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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
• • 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
  • C25B3/01—Products
• • 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
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds
• • 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
  • C25B3/01—Products
  • C25B3/09—Nitrogen containing compounds
• • 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
  • C25B3/01—Products
  • C25B3/11—Halogen containing compounds

Definitions

• the invention relates to a process for the preparation of unsymmetrical biaryl alcohols, which is carried out by anodic dehydrodimerization of substituted ortho-alkoxy aryl alcohols in the presence of partially and / or perfluorinated mediators and a conductive salt.
• Biaryls are known as such and are used industrially. Compounds such as 3,3 ', 5,5'-tetramethylbiphenyl-2,2'-diol are of great interest as backbones for ligands.
• One possible approach to this class of compounds is the (electrochemical) oxidative dimerization of phenols. However, this is often unselective.
• Diamond electrodes can be realized using conductive salts and fluorinated mediators as described by A. Kirste, M. Nieger, IM Malkowsky, F. Stecker, A. Fischer, SR Waldvogel in Chem. Eur. J. 2009, 15, 2273 and described in WO-A 2006/077204. A process for preparing the unsymmetrical biaryl alcohols is not described.
• the object of the present invention is to provide a process which enables the selective and efficient anodic dehydrodimerization of substituted ortho-alkoxyaryl alcohols to unsymmetrical biaryl alcohols.
• the process according to the invention is advantageous if the OH group of the ortho-alkoxyaryl alcohols used is bound directly to the aromatic compound.
• the process according to the invention is advantageous if the substituted orthoalkoxyaryl alcohols used are identical.
• the process according to the invention is advantageous if the substituted orthoalkoxyaryl alcohols used are mononuclear or dinuclear.
• the process according to the invention is advantageous if the dimerization takes place in the ortho position to the one and in the meta position relative to the other alcohol group of the ortho-alkoxyaryl alcohols.
• 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, in which the conductive salts used are those which are selected from the group of alkali metal, 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 method according to the invention is advantageous if a nickel cathode is used.
• 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 ortho-alkoxyaryl alcohol.
• the inventive method when the anode is selected from the group of graphite and boron doped diamond electrode.
• ortho-alkoxyaryl alcohol is understood as meaning aromatic alcohols which are substituted ortho-substituted by an alkoxy group and in which the hydroxyl group is bonded directly to the aromatic nucleus.
• the aromatic which is based on the ortho-Alkoxyarylalkohol, may be mononuclear or polynuclear.
• the aromatic is preferably mononuclear (phenol derivatives) according to formula I or binuclear (naphthol derivatives) according to formula II, particular preference is given to mononuclear aromatics.
• the alkoxy group (OAlk) of the ortho-alkoxyaryl alcohols which are used in the process according to the invention are C.sub.1- to C.sub.10-alkoxy group, preferably methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butyl Butoxy groups, more preferably, methoxy, ethoxy, n-propoxy, most preferably methoxy groups.
• the ortho-Alkoxyarylalkohle can carry further substituents R1 to R6.
• R 1 to R 6 are independently selected from the group of C 1 -C 10 -alkyl groups, halogens, C 1 -C 10 -alkoxy groups, alkylene or arylene radicals interrupted by oxygen or sulfur, C 1 -C 10 -alkoxycarboxylic, nitrile, nitro- and Ci-Cio-Alkoxycarbamoyl phenomenon.
• the substituents are preferably selected from the group of methyl, ethyl, n-propyl, isopropyl, n-butyl, trifluoromethyl, fluorine, chlorine, bromine, iodine, methoxy, ethoxy, methylene, ethylene, propylene, isopropylene, benzylidene, nitrile, nitro ,
• the substituents are particularly preferably selected from the group of methyl, methoxy, methylene, ethylene, trifluoromethyl, fluorine and bromine.
• the unsymmetrical biaryl alcohol is produced electrochemically, with the corresponding ortho-alkoxyaryl alcohol being anodically oxidized.
• the process according to the invention is referred to below as electrodimerization. It has surprisingly been found that the unsymmetrical biaryl alcohols are produced selectively and in high yield by the process according to the invention using mediators. Furthermore, it has been found that by the These methods can be applied to undivided cell structures as well as solvent-free methods.
• the electrolyte solution is worked up by general separation methods.
• 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.
• 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. 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 method according to the invention, very particular preference is given to a support of niobium, if a diamond electrode is used.
• the anode is selected from the group of graphite and diamond electrode, wherein the diamond electrode may also be doped with other elements. 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.
• the cathode material is selected from the group of iron, steel, stainless steel, nickel, precious metals such as platinum, graphite, carbon materials and diamantelekt- roden.
• the cathode is selected from the group of nickel, steel and stainless steel.
• the cathode is particularly preferably made of nickel.
• Preferred electrode material combinations for anode and cathode are a combination of graphite anode and nickel cathode and the combination of boron-doped diamond anode and nickel cathode.
• 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 Plattenstapelzellen, in which the electrodes are designed as plates and are arranged plane-parallel as in Ullmann's Encyclopedia of Industrial Chemistry, 1999 electronic release, Sixth Edition, Wiley-VCH-Weinheim, (doi: 10 1002 / 14356007.a09_183.pub2) and in Electrochemistry, Chapter 3.5. special cell designs as well as Chapter 5, Organic Electrochemistry, Subchapter 5.4.3.2 Cell Design.
• 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 from -20 to 100 ° C., preferably from 10 to 60 ° C.
• the reaction is generally carried out under atmospheric pressure. Higher pressures are preferably used when operating at higher temperatures to avoid boiling of the co-solvents or mediators.
• the ortho-alkoxyaryl alcohol compound 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 ortho-alkoxyaryl alcohol compound itself serves as 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 fully halogenated, such as 1, 1, 1, 3,3,3-hexafluoroisopropanol (HFIP) or trifluoroacetic acid (TFA).
• HFIP 1, 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 -C 6 -alkyl) ammonium, preferably tri (C 1 -C 6 -alkyl) methylammonium salts.
• Suitable counterions are sulfates, hydrogen sulfates, alkyl sulfates, aryl sulfates, halides, phosphates, carbonates, alkyl phosphates, alkyl carbonates, nitrates, alkoxides, 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
• the electrolyte consisting of 2.76 g of 4-methylguajacol, 0.68 g of methyltriethylammonium methyl sulfate (MTES) and 30 ml of hexafluoroisopropanol (HFIP) according to Table 1 submitted.
• MTES methyltriethylammonium methyl sulfate
• HFIP hexafluoroisopropanol
• the electrolysis is carried out under galvanostatic control and at current densities between 2.8-9.5 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 into a flask, from which toluene and the fluorinated solvent used are almost completely removed on a rotary evaporator. Excess phenol can be recovered by short path distillation at 1, 0 * 10 1 mbar and 125 0 C.

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• 2010
  • 2010-06-01 EP EP10724438A patent/EP2438215A1/de not_active Withdrawn
  • 2010-06-01 US US13/375,100 patent/US8747645B2/en not_active Expired - Fee Related
  • 2010-06-01 WO PCT/EP2010/057619 patent/WO2010139687A1/de not_active Ceased
  • 2010-06-01 CN CN2010800245846A patent/CN102459707A/zh active Pending
  • 2010-06-01 JP JP2012513596A patent/JP2012528825A/ja active Pending

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