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EP1606434A2 - Procede d'alcoxylation anodique de substrats organiques - Google Patents

Procede d'alcoxylation anodique de substrats organiques

Info

Publication number
EP1606434A2
EP1606434A2 EP04720604A EP04720604A EP1606434A2 EP 1606434 A2 EP1606434 A2 EP 1606434A2 EP 04720604 A EP04720604 A EP 04720604A EP 04720604 A EP04720604 A EP 04720604A EP 1606434 A2 EP1606434 A2 EP 1606434A2
Authority
EP
European Patent Office
Prior art keywords
alkoxylation
methoxylated
anodic
alkyl
mediator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04720604A
Other languages
German (de)
English (en)
Inventor
Christian Reufer
Thomas Lehmann
Rainer Sanzenbacher
Christoph Weckbecker
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Evonik Operations GmbH
Original Assignee
Degussa GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Degussa GmbH filed Critical Degussa GmbH
Publication of EP1606434A2 publication Critical patent/EP1606434A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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

Definitions

  • the invention is directed to a process for the anodic alkoxylation of organic substrates, in particular cyclic ethers, such as, in particular, furan and
  • Furan derivatives which can also be wholly or partially hydrogenated, N-substituted amides, carbonyl compounds, alkyl aromatics and heteroaromatics.
  • the anodic alkoxylation, in particular a methoxylation, is carried out in an undivided electrolysis cell in the absence of a solid electrolyte.
  • Alkoxylation reactions of saturated and unsaturated cyclic ethers and of N-alkylamides and alkylaromatics and alkylheteroaromatics are of technical importance since the resulting products or their hydrolysis products are valuable raw materials for pharmaceuticals and pesticides.
  • Various processes for the anodic alkoxylation of organic compounds are known.
  • U.S. Patent 2,714,576 teaches the electrolytic preparation of 2,5-dialkoxy-2,5-dihydrofurans by electrolyzing furan or a substituted furan in an aliphatic alcohol having 1 to 5 carbon atoms in the presence of a soluble electrolyte.
  • the electrolyte used is ammonium bromide, the effect of which is that it acts as a mediator.
  • the substrate to be alkoxylated is alkoxylated, that is, not directly but indirectly, namely via the intermediate step of brooding.
  • ammonium bomide other halogen compounds can also be used as the conductive salt and mediator.
  • a major disadvantage of anodic alkoxylation in the presence of a mediator, such as in particular a halogen compound, is that the mediator itself is used for the increased formation of Can lead to by-products and accordingly complicates the processing and cleaning of the alkoxylated substrate.
  • a mediator such as in particular a halogen compound
  • furan derivatives can also be anodically alkoxylated in the presence of conductive salts which do not act as mediators, such as concentrated sulfuric acid, borofluoride etherate, sodium formate and sodium nitrate.
  • mediators such as concentrated sulfuric acid, borofluoride etherate, sodium formate and sodium nitrate.
  • mediator-free anodic alkoxylation is that only very low current yields and product yields - the values are usually well below 50% - are available.
  • a catholyte and an anolyte are passed through the divided electrolytic cell, the catholyte of a previous reduction being used as the anolyte.
  • this process can produce purer alkoxylation products, the technical outlay is considerably greater than for alkoxylation in an undivided electrolysis cell.
  • processes have been developed which do not require additives to increase conductivity, but in which a solid polymer electrolyte (SPE) is used instead.
  • SPE solid polymer electrolyte
  • a plate stack cell with serial is used for the electrolytic oxidation, including an anodic alkoxylation switched stack electrodes are used, at least one stack electrode consisting of a graphite felt plate, a carbon felt plate or a fabric made of carbon covered educt contact surface.
  • the electrodes and the electrolyte are designed in such a way that, ideally, no electrolytes migrate through the stacked electrode.
  • the electrolyte phase touching the carbon-containing stack electrode is in fact a solid electrolyte.
  • the technical effort of the plate stack cell is considerable since the cell requires a specific structure and a suitable periphery.
  • mediators such as those used in the electrical oxidation and reduction of a wide variety of substrates, are regenerated electrochemically.
  • the connection used as a mediator is brought into contact with a diamond layer electrode, with the exchange of a redox equivalent.
  • the electrochemical regeneration is an oxidation or reduction of the compound used as a mediator, depending on whether the organic compound is to be reduced or oxidized by means of the mediator.
  • Mediators include those from the series of metal salts and halogen compounds available in several oxidation states, but also organic mediators.
  • Diamond layer electrode has a core made of titanium, silicon or graphite, for example, and a doped conductive diamond layer is applied to it.
  • Electrolysis cell can be carried out, he has the disadvantage of using a mediator.
  • diamond layer electrodes are doped with a trihydric to pentavalent element, such as, in particular, boron or phosphorus.
  • a trihydric to pentavalent element such as, in particular, boron or phosphorus.
  • J. Injesta et al. investigated the electrochemical oxidation of 3-methylpyridine on a boron-doped diamond layer electrode in an acid medium.
  • the object of the present invention is to show a further process for the anodic alkoxylation, in particular methoxylation, of organic substrates, in particular of cyclic ethers and N-substituted amides, which can be carried out in a simple manner and can also be used for the technical production of the alkoxylated products.
  • the process to be shown should neither have the disadvantages known from the SPE process, nor lead to an alkoxylation product with halogenated by-products.
  • Embodiments of the method according to the invention including the substrates to be preferably alkoxylated and the conductive salts preferably to be used, which lead to sufficient conductivity even in low concentrations and cannot be oxidized under the conditions of the electrysis, so that they do not act as a mediator.
  • the anodic alkylation according to the invention are in particular organic compounds from the series of cyclic ethers, N-substituted amides,
  • a first class of substrates that are easy to alkoxylate are cyclic ethers, which can be saturated, unsaturated or heteroaromatic.
  • the oxygen-containing ring system preferably has 5 to 7 ring members, preferably 5 or 6 ring members with an O atom, but other saturated or unsaturated ring systems, in particular benzene nuclei, can be fused to this ring system.
  • Examples of substances from the classes mentioned are furan, and furans substituted one to four times, and the dihydro and tetrahydro compounds derived therefrom, such as, for example, tetahydrofuran.
  • cyclic ethers are 1,2- and 1,4-pyrans and their di- and tetrahydro derivatives; Finally, 1,4-pyrones and their di- and tetrahydro derivatives are also available for anodic alkoxylation.
  • 1,2-Pyrones can also be alkoxylated, but these are lactams.
  • the substituents are in particular alkyl groups, which in turn can have a functional group such as hydroxyl, acetoxy, alkoxycarbonyl, amidocarbonyl, carboxyalkyl, nitrile and amino. Such a functional group is expediently bound to the heterocyclic ring via a methylene or ethylene bridge.
  • substituents are alkoxy, halogen, carboxyl, acyl and the aldehyde group. If non-aromatic cyclic ethers are alkoxylated, they must have at least one abstractable H atom on a C atom adjacent to the ether oxygen.
  • the corresponding 2, 5-dihydro-2, 5-dialkoxyfurans are formed by the anodic alkoxylation according to the invention with a generally high material yield and a very high current yield.
  • the hydrogenated furans or other cyclic ethers such as pyrans, pyrones, dioxane and morpholine
  • the corresponding mono- and / or dialkoxy derivatives are formed, the Alkoxy groups are on the carbon atom (s) adjacent to the ether oxygen.
  • linear and cyclic ' N-substituted amides can be alkoxylated.
  • the amide nitrogen atom has one or two alkyl substituents which can also form a saturated or unsaturated, optionally heteroaromatic ring with the N atom.
  • at least one carbon atom bound to the nitrogen has at least one abstractable hydrogen atom, or the nitrogen atom is a ring member of a heteroaromatic ring.
  • amides examples include lactams with 5 to 7 ring members, where the amide nitrogen can also be alkylated.
  • the lactams are, for example, N-alkylpyrrolidone, and the heterocyclic ring can additionally contain one or more substituents.
  • the alkyl group bonded to the nitrogen is particularly preferably methyl. Further examples are N-alkylvalerolactam and N-alkylcaprolactam.
  • N-acylated saturated and unsaturated N-heterocycles which contain at least one abstractable atom from at least one of the carbon atoms adjacent to the nitrogen
  • N-acylated pyrroles pyrrolines and pyrrolidines optionally substituted on the ring one or more times.
  • the acyl group is, for example, formyl, acetyl, propionyl, benzoyl.
  • the substituents which are bonded to one or more carbon atoms of the N-heterocyclic ring are those which have previously been associated with the cyclic ethers were listed.
  • the substituents are particularly preferably an alkyl group having 1 to 4 carbon atoms, in particular methyl or ethyl, hydroxymethyl, acetoxymethyl and carboxymethyl.
  • open-chain N-alkyl or N, N-dialkyl fatty acid amides in particular amides of fatty acids with 1 to 6 carbon atoms, can also be alkoxylated. It is also possible to use substrates which have two N-alkylamide structural elements in one molecule.
  • ketones with a methyl group or methylene group bonded to the carbonyl carbon atom are alkoxylated, in particular methoxylated or ethoxylated.
  • alkoxylated in particular methoxylated or ethoxylated.
  • Examples are aliphatic ketones with 3 to 12 carbon atoms, aromatic-aliphatic ketones, such as acetophenone, and methylbenzyl ketone.
  • the resulting alkoxy ketones are usually converted directly into the corresponding ketal.
  • alkylated aromatic and heteroaromatic compounds are alkoxylated, the carbon atom being one on the aromatic or
  • Heteroaromatic alkyl group must have at least one abstractable hydrogen atom.
  • the substrates can additionally have substituents other than alkyl.
  • the aromatic or heteroaromatic expediently contains one or more alkyl groups from the series methyl, ethyl and n-propyl.
  • the corresponding alkoxyalkyl aromatics or heteroaromatics are formed by the alkoxylation according to the invention.
  • the substrate to be alkoxylated is in practice dissolved in the alcohol used for the alkoxylation as a solvent. After adding an effective amount of a conductive salt, this solution is passed through the undivided electrolytic cell. An advantageous work-up of the obtained after sufficient alkoxylation The reaction mixture takes place by distillation and / or extractive. The sump containing the conductive salt is returned to the process.
  • the anodic alkoxylation can be carried out batchwise or continuously.
  • the conducting salt is a substance whose ions are neither oxidized nor reduced in the selected potential window, so that the conducting salt does not act as a mediator and accordingly does not have any or no significant side reactions.
  • Particularly preferred conductive salts are tetraalkylammonium salts.
  • the alkyl groups of the tetraalkylammonium ion are in particular alkyl having 1 to 6 C atoms, particularly preferably 3 or 4 C atoms. Two alkyl groups can form a ring system together with the ammonium nitrogen, in particular a five or six ring. These can also be used
  • Tetraalkylammonium salts in which three alkyl groups form a bicyclic ring system Tetraalkylammonium salts in which three alkyl groups form a bicyclic ring system.
  • the anions of the conductive salts to be preferably used according to the invention are preferably those from the series C10 " , BF ⁇ , PF 6 " , SbF 6 " , R-S0 3 " and R-S0 4 ⁇ ;
  • R stands for alkyl, which can also be halogenated, in particular CF 3 -, CC1 3 - or CF 3 CH 2 -, R can also stand for aryl, which in turn can be substituted.
  • other conductive salts can also be used, for example sulfates, nitrates, phosphates, phosphonates, carboxylates and alcoholates, but in this case the yields are usually lower than when using the preferred conductive salts mentioned above.
  • tetra-n-butylammonium tetrafluoroborate is used as the conductive salt.
  • the conductive salts are essentially completely inert under the electrolysis conditions, there are no side reactions and, moreover, these conductive salts can be removed without problems.
  • the person skilled in the art will determine the amount of the conductive salts by preliminary tests such that a sufficient conductivity of the electrolyzing solution is achieved.
  • the amount of conductive salt used is usually in the range from 0.1 to 5% by weight, preferably 0.3 to 3% by weight, based on the solution to be electrolyzed.
  • the anodic oxidation is generally carried out at a voltage in the range from 1 to 70 volts, in particular 5 to 25 volts.
  • a current density in the range from 1 to 25 A / dm 2 is expediently set, but the limit values can also be exceeded or fallen short of. become.
  • the anode is one with a diamond layer.
  • Backing material for. the diamond layer is preferably a material from the series of graphite, graphite / gold, silicon or a passivating metal, such as titanium, zirconium, niobium, tantalum, tungsten and molybdenum or a carbide or nitride of the elements Ti, Si, Nb, Ta, Zr and Mon.
  • the material used for the cathode is one which is stable in the reaction medium.
  • a material from the series of graphite, platinum, nickel, stainless steel and diamond layer is particularly suitable if the reaction medium is essentially anhydrous. If aqueous media are electrolyzed, a cathode material with high hydrogen or oxygen overvoltage, preferably a diamond layer electrode, is preferably used.
  • the use of a diamond layer electrode, in particular a boron-doped diamond layer electrode, in the anodic alkoxylation in an undivided electrolysis cell in the absence of a mediator achieves significantly higher current yields than when using the electrodes customary hitherto.
  • some material and current yields of the mediator-free methoxylation of furan are given, as can be derived or calculated from the prior art.
  • the invention in contrast to the very low yields in the prior art, in the invention
  • Diamond layer electrodes which become conductive through a suitable doping, have a high corrosion resistance and a significantly lower susceptibility to electrode fouling. In contrast to other electrodes, according to current knowledge, there are no adsorption phenomena on the diamond layer electrodes to be used, as a result of which the selectivity could be reduced. Similar good results are achieved with a gold anode.
  • the absence of a mediator simplifies the processing of the electrolysis product. At the same time, a higher purity of the alkoxylation product is achieved because by-products formed by mediators, including reaction products between the substrate or the alkoxylation product and the mediator, are eliminated.
  • the structure of an electrolysis device to be used is known per se.
  • Known materials can also be used as the cathode, but also a diamond layer electrode.
  • the crude electrolysis product produced was light yellow and clear.
  • the anodic methoxylation of furan in the presence of sodium methylate has the advantage that the conductive salt used can be one whose anion corresponds to that of the alkoxylating agent. However, this advantage is bought with a lower material yield.
  • Gr graphite

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Abstract

Des substrats organiques, tels que des éthers cycliques, des amides à substitution N, des cétones, des composés alkylaromatiques et des composés alkylhétéroaromatiques peuvent être alcoxylés, en particulier méthoxylés, de manière anodique en présence d'un alcool. L'alcoxylation en présence d'un médiateur ou dans une cellule divisée avec un électrolyte solide est connue. L'alcoxylation selon la présente invention se produit en présence d'un médiateur dans une cellule d'électrolyse non divisée, à l'aide d'une anode à couche de diamant ou d'une anode en or. On obtient ainsi des rendements élevés en matières et en courant.
EP04720604A 2003-03-25 2004-03-15 Procede d'alcoxylation anodique de substrats organiques Withdrawn EP1606434A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10313169A DE10313169A1 (de) 2003-03-25 2003-03-25 Verfahren zur anodischen Alkoxylierung von organischen Substraten
DE10313169 2003-03-25
PCT/EP2004/002665 WO2004085710A2 (fr) 2003-03-25 2004-03-15 Procede d'alcoxylation anodique de substrats organiques

Publications (1)

Publication Number Publication Date
EP1606434A2 true EP1606434A2 (fr) 2005-12-21

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EP04720604A Withdrawn EP1606434A2 (fr) 2003-03-25 2004-03-15 Procede d'alcoxylation anodique de substrats organiques

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Country Link
US (1) US20060157353A1 (fr)
EP (1) EP1606434A2 (fr)
DE (1) DE10313169A1 (fr)
WO (1) WO2004085710A2 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009001008A1 (de) * 2009-02-19 2010-08-26 Evonik Degussa Gmbh Reaktivextraktion von freien organischen Säuren aus deren Ammoniumsalzen
CN105198840B (zh) * 2015-09-28 2018-06-26 乐平市康鑫医药化工有限公司 固定床法制备2,5-二甲氧基二氢呋喃的方法
CN113897627B (zh) * 2020-07-06 2023-03-03 万华化学集团股份有限公司 一种电化学制备五元杂环二烷氧基化合物的方法

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US2714579A (en) * 1951-07-18 1955-08-02 Exxon Research Engineering Co Lubricating oil additives
DE2848397C2 (de) * 1978-11-08 1982-09-23 Basf Ag, 6700 Ludwigshafen Elektrochemische Herstellung von in 4-Stellung substituierten Benzaldehyddialkylacetalen
DE3142626A1 (de) * 1981-10-28 1983-05-05 Basf Ag, 6700 Ludwigshafen Elektrochemisches verfahren zur herstellung von 2,5-dialkoxy-2,5-dihydrofuranen
DE3529074A1 (de) * 1985-08-14 1987-02-19 Basf Ag Verfahren zur herstellung von benzoesaeureorthoestern sowie verbindungen dieser klasse
DE3605451A1 (de) * 1986-02-20 1987-08-27 Bayer Ag Benzaldehyd-dialkylacetale
DE3708337A1 (de) * 1987-03-14 1988-09-22 Basf Ag Verfahren zur herstellung von methoxiacetaldehyddialkylacetalen
US5074974A (en) * 1990-06-08 1991-12-24 Reilly Industries, Inc. Electrochemical synthesis and simultaneous purification process
DE19911746A1 (de) * 1999-03-16 2000-09-21 Basf Ag Diamantelektroden

Non-Patent Citations (1)

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Title
See references of WO2004085710A2 *

Also Published As

Publication number Publication date
WO2004085710A2 (fr) 2004-10-07
US20060157353A1 (en) 2006-07-20
WO2004085710A3 (fr) 2005-04-21
DE10313169A1 (de) 2004-10-14

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