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 present invention relates to a process for preparing 2-alkyne 1-acetals.
• R 3 is a radical of the general formula II.
• the radical R 1 which occurs therein 3 times preferably has the same meaning on each occurrence.
• the compound of the general formula III is used as such, i.e. no alcohol A is used but instead the starting compound of the general formula III performs the function of the alcohol A which acetalates the oxidation product of the compound of the general formula III.
• radical R 1 preference is given to compounds of the general formula I in which is hydrogen, a C 1 -C 6 -alkyl radical or a C 1 -C 6 -alkyl radical substituted by a hydroxyl group. Accordingly, compounds of the general formula 11 in which the radical R 1 is hydrogen, a C 1 -C 6 -alkyl radical or a C 1 -C 6 -alkyl radical substituted by a hydroxyl group are then used as starting compounds.
• a further compound of the general formula I which is very particularly preferably prepared is 1,1,4,4-tetramethoxybut-2-yne.
• Starting materials used then are 2-butyne-1,4-diol as compound of the general formula III and methanol as alcohol A.
• the alcohols A and the compound of the general formula III are generally used in a molar ratio of 2:1, based on the alcoholic hydroxyl groups present in the compound of the formula III, or the alcohol A is used in excess and then serves simultaneously as solvent or diluent for the compound of the general formula III and the compound of the general formula I formed.
• customary cosolvents are added to the electrolysis solution. These are the inert solvents having a high oxidation potential which are customarily used in organic chemistry. Examples which may be mentioned are dimethyl carbonate and propylene carbonate.
• Water is also suitable in principle as cosolvent; the proportion of water in the electrolyte is preferably less than 20% by weight.
• Electrolyte salts present in the electrolysis solution are generally alkali metal, tetra(C 1 -C 6 -alkyl)ammonium, preferably tri(C 1 -C 6 -alkyl)methylammonium, salts.
• Suitable counterions are sulfate, hydrogensulfate, alkylsulfates, arylsulfates, halides, phosphates, carbonates, alkylphosphates, alkylcarbonates, nitrate, alkoxides, tetrafluoroborate and perchlorate.
• acids derived from the abovementioned anions are also possible as electrolyte salts, i.e., for example, sulfuric acid, sulfonic acids and carboxylic acids.
• electrolyte salts are ionic liquids.
• Suitable ionic liquids are described in “Ionic Liquids in Synthesis”, Editors Peter Wasserscheid, Tom Welton, Verlag Wiley VCH, 2003, Chapters 1 to 3.
• the process of the invention can be carried out in all customary types of divided or undivided electrolysis cells. It is preferably carried out continuously in undivided flow-through cells.
• Bipolar capillary gap cells or plate stack cells in which the electrodes are configured as plates and arranged in a parallel fashion are very particularly suitable.
• Graphite is preferred as electrode material.
• the feed rate of the starting materials is generally chosen so that the weight ratio of the compounds of the general formula 11 used to the compounds of the general formula I formed in the electrolyte is from 10:1 to 0.05:1.
• the current densities at which the process is carried out are generally in the range from 1 to 1000 mA/cm 2 , preferably from 10 to 100 mA/cm 2 .
• the process is generally carried out at atmospheric pressure. Higher pressures are preferably employed when the process is to be carried out at relatively high temperatures, so as to avoid boiling of the starting compounds or the solvent.
• Suitable anode materials are, for example, noble metals such as platinum or metal oxides such as ruthenium or chromium oxide or mixed oxides of the RuO x TiO x type and also diamond electrodes. Preference is given to graphite or carbon electrodes.
• Possible cathode materials are, for example, iron, steel, stainless steel, nickel or noble metals such as platinum and also graphite or carbon materials and also diamond electrodes. Preference is given to the system graphite as anode and cathode and also graphite as anode and nickel, stainless steel or steel as cathode.
• the electrolyte solution is worked up by conventional separation methods.
• the electrolysis solution is in general firstly distilled and the individual compounds are obtained separately in the form of different fractions. Further purification can be carried out, for example, by crystallization, extraction, distillation or chromatography.
• An undivided plate stack cell having graphite anodes and steel cathodes was used. 160 g of 2-propyn-1-ol in 640 g of methanol were reacted with 5.3 g of sulfuric acid at a temperature of 20° C. for 19 hours. The electrolysis was carried out at 3.4 A/dm2 and an amount of charge of 2 F based on the 2-propyn-1-ol used was passed through the cell. The output from the electrolysis contained 8.8 GC-% by area of 1,1-dimethoxy-2-propyne (conversion: 49%, yield: 30%).
• a divided parallel plate cell having a graphite anode and steel cathode was used.
• 401 g of 2-propynol in 1400 g of methanol and 38 g of MTBS (methyltributylammonium methylsulfate) in the anode space and 941 g of methanol and 24 g of MTBS in the cathode space were reacted at a temperature of 20° C. for 38 hours.
• the electrolysis was carried out at 3.1 A/dm 2 and an amount of charge of 2 F based on the 2-propyn-1-ol used was passed through the cell.
• the anolyte contained 8.3 GC-% by area of 1,1-dimethoxy-2-propyne (conversion: 91%, yield 19%).
• a divided parallel plate cell having a graphite anode and steel cathode was used. 13 g of 2-butyne-1,4-diol in 117 g of methanol and 3.8 g of MTBS (methyltributylammonium methylsulfate) in the anode space and 130 g of methanol and 3.8 g of MTBS in the cathode space were reacted at a temperature of 19° C. for 14 hours. The electrolysis was carried out at 3.4 A/dm 2 and an amount of charge of 4 F based on the 2-butyne-1,4-diol used was passed through the cell.
• MTBS methyltributylammonium methylsulfate

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Steroid Compounds (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2004
  • 2004-07-23 DE DE102004035860A patent/DE102004035860A1/de not_active Withdrawn
• 2005
  • 2005-06-18 EP EP05013192A patent/EP1619273B1/de not_active Not-in-force
  • 2005-06-18 AT AT05013192T patent/ATE401433T1/de not_active IP Right Cessation
  • 2005-06-18 DE DE502005004699T patent/DE502005004699D1/de active Active
  • 2005-07-21 US US11/186,100 patent/US20060016695A1/en not_active Abandoned
  • 2005-07-22 JP JP2005213194A patent/JP4755458B2/ja not_active Expired - Fee Related
  • 2005-07-22 CN CN200510085307A patent/CN100585012C/zh not_active Expired - Fee Related

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