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
• • 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

Definitions

• the invention relates to a new electrochemical process for the preparation of methoxy acetaldehyde dialkyl acetals.
• alkylbenzenes such as toluene or p-xylene
• benzoic acid esters in the presence of alkanols and triarylamines of the formula III.
• the advantageous result of the process of this invention is surprising, because here the acetals are formed in high selectivities and are not further oxidized to the corresponding esters.
• R represents an alkyl group having 1 to 4 carbon atoms
• R is e.g. one of the residues: -CH3, -C2H5, -C3H7 or -C4H9.
• the preferred starting material is 1,2-dimethoxyethane.
• alkanols of the formula ROH examples include Ethanol, propanol, isopropanol, butanol, isobutanol and preferably methanol.
• Triarylamine compounds of the formula III are compounds of the following structure They contain, for example, F, Cl or Br atoms as halogen atoms.
• Compounds of the formula III are, for example, tris (4-bromophenyl) amine, bis (4-bromophenyl) - (2,4-dibromophenyl) amine, bis (2,4-dibromophenyl) -4-bromophenylamine, tris (2,4-dibromophenyl) amine, tris- (4-chlorophenyl) amine, bis- (4-chlorophenyl) - (2,4-dichlorophenyl) amine, bis- (2,4-dichlorophenyl) - (4th -chlorophenyl) amine and tris (2,4-dichlorophenyl) amine, of which tris (2,4-dibromophenyl) amine and tris (2,4-dich
• the electrolyte is supplemented with the conductive salts commonly used in organic electrochemistry, such as salts of tetrafluoroboric acid, salts of alkyl or arylsulfonic acids or salts of alkylsulfuric acids and salts of perchloric acid.
• conductive salts commonly used in organic electrochemistry, such as salts of tetrafluoroboric acid, salts of alkyl or arylsulfonic acids or salts of alkylsulfuric acids and salts of perchloric acid.
• alcoholates such as NaOCH3 and KOCH3 come into consideration.
• cosolvents can be added to the electrolyte.
• co-solvents come e.g. B. halogenated hydrocarbons, such as methylene chloride, dichloroethane, 1,2-dichloropropane or nitriles, such as acetonitrile.
• the cosolvents are the alcohol z. B. in amounts up to 60 parts by weight per 100 parts by weight of alkanol.
• the method according to the invention does not require a special electrolysis cell; an undivided flow cell is preferably used.
• All anode materials which are customary per se and which are stable under the electrolysis conditions such as noble metals, e.g. B. gold or platinum.
• Graphite is preferably used.
• cathode material u. a. Graphite, iron, steel, nickel or even noble metals such as platinum.
• the electrolyte used in electrooxidation has the following composition, for example: 1 to 70% by weight of starting compound of the formula II 30 to 96% by weight alkanol with or without cosolvent 0.3 to 5% by weight of triarylamine compounds of the formula III 0.3 to 4% by weight of conductive salt
• Electrolysis is carried out at current densities of 0.25 to 10 A / dm2, advantageously from 0.5 to 5 A / dm2, preferably at 1.0 to 4 A / dm2.
• the amount of charge is 1 to 10, preferably 2 to 8 F per mole of starting material.
• the upper limit of the electrolysis temperatures is the boiling point of the alkanol or the cosolvent. Expediently, electrolysis is carried out at temperatures up to 5 ° C. below the boiling point of the electrolyte. When using methanol e.g. at temperatures up to 60 ° C, preferably at 20 to 60 ° C, electrolyzed. The process can be carried out batchwise or continuously.
• the electrolysis discharges are worked up using methods known per se.
• the electrolysis discharge is expediently worked up by distillation. Excess alkanol and any cosolvent used are first distilled off, conductive salt and triarylamino compound are filtered off and the methoxiacetaldehyde dialkyl acetals become cleaned, e.g. B. by distillation. Alkanol, cosolvent, conductive salt and triarylamino compound and unreacted compounds of the formula II can be recycled to the electrolysis.
• the methoxy acetaldehyde dialkyl acetals obtainable by the process according to the invention are valuable intermediates for the synthesis of medicaments, in particular sulfonamides.
• Apparatus undivided cell with 6 electrodes, bipolar electrode arrangement, electrode spacing: 0.5 mm, anodes and cathodes: graphite.
• Composition of the electrolyte 1225 g (13.61 mol) of 1,2-dimethoxyethane 12.3 g sodium benzenesulfonate 12.3 g sodium methylate 12.3 g tris (2,4-dibromophenyl) amine 1188 g of methanol Current density: 3.3 A / dm2 Temperature: 27 to 28 ° C Electrolysis with 2.2 F / mol 1,2-dimethoxyethane
• the electrolyte is pumped through the cell at 200 l / h via a heat exchanger.
• the electrolysis discharge is examined by gas chromatography. Thereafter, in addition to 938 g of unreacted 1,2-dimethoxyethane, 269 g of CH3O-CH2CH (OCH3) 2 and 61 g of CH3O-CH2-CH2-O-CH2-OCH3.

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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)

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Cited By (1)

Citations (3)

• 1987
  • 1987-03-14 DE DE19873708337 patent/DE3708337A1/de not_active Withdrawn
• 1988
  • 1988-03-05 DE DE8888103423T patent/DE3862329D1/de not_active Expired - Lifetime
  • 1988-03-05 EP EP88103423A patent/EP0283807B1/fr not_active Expired - Lifetime

Patent Citations (3)

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