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EP0638665B1 - Procédé pour la préparation d'acetals dialkyls de benzaldehyde - Google Patents

Procédé pour la préparation d'acetals dialkyls de benzaldehyde Download PDF

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Publication number
EP0638665B1
EP0638665B1 EP94112334A EP94112334A EP0638665B1 EP 0638665 B1 EP0638665 B1 EP 0638665B1 EP 94112334 A EP94112334 A EP 94112334A EP 94112334 A EP94112334 A EP 94112334A EP 0638665 B1 EP0638665 B1 EP 0638665B1
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EP
European Patent Office
Prior art keywords
tert
reaction solution
electrolysis cell
pressure
alkyl
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EP94112334A
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German (de)
English (en)
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EP0638665A1 (fr
Inventor
Dieter Dr. Hermeling
Heinz Hannebaum
Hartwig Dr. Voss
Andreas Dr. Weiper-Idelmann
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BASF SE
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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
    • C25B3/23—Oxidation

Definitions

  • This invention relates to an improved process for the preparation of benzaldehyde dialkyl acetals of the general formula I in which R 1 is C 1 -C 6 alkyl and R 2 is C 1 -C 6 alkyl, C 1 -C 6 alkoxy, halogen, cyano or carboxyalkyl having 1 to 6 carbon atoms in the alkyl group and n is an integer from 1 to 3, where the radicals R 2 in the case of n> 1 may be the same or different, by electrochemical oxidation of substituted toluene compounds of the general formula II
  • Process products I serve as intermediates for the production of crop protection agents and pharmaceuticals.
  • DE-A 41 06 661 relates to a process for the preparation of substituted 2-methylbenzaldehyde dialkyl acetals. According to the teaching of this document, the process can be carried out continuously or discontinuously at normal pressure or elevated pressure. However, the selectivities to be achieved according to the teaching of this publication are not sufficient in all cases for large-scale practice of the process.
  • EP-12 240 relates to the electrochemical oxidation of optionally substituted toluene compounds to the corresponding benzaldehyde dialkyl acetals in the presence of alkanols and of conductive salts which are derived from sulfuric acid or phosphoric acid.
  • the reaction mixture can be worked up by distillation to give the process product and the by-products isolated in this way the oxidation level can be returned.
  • By-products that can interfere with the oxidation reaction are subjected to hydrogenation before being recycled.
  • the object was therefore to provide a process which allows the continuous electrochemical production of benzaldehyde dialkyl acetals both with high conversions and with high selectivities.
  • those of the formula III are preferred among the compounds II in which the substituent R 3 is a C 1 -C 6 -alkyl radical or C 1 -C 4 -alkoxy radical.
  • the process according to the invention can be carried out batchwise or continuously. Both embodiments have in common that the electrochemical oxidation of the starting compound II is carried out in the electrolysis cell and the resulting reaction solution is expanded to a pressure which is 10 mbar to 10 bar lower than the pressure in the electrolysis cell.
  • the electrolysis cell preferably has an overpressure, based on normal pressure, of 0.1 to 6 bar. This pressure can preferably be built up in the electrolysis cell by means of a pump, but can also be generated by an inert gas such as nitrogen. After the oxidation step, the reaction solution is preferably let down to normal pressure.
  • gas released during the expansion of the reaction solution after the electrolysis which is predominantly hydrogen discharged from the electrolysis cell, is separated off.
  • the reaction solution is then returned to the electrolysis cell, electrolyzed and then relaxed.
  • This sequence of process steps is referred to below as cycles. It has proven to be advantageous to expose the reaction solution to a large number of cycles, as a result of which a higher yield can be achieved economically than in only two cycles. 20 to 1000 cycles are preferred, particularly preferably 100 to 800.
  • the oxidation of the starting compound II in one cycle is generally not carried out until complete conversion. Depending on the number of cycles, the turnover is generally 0.1 to 5% of the theoretical turnover.
  • the reaction solution is worked up onto the product. This is done in a manner known per se, predominantly by distillation. If a solvent is present in the reaction solution, it is distilled off. If neutral salts are used as auxiliary electrolyte, these can then be filtered off before the acetal I is distilled. Solvents, electrolyte and unreacted starting compound can be used again in further process approaches.
  • the continuous embodiment of the present invention is preferred.
  • a partial stream of the reaction solution is separated off and worked up.
  • This partial stream is generally less than 5% by weight, preferably 0.01 to 1% by weight, of the total stream.
  • Part of the gas dissolved in the reaction solution is discharged from the electrolysis circuit through this partial flow.
  • a separate degassing of the entire reaction solution is not necessary, but can be advantageous in the case of small partial flows and relatively large amounts of gas.
  • the partial flow is worked up as described above.
  • Solvents, auxiliary electrolyte, starting compounds and, if appropriate, incompletely oxidized intermediates can be added to the reaction solution which is returned to the electrolytic cell.
  • the recycled reaction solution is further replaced by the amount of starting compounds which corresponds to the amount of the separated product. After recycling and oxidation, the cycle described is repeated as often as required.
  • the reaction is carried out in the presence of an auxiliary electrolyte.
  • an auxiliary electrolyte This is generally in a concentration of 0.1 to 6% by weight, based on the reaction mixture.
  • Protonic acids such as organic acids, e.g. Methylsulfonic acid, benzenesulfonic acid or toluenesulfonic acid, but also mineral acids such as sulfuric acid and phosphoric acid.
  • Neutral salts can also be used as auxiliary electrolytes.
  • Metal cations of lithium, sodium, potassium, but also tetraalkylammonium compounds such as tetramethylammonium, tetraethylammonium, tetrabutylammonium and dibutyldimethylammonium are suitable as cations.
  • anions fluoride, tetrafluoroborate, sulfonates such as methyl sulfonate, benzenesulfonate, toluenesulfonate, sulfates such as sulfate, methyl sulfate, ethyl sulfate, phosphates such as methyl phosphate, ethyl phosphate, dimethyl phosphate, diphenyl phosphate, hexafluorophosphate and phosphonyl methylphosphate, phosphonyl methylphosphate such as phosphonate methyl phosphonate.
  • fluoride tetrafluoroborate
  • sulfonates such as methyl sulfonate, benzenesulfonate, toluenesulfonate
  • sulfates such as sulfate, methyl sulfate, ethyl sulfate
  • phosphates such
  • Unbranched C 1 -C 6 -alkanols are preferably used as alkanols; methanol and ethanol are particularly preferred.
  • the concentration of the alkanol in the feed to the electrolysis cell is generally 50 to 98% by weight, preferably 70 to 95% by weight.
  • the reaction mixture can contain one or more additional inert solvents.
  • additional inert solvents Compounds such as methylene chloride, acetonitrile, methyl tert-butyl ether, butyrolactone or dimethyl carbonate are suitable for this.
  • the concentration of these solvents can be 0 to 30% by weight, based on the reaction mixture.
  • the current density in the process according to the invention is generally 2 to 10 A / dm 2 , preferably 3 to 8 A / dm 2 .
  • the total amount of charge transferred to the starting compound II in the process according to the invention is generally 3 to 9 F / mol II, preferably 4 to 8 F / mol II.
  • Precious metals such as platinum and oxides such as chromium or ruthenium oxide and mixed oxides such as Ti / RuO x are suitable as anode materials.
  • platinum and oxides such as chromium or ruthenium oxide and mixed oxides such as Ti / RuO x are suitable as anode materials.
  • graphite is the preferred anode material.
  • the electrochemical oxidations can be carried out in divided, but preferably in undivided, flow cells.
  • the oxidation is generally carried out at temperatures from 0 to 120 ° C., preferably at 20 to 80 ° C.
  • Process products I can be hydrolyzed to the corresponding aldehydes in a manner known per se.
  • the compounds I thus represent storage-stable depot compounds for the much more sensitive aldehydes.
  • the process according to the invention allows the starting compounds II to be converted into the products I with high conversion. Remarkably, the electrochemical oxidations proceed with high selectivity under these conditions.
  • the by-products possibly formed in the reaction can be returned to the reaction without any special work-up steps. No interfering side reactions from such by-products were found.
  • the electrolyte was neutralized with sodium methylate, the methanol was distilled off and the precipitated salt was filtered off. The stated products were obtained after vacuum distillation.
  • the electrooxidation was carried out in a cell as described in Example 1 at 55 ° C.
  • the current density was 3.4 A / dm 2 .
  • the different charge quantities can be found in the following table.
  • the procedure was analogous to Example 1.
  • the reaction solution was freed from methanol by distillation, the salt which precipitated was filtered off and the acetal was purified by distillation.
  • the electrolyte was pumped around at 200 l / h.
  • the recycle stream contained the components which boiled more easily than the product when the substream was worked up by distillation.

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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)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Claims (4)

  1. Procédé de préparation de benzaldéhydedialkylacétals de la formule générale I :
    Figure imgb0011
     dans laquelle R1 représente un radical alkyle en C1 à C6 et R2 représente un radical alkyle en C1 à C6, alcoxy en C1 à C6, un atome d'halogène, un radical cyano ou carboxyalkyle qui comporte de 1 à 6 atomes de carbone dans le radical alkyle et n désigne un nombre entier dont la valeur varie de 1 à 3, où les restes R2 peuvent être identiques ou différents dans le cas où n est supérieur à 1, par l'oxydation électrochimique de composés du toluène substitués de la formule générale II :
    Figure imgb0012
     caractérisé en ce que l'on oxyde un composé du toluène substitué II en présence d'un alcool R1-OH et d'un électrolyte adjuvant dans une cellule d'électrolyse, on détend la solution réactionnelle ainsi obtenue à l'extérieur de la cellule d'électrolyse jusqu'à une pression plus faible de 10 mbars à 10 bars à la pression qui règne dans la cellule d'électrolyse, et
    A) dans le cas d'un fonctionnement continu, on sépare le gaz libéré au cours de la détente du mélange réactionnel, on recycle, électrolyse, détend et redébarrasse du gaz libéré la solution réactionnelle au moins une fois dans la cellule d'électrolyse et on poursuit ensuite le traitement pour obtenir le produit, ou bien
    B) dans le cas d'un fonctionnement discontinu, on traite une partie de la solution réactionnelle pour obtenir le produit, on ajoute à la partie résiduelle de la solution réactionnelle une proportion de la solution réactionnelle mise en oeuvre à l'origine correspondant à la partie prélevée, on recycle, électrolyse et détend alors cette partie résiduelle ainsi complétée dans la cellule d'électrolyse.
  2. Procédé suivant la revendication 1, caractérisé en ce que l'on fait réagir des composés du toluène substitués de la formule III :
    Figure imgb0013
     dans laquelle R3 représente un radical alkyle en C1 à C6 ou alcoxy en C1 à C4.
  3. Procédé suivant la revendication 1 ou 2,
    caractérisé en ce que l'on détend la solution réactionnelle jusqu'à la pression normale.
  4. Procédé suivant la revendication 1 ou 2,
    caractérisé en ce que l'on détend la solution réactionnelle jusqu'à une pression inférieure de 0,1 à 6 bars à la pression qui règne dans la cellule d'électrolyse.
EP94112334A 1993-08-14 1994-08-08 Procédé pour la préparation d'acetals dialkyls de benzaldehyde Expired - Lifetime EP0638665B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4327361A DE4327361A1 (de) 1993-08-14 1993-08-14 Verfahren zur Herstellung von Benzaldehyddialkylacetalen
DE4327361 1993-08-14

Publications (2)

Publication Number Publication Date
EP0638665A1 EP0638665A1 (fr) 1995-02-15
EP0638665B1 true EP0638665B1 (fr) 1996-10-30

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US (1) US5507922A (fr)
EP (1) EP0638665B1 (fr)
JP (1) JPH0776545A (fr)
DE (2) DE4327361A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102365393B (zh) * 2009-03-27 2014-10-29 巴斯夫欧洲公司 生产3-叔丁基苯甲醛缩二甲醇的电化学方法
CN102762774A (zh) * 2010-02-12 2012-10-31 巴斯夫欧洲公司 生产4-异丙基环己基甲醇的方法
US8889920B2 (en) 2010-02-12 2014-11-18 Basf Se Process for preparing 4-isopropylcyclohexylmethanol
EP2616424B1 (fr) 2010-09-16 2015-08-26 Basf Se Procédé de production de 2-méthyl-3-(4-tert-butylphényl)-propanal à pureté élevée en isomère para
CN109930171B (zh) * 2019-04-12 2020-01-17 天津理工大学 一种绿色高效合成缩醛的方法
CN112195481B (zh) * 2020-11-02 2021-12-10 上海漫关越水处理有限公司 膜电解合成四甲氧基乙烷的方法
CN113604824B (zh) * 2021-07-16 2023-05-30 万华化学集团股份有限公司 制备1,8-二烷氧基-1,3,6,8-四烷氧基-2,7-二甲基-4-辛烯的方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4318783A (en) * 1978-11-30 1982-03-09 Bayer Aktiengesellschaft Process for the preparation of optionally substituted benzaldehyde dialkyl acetals
DE4106661A1 (de) * 1991-03-02 1992-09-03 Basf Ag 2-methylbenzaldehyddialkylacetale
DE4122314A1 (de) * 1991-07-05 1993-01-07 Basf Ag O-phthaldialdehydtetraalkylacetale, ihre herstellung und ihre verwendung als depotverbindung

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Publication number Publication date
EP0638665A1 (fr) 1995-02-15
US5507922A (en) 1996-04-16
DE4327361A1 (de) 1995-02-16
JPH0776545A (ja) 1995-03-20
DE59400935D1 (de) 1996-12-05

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