluorinated arenes towards transition metals can also be used for such a transformation. In contrast, hypervalent iodine compounds such as PIFA (phenyliodine bis (trifluoroacetate) and derivatives, upon activation with a Lewis acid, can coordinate to a π system, thus initiating the reaction sequence by electron transfer T. Dohi, Motoki Ito, K. Morimoto, M. Iwata, Y. Day care, in Angew. Chem. 2008, 120, 1321 ; and in Angew. Chem. Int. Ed. 2008, 47, 3787 is described. A disadvantage of both approaches is that in each case only a very limited range of substrates can be implemented and in the transformation relatively much and usually toxic waste is generated. In addition, the reagents are characterized by a high price.

Oxidative Kreuzkupplungen von Phenolen mit Anilinen oder anderen elektronenreichen aromatischen Komponenten können in wenigen Fällen entweder durch bestimmte Lewis-Säureadditive wie es von G. Satori, R. Maggi, F. Bigi, A. Arienti, G. Casnati, in Tetrahedron, 1992, 43, 9483 beschrieben ist oder durch vorangehende Co-Kristallisation erreicht werden. In letzterem Beispiel findet eine Vororganisation via Wasserstoffbrückenbindung statt wie es von M. Smrcina, S. Vyskocil, A. B. Abbott, P. Kocovsky, in J. Org. Chem. 1994, 59, 2156 ; von K. Ding, Q. Xu, Y. Wang, J. Liu, Z. Yu, B. Du, Y. Wu, H. Koshima, T. Matsuura, in J. Chem. Soc., Chem. Commun. 1997, 693 und von S. Vyskocil, M. Smrcina, B Maca, M. Polasek, T. A. Claxton, A. B. Abbott, P. Kocovsky, in J. Chem. Soc., Chem. Commun. 1998, 586 beschrieben wird.Oxidative cross-coupling reactions of phenols with anilines or other electron-rich aromatic moieties can, in a few cases, be achieved either by certain Lewis acid additives such as by G. Satori, R. Maggi, F. Bigi, A. Arienti, G. Casnati, in Tetrahedron, 1992, 43, 9483 is described or achieved by prior co-crystallization. In the latter example, there is a preorganization via hydrogen bonding as it is by M. Smrcina, S. Vyskocil, AB Abbott, P. Kocovsky, J. Org. Chem. 1994, 59, 2156 ; by K. Ding, Q. Xu, Y. Wang, J. Liu, Z. Yu, B. Du, Y. Wu, H. Koshima, T. Matsuura, in J. Chem. Soc., Chem. Commun. 1997, 693 and by S. Vyskocil, M. Smrcina, B Maca, M. Polasek, TA Claxton, AB Abbott, P. Kocovsky, in J. Chem. Soc., Chem. Commun. 1998, 586 is described.

Es konnte gezeigt werden, dass die symmetrische Phenolkupplung an bordotierten Diamantelektroden (BDD) unter Verwendung von Leitsalzen realisiert werden kann wie es von A. Kirste, M. Nieger, I. M. Malkowsky, F. Stecker, A. Fischer, S. R. Waldvogel, Chem. Eur. J. 2009, 15, 2273 und in WO 2006/077204 beschrieben wurde. Unter Verwendung von anderen Kohlenstoffelektroden und auch fluorierten Carbonsäuren als Mediatoren kann eine selektive und effiziente Biphenolkupplung von z.B. 2,4-Dimethylphenol erreicht werden. Das lösungsmittelfreie Verfahren benötigt lediglich ungeteilte Elektrolysenzellen, wie es von A. Fischer, I. M. Malkowsky, F. Stecker, A. Kirste, S. R. Waldvogel in Anodic Preparation of Biphenols on BDD electrodes und WO 2010/023258 beschrieben wurde.It could be shown that the symmetric phenol coupling can be realized on boron doped diamond electrodes (BDD) using conductive salts as it is by A. Kirste, M. Nieger, IM Malkowsky, F. Stecker, A. Fischer, SR Waldvogel, Chem. Eur. J. 2009, 15, 2273 and in WO 2006/077204 has been described. By using other carbon electrodes and also fluorinated carboxylic acids as mediators, a selective and efficient biphenol coupling of eg 2,4-dimethylphenol can be achieved. The solvent-free process requires only undivided electrolysis cells, as described by A. Fischer, IM Malkowsky, F. Plug, A. Kirste, SR Waldvogel in Anodic Preparation of Biphenols on BDD electrodes and WO 2010/023258 has been described.

Die Aufgabe der vorliegenden Erfindung besteht darin, ein Verfahren bereitzustellen, mit dem die anodische Kreuz-Dehydrodimerisierung von substituierten Arylalkoholen mit Arenen ermöglicht wird, ohne kostspielige Katalysatoren, und Verbindungen mit speziellen Abgangsgruppen verwenden zu müssen und ohne toxische Abfallprodukte zu generieren.The object of the present invention is to provide a process which enables the anodic cross-dehydrodimerization of substituted aryl alcohols with arenes without having to use expensive catalysts and compounds having specific leaving groups and without generating toxic waste products.

Diese Aufgabe wird gelöst durch ein Verfahren zur Herstellung von Biarylen, wobei substituierte Arylalkohole bei denen die OH-Gruppe der eingedetzten Arylalkohole direkt an den Aromaten gebunden ist, in Gegenwart von teil- und/oder perfluorierten Mediatoren und wenigstens einem Leitsalz mit Arenen anodisch unter Bildung der Kreuzkupplungsprodukte dehydrodimerisiert werden.This object is achieved by a process for the preparation of biaryls, wherein substituted aryl alcohols in which the OH group of the imbedded aryl alcohols is bonded directly to the aromatic, in the presence of partially and / or perfluorinated mediators and at least one conductive salt with arenes anodically to form the cross-coupling products are dehydrodimerized.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die eingesetzten substituierten Arylalkohole ein- oder zweikernig sein können.The process according to the invention is advantageous if the substituted aryl alcohols used can be mono- or binuclear.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die eingesetzten substituierten Arene ein- oder zweikernig sein können.The process of the invention is advantageous if the substituted arenes used can be mononuclear or binuclear.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die Dimerisierung in ortho-Stellung zur Alkoholgruppe des Arylalkohols stattfindet.The process according to the invention is advantageous if the dimerization takes place ortho to the alcohol group of the aryl alcohol.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die eingesetzten Mediatoren teil- und/oder perfluorierte Alkohole und/oder Säuren sind.The process according to the invention is advantageous if the mediators used are partially and / or perfluorinated alcohols and / or acids.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn als Mediatoren 1,1,1,3,3,3-Hexafluorisopropanol und/oder Trifluoressigsäure eingesetzt werden.The process according to the invention is advantageous if 1,1,1,3,3,3-hexafluoroisopropanol and / or trifluoroacetic acid are used as mediators.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn als Leitsalze solche eingesetzt werden, die ausgewählt sind aus der Gruppe von Alkali-, Erdalkali-, Tetra(C1- bis C6-alkyl)ammoniumsalzen.The process according to the invention is advantageous if the conductive salts used are those which are selected from the group of alkali, alkaline earth metal, tetra (C 1 to C 6 alkyl) ammonium salts.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die Gegenionen der Leitsalze ausgewählt sind aus der Gruppe von Sulfat, Hydrogensulfat, Alkylsulfate, Arylsulfate, Halogenide, Phosphate, Carbonate, Alkylphosphate, Alkylcarbonate, Nitrat, Alkoholate, Tetrafluorborat, Hexafluorophosphat und Perchlorat.The process according to the invention is advantageous if the counterions of the conducting salts are selected from the group consisting of sulfate, hydrogensulfate, alkyl sulfates, aryl sulfates, halides, phosphates, carbonates, alkyl phosphates, alkyl carbonates, nitrate, alcoholates, tetrafluoroborate, hexafluorophosphate and perchlorate.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn für die Elektrolyse kein weiteres Lösungsmittel eingesetzt wird.The process according to the invention is advantageous if no further solvent is used for the electrolysis.

Vorteilhaft ist das erfindungsgemäße Verfahren, wobei eine Diamantanode und eine Nickelkathode verwendet werden.Advantageously, the inventive method, wherein a diamond anode and a nickel cathode are used.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn es sich bei der Diamantelektrode um eine bordotierte Diamantelektrode handelt.The method according to the invention is advantageous if the diamond electrode is a boron-doped diamond electrode.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn für die Elektrolyse eine Durchflusszelle eingesetzt wird.The process according to the invention is advantageous if a flow cell is used for the electrolysis.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn Stromdichten von 1 bis 1000 mA/cm2 eingesetzt werden.The process according to the invention is advantageous when current densities of 1 to 1000 mA / cm 2 are used.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn die Elektrolyse bei Temperaturen im Bereich von -20 bis 100°C und Normaldruck durchgeführt wird.The process according to the invention is advantageous if the electrolysis is carried out at temperatures in the range from -20 to 100 ° C. and atmospheric pressure.

Vorteilhaft ist das erfindungsgemäße Verfahren, wenn als Arylalkohol 4-Methylguajacol eingesetzt wird.The process according to the invention is advantageous if 4-methylguajacol is used as the aryl alcohol.

Unter Arylalkohol werden im Rahmen der vorliegenden Erfindung aromatische Alkohole verstanden, bei denen die Hydroxylgruppe direkt an den aromatischen Kern gebunden ist.For the purposes of the present invention, aryl alcohol is understood as meaning aromatic alcohols in which the hydroxyl group is bonded directly to the aromatic nucleus.

Der Aromat, der dem Arylalkohol zugrunde liegt, kann ein- oder mehrkernig sein. Vorzugsweise ist der Aromat einkernig (Phenolderivate) gemäß Formel I oder zweikernig (Naphtholderivate) gemäß Formel II der III, insbesondere einkernig. Ein sp2-hybridisiertes Ringkohlenstoffatom des Aromaten, der dem Arylalkohol zugrunde liegt, kann darüber hinaus durch ein Stickstoffatom ersetzt sein (Pyridin-, Chinolin- bzw. Isochinolinderivat).

Figure imgb0001
Figure imgb0002
 The aromatic, which is based on the aryl alcohol, may be mononuclear or polynuclear. The aromatic is preferably mononuclear (phenol derivatives) according to formula I or binuclear (naphthol derivatives) according to formula II of III, in particular mononuclear. An sp 2 -hybridized ring carbon atom of the aromatic, which is the basis of the aryl alcohol, can also be replaced by a nitrogen atom (pyridine, quinoline or isoquinoline derivative).
Figure imgb0001
Figure imgb0002

Die Arylalkohole können auch noch weitere Substituenten R1 bis R7 tragen. Diese Substituenten R1 bis R7 sind unabhängig voneinander ausgewählt aus der Gruppe von C1-C10-Alkylgruppen, Halogenen, Hydroxy, C1-C10-Alkoxygruppen, durch Sauerstoff oder Schwefel unterbrochene Alkylen- oder Arylenreste, C1-C10-Alkoxycarboxyl, Amino, Nitril, Nitro sowie C1-C10-Alkoxycarbamoyl. Bevorzugt sind die Substituenten R1 bis R7 ausgewählt aus der Gruppe von Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Trifluormethyl, Fluor, Chlor, Brom, lod, Hydroxy, Methoxy, Ethoxy, Methylen, Ethylen, Propylen, Isopropylen, Benzyliden, Amino, Nitril, Nitro. Besonders bevorzugt sind die Substituenten R1 bis R7 ausgewählt aus der Gruppe von Methyl, Methoxy, Methylen, Ethylen, Trifluormethyl, Fluor und Brom. Ganz besonders bevorzugt sind 4-Alkyl- sowie 2,4-dialkylsubstituierte Phenole.The aryl alcohols may also carry further substituents R1 to R7. These substituents R 1 to R 7 are independently selected from the group of C 1 -C 10 -alkyl groups, halogens, hydroxy, C 1 -C 10 -alkoxy groups, alkylene or arylene radicals interrupted by oxygen or sulfur, C 1 -C 10 -alkoxycarboxyl , Amino, nitrile, nitro and C 1 -C 10 alkoxycarbamoyl. The substituents R 1 to R 7 are preferably selected from the group of methyl, ethyl, n-propyl, isopropyl, n-butyl, trifluoromethyl, fluorine, chlorine, bromine, iodine, hydroxy, methoxy, ethoxy, methylene, ethylene, propylene, isopropylene, Benzylidene, amino, nitrile, nitro. The substituents R1 to R7 are particularly preferably selected from the group of methyl, methoxy, methylene, ethylene, trifluoromethyl, fluorine and bromine. Very particular preference is given to 4-alkyl- and 2,4-dialkyl-substituted phenols.

Als Substrate für die Elektrodimerisierung nach der vorliegenden Erfindung eignen sich prinzipiell sämtliche Arene, sofern diese aufgrund ihrer räumlichen Struktur und sterischen Anforderungen zu einer Kreuz-Dehydrodimerisierung in der Lage sind. Unter Aren werden im Rahmen der vorliegenden Erfindung aromatische Kohlenstoffverbindungen und Heteroaromaten verstanden. Bevorzugt sind hierbei Kohlenstoffverbindungen und Heteroaromaten der allgemeinen Formel IV bis VIII. Der Aromat, der dem Aren zugrunde liegt, kann ein- oder mehrkernig sein. Vorzugsweise ist der Aromat einkernig (Benzolderivate) oder zweikernig (Naphthalinderivate), insbesondere einkernig. Die Arene können auch noch weitere Substituenten tragen. Bevorzugte Arene sind solche der Formel IV bis VIII. Ein sp2-hybridisiertes Ringkohlenstoffatom der Arene nach Formeln IV und V kann darüber hinaus durch ein Stickstoffatom ersetzt sein (Pyridin-, Chinolin- bzw. Isochinolinderivat).

Figure imgb0003
Figure imgb0004
 Suitable substrates for the electrodimerization according to the present invention are in principle all arenes, provided that they are capable of cross-dehydrodimerization because of their spatial structure and steric requirements. Arene in the context of the present invention is understood as meaning aromatic carbon compounds and heteroaromatics. Preference is given in this connection to carbon compounds and heteroaromatics of the general formula IV to VIII. The aromate on which the arene is based can be mononuclear or polynuclear. The aromatic is preferably mononuclear (benzene derivatives) or binuclear (naphthalene derivatives), in particular mononuclear. The arenes can also carry further substituents. Preferred arenes are those of the formula IV to VIII. An sp 2 -hybridized ring carbon atom of the arenes Moreover, according to formulas IV and V, it may be replaced by a nitrogen atom (pyridine, quinoline or isoquinoline derivative).
Figure imgb0003
Figure imgb0004

Diese tragen Substituenten R8 bis R 37, die unabhängig voneinander ausgewählt aus der Gruppe von C1-C10-Alkylgruppen, Halogenen, Hydroxy, C1-C10-Alkoxygruppen, durch Sauerstoff oder Schwefel unterbrochene Alkylen- oder Arylenreste, C1-C10-Alkoxycarboxyl-, Amino-, Nitril-, Nitro- sowie C1-C10-Alkoxycarbamoylreste. Bevorzugt sind die Substituenten ausgewählt aus der Gruppe von Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Trifluormethyl, Fluor, Chlor, Brom, Iod, Hydroxy, Methoxy, Ethoxy, Methylen, Ethylen, Propylen, Isopropylen, Benzyliden, Amino, Nitril, Nitro. Besonders bevorzugt sind die Substituenten ausgewählt aus der Gruppe von Methyl, Methoxy, Methylen, Ethylen, Trifluormethyl, Fluor und Brom. Ganz besonders bevorzugt sind Arene ausgewählt aus der Gruppe von einfach oder mehrfach substituierte Benzolderivate, einfach oder mehrfach substituierte Naphthalinderivate, einfach oder mehrfach substituierte Benzodioxolderivate, einfach oder mehrfach substituierte Furanderivate, einfach oder mehrfach substituierte Indolderivate.These carry substituents R8 to R 37, which are independently selected from the group of C 1 -C 10 alkyl groups, halogens, hydroxy, C 1 -C 10 alkoxy, interrupted by oxygen or sulfur alkylene or arylene radicals, C 1 -C 10- Alkoxycarboxyl-, amino, nitrile, nitro and C 1 -C 10 alkoxycarbamoyl radicals. The substituents are preferably selected from the group of methyl, ethyl, n-propyl, isopropyl, n-butyl, trifluoromethyl, fluorine, chlorine, bromine, iodine, hydroxyl, methoxy, ethoxy, methylene, ethylene, propylene, isopropylene, benzylidene, amino , Nitrile, nitro. The substituents are particularly preferably selected from the group of methyl, methoxy, methylene, ethylene, trifluoromethyl, fluorine and bromine. Very particular preference is given to arenes selected from the group of singly or multiply substituted benzene derivatives, singly or multiply substituted naphthalene derivatives, singly or multiply substituted benzodioxole derivatives, singly or multiply substituted furan derivatives, singly or multiply substituted indole derivatives.

Die Herstellung des Biaryls erfolgt elektrochemisch, wobei der entsprechende Arylalkohol anodisch oxidiert wird. Das erfindungsgemäße Verfahren wird nachfolgend Elektrodimerisierung genannt. Es wurde überraschender Weise gefunden, dass durch das erfindungsgemäße Verfahren unter Verwendung von Mediatoren die Biaryle selektiv und in hoher Ausbeute entstehen. Des Weiteren wurde gefunden, dass durch das erfindungsgemäße Verfahren ungeteilte Zellaufbauten sowie lösungsmittelfreie Verfahren angewendet werden können.
Die Aufarbeitung und Gewinnung der gewünschten Biaryle gestaltet sich sehr einfach. Nach Beendigung der Reaktion wird die Elektrolytlösung nach allgemeinen Trennmethoden aufgearbeitet. Hierzu wird die Elektrolytlösung im Allgemeinen zuerst destilliert und die einzelnen Verbindungen in Form von unterschiedlichen Fraktionen getrennt gewonnen. Eine weitere Reinigung kann beispielsweise durch Kristallisation, Destillation, Sublimation oder chromatographisch erfolgen.The preparation of the biaryl is carried out electrochemically, wherein the corresponding aryl alcohol is anodized. The process according to the invention is referred to below as electrodimerization. It has surprisingly been found that the biaryls are produced selectively and in high yield by the method according to the invention using mediators. It has furthermore been found that undivided cell structures and solvent-free methods can be used by the method according to the invention.
The processing and recovery of the desired biaryle is very simple. After completion of the reaction, the electrolyte solution is worked up by general separation methods. For this purpose, the electrolyte solution is generally first distilled and recovered the individual compounds in the form of different fractions separately. Further purification can be carried out, for example, by crystallization, distillation, sublimation or chromatographic.

Für das erfindungsgemäße Verfahren wird eine Diamantelektrode eingesetzt. Diese Diamantelektroden entstehen in dem man auf ein Trägermaterial ein oder mehrere Diamantschichten aufbringt. Als mögliche Trägermaterialien eignen sich Niob, Silizium, Wolfram, Titan, Siliziumcarbid, Tantal, Graphit oder keramische Träger wie Titansuboxid. Bevorzugt für das erfindungsgemäße Verfahren ist jedoch ein Träger aus Niob, Titan oder Silizium, ganz besonders bevorzugt ist ein Träger aus Niob.For the inventive method, a diamond electrode is used. These diamond electrodes are formed by applying one or more diamond layers to a substrate. Possible support materials are niobium, silicon, tungsten, titanium, silicon carbide, tantalum, graphite or ceramic supports such as titanium suboxide. However, a support of niobium, titanium or silicon is preferred for the process according to the invention, very particular preference is given to a support of niobium.

Für das erfindungsgemäße Verfahren sind Elektroden ausgewählt aus der Gruppe von Eisen, Stahl, Edelstahl, Nickel, Edelmetalle wie Platin, Graphit, Kohlematerialien wie die Diamantelektroden. Als Anodenmaterialien eignen sich beispielsweise Edelmetalle wie Platin oder Metalloxide wie Ruthenium oder Chromoxid oder Mischoxide des Typs RuOxTiOx sowie Diamantelektroden. Bevorzugt sind Graphit-, Kohle-, Glaskohlenstoff- oder Diamantelektroden, besonders bevorzugt Diamantelektroden. Bevorzugt ist für die Anode eine Diamantelektrode, die auch noch mit weiteren Elementen dotiert ist. Als Dotierungselemente sind Bor und Stickstoff bevorzugt. Ganz besonders bevorzugt ist das erfindungsgemäße Verfahren mit einer bordotierten Diamantelektrode (BDD-Elektrode) als Anode.Electrodes selected from the group of iron, steel, stainless steel, nickel, noble metals such as platinum, graphite, carbon materials such as the diamond electrodes are used for the process according to the invention. Suitable anode materials are, for example, noble metals such as platinum or metal oxides such as ruthenium or chromium oxide or mixed oxides of the type RuO x TiO x and diamond electrodes. Preference is given to graphite, carbon, glassy carbon or diamond electrodes, more preferably diamond electrodes. For the anode, a diamond electrode which is also doped with further elements is preferred. Boron and nitrogen are preferred as doping elements. The process according to the invention with a boron-doped diamond electrode (BDD electrode) as anode is very particularly preferred.

Das Kathodenmaterial ist dabei ausgewählt aus der Gruppe von Eisen-, Stahl-, Edelstahl-, Nickel-, Edelmetalle- wie Platin-, Graphit-, Kohle-, Glaskohlenstoffmaterialien und Diamantelektroden. Bevorzugt ist die Kathode ausgewählt aus der Gruppe von Nickel, Stahl und Edelstahl. Besonders bevorzugt ist die Kathode aus Nickel.The cathode material is selected from the group of iron, steel, stainless steel, nickel, precious metals such as platinum, graphite, carbon, glassy carbon materials and diamond electrodes. Preferably, the cathode is selected from the group of nickel, steel and stainless steel. The cathode is particularly preferably made of nickel.

Als Mediatoren werden im erfindungsgemäßen Verfahren teil- und/oder perfluorierte Alkohole und/oder Säuren, bevorzugt perfluorierte Alkohole sowie Carbonsäuren, ganz besonders bevorzugt 1,1,1,3,3,3-Hexafluorisopropanol oder Trifluoressigsäure verwendet.Partially and / or perfluorinated alcohols and / or acids, preferably perfluorinated alcohols and carboxylic acids, very particularly preferably 1,1,1,3,3,3-hexafluoroisopropanol or trifluoroacetic acid, are used as mediators in the process according to the invention.

Im Elektrolyten sind keine weiteren Lösungsmittel erforderlich.No additional solvents are required in the electrolyte.

Die Elektrolyse wird in den üblichen, dem Fachmann bekannten Elektrolysezellen durchgeführt. Geeignete Elektrolysezellen sind dem Fachmann bekannt. Vorzugsweise arbeitet man kontinuierlich in ungeteilten Durchflusszellen oder diskontinuierlich in Becherglaszellen.
Ganz besonders geeignet sind bipolar geschaltete Kapillarspaltzellen oder Plattenstapelzellen, bei denn die Elektroden als Platten ausgestaltet sind und planparallel angeordnet sind wie es in Ullmann's Encyclopedia of Industrial Chemistry, Electrochemistry, 1999 electronic release, Sixth Edition, Wiley-VCH Weinheim (doi: 10.1002/14356007.a09_183.pub2) und in Electrochemistry, Chapter 3.5. special cell designs sowie Chapter 5, Organic Electrochemistry, Subchapter 5.4.3.2 Cell Design beschrieben ist.The electrolysis is carried out in the usual, known in the art electrolysis cells. Suitable electrolysis cells are known to the person skilled in the art. Preferably, one works continuously in undivided flow cells or discontinuously in beaker cells.
Particularly suitable are bipolar switched capillary gap cells or plate stack cells, in which the electrodes are designed as plates and are arranged plane-parallel as in Ullmann's Encyclopaedia of Industrial Chemistry, Electrochemistry, 1999 electronic release, Sixth Edition, Wiley-VCH Weinheim (doi: 10.1002 / 14356007.a09_183.pub2) and in Electrochemistry, Chapter 3.5. special cell designs and Chapter 5, Organic Electrochemistry, Subchapter 5.4.3.2 Cell Design is described.

Die Stromdichten, bei denen das Verfahren durchgeführt wird, betragen im allgemeinen 1 - 1000, bevorzugt 5 - 100 mA/cm2. Die Temperaturen betragen üblicherweise -20 bis 100°C, bevorzugt 10 bis 60°C. Im Allgemeinen wird bei Normaldruck gearbeitet. Höhere Drücke werden bevorzugt dann angewandt, wenn bei höheren Temperaturen gearbeitet werden soll, um ein Sieden der Ausgangsverbindungen bzw. Cosolventien bzw. Mediatoren zu vermeiden.The current densities at which the process is carried out are generally 1 to 1000, preferably 5 to 100 mA / cm 2 . The temperatures are usually -20 to 100 ° C, preferably 10 to 60 ° C. In general, working at atmospheric pressure. Higher pressures are preferably used when operating at higher temperatures to avoid boiling of the co-solvents or mediators.

Zur Durchführung der Elektrolyse werden die Arylalkoholverbindung und das Aren in einem geeigneten Lösungsmittel gelöst. Es eignen sich die üblichen, dem Fachmann bekannten Lösungsmittel, vorzugsweise Lösungsmittel aus der Gruppe der polaren protischen und polaren aprotischen Lösungsmittel. Besonders bevorzugt dient die Arylalkoholverbindung selbst als Lösungsmittel und Reagenz.
Beispiele für polare aprotische Lösungsmittel umfassen Nitrile, Amide, Carbonate, Ether, Harnstoffe, Chlorkohlenwasserstoffe. Beispiele für besonders bevorzugte polare aprotische Lösungsmittel umfassen Actonitril, Dimethylformamid, Dimethylsulfoxid, Propylencarbonat und Dichlormethan. Beispiele für polare protische Lösungsmittel umfassen Alkohole, Carbonsäuren und Amide. Beispiele für besonders bevorzugte polare protische Lösungsmittel umfassen Methanol, Ethanol, Propanol, Butanol, Pentanol und Hexanol. Diese können auch teilweise oder vollständig halogeniert sein, wie 1,1,1,3,3,3-Hexafluorisopropanol (HFIP) oder Trifluoressigsäure (TFA).To carry out the electrolysis, the aryl alcohol compound and the arene are dissolved in a suitable solvent. The usual solvents known to the person skilled in the art, preferably solvents from the group of polar protic and polar aprotic solvents, are suitable. Particularly preferably, the aryl alcohol compound itself serves as a solvent and reagent.
Examples of polar aprotic solvents include nitriles, amides, carbonates, ethers, ureas, chlorinated hydrocarbons. Examples of particularly preferred polar aprotic solvents include acetonitrile, dimethylformamide, dimethyl sulfoxide, propylene carbonate and dichloromethane. Examples of polar protic solvents include alcohols, carboxylic acids and amides. Examples of particularly preferred polar protic solvents include methanol, ethanol, propanol, butanol, pentanol and hexanol. These may also be partially or completely halogenated, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) or trifluoroacetic acid (TFA).

Gegebenenfalls setzt man der Elektrolyselösung übliche Cosolvenzien zu. Dabei handelt es sich um die in der organischen Chemie üblichen inerten Lösungsmittel mit einem hohen Oxidationspotential. Beispielhaft genannt seinen Dimethylcarbonat, Propylencarbonat, Tetrahydrofuran, Dimethoxyethan, Acetonitril oder Dimethylformamid.Optionally, the electrolysis solution is added to customary cosolvents. These are the inert solvents customary in organic chemistry with a high oxidation potential. Examples include its dimethyl carbonate, propylene carbonate, tetrahydrofuran, dimethoxyethane, acetonitrile or dimethylformamide.

Als Leitsalze, die in der Elektrolyselösung enthalten sind, handelt es sich im Allgemeinen um Alkali-, Erdalkali-, Tetra(C1- bis C6-alkyl)ammonium-, bevorzugt Tri(C1- bis C6-alkyl)-methylammoniumsalze. Als Gegenion kommen Sulfate, Hydrogensulfate, Alkylsulfate, Arylsulfate, Halogenide, Phosphate, Carbonate, Alkylphosphate, Alkylcarbonate, Nitrat, Alkoholate, Tetrafluorborat, Hexafluorophosphat oder Perchlorat in Betracht. Weiterhin kommen die von den vorstehend genannten Anionen abgeleiteten Säuren als Leitsalze in Betracht.
Ganz besonders bevorzugt sind Methyltributylammoniummethylsulfate (MTBS), Methyltriethylammoniummethylsulfat (MTES), Methyltripropylmethylammoniummethylsulfate, oder Tetrabutylammonium, Tetrafluoroborat (TBABF).Conducting salts which are contained in the electrolysis solution are generally alkali metal, alkaline earth metal, tetra (C 1 - to C 6 -alkyl) ammonium, preferably tri (C 1 - to C 6 -alkyl) -methylammonium salts , Suitable counterions are sulfates, hydrogen sulfates, alkyl sulfates, aryl sulfates, halides, phosphates, carbonates, alkyl phosphates, alkyl carbonates, nitrate, alcoholates, tetrafluoroborate, hexafluorophosphate or perchlorate. Furthermore, the acids derived from the abovementioned anions are suitable as conductive salts.
Very particular preference is given to methyltributylammonium methylsulfates (MTBS), methyltriethylammonium methylsulfate (MTES), methyltripropylmethylammonium methylsulfates, or tetrabutylammonium, tetrafluoroborate (TBABF).

Beispiele:Examples: Beispiel 1: Anodische Oxidation von 4-Methylguajacol und substituierten Benzolen an einer BDD-Anode mit HexafluorisopropanolExample 1: Anodic oxidation of 4-methyl guaiacol and substituted benzenes at a BDD anode with hexafluoroisopropanol

Figure imgb0005
Figure imgb0005

In einer Elektrolysezelle, die über einen Flansch an eine BDD-beschichtete Siliziumplatte angebracht und als Anode geschaltet ist, wird der Elektrolyt bestehend aus substituiertem Benzol und 4-Methylguajacol im Stoffmengenverhältnis 10:1 gemäß Tabelle 1, 0,68 g Methyltriethylammoniummethylsulfat (MTES) und 30 mL Hexafluorisopropanol vorgelegt. Dabei ist die Anodenoberfläche vollständig mit Elektrolyt bedeckt. Als Kathode wird ein Nickelnetz verwendet, das in einer Distanz von 1 cm zur BDD-Anode in den Elektrolyten getaucht wird. Die Zelle wird in einem Sandbad temperiert (50°C). Die Durchführung der Elektrolyse erfolgt unter galvanostatischer Kontrolle und einer Stromdichte von 4,7 mA/cm2. Die Umsetzung wird nach Erreichen des eingestellten Ladungslimits (1 F pro mol 4-Methylguajacol) abgebrochen. Das erkaltete Reaktionsgemisch wird mit ca. 20 mL Toluol in einen Kolben überführt, woraus am Rotationsverdampfer Toluol und das verwendete fluorierte Lösungsmittel nahezu vollständig entfernt werden. Überschüssige Edukte können mittels Kurzwegdestillation bei Unterdruck zurückgewonnen werden. Durch säulenchromatographische Aufreinigung des Destillationsrückstands an Kieselgel 60 und anschließendem Waschen mit wenig kaltem n-Heptan kann das Produkt als farbloser, kristalliner Feststoff isoliert werden.In an electrolysis cell attached via a flange to a BDD-coated silicon plate and connected as an anode, the electrolyte consisting of substituted benzene and 4-methyl guaiacol in a molar ratio of 10: 1 according to Table 1, 0.68 g Methyltriethylammoniummethylsulfat (MTES) and 30 mL hexafluoroisopropanol presented. The anode surface is completely covered with electrolyte. The cathode used is a nickel mesh which is immersed in the electrolyte at a distance of 1 cm from the BDD anode. The cell is heated in a sand bath (50 ° C). The electrolysis is carried out under galvanostatic control and a current density of 4.7 mA / cm 2 . The reaction is stopped after reaching the set charge limit (1 F per mole of 4-methylguajacol). The cooled reaction mixture is transferred with about 20 mL of toluene in a flask from which toluene and the fluorinated solvent used are almost completely removed on a rotary evaporator. Excess starting materials can be recovered by short path distillation at reduced pressure. By column chromatographic purification of the distillation residue on silica gel 60 and subsequent washing with a little cold n-heptane, the product can be isolated as a colorless, crystalline solid.

Analytische Daten der KreuzkupplungsprodukteAnalytical data of the cross-coupling products 2-Hydroxy-2',3-dimethoxy-5,5'-dimethylbiphenyl:2-hydroxy-2 ', 3-dimethoxy-5,5'-dimethylbiphenyl:

H NMR (400 MHz, CDCl3) δ = 7.16 - 7.11 (m, 2H), 6.91 (d, J=8.3, 1 H), 6.72 (d, J=1.7, 1 H), 6.68 (d, J=1.8, 1H), 5.89 (s, 1 H), 3.91 (s, 4H), 3.82 (s, 4H), 2.33 (s, 8H); 13C NMR (101 MHz, CDCl3) δ = 154.14, 147.34, 140.90, 132.40, 130.42, 129.29, 129.16, 126.80, 125.58, 123.47, 111.40, 111.38, 56.15, 55.99, 49.43, 21.12, 20.46.H NMR (400 MHz, CDCl 3) δ = 7:16 to 7:11 (m, 2H), 6.91 (d, J = 8.3, 1 H), 6.72 (d, J = 1.7, 1 H), 6.68 (d, J = 1.8, 1H), 5.89 (s, 1H), 3.91 (s, 4H), 3.82 (s, 4H), 2.33 (s, 8H); 13 C NMR (101 MHz, CDCl3) δ = 154.14, 147.34, 140.90, 132.40, 130.42, 129.29, 129.16, 126.80, 125.58, 123.47, 111.40, 111.38, 56.15, 55.99, 49.43, 12.21, 20:46.

2-Hydroxy-2',3,5`-trimethoxy-5-methylbiphenyl:2-hydroxy-2 ', 3,5`-trimethoxy-5-methylbiphenyl:

1H NMR (400 MHz, CDCl3) δ = 6.89 - 6.79 (m, 3H), 6.65 (d, J=1.7, 1 H), 6.62 (d, J=1.6, 1 H), 5.90 (s, 1 H), 3.83 (s, 3H), 3.72 (s, 6H), 2.25 (s, 3H); 13C NMR (101 MHz, CDCl3) δ = 153.95, 150.45, 147.44, 140.90, 129.27, 128.12, 125.36, 123.34, 117.25, 113.89, 112.88, 111.54, 56.81, 56.00, 55.74, 21.13. 1 H NMR (400 MHz, CDCl 3) δ = 6.89 - 6.79 (m, 3H), 6.65 (d, J = 1.7, 1 H), 6.62 (d, J = 1.6, 1 H), 5.90 (s, 1 H), 3.83 (s, 3H), 3.72 (s, 6H), 2.25 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ = 153.95, 150.45, 147.44, 140.90, 129.27, 128.12, 125.36, 123.34, 117.25, 113.89, 112.88, 111.54, 56.81, 56.00, 55.74, 21:13.

2-Hydroxy-3,4'-dimethoxy-3',5-dimethylbiphenyl:2-hydroxy-3,4'-dimethoxy-3 ', 5-dimethylbiphenyl:

1H NMR (500 MHz, CDCl3) δ = 7.43 (dd, J=2.3, 8.4, 1H), 7.39 (d, J=2.0, 1 H), 6.91 (d, J=8.4, 1 H), 6.77 (d, J=1.8, 1 H), 6.68 (d, J=1.7, 1 H), 5.67 (s, 1 H), 3.92 (s, 4H), 3.88 (s, 4H), 2.35 (s, 4H), 2.29 (s, 4H); 13C NMR (126 MHz, CDCl3) δ = 156.95, 146.54, 140.33, 131.41, 129.75, 128.88, 127.48, 127.20, 126.29, 122.73, 110.17, 109.69, 56.08, 55.32, 21.10, 16.31. 1 H NMR (500 MHz, CDCl 3) δ = 7.43 (dd, J = 2.3, 8.4, 1H), 7:39 (d, J = 2.0, 1 H), 6.91 (d, J = 8.4, 1 H), 6.77 (d, J = 1.8, 1H), 6.68 (d, J = 1.7, 1H), 5.67 (s, 1H), 3.92 (s, 4H), 3.88 (s, 4H), 2.35 (s, 4H ), 2.29 (s, 4H); 13 C NMR (126 MHz, CDCl3) δ = 156.95, 146.54, 140.33, 131.41, 129.75, 128.88, 127.48, 127.20, 126.29, 122.73, 110.17, 109.69, 56.08, 55.32, 10.21, 16:31.

2-Hydroxy-2',3,4',6'-tetramethoxy-5-methylbiphenyl:2-hydroxy-2 ', 3,4', 6'-tetramethoxy-5-methylbiphenyl:

1H NMR (300 MHz, CDCl3) δ = 6.68 (d, J=1.8, 1 H), 6.60 (d, J=1.9, 1 H), 6.25 (s, 2H), 5.37 (s, 1 H), 3.89 (s, 3H), 3.86 (s, 3H), 3.75 (s, 6H), 2.32 (s, 3H); 13C NMR (75 MHz, CDCl3) δ = 161.01, 158.70, 146.61, 141.24, 128.29, 124.62, 120.40, 111.02, 107.48, 91.16, 56.06, 55.76, 55.32, 21.22; HRMS: m/z für C17H20O5 berechnet: 304.1311, gefunden: 304.1307; MS (EI): m/z (%): 304.1 (100), 289.1 (8), 273.1 (32), 258.1 (25), 229.1 (8), 181.1 (8), 168.1 (26), 151.0 (7), 139.0 (17), 122.0 (15), 97.0 (6), 83.0 (7), 71.0 (7), 57.0 (12). 1 H NMR (300 MHz, CDCl 3) δ = 6.68 (d, J = 1.8, 1 H), 6.60 (d, J = 1.9, 1 H), 6.25 (s, 2H), 5:37 (s, 1 H) , 3.89 (s, 3H), 3.86 (s, 3H), 3.75 (s, 6H), 2.32 (s, 3H); 13 C NMR (75 MHz, CDCl3) δ = 161.01, 158.70, 146.61, 141.24, 128.29, 124.62, 120.40, 111.02, 107.48, 91.16, 56.06, 55.76, 55.32, 21.22; HRMS: m / z calculated for C 17 H 20 O 5 : 304.1311, found: 304.1307; MS (EI): m / z (%): 304.1 (100), 289.1 (8), 273.1 (32), 258.1 (25), 229.1 (8), 181.1 (8), 168.1 (26), 151.0 (7 ), 139.0 (17), 122.0 (15), 97.0 (6), 83.0 (7), 71.0 (7), 57.0 (12).

2-Hydroxy-2',3,4',5'-tetramethoxy-5-methylbiphenyl:2-hydroxy-2 ', 3,4', 5'-tetramethoxy-5-methylbiphenyl:

1H NMR (300 MHz, CDCl3) δ = 6.77 (s, 1 H), 6.63 (d, J=1.7, 1 H), 6.61 (d, J=1.8, 1 H), 6.57 (s, 1 H), 5.86 (s, 1 H), 3.85 (s, 4H), 3.82 (s, 4H), 3.77 (s, 4H), 3.72 (s, 4H), 2.25 (s, 4H); 1H NMR (300 MHz, CDCl3) δ = 6.77, 6.62, 6.61, 6.61, 6.57, 5.86, 3.85, 3.82, 3.77, 3.72,2.25. 1 H NMR (300 MHz, CDCl 3) δ = 6.77 (s, 1 H), 6.63 (d, J = 1.7, 1 H), 6.61 (d, J = 1.8, 1 H), 6:57 (s, 1 H ), 5.86 (s, 1H), 3.85 (s, 4H), 3.82 (s, 4H), 3.77 (s, 4H), 3.72 (s, 4H), 2.25 (s, 4H); 1 H NMR (300 MHz, CDCl 3) δ = 6.77, 6.62, 6.61, 6.61, 6:57, 5.86, 3.85, 3.82, 3.77, 3.72,2.25.

2-Hydroxy-2',3,3',4'-tetramethoxy-5,6'-dimethylbiphenyl2-hydroxy-2 ', 3,3', 4'-tetramethoxy-5,6'-dimethylbiphenyl

1H NMR (400 MHz, CDCl3) δ = 6.70 (d, J=1.6, 1 H), 6.62 (s, 1 H), 6.52 (d, J=1.7, 1 H), 5.44 (s, 1 H), 3.91 (s, 3H), 3.89 (s, 3H), 3.88 (s, 3H), 3.68 (s, 3H), 2.32 (s, 3H), 2.06 (s, 3H); 13C NMR (101 MHz, CDCl3) δ = 152.49, 151.62, 146.35, 140.72, 140.05, 132.69, 128.67, 123.89, 123.63, 123.28, 110.65, 108.92, 60.98, 60.86, 55.85, 55.81, 21.15, 20.00. 1 H NMR (400 MHz, CDCl 3) δ = 6.70 (d, J = 1.6, 1 H), 6.62 (s, 1 H), 6:52 (d, J = 1.7, 1 H), 5:44 (s, 1 H ), 3.91 (s, 3H), 3.89 (s, 3H), 3.88 (s, 3H), 3.68 (s, 3H), 2.32 (s, 3H), 2.36 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ = 152.49, 151.62, 146.35, 140.72, 140.05, 132.69, 128.67, 123.89, 123.63, 123.28, 110.65, 108.92, 60.98, 60.86, 55.85, 55.81, 21:15, 20:00.

5'-Brom-2-hydroxy-2',3,4'-trimethoxy-5-methylbiphenyl:5'-Bromo-2-hydroxy-2 ', 3,4'-trimethoxy-5-methylbiphenyl:

1H NMR (300 MHz, CDCl3) δ = 7.46 (s, 1 H), 6.70 (d, J=1.7, 2H), 6.64 (d, J=1.8, 2H), 6.59 (s, 2H), 5.28 (s, 1 H), 3.95 (s, 5H), 3.90 (s, 5H), 3.84 (s, 5H), 2.32 (s, 5H); 13C NMR (75 MHz, CDCl3) δ = 156.83, 156.13, 146.84, 140.90, 135.15, 129.03, 123.49, 123.46, 120.78, 111.23, 102.30, 97.08, 56.37, 56.31, 55.97, 21.07. Tabelle 1: Umsetzung von 4-Methylguajacol mit substituierten Benzolen an BDD unter Verwendung von HFIP. Elektrolyt T [°C] Umax [V] F [1/mol] j [mA/cm2] Ab [%] (Nr.) SA [%] 3,05 g 4-Methylanisol / 50 6 1,0 4,7 5 (3) 7 0,36 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 6,91 g 4-Methoxyanisol / 50 8 1,0 4,7 2 (4) 4 0,69 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 6,11 g 2-Methylanisol / 50 7 1,0 4,7 4 (5) 9 0,69 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 8,43 g 1,3,5-Trimethoxybenzen / 50 5 1,0 4,7 12 (2) 23 0,69 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 8,43 g 1,2,4-Trimethoxybenzen 50 10 1,0 4,7 17 (6) 34 0,69 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 4,74 g 1,2,3-Trimethoxy-5-methylbenzen / 50 6 1,0 4,7 11 (8) 23 0,36 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP 10,85 g 1-Brom-2,4-dimethoxybenzen / 50 7 1,0 4,7 18 (7) 37 0,69 g 4-Methylguajacol / 0,68 g MTES / 30 mL HFIP b Bezogen auf eingesetztes 4-Methylguajacol.
A: Ausbeute
SA: Stromausbeute 1 H NMR (300 MHz, CDCl 3) δ = 7.46 (s, 1 H), 6.70 (d, J = 1.7, 2H), 6.64 (d, J = 1.8, 2H), 6:59 (s, 2H), 5.28 (s, 1H), 3.95 (s, 5H), 3.90 (s, 5H), 3.84 (s, 5H), 2.32 (s, 5H); 13 C NMR (75 MHz, CDCl 3) δ = 156.83, 156.13, 146.84, 140.90, 135.15, 129.03, 123.49, 123.46, 120.78, 111.23, 102.30, 97.08, 56.37, 56.31, 55.97, 21.07. Table 1: Reaction of 4-methyl guaiacol with substituted benzenes on BDD using HFIP. electrolyte T [° C] U max [V] F [1 / mol] j [mA / cm 2 ] A b [%] (No.) SA [%] 3.05 g of 4-methylanisole 50 6 1.0 4.7 5 (3) 7 0.36 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 6.91 g of 4-methoxyanisole / 50 8th 1.0 4.7 2 (4) 4 0.69 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 6.11 g of 2-methylanisole 50 7 1.0 4.7 4 (5) 9 0.69 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 8.43 g of 1,3,5-trimethoxybenzene / 50 5 1.0 4.7 12 (2) 23 0.69 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 8.43 g of 1,2,4-trimethoxybenzene 50 10 1.0 4.7 17 (6) 34 0.69 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 4.74 g of 1,2,3-trimethoxy-5-methylbenzene / 50 6 1.0 4.7 11 (8) 23 0.36 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP 10.85 g of 1-bromo-2,4-dimethoxybenzene / 50 7 1.0 4.7 18 (7) 37 0.69 g 4-methyl guaiacol / 0.68 g MTES / 30 mL HFIP b Based on 4-Methylguajacol used.
A: Yield
SA: current efficiency

Claims (15)

  1. A process for preparing biaryls, wherein substituted aryl alcohols in which the OH group is bound directly to the aromatic, are anodically dehydrodimerized with arenes in the presence of partially fluorinated and/or perfluorinated mediators and at least one supporting electrolyte to form the cross-coupling products.
  2. The process according to claim 1, wherein the substituted aryl alcohols used can be monocyclic or bicyclic.
  3. The process according to either claim 1 or 2, wherein the substituted arenes used can be monocyclic or bicyclic.
  4. The process according to any of claims 1 to 3, wherein the dimerization takes place in the ortho position relative to the alcohol group of the aryl alcohol.
  5. The process according to any of claims 1 to 4, wherein the mediators used are partially fluorinated and/or perfluorinated alcohols and/or acids.
  6. The process according to any of claims 1 to 5, wherein 1,1,1,3,3,3-hexafluoroisopropanol and/or trifluoroacetic acid are used as mediators.
  7. The process according to any of claims 1 to 6, wherein salts selected from the group consisting of alkali metal, alkaline earth metal, tetra (C1-C6-alkyl)ammonium salts are used as supporting electrolytes.
  8. The process according to any of claims 1 to 7, wherein the counterions of the supporting electrolytes are selected from the group consisting of sulfate, hydrogensulfate, alkylsulfates, arylsulfates, halides, phosphates, carbonates, alkylphosphates, alkylcarbonates, nitrate, alkoxides, tetrafluoroborate, hexafluorophosphate and perchlorate.
  9. The process according to any of claims 1 to 8, wherein no further solvent is used for the electrolysis.
  10. The process according to any of claims 1 to 9, wherein a diamond anode and a nickel cathode are used.
  11. The process according to any of claims 1 to 10, wherein the diamond electrode is a boron-doped diamond electrode.
  12. The process according to any of claims 1 to 11, wherein a flow cell is used for the electrolysis.
  13. The process according to any of claims 1 to 12, wherein current densities of from 1 to 1000 mA/cm2 are used.
  14. The process according to any of claims 1 to 13, wherein the electrolysis is carried out at temperatures in the range from -20 to 100°C and atmospheric pressure.
  15. The process according to any of claims 1 to 14, wherein 4-methylguaiacol is used as aryl alcohol.
EP10724436.0A 2009-06-05 2010-06-01 Method for anodic cross-dehydrodimerization of arenes Not-in-force EP2438214B1 (en)

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CN107089895B (en) * 2017-05-05 2020-02-18 乐山师范学院 Method for preparing coupled aromatic hydrocarbon by ionizing discharge coupling of halogenated aromatic hydrocarbon
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