WO2023161206A1 - Procede de production de benzoquinones - Google Patents

Procede de production de benzoquinones Download PDF

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WO2023161206A1
WO2023161206A1 PCT/EP2023/054261 EP2023054261W WO2023161206A1 WO 2023161206 A1 WO2023161206 A1 WO 2023161206A1 EP 2023054261 W EP2023054261 W EP 2023054261W WO 2023161206 A1 WO2023161206 A1 WO 2023161206A1
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vol
group
ring
fused
electrochemical oxidation
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Fiona SPRANG
Siegfried R. Waldvogel
Jan Schuetz
Werner Bonrath
Roman GOY
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Dsm Ip Assets B.V.
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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
    • C25B3/01—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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/042—Electrodes formed of a single material
    • C25B11/043—Carbon, e.g. diamond or graphene
    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
    • 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
    • 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
    • C25B3/23—Oxidation
    • 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
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/13—Single electrolytic cells with circulation of an electrolyte
    • C25B9/15—Flow-through cells

Definitions

  • the present invention relates to a process for producing benzoquinones by electrochemical oxidation of phenols.
  • Benzoquinones represent a versatile class of compounds with manifold fields of applications. They are ubiquitous in nature and play crucial roles in biological redox processes, making them pivotal for life. Moreover, their unique redox properties often equip them with remarkable biochemical activity. This allowed them to gain attention as a privileged motif for pharmaceutical agents. Furthermore, they serve as multifunctional building blocks and intermediates in organic chemistry e.g., in the synthesis of food additives from the vitamin E and K.
  • Electric current is an excellent and sustainable oxidant for the phenol oxidation since it serves as a traceless oxidant.
  • Electrochemistry is now widely recognized as alternative “green” synthesis protocols. However, methods for the direct electrochemical oxidation of readily available phenols to benzoquinones are underdeveloped.
  • the present invention provides an electrochemical process for producing a benzoquinone compound of formula (I):
  • R' at each occurrence, is independently C1-C6 alkyl, aryl, C1-C6 alkoxy, cyano or halogen, optionally substituted with at least one substituent, or two adjacent R’, together with the atoms to which they are attached, form a fused C3-C8 cycloalkyl ring, a fused 5- or 6-membered heterocycloalkyl ring, a fused aryl ring, or a fused 5- or 6-membered heteroaryl ring, optionally substituted with at least one substituent; and the subscript n is 0, 1, 2, 3 or 4.
  • the process of the present invention is versatile in converting hydroquinone and a broad range of phenols such as 4-halophenols, 4-methoxyphenols and 4-methoxyanisoles into the benzoquinone compound of formula (I) in an attractive yield and selectivity without the need to modify the protocol.
  • the process of the present invention avoids cost-intensive catalysts, reagents and oxidants and does not provide reagent waste, so it is cost effective and environment friendly.
  • the term “C1-C6 alkyl”, employed alone or in combination with other terms refers to a saturated hydrocarbon group that may be straight-chain or branched, having 1 to 6 carbons.
  • the alkyl group contains from 1 to 5 carbon atoms or from 1 to 4 carbon atoms, or from 1 to 3 carbon atoms.
  • the alkyl moieties include, but are not limited to, chemical groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl.
  • Example of the alkoxy groups include methoxy, ethoxy, and propoxy (e.g., n-propoxy and iso-propoxy).
  • the alkyl group has from 1 to 3 carbon atoms.
  • the term “aryl”, “aryl ring” or “aryl group”, employed alone or in combination with other terms refers to a monocyclic or polycyclic (e.g., having 2, 3 or 4 fused rings) aromatic hydrocarbon, such as, but not limited to, phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, phenanthrenyl, and the like.
  • the aryl is C 6 -C 10 aryl.
  • the aryl group is a naphthalene ring or phenyl ring. In some embodiments, the aryl group is phenyl.
  • cycloalkyl moieties that have one or more aromatic rings fused (i.e., having a bond in common with) to the cycloalkyl ring, for example, benzo derivatives of cyclopentane, cyclopentene, cyclohexane, and the like.
  • a cycloalkyl group that includes a fused aromatic ring can be attached to the core or scaffold via any ring-forming atom, including a ring- forming atom of the fused aromatic group.
  • One or more ring-forming carbon atoms of a cycloalkyl group can be oxidized to form carbonyl linkages.
  • cycloalkyl is C3-C8 cycloalkyl, C 3 -C 7 cycloalkyl, or C 5 -C 6 cycloalkyl.
  • exemplary cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclohexenyl, cyclohexadienyl, cycloheptatrienyl, norbornyl, norpinyl, norcarnyl, and the like.
  • exemplary cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.
  • the term “heterocycloalkyl” or “heterocycloalkyl ring”, employed alone or in combination with other terms refers to non-aromatic heterocyclic ring system, which may optionally contain one or more unsaturation as part of the ring structure, and which has at least one heteroatom ring member independently selected from nitrogen, sulphur and oxygen.
  • the heterocycloalkyl group has 1, 2, 3, or 4 heteroatom ring members.
  • the heterocycloalkyl group has 1, 2, or 3 heteroatom ring members.
  • the heterocycloalkyl group has 1 or 2 heteroatom ring members. In some embodiments, the heterocycloalkyl group has 1 heteroatom ring member. When the heterocycloalkyl group contains more than one heteroatom in the ring, the heteroatoms may be the same or different.
  • Example ring- forming members include CH, CH2, C(O), N, NH, O, S, S(O), and S(O)2.
  • Heterocycloalkyl groups can include mono- or polycyclic (e.g., having 2, 3 or 4 fused rings) ring systems, including spiro systems.
  • heterocycloalkyl moieties that have one or more aromatic rings fused to (i.e., having a bond in common with) the non-aromatic ring, for example, 1,2,3,4-tetrahydro- quinoline, dihydrobenzofuran, and the like.
  • a heterocycloalkyl group including a fused aromatic ring can be attached to the core or scaffold via any ring-forming atom, including a ring-forming atom of the fused aromatic group.
  • the S or N ring-forming atoms can be optionally “oxidized” to include one or two oxo groups as valency permits (e.g., sulfonyl or sulfinyl or N-oxide).
  • One or more ring-forming carbon atoms of the heterocycloalkyl group can include an oxo moiety to form a ring-forming carbonyl.
  • a ring-forming nitrogen atom can be quaternized.
  • the heterocycloalkyl is 5- to 10-membered, 4- to 10-membered, 4- to 7-membered, 5- membered, or 6-membered.
  • heterocycloalkyl groups include 1,2,3,4-tetrahydro- quinolinyl, dihydrobenzofuranyl, azetidinyl, azepanyl, pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, dihydrofuranyl, tetrahydrofuranyl, 2-oxopyrrolidinyl, 3-oxomorpholinyl, 2-oxooxazolidinyl, and pyranyl.
  • heterocycloalkyl groups include 2,3-dihydro-1H- pyrrolyl; 2-oxo-2,3-dihydro-1H-pyrrolyl; 2,3-dihydro-oxazolyl; 2-oxo-2,3-dihydro-oxazolyl; 3,4- dihydro-2H-1,4-oxazinyl; 3-oxo-3,4-dihydro-2H-1,4-oxazinyl; or 2,3-dihydro-furanyl.
  • the heterocycloalkyl group is azetidinyl, piperidinyl, pyrrolidinyl, diazapanyl, or diazaspirononanyl.
  • the heterocycloalkyl group is 2,3-dihydro-1H-indolyl; 2,3-dihydro-1,3-benzoxazolyl; 3,4-dihydro-2H-pyrido[3,2-b][1,4]oxazinyl; 3,4-dihydro-2H-1,4- benzoxazinyl; or 2,3-dihydro-1-benzofuran.
  • heteroaryl or “heteroaryl ring”, employed alone or in combination with other terms, refers to a monocyclic or polycyclic (e.g., having 2, 3 or 4 fused rings) aromatic heterocylic moiety, having one or more heteroatom ring members selected from nitrogen, sulphur and oxygen.
  • the heteroaryl group has 1, 2, 3, or 4 heteroatom ring members.
  • the heteroaryl group has 1, 2, or 3 heteroatom ring members.
  • the heteroaryl group has 1 or 2 heteroatom ring members.
  • the heteroaryl group has 1 heteroatom ring member.
  • the heteroaryl group is 5- membered.
  • the heteroaryl group is 6-membered.
  • the heteroaryl group contains more than one heteroatom ring member, the heteroatoms may be the same or different.
  • the nitrogen atoms in the ring(s) of the heteroaryl group can be oxidized to form N-oxides.
  • heteroaryl groups include, but are not limited to, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, pyrrolyl, pyrazolyl, azolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, furanyl, thienyl, triazolyl, tetrazolyl, thiadiazolyl, quinolinyl, isoquinolinyl, indolyl, benzothienyl, benzofuranyl, benzisoxazolyl, imidazo[1,2-b]thiazolyl, purinyl, triazinyl, and the like.
  • the heteroaryl group is pyridyl, 1H-indazolyl, 1H-pyrrolo[2,3-b]pyridinyl, or 1H-benzo[d]imidazolyl.
  • a 5-membered heteroaryl is a heteroaryl group having five ring-forming atoms comprising wherein one or more of the ring-forming atoms are independently selected from nitrogen, sulphur and oxygen.
  • the 5-membered heteroaryl group has 1, 2, 3, or 4 heteroatom ring members.
  • the 5-membered heteroaryl group has 1, 2, or 3 heteroatom ring members.
  • the 5-membered heteroaryl group has 1 or 2 heteroatom ring members.
  • the 5-membered heteroaryl group has 1 heteroatom ring member.
  • Example ring-forming members include CH, N, NH, O, and S.
  • Examples of 5-membered heteroaryls are thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, pyrazolyl, isothiazolyl, isoxazolyl, 1,2,3-triazolyl, tetrazolyl, 1,2,3-thiadiazolyl, 1,2,3-oxadiazolyl, 1,2,4-triazolyl, 1,2,4-thiadiazolyl, 1,2,4-oxadiazolyl, 1,3,4-triazolyl, 1,3,4-thiadiazolyl, and 1,3,4-oxadiazolyl.
  • a 6-membered heteroaryl is a heteroaryl group having six ring-forming atoms wherein one or more of the ring-forming atoms are independently selected from nitrogen, sulphur and oxygen.
  • the 6-membered heteroaryl group has 1, 2, or 3 heteroatom ring members.
  • the 6-membered heteroaryl group has 1 or 2 heteroatom ring members.
  • the 6-membered heteroaryl group has 1 heteroatom ring member.
  • Example ring- forming members include CH, N, NH, O, and S.
  • Example six-membered ring heteroaryls are pyridyl, pyrazinyl, pyrimidinyl, triazinyl, and pyridazinyl.
  • halo refers to a halogen atom selected from F, Cl, I or Br. In some embodiments, “halo” refers to a halogen atom selected from F, Cl, or Br. In some embodiments, the halo is I.
  • substituted or substituted refers to C1-C6 alkyl, aryl, C1-C6 alkoxyl, OH, halo, -NH2, -NO2, carbaldehyde, carboxylic acid, esters, sulfonic acid, cyano and/or isocyano.
  • the present invention provides a process for producing a compound of formula (I), comprising electrochemical oxidation of a compound of formula (II) to obtain the compound of formula (I):
  • R is H or C1-C6 alkyl, optionally substituted with at least one substituent
  • X is H, OH, halogen or C1-C6 alkoxy, optionally substituted with at least one substituent
  • R' at each occurrence, is independently C1-C6 alkyl, aryl, C1-C6 alkoxy, cyano or halogen, optionally substituted with at least one substituent, or two adjacent R’, together with the atoms to which they are attached, form a fused C3-C8 cycloalkyl ring, a fused 5- or 6-membered heterocycloalkyl ring, a fused aryl ring or a fused 5- or 6-membered heteroaryl ring, optionally substituted with at least one substituent; and the subscript
  • R is H, methyl or ethyl; more preferably, R is H or methyl; and the most preferably, R is H.
  • X is H, OH, halogen or methoxy; more preferably X is H, OH, Cl, Br, I or methoxy; and the most preferably X is H, OH or methoxy.
  • R’, at each occurrence, is independently C1-C6 alkyl, aryl, C1-C6 alkoxy, cyano or halogen. More preferably, R’, at each occurrence, is independently methyl, ethyl, propyl, butyl, methoxy, phenyl, cyano and halogen.
  • two adjacent R’ together with the atoms to which they are attached, form a fused C3-C8 cycloalkyl ring such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl; a fused 5- or 6- membered heterocycloalkyl ring such as azetidinyl, piperidinyl and pyrrolidinyl; a fused aryl ring such as phenyl, 1-naphthyl, 2-naphthyl, anthracenyl and phenanthrenyl; or a fused 5- or 6-membered heteroaryl ring such as pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, pyrrolyl, pyrazolyl, azolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imid
  • two adjacent R’ together with the atoms to which they are attached, form a fused C3-C8 cycloalkyl ring such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl; or a fused aryl ring such as phenyl, 1-naphthyl, 2-naphthyl, anthracenyl and phenanthrenyl.
  • the compound of formula (I) is any one of the following compounds:
  • the anode used for the electrochemical oxidation is made of the material selected from the group consisting of dimensional stable anodes (DSA), boron-doped diamond (BDD), and carbon-based materials such as graphite and glassy carbon.
  • the anode used in the present invention is a dimensional stable anode.
  • the dimensional stable anode may contain, on a substrate such as titanium or tantalum, a coating of at least two metal oxides selected from the group consisting of RuO2, IrO2, PtO2, TiO2 and TaOx (x is 1 or 2), preferably selected from the group consisting of RuO2, IrO2 and TiO2, more preferably the dimensional stable anode contains a coating of RuO2 and IrO2.
  • the material of the cathode is not critical and can be any suitable materials known in the art, such as steel, glassy carbon and platinum.
  • the form and size (which also means the surface area) of the electrodes in the present invention are also not critical.
  • the cell may be in any size and in any form, such as in a form of a wire, a rod, a cell, a mesh, a grid, a sponge, or any other design suitable for the electrochemical reactor (cell) used in the process of the present invention.
  • the cell also known as voltaic cells or galvanic cells, used in the process according to the present invention can be any one of those known by a person skilled in the art. Usually and preferably it is a two-compartments electrochemical flow-cell.
  • the electrochemical oxidation is carried out in a medium which may be water or a non-aqueous solvent or mixture thereof.
  • non-aqueous solvent examples include but are not limited to alkylene carbonates (such as propylene carbonate and butylene carbonate), polyethylene glycol, N-methyl-2-pyrrolidone, N-butylpyrrolidone (NBP), alcohols (such as methanol, ethanol and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP)), acetone, acetic acid, sulpholane, dimethylsulphoxide (DMSO), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (MeTHF), dimethylformamide (DMF), hexa-methylphosphoramide, acetonitrile (MeCN), dichloromethane (DCM), dimethoxyethane (DME), pyridine and hexafluoro-2-propanol, and mixture thereof.
  • alkylene carbonates such as propylene carbonate and butylene carbonate
  • polyethylene glycol N-methyl-2-pyr
  • the medium used in the present invention is a non-aqueous solvent or mixture thereof. More preferably, the medium used in the present invention is acetic acid, MeCN, DME or HFIP, or mixture thereof. The more preferably, the medium is MeCN.
  • the “non-aqueous solvent” means that no water is included in the solvent on purpose. However, it might be possible that the solvent comprises traces of water (usually below 5 wt%, based on the total weight of the solvent).
  • the medium essentially comprises at least one supporting electrolyte, which may be added to in the form of a salt and/or in form of an acid. Any commonly known and commonly used supporting electrolyte can be used.
  • Suitable supporting electrolytes include but are not limited to HCl, H 2 SO 4 , Na 2 SO 4 , NaCl, NaHSO 4 , alkyl- or arylsulfonic acids (such as methanesulfonic acid and p-toluenesulfonic acid), phosphoric acid, phosphates, and tetraalkylammonium salts (such as tetrabutylammonium acetate (NBu4OAc), tetrabutylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate).
  • alkyl- or arylsulfonic acids such as methanesulfonic acid and p-toluenesulfonic acid
  • phosphoric acid such as methanesulfonic acid and p-toluenesulfonic acid
  • phosphates phosphoric acid
  • phosphates phosphates
  • the supporting electrolyte used in the present invention is an acid such as HCl, H2SO4, phosphoric acid or mixture thereof. More preferably, the supporting electrolyte used in the present invention is H2SO4.
  • the concentration of the supporting electrolyte in the medium is up to 5 mol/L (M), preferably from 0.01 M to 4 M, more preferably from 0.05 M to 3 M, the most preferably from 0.5 M to 1.5 M.
  • an oxygen source is added into the reaction of the present invention. Any material which can donate oxygen in the electro-oxidation environment of the present invention is suitable.
  • the oxygen source includes but are not limited to water, methanol, acetic acid, tert- butanol, isopropanol, ethanol, hydrogen peroxide, tert-butyl hydroperoxide and oxygen.
  • the oxygen source is selected from the group consisting of water, methanol, acetic acid, tert-butanol, isopropanol and ethanol. More preferably, the oxygen source is water and/or methanol. The most preferably, the oxygen source is water and methanol.
  • the oxygen source is included in the medium in an amount of from 0.1 vol% to 20 vol%, preferably from 0.5 vol% to 15.0 vol%, more preferably from 1.0 vol% to 10 vol%, such as 1 vol%, 2 vol%, 3 vol%, 3.5 vol%, 4 vol%, 4.5 vol%, 5 vol%, 5.5 vol%, 6 vol%, 6.5 vol%, 7 vol%, 7.5 vol%, 8 vol%, 8.5 vol%, 9 vol%, 9.5 vol% and 10 vol%.
  • the oxygen source is water, and it is included in the medium in an amount of from 1.0 vol% to 10 vol%, preferably from 2.0 vol% to 7.5 vol%, more preferably from 4.0 vol% to 6.0 vol% such as 4.0 vol%, 4.5 vol% and 5.0 vol%.
  • the oxygen source is methanol, and it is included in the medium in an amount of from 0.1 vol% to 10 vol%, preferably from 0.5 vol% to 7.5 vol%, more preferably from 1.0 vol% to 6.0 vol% such as 1.0 vol%, 2.0 vol%, 3.0 vol%, 4.0 vol% and 5.0 vol%.
  • the oxygen source is water and methanol
  • water is included in the medium in an amount of from 1.0 vol% to 10 vol%, preferably from 2.0 vol% to 7.5 vol%, more preferably from 4.0 vol% to 6.0 vol% such as 4.0 vol%, 4.5 vol% and 5.0 vol%
  • methanol is included in the medium in an amount of from 0.1 vol% to 10 vol%, preferably from 0.5 vol% to 7.5 vol%, more preferably from 1.0 vol% to 6.0 vol% such as 1.0 vol%, 2.0 vol%, 3.0 vol%, 4.0 vol% and 5.0 vol%.
  • electric current is used oxidant in the process of the present application.
  • the compound of formula (II) may be added into the medium in an amount of from 10 mmol/L (mM) to 100 mM, preferably from 20 mM to 75 mM, more preferably from 25 mM to 50 mM.
  • the transferred charge for the electrochemical oxidation may be 10 Faraday (F) or less.
  • F Faraday
  • a suitable range is 1-15 F, preferred is 2-10 F; more preferred is 3-9 F; most preferred is 4-8 F such as 4, 5, 6, 7 and 8 F.
  • the current density used in the electrochemical oxidation may be from 0.5 mA/cm 2 to 100 mA/cm 2 , preferably from 1 mA/cm 2 to 50 mA/cm 2 , preferably from 2 mA/cm 2 to 20 mA/cm 2 .
  • the electrochemical oxidation according to the present invention can be carried out in galvanostatic or potentiostatic mode. Depending on the cell, the electrochemical oxidation according to the present invention can be carried out batch-wise, semi-batch, or in a continuous way, preferably in a continuous way.
  • the electrochemical oxidation according to the present invention is carried out at a temperature range of from 10 °C to 75 °C, preferably from 15 °C to 60 °C, more preferably at ambient temperature.
  • the electrochemical oxidation according to the present invention is usually carried out at ambient pressure.
  • the obtained compound of formula (I) according to the present invention can be isolated from the reaction medium using commonly methods.
  • the process of the present invention can convert a broad range of phenols and analogues, especially hydroxyarenes and methoxyarenes, into the desired compound of formula (I) in an attractive yield without the need to modify the protocol.
  • the process uses electricity as oxidant which is safe and inexpensive, avoids cost-intensive catalysts and oxidants, and does not provide reagent waste, so it is cost effective and environment friendly.
  • the present invention is further illustrated by the following examples.
  • the electrodes were obtained from commercial suppliers: DSA electrodes (De Nora, Italy), boron- doped diamond (DIACHEM®, CONDIAS GmbH, Germany), platinum ( ⁇ gussa, Austria), graphite (Sigrafine® V2100, Bonn-Bad Godesberg, Germany).
  • Example 1 Electrochemical synthesis of 2,6-dimethoxycyclohexa-2,5-diene-1,4-dione (2a) under alteration of the anode material
  • the electrochemical oxidation was performed in a divided Teflon ® electrolysis cell equipped with magnetic stir bars (VWR brand, Germany). A glass frit was used as a separator. A platinum foil on a PTFE support was used as cathode and various materials (2.5 cm 2 ) as listed in Table 1 were used as anode.
  • the electrolyte was prepared, by adding 5 vol% H2O and 1 M concentrated sulfuric acid (98%) to acetonitrile at 0 °C. Afterwards the electrolyte was allowed to reach room temperature.
  • the 2,6- dimethoxyphenol (0.123 mmol, 25 mM) was added to the anodic compartment of the cell and 5 mL electrolyte was added to each compartment. The mixture was stirred with 300 rpm. The electrolysis was performed at 22 o C and at a constant current of 25 mA, a charge of 6 F and a current density of 6 mA/cm 2 . The reaction mixture was transferred to an Erlenmeyer flask afterwards, and the cell was washed with 20 mL dichloromethane. The pH value was adjusted to pH 7 by the addition of saturated aqueous sodium carbonate solution. The mixture was transferred to a separatory funnel and extracted with dichloromethane three times (3 ⁇ 20 mL).
  • Example 2 Electrochemical synthesis of 2,6-dimethoxycyclohexa-2,5-diene-1,4-dione (2a) under various contents of oxygen source The electrochemical oxidation was performed in a flow electrolysis cell ElectraSyn flow (IKA ® - Maschinene GmbH & Co. KG, Germany) with ruthenium-iridium oxide on titanium support (12 cm 2 ) (Industrie De Nora S.p.A., Italy) as anode and platinum (12 cm 2 ) as cathode.
  • a Nafion TM N324 membrane DuPont, United States
  • was used as a separator and a 0.25 mm Teflon® spacer IKA ® -Werke GmbH & Co.
  • the electrolyte solutions were prepared by dissolving 1 M concentrated sulfuric acid (98%), 4.5 vol% H2O and various amount of methanol as shown in Table 3 in acetonitrile at 0 °C. To the anolyte, appropriate amounts of the substrate 2,6-dimethoxyphenol, to maintain a concentration of 25 mM, were added. The anolyte solution was stirred during the course of the electrolysis. A multi-channel peristaltic pump was used to simultaneously pump both solutions through the half cells.
  • the electrolysis was performed as single-pass electrolysis at 22 o C and at a constant current of 24 mA, a charge of 4 F and a current density of 2 mA/cm 2 .
  • the first 5 mL of electrolyzed solutions were discarded. Afterwards the solutions were collected 30 in two graduate cylinders. After appropriate amounts of solutions were collected, 5 mL of each graduate cylinder were transferred to an Erlenmeyer flask using a bulb pipette. 20 mL dichloromethane were added, and the pH value was adjusted to 7 by the addition of saturated aqueous sodium carbonate solution.
  • the solution was transferred to a separatory funnel and extracted two more times with 20 mL (3 ⁇ 20 mL) dichloromethane.

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Abstract

La présente invention concerne un procédé électrochimique de production d'un composé benzoquinone, qui est polyvalent en ce qu'il permet la conversion d'hydroquinone et d'une large gamme de phénols en benzoquinones avec un rendement et une sélectivité attractifs, sans qu'il soit nécessaire de modifier le protocole. Le procédé de la présente invention évite des catalyseurs, des réactifs et des oxydants coûteux et ne fournit pas de déchets de réactif, de sorte qu'il est économique et respectueux de l'environnement.
PCT/EP2023/054261 2022-02-25 2023-02-21 Procede de production de benzoquinones WO2023161206A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4963234A (en) * 1988-10-14 1990-10-16 Rhone-Poulenc Chimie Electrolytic production of quinone from hydroquinone
JPH0565682A (ja) * 1991-09-10 1993-03-19 Nisshin Flour Milling Co Ltd アルキルベンゾキノンの製造法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4963234A (en) * 1988-10-14 1990-10-16 Rhone-Poulenc Chimie Electrolytic production of quinone from hydroquinone
JPH0565682A (ja) * 1991-09-10 1993-03-19 Nisshin Flour Milling Co Ltd アルキルベンゾキノンの製造法

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