EP0028430A1 - A process for the electroreductive preparation of organic compounds - Google Patents
A process for the electroreductive preparation of organic compounds Download PDFInfo
- Publication number
- EP0028430A1 EP0028430A1 EP80200992A EP80200992A EP0028430A1 EP 0028430 A1 EP0028430 A1 EP 0028430A1 EP 80200992 A EP80200992 A EP 80200992A EP 80200992 A EP80200992 A EP 80200992A EP 0028430 A1 EP0028430 A1 EP 0028430A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- group
- process according
- hydrogen atom
- electroreduction
- carbon atoms
- 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.)
- Granted
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
-
- 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
- C25B3/25—Reduction
Definitions
- the present invention relates to electrochemical reactions which can be carried out suitably in a non-aqueous or aprotic environment.
- the present invention relates in particular to electrochemical reductions, e.g. electrocarboxylations, which can be carried out in an aprotic environment in undivided cells.
- electrochemical processes require the simultaneous occurrence of cathodic and anodic reactions. Since electrochemical processes are normally aimed at the production of preferably one compound at one particular electrode (the working electrode), less or virtually no interest is paid to the process or processes occurring simultaneously at the other electrode (counter electrode). In a number of cases, the reaction at the counter-electrode will not constitute a major problem. For instance, when the reaction at the counter-electrode occurs at a sufficiently low potential the products formed at the working electrode will not be destructed electrochemically at the counter-electrode.
- diaphragms based on ion-exchange resins can be suitably used, but such diaphragms can not be used satisfactorily in a non-aqueous or an aprotic environment as they become very poorly conducting so that thermal damage may occur even at low current densities.
- diaphragms based on the principle of diffusion limitation are unsuitable for use in non-aqueous, in particular in aprotic environments since the requirements to combine a high electrical conductivity with little diffusion and sufficient mechanical strength appear to be incompatible.
- the present invention therefore relates to a process for the electroreductive preparation of organic compounds in an undivided cell which comprises as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents an alkali or alkaline earth metal moiety; a group of formula NR 1 R 2 R 3 R 4 , wherein each of R , R 2 , R 3 and R which may be the same or different, represents a hydrogen atom, an alkyl group of up to 8 carbon atoms, or an (alk)aryl group, which may be substituted by one or more lower alkyl groups; or a pyridinium ion which may be substituted by one or more lower alkyl groups and B represents an azide group or a group wherein R 5 represents a hydrogen atom, a group wherein R 6 represents a hydrogen atom, an alkyl group of up to 8 carbon atoms or a group A, or a group -CH 2 OR 7 , wherein
- the present invention is of particular interest in that the products obtained at the counter-electrode in the electrooxidation step (i.a. carbon dioxide and nitrogen) in an undivided cell do not interfere adversely with the products obtained in the electroreduction step and are also of no environmental concern.
- the products obtained at the counter-electrode in the electrooxidation step i.a. carbon dioxide and nitrogen
- formate ions is of great importance in that they provide the unique system of having both carbon dioxide and protons available in a non-aqueous or even aprotic environment which opens up wide perspectives in preparative organic electrochemistry.
- the present invention relates in particular to a process for the electroreductive preparation of organic compounds in an undivided cell in a non-aqueous or aprotic environment which comprises as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents an alkali or alkaline earth metal moiety, a group of formula NR 1 R 2 R 3 R 4 wherein each of R , R 2 , R 3 and R , which may be the same or different, represents an alkyl group of up to 4 carbon atoms, a phenyl group or a pyridinium ion and B represents a group wherein R 5 represents a hydrogen atom, a group , wherein R 6 represents a hydrogen atom, an alkyl group of up to 8 carbon atoms or a group A, or a group -CH 2 OR 7 , wherein R represents a hydrogen atom or an alkyl group of up to 8 carbon atoms.
- A represents
- Preferred processes according to the present invention are electroreductive preparations of organic compounds in an undivided cell in non-aqueous or aprotic environments, which comprise as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents a group of formula NR 1 R 2 R 3 R 4 , wherein each of R , R 2 1 R 3 and R 4 , which may be the same or different, represents a methyl or ethyl group, and B represents a group , wherein R 5 represents a hydrogen atom or a group wherein R 6 represents a hydrogen atom, an alkyl group of up to 4 carbon atoms or a group A.
- Examples of preferred compounds comprise di-tetraethyl ammonium oxalate (DTEAOx) and tetraethyl ammonium formate (TEAF).
- electrocarboxylation reactions i.e. reactions in which carbon dioxide is reacted with electro- generated (carb)anions.
- Suitable electrocarboxylation reactions comprise the carboxylations of activated olefins, imines, and related species such as azo-compounds, ketones as well as of halogen compounds.
- Preferred electrocarboxylations are those wherein an activated olefin is the compound to be reduced electrochemically.
- Activated olefins which can be electrocarboxylated using the process according to the present invention can be represented by the general formula wherein R 8 , R 9 and R , which may be the same or different, each represents a hydrogen atom, an alkyl group of up to 8 carbon atoms, a phenyl group which may be substituted by one or more halogen atoms and/or lower alkyl groups or a group A 1 ; and A represents a group -CN or a group wherein R" represents an alkyl group of up to 8 carbon atoms, or a phenyl group which may be substituted with one or more halogen atoms and/or lower alkyl groups and n is 0 or 1.
- Preferred compounds according to the general formula I to be used in the process according to the present invention are those wherein A represents a group -CN, a group wherein R" represents a methyl group and n is 0 or 1, or a phenyl group and each of R 8 , R 9 and R 10 represents a hydrogen atom or a lower alkyl group or at least one of 8 9 10 1 R , R and R represents a group A .
- Especially preferred compounds according to the general formula I to be used in the process according to the present invention are those which possess two groups A 1 . Examples of preferred compounds comprise dimethyl maleate, acrylonitrile methyl vinyl ketone and alpha-methyl styrene; dimethyl maleate being especially preferred.
- the electrocarboxylations according to the present invention can be performed using carbon dioxide generated at the anode as the sole carbon dioxide source. If desired, the electrocarboxylations can also be performed using additional carbon dioxide. Even in those events wherein a large molar excess of non-electrochemically generated carbon dioxide is used, the electrooxidation of the anions according to the general formula AB still generates either potential reactants (carbon dioxide), or harmless co-products (nitrogen). Moreover, the formate and oxalate ions appear to be oxidized at rather low potential (at about +1.2 V vs SCE and +0.2 V vs SCE respectively) which widens the range of electroreduction reactions applicable.
- the products obtained by the electrocarboxylations according to the present invention are (poly)carboxylic acids.
- the exact nature of the products depends to some extent on the particular reaction conditions and electrodes used.
- Examples of imines which can be suitably electrocarboxylated comprise (substituted) benzalanilines which are converted into the corresponding alpha-phenyl phenyl glycines.
- Suitable ketones comprise aromatic ketones, such as acetophenone and substituted acetophenones, benzophenone and related compounds.
- the electrocarboxylation of aromatic ketones affords alpha-aryl-alpha-hydroxy acids as well as minor amounts of the corresponding pinacols.
- the process according to the present invention is also of great interest for the preparation of carboxylic acids from the corresponding halogen compounds.
- 1-bromo-2-methyl pentane could be converted almost quantitatively into 3-methyl hexanoic acid using tetraethyl ammonium oxalate as the compound AB as well as the conducting salt.
- acid chlorides can be converted using the process according to the present invention. For instance, pivaloyl chloride was converted in a fair yield to pivalic acid ( analysesd as methyl pivalate).
- the present invention also relates to non-carboxylating electroreductions.
- suitable compounds which can be reduced electrochemically without the introduction of carbon dioxide (whether electrochemically generated or not) into the intermediate to give a carboxylated final product, comprise sulphonium salts, especially aromatic sulphonium salts such as (p-nitro)tosylsulphonium salts, and sulphonamides and 1,2-dihaloalkanes, such as 1,2-dibromo-1,2-diphenyl ethane and related compounds.
- a further example comprises the electroreduction of 1,10-bis(p-toluene sulphonyl)-1,10-diaza-4,7,13,16-tetraoxacyclooctadecane into 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane (also known as 1,10-diaza-1S-crown-6) in almost quantitative yields using tetraethyl ammonium formate as the compound AB as well as conducting salt.
- a non-carboxylating electroreduction is the virtually quantitative pinacolization of acetophenone. However, depending on the reaction conditions electrocarboxylation of acetophenone yielding (after reaction with methyl iodide for product analysis) the methyl ester of alpha-phenyllactic acid may also be achieved.
- the process according to the present invention will normally be carried out in the presence of a solvent for the compound to be electroreduced as well as for the compound AB.
- a solvent for the compound to be electroreduced as well as for the compound AB.
- the choice of the solvent to be applied will depend mainly on the kind of electroreduction envisaged. For instance, when electrocarboxylation reactions are to be carried out, the solvent should be non-aqueous and preferably aprotic. Moreover, the solvent applied should preferably have a fairly high dielectric constant in order to lower the electrical resistance within the cell.
- Suitable solvents comprise ethers such as dimethoxy ethane, diethyl ether, tetrahydrofuran and macrocyclic polyethers such as for instance the so-called crown ethers (1,4,7,10,13,16-tetraoxacyclooctadecane and related compounds), chlorinated or fluorinated hydrocarbons, such as dichloromethane and carbon tetrachloride, nitriles such as acetonitrile, lower alkanols such as methanol or ethanol, formamides such as dimethyl formamide, sulpholane and alkylsubstituted sulpholanes, organic carbonates such as ethylene carbonate and propylene carbonate, nitromethane, N-methyl pyrrolidone and hexamethylene phosphortriamide.
- ethers such as dimethoxy ethane, diethyl ether, tetrahydrofuran and macrocyclic polyethers such
- aprotic As well as of protic solvents.
- the solvents described hereinabove can be used suitably, preference being given to the use of lower alkanols such as methanol and ethanol.
- lower alkanols such as methanol and ethanol.
- the presence of water even in amounts of up to 50 %v, calculated on total solvent, can be tolerated.
- the amount of water present is rather small, e.g. less than 10 %v.
- the compound AB apart from being a reagent also will function as a supporting electrolyte.
- the compound AB when it is dissolved at the beginning of the electrochemical process it will have a better supporting function. It is also possible to introduce a further supporting electrolyte. Use can be made of the supporting electrolytes which are well-known in the art.
- salts of amines or quarternary ammonium salts such as tetraalkyl ammonium, heterocyclic and (alk) aryl ammonium salts, the corresponding anions comprising inorganic as well as organic anions, e.g. phosphates, halides, perchlorates, sulphates, arylsulphonates or alkylsulphonates.
- the amount of additional supporting electrolyte present in the reaction mixture may vary within wide limits. Amounts up to 50 %w on solvent/reagent applied can be used, suitable concentrations often being in the range of from 0.5 %w to 15 %w.
- mixtures of two or more compounds according to the general formula AB as well as mixtures comprising at least one compound according to the general formula AB and at least one additional supporting electrolyte can be suitably used.
- compounds according to the general formula AB an oxalate (i.e. a compound wherein B represents a group wherein R 5 represents a group wherein R 6 is as defined hereinbefore) and a formate (i.e. a compound wherein B represents a group wherein R 5 represents a hydrogen atom) are used
- advantage can be taken from both a carbon dioxide and a proton source within the same reaction mixture. This is of special importance for electrocarboxylation reactions as the presence of protons may influence the composition of the final products.
- the process according to the present invention can be carried out in a one-compartment electrolysis cell, i.e. in an electrolysis cell which does not have a cell divider (membrane, diaphragm) to separate the electrodes.
- the process can be carried out batch-wise or (semi)-continuously.
- One-compartment cells especially suited for continuous operation comprise the so-called capillary gap cells. These cells consist of a stack of circular electrode plates separated from each other by spacers and provided with a central bore. The electrolyte is pumped through the central hole and is forced to flow through the narrow gap between the electrode plates. A constant potential applied over the stack produces a dipolar electrode arrangement, each capillary gap thus serving as a separate cell.
- capillary gap cell such as the pump cell (rotation of one of the circular electrode plates causes the electrolyte to flow outwards through the gap, the cell thus acting as its own pump) and the trickle-tower cell (consisting of layers of conducting rings separated from each other by a nonconducting gauze while the electrolyte is sprayed over the top of the column and trickles down over the rings whilst a certain voltage is maintained over the column) can be used to carry out the process according to the present invention.
- the pump cell rotation of one of the circular electrode plates causes the electrolyte to flow outwards through the gap, the cell thus acting as its own pump
- trickle-tower cell consisting of layers of conducting rings separated from each other by a nonconducting gauze while the electrolyte is sprayed over the top of the column and trickles down over the rings whilst a certain voltage is maintained over the column
- the electrodes to be used in the process according to the present invention can be of any electrode material which is relatively inert under the reaction conditions. Suitable anodes are those comprising platinum or carbon although other materials (e.g. lead dioxide) can be used as well. Cadmium, lead, mercury and mercurated lead are very good materials for the cathode to be used in the process according to the present invention although other materials can be used as well. Very good results can be obtained using a platinum or carbon anode and a lead or mercurated lead cathode.
- the choice of the electrodes will also depend to some extent on the electroreduction envisaged taking into account the oxidation of especially oxalate and/or formate anions at the anode. Also impurities present in one or both electrodes may have some impact on the products obtained.
- the process according to the present invention can be carried out in a wide range of temperatures. It has been found that ambient temperatures can be suitably applied but higher as well as lower temperatures (e.g. between +80 o C and -20°C) are by no means excluded. It is sometimes found that temperatures less than ambient are to be preferred from a yield point of view. It may then be necessary to cool the reaction medium concerned. Normally, good results are obtained when the electrochemical process is carried out at ambient temperature or slightly below.
- electrocarboxylation reactions can be carried out advantageously when carbon dioxide is available at atmospheric or higher pressures. Pressures up to 100 bar can be suitably applied, preference being given to pressures up to 50 bar. As discussed hereinbefore, it is also possible to carry out the electrocarboxylation reactions without the presence of an external carbon dioxide source when oxalates and/or formates are used as the compounds to be electro-oxidized. Non-carboxylating electroreduction reactions are normally carried out at autogeneous pressure, although higher pressures can be used as well.
- the products obtained according to the process according to the present invention can be recovered by a variety of procedures. These procedures are well-known in the art and depend on the particular type of product to be recovered. For instance, in electrocarboxylation processes it may be useful to convert the acids produced into the corresponding alkyl esters by treatment with an alkyl halide such as methyl iodide. It may then be easier to separate the esters produced from the starting materials by chromatographic techniques or by distillation, extraction or a combination of such recovery techniques. It is also possible to treat the acids obtained with a suitable base and extracting the salts obtained from the reaction mixture. When macro(hetero) cyclic polyethers are produced according to the electrochemical process according to the present invention use can be made of the well-known complexing aspects of such products for their recovery in a high yield and with a high degree of purity.
- carboxylic acids can be used in the preparation of the corresponding esters which can be used per se, e.g. as plasticizers or serve as starting materials for the preparation of polyesters by reacting them with the appropriate polyalcohols.
- Macro(hetero) cyclic polyethers such as 18-crown-6 or 1,10-diaza-18-crown-6 can be used for instance as solvents or as phase transfer agents.
- the experiment described in Example II was carried out in a capillary gap cell.
- the capillary gap cell used comprises a series of cylindrical, bipolar graphite discs with a central orifice through which the electrolyte and the appropriate substrates enter. They flow radially to the periphery of the discs where they are collected and withdrawn.
- the carbon dioxide pressure applied was 2 bar and the flow rate of the electrolyte used was 3 1/min
- oxalates and formates to be used in the process according to the present invention can be prepared by methods known in the art.
- a suitable manner for preparing ditetraethyl ammonium oxalate comprises neutralizing a solution of tetraethyl ammonium hydroxide (25 %) in water with the appropriate amount of oxalic acid. Water is then removed using a rotatory evaporator and the residue obtained dried further over a drying agent such as phosphorous pentoxide under reduced pressure. The dry salt obtained appears to be hygroscopic and should therefore be handled in the absence of moisture.
- the compounds may also be prepared by reaction of tertiary amines and the appropriate alkyl esters or by cation-exchange of the carboxylic acid or the appropriate carboxylate(s).
- the products obtained were identified by one or more of the following techniques: gas/liquid chromatography, mass spectrometry, proton magnetic resonance, 13 C magnetic resonance and infrared spectroscopy.
- the electrocarboxylation of dimethyl maleate was carried out in a capillary gap cell as described hereinbefore.
- the electrocarboxylation was carried out in the presence of gaseous carbon dioxide (pressure 2 bar) at a flow rate of the electrolyte system ditetraethyl ammonium oxalate/ acetonitrile of 3 l.min 1.
- the yield of the crude polycarboxylic acids was 77 %.
- the addition of methanol caused precipitation of hexamethyl-1,1,2,3,4,4-butanehexacarboxylate (yield 20 %).
- the electrocarboxylation of acrylonitrile (0.23 mol.l -1 ) was carried out in the vessel described in Example I using a lead cathode and a platinum anode.
- the reduction potential was -2.14 V vs SCE and the current density was 30 mA/cm 2 .
- the current consumed was 1.67 F.mol .
- the compound 1-cyano-dimethyl-1,2-ethanedicarboxylate was obtained after distillation in 34 % chemical yield (41 % current yield).
- Methyl vinyl ketone (0.46 mol.l 1 ) was electrocarboxylated under the conditions described in Example III at a reduction potential of -1.92 V vs SCE and at a current density of 25 mA/cm . The current consumed was 0.90 F.mol -1 . After working up in the usual manner the methyl ester of levulinic acid was obtained in 4 % chemical yield (9 % current yield).
- Example IV The experiment described in Example IV was repeated using alpha-methyl styrene as the compound to be electrocarboxylated.
- the reduction potential was -2.20 V vs SCE and the current density was 18 mA/cm .
- the current consumed was 1.97 F.mol -1 .
- the methyl ester of 2-methyl-2-phenyl succinic acid was obtained in 19 % chemical yield (19 % current yield). Also a trace of the methyl ester of 3-phenyl butanoic acid could be detected.
- Benzalaniline was electrocarboxylated in the manner as described in Example I using a lead cathode and a platinum anode.
- concentration of benzalaniline amounted to 0.20 mol.l -1 and that of DTEAOx to 0.23 mol.l -1 , the solvent being dry acetonitrile.
- the electrocarboxylation was performed at a reduction potential of -1.80 V vs SCE and at a current density of 20 mA/cm .
- the current consumed was 1.50 F.mol .
- methyl-2-phenyl-2-anilino acetate was obtained in 58 % chemical yield (79 % current yield).
- Example VI The experiment described in Example VI was repeated using acetophenone (0.23 mol.l -1 ) as the compound to be electrocarboxylated.
- the reduction potential was -1.80 V vs SCE and the current density was 25 mA/cm .
- the current consumed was 1.06 F.mol -1 .
- the methyl ester of alpha-phenyl lactic acid was obtained as the main product (40 % chemical yield, 58 % current yield).
- acetophenone pinacol (2,3-dihydroxy-2,3-diphenylbutane) had been formed in 29 % chemical yield (21 % current yield).
- Example VII The experiment described in Example VII was repeated using azobenzene (0.23 mol.l 1 ) as the compound to be electrocarboxylated.
- the reduction potential was -1.31 V vs SCE and the current density was 13 mA/cm .
- the current consumed was 1.06 F.mol -1 .
- a mixture of the methyl esters of the mono- and dicarboxylic acid of azobenzene was obtained:
- the electroreduction of p-nitrobenzyl dimethyl sulphonium chloride was performed in the vessel described in Example Ia. The electroreduction was carried out at room temperature using a lead cathode and a platinum anode. Methanol was used as the solvent and the concentration of the sulphonium compound amounted to 0.025 mol.l -1 whereas the concentration of the conducting salt DTEAOx amounted to 0.23 mol.l -1 .
- the reduction potential was -1.0 V vs SCE and the current density was 3 mA/cm2. The current consumed was 1.4 F.mol -1 .
- the reaction products found were para-nitrotoluene in 22 % yield (55 % current yield) and 4,4'-dinitrobibenzyl in 13 % yield (9 % current yield).
- Example VII The experiment described in Example XIIa was repeated using acetonitrile as the solvent.
- the reduction potential was -1.80 V vs SCE at a current density of 2 mA/cm 2 .
- the current consumed was 1.59 F.mol -1 and acetophenone pinacol was obtained in 46 % chemical yield (29 % current yield). Again no carboxylation product could be detected (cf. Example VII).
- Example XIIa The experiment described in Example XIIa was repeated using tetraethyl ammonium glycolate as the conducting salt (0.23 mol.l -1 ). The electroreduction was carried out at a reduction potential of -1.71 V vs SCE at a current density of 16 mA/cm . The current consumed was 1.46 F.mol -1 . Acetophenone pinacol was obtained in 90 % chemical yield (60 % current yield).
- Example XIIc The experiment described in Example XIIc was repeated using the methyl ether of tetramethyl ammonium glycolate as the conducting salt (0.25 mol.l -1 ). The electroreduction was carried out at a reduction potential of -1.68 V vs SCE at a current density of 13 mA/cm . The current consumed was 1.40 F.mol . Acetophenone pinacol was obtained in 87 % chemical yield (62 % current yield).
- Example XIIIa The experiment described in Example XIIIa was repeated using acetonitrile containing 10 %w H 2 0 as the solvent. Ditetraethyl ammonium oxalate was used as the conducting salt (0.25 mol.l ). The electroreduction was carried out at 80 °C and at a reduction potential of -1.50 V vs SCE at a current density of 18 mA/cm 2 . The current consumed was 2.04 F.mol -1 . After working up trans-stilbene was obtained in 93 % chemical yield (91% current yield).
- Example XIIIb The experiment described in Example XIIIb was repeated using acetonitrile/water (1:1) as the solvent mixture. The electroreduction was carried out at a reduction potential of -1.70 V vs SCE at a current density of 5 mA/cm 2 . The current consumed was 2.35 F.mol -1 . After working up trans-stilbene was obtained in 75 % chemical yield (64 % current yield.
- Example XIIIc The experiment described in Example XIIIc was repeated using dry methanol as the solvent and ammonium- formate (0.2 mol.l -1 ) as the conducting salt. The electroreduction was carried out at a reduction potential of -1.54 V vs SCE at a current density of 9 mA/cm . The current consumed was 5.1 F.mol -1 . After working up trans-stilbene was obtained in 92 % chemical yield (36 % current yield).
Landscapes
- 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)
Abstract
Description
- The present invention relates to electrochemical reactions which can be carried out suitably in a non-aqueous or aprotic environment. The present invention relates in particular to electrochemical reductions, e.g. electrocarboxylations, which can be carried out in an aprotic environment in undivided cells.
- It will be clear that electrochemical processes require the simultaneous occurrence of cathodic and anodic reactions. Since electrochemical processes are normally aimed at the production of preferably one compound at one particular electrode (the working electrode), less or virtually no interest is paid to the process or processes occurring simultaneously at the other electrode (counter electrode). In a number of cases, the reaction at the counter-electrode will not constitute a major problem. For instance, when the reaction at the counter-electrode occurs at a sufficiently low potential the products formed at the working electrode will not be destructed electrochemically at the counter-electrode.
- However, if no such reaction at the counter-electrode can be found it will be necessary to separate the anode and the cathode. In protic media diaphragms based on ion-exchange resins can be suitably used, but such diaphragms can not be used satisfactorily in a non-aqueous or an aprotic environment as they become very poorly conducting so that thermal damage may occur even at low current densities. Also diaphragms based on the principle of diffusion limitation are unsuitable for use in non-aqueous, in particular in aprotic environments since the requirements to combine a high electrical conductivity with little diffusion and sufficient mechanical strength appear to be incompatible. Furthermore, the possibility of electrolysis of the solvent as the reaction at the counter-electrode which can be used nicely for electrochemical processes to be carried out in a protic environment is not available for electrochemical processes to be carried out in a non-aqueous or in an aprotic environment since this would generate highly active species, which would unavoidably lead to the occurrence of a great many undesired side reactions.
- It would be of great importance when use could be made in electrochemical processes which have to be carried out in a non-aqueous, and in particular in an aprotic environment in an undivided cell of a reaction at the counter-electrode which not only works at a potential which protects starting materials and products formed at the working electrode from electrochemical destruction at the counter-electrode but also has the advantage that the materials to be converted at the counter-electrode as well as the products obtained do not interfere in an adverse way with the reaction and/or reaction products at the working electrode.
- It has now been found that electroreduction processes can be carried out conveniently in a non-aqueous or aprotic environment in an undivided cell when use is made in the electrooxidation step of certain specific compounds which fulfill the requirements set out hereinabove.
- The present invention therefore relates to a process for the electroreductive preparation of organic compounds in an undivided cell which comprises as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents an alkali or alkaline earth metal moiety; a group of formula NR1R2R3R4, wherein each of R , R2, R3 and R which may be the same or different, represents a hydrogen atom, an alkyl group of up to 8 carbon atoms, or an (alk)aryl group, which may be substituted by one or more lower alkyl groups; or a pyridinium ion which may be substituted by one or more lower alkyl groups and B represents an azide group or a group
- The present invention is of particular interest in that the products obtained at the counter-electrode in the electrooxidation step (i.a. carbon dioxide and nitrogen) in an undivided cell do not interfere adversely with the products obtained in the electroreduction step and are also of no environmental concern. Moreover, in electrocarboxylation reactions use can be made of the electrooxidation of anions of the type
- The present invention relates in particular to a process for the electroreductive preparation of organic compounds in an undivided cell in a non-aqueous or aprotic environment which comprises as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents an alkali or alkaline earth metal moiety, a group of formula NR1R2R3R4 wherein each of R , R2, R3 and R , which may be the same or different, represents an alkyl group of up to 4 carbon atoms, a phenyl group or a pyridinium ion and B represents a group
- Preferred processes according to the present invention are electroreductive preparations of organic compounds in an undivided cell in non-aqueous or aprotic environments, which comprise as reaction at the counter-electrode the oxidation of anions of one or more compounds according to the general formula AB, wherein A represents a group of formula NR1R2R3R4, wherein each of R , R 2 1 R 3 and R4, which may be the same or different, represents a methyl or ethyl group, and B represents a group
- The process according to the present invention is of particular interest for electrocarboxylation reactions, i.e. reactions in which carbon dioxide is reacted with electro- generated (carb)anions. Suitable electrocarboxylation reactions comprise the carboxylations of activated olefins, imines, and related species such as azo-compounds, ketones as well as of halogen compounds. Preferred electrocarboxylations are those wherein an activated olefin is the compound to be reduced electrochemically.
- Activated olefins which can be electrocarboxylated using the process according to the present invention can be represented by the general formula
- Preferred compounds according to the general formula I to be used in the process according to the present invention are those wherein A represents a group -CN, a group
- It should be noted that the electrocarboxylations according to the present invention can be performed using carbon dioxide generated at the anode as the sole carbon dioxide source. If desired, the electrocarboxylations can also be performed using additional carbon dioxide. Even in those events wherein a large molar excess of non-electrochemically generated carbon dioxide is used, the electrooxidation of the anions according to the general formula AB still generates either potential reactants (carbon dioxide), or harmless co-products (nitrogen). Moreover, the formate and oxalate ions appear to be oxidized at rather low potential (at about +1.2 V vs SCE and +0.2 V vs SCE respectively) which widens the range of electroreduction reactions applicable.
- The products obtained by the electrocarboxylations according to the present invention are (poly)carboxylic acids. The exact nature of the products depends to some extent on the particular reaction conditions and electrodes used.
- For instance, starting from dimethyl maleate in a one-compartment (undivided) cell at room temperature in acetonitrile using tetraethyl ammonium oxalate as the compound to be oxidized as well as being the conducting salt, a crude polycarboxylic acid product mixture had been formed (esterified with methyl iodide for product analysis) with a current yield as high as 80 %. After further purification hexamethyl-1,1,2,3,4,4-butane hexacarboxylate was isolated in 40 % yield.
- However, when tetraethyl ammonium formate was used as the compound AB as well as conducting salt the product distribution of the polycarboxylic acid esters obtained was significantly changed in that the main products appeared to be trimethyl-1,1,2-ethane tricarboxylate (59 % current yield) and tetramethyl-1,2,3,4-butane tetracarboxylate (20 % current yield); no hexamethyl hexacarboxylate could be detected. Without wishing to be bound to any particular theory, it would appear that the change in product distribution has to be ascribed to an increased protonationversus carboxylation of anionic intermediates due to the production of protons from the anodic oxidation reaction.
- The electrocarboxylation of acrylonitrile yielded dimethyl cyanosuccinate in 41 % yield after distillation of the methylated product whereas the main products in the electrocarboxylation of methyl vinyl ketone and alpha-methyl styrene were levulinic acid and 2-methyl-2-phenyl- succinic acid, respectively.
- Examples of imines which can be suitably electrocarboxylated comprise (substituted) benzalanilines which are converted into the corresponding alpha-phenyl phenyl glycines. Suitable ketones comprise aromatic ketones, such as acetophenone and substituted acetophenones, benzophenone and related compounds. The electrocarboxylation of aromatic ketones affords alpha-aryl-alpha-hydroxy acids as well as minor amounts of the corresponding pinacols. The process according to the present invention is also of great interest for the preparation of carboxylic acids from the corresponding halogen compounds. For instance, 1-bromo-2-methyl pentane could be converted almost quantitatively into 3-methyl hexanoic acid using tetraethyl ammonium oxalate as the compound AB as well as the conducting salt. Also acid chlorides can be converted using the process according to the present invention. For instance, pivaloyl chloride was converted in a fair yield to pivalic acid (analysed as methyl pivalate).
- Apart from electrocarboxylation reactions as discussed hereinbefore, the present invention also relates to non-carboxylating electroreductions. Examples of suitable compounds which can be reduced electrochemically without the introduction of carbon dioxide (whether electrochemically generated or not) into the intermediate to give a carboxylated final product, comprise sulphonium salts, especially aromatic sulphonium salts such as (p-nitro)tosylsulphonium salts, and sulphonamides and 1,2-dihaloalkanes, such as 1,2-dibromo-1,2-diphenyl ethane and related compounds. Without wishing to be bound to any particular theory it would appear that non-carboxylating electroreductions will occur primarily when reactions such as dimerisation, elimination and/or hydrogen abstraction from the solvent become faster reactions than the electrocarboxylation reaction. It is likely that the reduction potential of the intermediary radical species will be a decisive factor in governing the course of the reaction. For instance, 4,4'-dinitrobibenzyl as well as p-nitrotoluene were obtained when electroreducing dimethyl (p-nitro)tosyl sulphonium chloride in methanol according to the process according to the present invention.
- A further example comprises the electroreduction of 1,10-bis(p-toluene sulphonyl)-1,10-diaza-4,7,13,16-tetraoxacyclooctadecane into 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane (also known as 1,10-diaza-1S-crown-6) in almost quantitative yields using tetraethyl ammonium formate as the compound AB as well as conducting salt. Yet a further example of a non-carboxylating electroreduction is the virtually quantitative pinacolization of acetophenone. However, depending on the reaction conditions electrocarboxylation of acetophenone yielding (after reaction with methyl iodide for product analysis) the methyl ester of alpha-phenyllactic acid may also be achieved.
- The process according to the present invention will normally be carried out in the presence of a solvent for the compound to be electroreduced as well as for the compound AB. It will be clear that the choice of the solvent to be applied will depend mainly on the kind of electroreduction envisaged. For instance, when electrocarboxylation reactions are to be carried out, the solvent should be non-aqueous and preferably aprotic. Moreover, the solvent applied should preferably have a fairly high dielectric constant in order to lower the electrical resistance within the cell. Suitable solvents comprise ethers such as dimethoxy ethane, diethyl ether, tetrahydrofuran and macrocyclic polyethers such as for instance the so-called crown ethers (1,4,7,10,13,16-tetraoxacyclooctadecane and related compounds), chlorinated or fluorinated hydrocarbons, such as dichloromethane and carbon tetrachloride, nitriles such as acetonitrile, lower alkanols such as methanol or ethanol, formamides such as dimethyl formamide, sulpholane and alkylsubstituted sulpholanes, organic carbonates such as ethylene carbonate and propylene carbonate, nitromethane, N-methyl pyrrolidone and hexamethylene phosphortriamide. The optimum choice will depend on the potential to be worked at in the electrochemical reaction. For electrocarboxylations preference is given to the use of acetonitrile, dimethyl formamide and methanol, the use of acetonitrile being particularly preferred.
- When non-carboxylating electroreductions are to be carried out according to the process according to the present invention use can be made of aprotic as well as of protic solvents. In general the solvents described hereinabove can be used suitably, preference being given to the use of lower alkanols such as methanol and ethanol. Under those circumstances the presence of water, even in amounts of up to 50 %v, calculated on total solvent, can be tolerated. However, better results will generally be obtained when the amount of water present is rather small, e.g. less than 10 %v.
- It will be clear that the compound AB apart from being a reagent also will function as a supporting electrolyte. For this purpose it is not absolutely necessary to have the compound AB completely dissolved in the reaction medium as dissolution of non-dissolved material will occur gradually during the electrochemical process concerned. However, when the compound AB is dissolved at the beginning of the electrochemical process it will have a better supporting function. It is also possible to introduce a further supporting electrolyte. Use can be made of the supporting electrolytes which are well-known in the art. Reference is made to salts of amines or quarternary ammonium salts such as tetraalkyl ammonium, heterocyclic and (alk) aryl ammonium salts, the corresponding anions comprising inorganic as well as organic anions, e.g. phosphates, halides, perchlorates, sulphates, arylsulphonates or alkylsulphonates.
- The amount of additional supporting electrolyte present in the reaction mixture may vary within wide limits. Amounts up to 50 %w on solvent/reagent applied can be used, suitable concentrations often being in the range of from 0.5 %w to 15 %w.
- If desired, mixtures of two or more compounds according to the general formula AB as well as mixtures comprising at least one compound according to the general formula AB and at least one additional supporting electrolyte can be suitably used. In the event that as compounds according to the general formula AB an oxalate (i.e. a compound wherein B represents a group
- Various current densities can be employed in the process according to the present invention. It will be advantageous to employ relatively high current densities in order to achieve high use of electrolysis cell capacity depending on factors such as cost and source of electrical current, resistance of the reaction medium, heat dissipation problems and impact upon yields. It has been found that current densities of from 5-1000 mA/cm 2 can suitably be used for the process according to the present invention. Preference being given to current densities of 25 mA/cm 2 and above.
- As disclosed hereinbefore, the process according to the present invention can be carried out in a one-compartment electrolysis cell, i.e. in an electrolysis cell which does not have a cell divider (membrane, diaphragm) to separate the electrodes. The process can be carried out batch-wise or (semi)-continuously. One-compartment cells especially suited for continuous operation, comprise the so-called capillary gap cells. These cells consist of a stack of circular electrode plates separated from each other by spacers and provided with a central bore. The electrolyte is pumped through the central hole and is forced to flow through the narrow gap between the electrode plates. A constant potential applied over the stack produces a dipolar electrode arrangement, each capillary gap thus serving as a separate cell. Also modifications of the capillary gap cell such as the pump cell (rotation of one of the circular electrode plates causes the electrolyte to flow outwards through the gap, the cell thus acting as its own pump) and the trickle-tower cell (consisting of layers of conducting rings separated from each other by a nonconducting gauze while the electrolyte is sprayed over the top of the column and trickles down over the rings whilst a certain voltage is maintained over the column) can be used to carry out the process according to the present invention.
- The electrodes to be used in the process according to the present invention can be of any electrode material which is relatively inert under the reaction conditions. Suitable anodes are those comprising platinum or carbon although other materials (e.g. lead dioxide) can be used as well. Cadmium, lead, mercury and mercurated lead are very good materials for the cathode to be used in the process according to the present invention although other materials can be used as well. Very good results can be obtained using a platinum or carbon anode and a lead or mercurated lead cathode. The choice of the electrodes will also depend to some extent on the electroreduction envisaged taking into account the oxidation of especially oxalate and/or formate anions at the anode. Also impurities present in one or both electrodes may have some impact on the products obtained.
- The process according to the present invention can be carried out in a wide range of temperatures. It has been found that ambient temperatures can be suitably applied but higher as well as lower temperatures (e.g. between +80oC and -20°C) are by no means excluded. It is sometimes found that temperatures less than ambient are to be preferred from a yield point of view. It may then be necessary to cool the reaction medium concerned. Normally, good results are obtained when the electrochemical process is carried out at ambient temperature or slightly below.
- With respect to pressure it should be noted that especially electrocarboxylation reactions can be carried out advantageously when carbon dioxide is available at atmospheric or higher pressures. Pressures up to 100 bar can be suitably applied, preference being given to pressures up to 50 bar. As discussed hereinbefore, it is also possible to carry out the electrocarboxylation reactions without the presence of an external carbon dioxide source when oxalates and/or formates are used as the compounds to be electro-oxidized. Non-carboxylating electroreduction reactions are normally carried out at autogeneous pressure, although higher pressures can be used as well.
- The products obtained according to the process according to the present invention can be recovered by a variety of procedures. These procedures are well-known in the art and depend on the particular type of product to be recovered. For instance, in electrocarboxylation processes it may be useful to convert the acids produced into the corresponding alkyl esters by treatment with an alkyl halide such as methyl iodide. It may then be easier to separate the esters produced from the starting materials by chromatographic techniques or by distillation, extraction or a combination of such recovery techniques. It is also possible to treat the acids obtained with a suitable base and extracting the salts obtained from the reaction mixture. When macro(hetero) cyclic polyethers are produced according to the electrochemical process according to the present invention use can be made of the well-known complexing aspects of such products for their recovery in a high yield and with a high degree of purity.
- It will be clear that the compounds produced according to the present invention can be used in various ways depending on their proper nature, e.g. carboxylic acids can be used in the preparation of the corresponding esters which can be used per se, e.g. as plasticizers or serve as starting materials for the preparation of polyesters by reacting them with the appropriate polyalcohols. Macro(hetero) cyclic polyethers such as 18-crown-6 or 1,10-diaza-18-crown-6 can be used for instance as solvents or as phase transfer agents.
- The invention will now be illustrated by means of the following Examples.
- The experiments described in the Examples I and III-XIII were carried out in a cylindrical glass cell of 100 ml provided with two electrodes, each having a surface-area of 6 cm . A reference electrode was situated within the vessel. The potential of the working electrode was controlled by means of a reference electrode contacted with the solution by a Luggin-capillary. The experiments were carried out in the presence of atmospheric carbon dioxide pressure.
- The experiment described in Example II was carried out in a capillary gap cell. The capillary gap cell used comprises a series of cylindrical, bipolar graphite discs with a central orifice through which the electrolyte and the appropriate substrates enter. They flow radially to the periphery of the discs where they are collected and withdrawn. The carbon dioxide pressure applied was 2 bar and the flow rate of the electrolyte used was 3 1/min
- Normally available electrodes were used in the experiments with the exception of mercurated lead electrodes which were prepared by either reducing an aqueous solution of Hg(II) acetate at -0.90 V vs Standard Calomel Electrode (SCE)/ 180 mA for 15 minutes on a lead electrode or by rubbing polarographically pure mercury on a freshly cleaned lead surface.
- The oxalates and formates to be used in the process according to the present invention can be prepared by methods known in the art. For instance, a suitable manner for preparing ditetraethyl ammonium oxalate (DTEAOx) comprises neutralizing a solution of tetraethyl ammonium hydroxide (25 %) in water with the appropriate amount of oxalic acid. Water is then removed using a rotatory evaporator and the residue obtained dried further over a drying agent such as phosphorous pentoxide under reduced pressure. The dry salt obtained appears to be hygroscopic and should therefore be handled in the absence of moisture.
- The compounds may also be prepared by reaction of tertiary amines and the appropriate alkyl esters or by cation-exchange of the carboxylic acid or the appropriate carboxylate(s).
- The products obtained were identified by one or more of the following techniques: gas/liquid chromatography, mass spectrometry, proton magnetic resonance, 13C magnetic resonance and infrared spectroscopy.
-
- a) The experiment was performed in the vessel as described hereinbefore. The electrocarboxylation reaction was carried out in dry acetonitrile as the solvent, using a lead cathode and a platinum anode. The reaction was carried out at room temperature using dimethyl maleate in a concentration of 0.46 mol.l and ditetraethyl ammonium oxalate as the carbon dioxide source/conducting salt (0.23 mol.l-1). The reduction potential applied was -1.60 V vs SCE at a current density of 100 mA/cm2.
After the reaction had been stopped a crude polycarboxylic acid product mixture had been obtained which was then esterified using methyl iodide to facilitate product analysis in the form of the corresponding methyl esters. The current consumed was 0.95 F.mol-1 and the current yield of the crude polycarboxylic acid product mixture was 80 %. From this mixture of polycarboxylic acid methyl esters hexamethyl-1,1,2,3,4,4-butane- hexacarboxylate was isolated by crystallization from methanol in 39 % chemical yield (41 % current yield). - b) The experiment described in Example Ia was repeated using a carbon anode. The reduction potential was again -1.60 V vs SCE and the current density applied was 65 mA/cm2. The current consumed was 0.94 F.mol 1. After working-up in the manner as described hereinbefore hexamethyl-1,1,2,3,3,4-butanehexacarboxylate was obtained in 42 % chemical yield (45 % current yield).
- c) The experiment described in Example Ib was repeated using tetraethyl ammonium formate (0.46 mol.l ) as the carbon dioxide source/conducting salt. The electrocarboxylation was performed at a reduction potential of -1.60 V vs SCE and at a current density of 38 mA/cm2. The current consumed was 1.18 F.mol-1. After a working-up procedure similar to that described in Example Ib two main products were identified in the form of the respective methyl esters: trimethyl-1,1,2-ethanetricarboxylate in 35 % chemical yield (59 % current yield) and tetramethyl-1,2,3,4-butanetetracarboxylate in 17 % chemical yield (20 % current yield). No hexamethyl-1,1,2,3,4,4-butanehexacarboxylate could be detected indicating the influence of protons originating from the oxidation of the formate ion on the reaction pattern.
- d) The experiment described in Example Ia was repeated using tetraethyl ammonium azide (0.23 mol.l-1) as the conducting salt. The electrocarboxylation was performed at a reduction potential of -1.53 V vs SCE at a current 2 density of 25 mA/cm . The current consumed was 1.02 F.mol-1. After working up in the manner as described hereinbefore polycarboxylic acids were obtainedd in 40 % chemical yield (40 % current yield) of which 11 % appeared to be hexamethyl-1,1,2,3,4,4-butanehexacarboxylate.
- e) The experiment described in Example Ia was repeated using methyl triethylmethylammonium oxalate (0.23 mol.l-1) as the conducting salt. The electrocarboxylation was performed at a reduction potential of -1.60 V vs SCE at 2 a current density of 40 mA/cm . The current consumed was 0.45 F.mol . After working up in the manner as described hereinbefore tetramethyl-1,2,3,4-butane tetracarboxylate was obtained in 38 % current yield.
- The electrocarboxylation of dimethyl maleate was carried out in a capillary gap cell as described hereinbefore. The electrocarboxylation was carried out in the presence of gaseous carbon dioxide (pressure 2 bar) at a flow rate of the electrolyte system ditetraethyl ammonium oxalate/ acetonitrile of 3 l.min 1. The yield of the crude polycarboxylic acids (isolated as the corresponding methyl esters and identified by gas/liquid chromatography) was 77 %. The addition of methanol caused precipitation of hexamethyl-1,1,2,3,4,4-butanehexacarboxylate (yield 20 %). Distillation of the residue afforded an additional 40 % yield of the following esters: trimethyl-1,1,2-ethanetricarboxylate (5 %) tetramethyl-1,1,2,2-ethanetetracarboxylate (24 %) and pentamethyl-1,1,2,3,4-butanepentacarboxylate (11 %).
- The electrocarboxylation of acrylonitrile (0.23 mol.l-1) was carried out in the vessel described in Example I using a lead cathode and a platinum anode. The concentration of the carbondioxide source/conducting salt DTEAOx amounted to 0.23 mol.l 1. The reduction potential was -2.14 V vs SCE and the current density was 30 mA/cm2. The current consumed was 1.67 F.mol . The compound 1-cyano-dimethyl-1,2-ethanedicarboxylate was obtained after distillation in 34 % chemical yield (41 % current yield).
- Methyl vinyl ketone (0.46 mol.l 1) was electrocarboxylated under the conditions described in Example III at a reduction potential of -1.92 V vs SCE and at a current density of 25 mA/cm . The current consumed was 0.90 F.mol-1. After working up in the usual manner the methyl ester of levulinic acid was obtained in 4 % chemical yield (9 % current yield).
- The experiment described in Example IV was repeated using alpha-methyl styrene as the compound to be electrocarboxylated. The reduction potential was -2.20 V vs SCE and the current density was 18 mA/cm . The current consumed was 1.97 F.mol-1. After working up in the usual manner the methyl ester of 2-methyl-2-phenyl succinic acid was obtained in 19 % chemical yield (19 % current yield). Also a trace of the methyl ester of 3-phenyl butanoic acid could be detected.
- Benzalaniline was electrocarboxylated in the manner as described in Example I using a lead cathode and a platinum anode. The concentration of benzalaniline amounted to 0.20 mol.l-1 and that of DTEAOx to 0.23 mol.l-1, the solvent being dry acetonitrile. The electrocarboxylation was performed at a reduction potential of -1.80 V vs SCE and at a current density of 20 mA/cm . The current consumed was 1.50 F.mol . After working up in the usual manner methyl-2-phenyl-2-anilino acetate was obtained in 58 % chemical yield (79 % current yield).
- The experiment described in Example VI was repeated using acetophenone (0.23 mol.l-1) as the compound to be electrocarboxylated. The reduction potential was -1.80 V vs SCE and the current density was 25 mA/cm . The current consumed was 1.06 F.mol-1. After working up in the usual manner the methyl ester of alpha-phenyl lactic acid was obtained as the main product (40 % chemical yield, 58 % current yield). Also acetophenone pinacol (2,3-dihydroxy-2,3-diphenylbutane) had been formed in 29 % chemical yield (21 % current yield).
- The experiment described in Example VII was repeated using azobenzene (0.23 mol.l 1) as the compound to be electrocarboxylated. The reduction potential was -1.31 V vs SCE and the current density was 13 mA/cm . The current consumed was 1.06 F.mol-1. After working up in the usual manner, a mixture of the methyl esters of the mono- and dicarboxylic acid of azobenzene was obtained:
-
- a) The experiment described in Example VIII was repeated using 1-bromo-2-methylpentane (0.23 mol.l 1) as the substrate. The reduction potential was -2.15 V vs SCE and the current density amounted to 8 mA/cm2. The current consumed was 2.03 F.mol-1. After working up in the usual manner the methyl ester of beta-methyl hexanoic acid was isolated in a very high yield: 96 % chemical yield and 95 % current yield.
- b) The experiment described in Example IXa was repeated using pivaloylchloride (0.23 mol.l-1) as the substrate. The reduction potential was -2.20 V vs SCE and the current density was 28 mA/cm. The current consumed was 1.61 F.mol-1. After the usual working up procedure methyl pivaloate was obtained in 50 % chemical yield (62 % current yield)
- c) The experiment described in Example IXa was repeated using 1,1,1,2,3,3,3-heptachloropropane as the substrate. After the usual working up procedure the methyl ester of alpha-trichloromethyl beta-trichloropropionic acid was isolated in 30 % current yield.
- d) The experiment described in Example IXa was repeated using 2,4-dibromo-2,4-dimethylpentan-3-one as the substrate. After the usual working up procedure a mixture of carboxylated products was obtained.
- The electroreduction of p-nitrobenzyl dimethyl sulphonium chloride was performed in the vessel described in Example Ia. The electroreduction was carried out at room temperature using a lead cathode and a platinum anode. Methanol was used as the solvent and the concentration of the sulphonium compound amounted to 0.025 mol.l-1 whereas the concentration of the conducting salt DTEAOx amounted to 0.23 mol.l-1. The reduction potential was -1.0 V vs SCE and the current density was 3 mA/cm2. The current consumed was 1.4 F.mol-1. The reaction products found were para-nitrotoluene in 22 % yield (55 % current yield) and 4,4'-dinitrobibenzyl in 13 % yield (9 % current yield).
- The experiment described in the previous Example was repeated using a mercury cathode and a lead anode whilst the compound to be electroreduced was 1,10-bis(p-toluene sulphonyl)-1,10-diaza-18-crown-6 dissolved in dimethyl formamide (0.0044 mol.l-1). The conducting salt was tetraethyl ammonium formate (0.20 mol.l-1) and the electroreduction was carried out at a reduction potential of -2.26 V vs SCE at a current density of 3 mA/cm . The current consumed was 5.4 F.mol . 1,10-Diaza-18-crown-6 was obtained in 85 % chemical yield (63 % current yield).
- a) The electroreduction described in the previous Example was repeated using a mercury cathode and a platinum anode whilst the compound to be electroreduced was acetophenone dissolved in methanol (0.23 mol.l-1). The conducting salt was ditetraethyl ammonium oxalate (0.23 mol.l-1) and the electroreduction was carried out at a reduction potential of -1.60 V vs SCE at a current density of 20 mA/cm2. The current consumed was 1.55 F.mol . Acetophenone pinacol was obtained in 94 % chemical yield (61 % current yield). No carboxylated product could be detected (cf. Example VII).
- b) The experiment described in Example XIIa was repeated using acetonitrile as the solvent. The reduction potential was -1.80 V vs SCE at a current density of 2 mA/cm2. The current consumed was 1.59 F.mol-1 and acetophenone pinacol was obtained in 46 % chemical yield (29 % current yield). Again no carboxylation product could be detected (cf. Example VII).
- c) The experiment described in Example XIIa was repeated using tetraethyl ammonium glycolate as the conducting salt (0.23 mol.l-1). The electroreduction was carried out at a reduction potential of -1.71 V vs SCE at a current density of 16 mA/cm . The current consumed was 1.46 F.mol-1. Acetophenone pinacol was obtained in 90 % chemical yield (60 % current yield).
- d) The experiment described in Example XIIc was repeated using the methyl ether of tetramethyl ammonium glycolate as the conducting salt (0.25 mol.l-1). The electroreduction was carried out at a reduction potential of -1.68 V vs SCE at a current density of 13 mA/cm . The current consumed was 1.40 F.mol . Acetophenone pinacol was obtained in 87 % chemical yield (62 % current yield).
- a) The electroreduction of 1,2-dibromo-1,2-diphenyl ethane in acetonitrile (0.31 mol.l-1) was carried out in the vessel described in Example I using a lead cathode and a platina anode. The concentration of the conducting salt ditetraethyl ammonium oxalate was 0.23 mol.l-1. The reduction potential was -1.35 V vs SCE at a current density of 20 mA/cm2. The current consumed was 1.95 F.mol-1. After working up stilbene was obtained in 84 % chemical yield (86 % current yield) in a cis/trans ratio of 38/62.
- b) The experiment described in Example XIIIa was repeated using acetonitrile containing 10 %w H20 as the solvent. Ditetraethyl ammonium oxalate was used as the conducting salt (0.25 mol.l ). The electroreduction was carried out at 80 °C and at a reduction potential of -1.50 V vs SCE at a current density of 18 mA/cm2. The current consumed was 2.04 F.mol-1. After working up trans-stilbene was obtained in 93 % chemical yield (91% current yield).
- c) The experiment described in Example XIIIb was repeated using acetonitrile/water (1:1) as the solvent mixture. The electroreduction was carried out at a reduction potential of -1.70 V vs SCE at a current density of 5 mA/cm2. The current consumed was 2.35 F.mol-1. After working up trans-stilbene was obtained in 75 % chemical yield (64 % current yield.
- d) The experiment described in Example XIIIc was repeated using dry methanol as the solvent and ammonium- formate (0.2 mol.l-1) as the conducting salt. The electroreduction was carried out at a reduction potential of -1.54 V vs SCE at a current density of 9 mA/cm . The current consumed was 5.1 F.mol-1. After working up trans-stilbene was obtained in 92 % chemical yield (36 % current yield).
Claims (21)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7937859 | 1979-11-01 | ||
GB7937859 | 1979-11-01 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0028430A1 true EP0028430A1 (en) | 1981-05-13 |
EP0028430B1 EP0028430B1 (en) | 1984-01-18 |
Family
ID=10508910
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP80200992A Expired EP0028430B1 (en) | 1979-11-01 | 1980-10-20 | A process for the electroreductive preparation of organic compounds |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0028430B1 (en) |
JP (1) | JPS5675584A (en) |
DE (1) | DE3066199D1 (en) |
Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4582577A (en) * | 1984-12-19 | 1986-04-15 | Monsanto Company | Electrochemical carboxylation of p-isobutylacetophenone |
WO2014042783A1 (en) * | 2012-09-14 | 2014-03-20 | Liquid Light, Inc. | Multiphase electrochemical reduction of co2 |
US8821709B2 (en) | 2012-07-26 | 2014-09-02 | Liquid Light, Inc. | System and method for oxidizing organic compounds while reducing carbon dioxide |
US8845878B2 (en) | 2010-07-29 | 2014-09-30 | Liquid Light, Inc. | Reducing carbon dioxide to products |
US8845877B2 (en) | 2010-03-19 | 2014-09-30 | Liquid Light, Inc. | Heterocycle catalyzed electrochemical process |
US8858777B2 (en) | 2012-07-26 | 2014-10-14 | Liquid Light, Inc. | Process and high surface area electrodes for the electrochemical reduction of carbon dioxide |
US8889897B2 (en) | 2011-12-23 | 2014-11-18 | Air Products And Chemicals, Inc. | Electrocarboxylation synthesis for obtaining intermediates useful for the synthesis of SPAN derivatives |
US8961774B2 (en) | 2010-11-30 | 2015-02-24 | Liquid Light, Inc. | Electrochemical production of butanol from carbon dioxide and water |
US8986533B2 (en) | 2009-01-29 | 2015-03-24 | Princeton University | Conversion of carbon dioxide to organic products |
US9085827B2 (en) | 2012-07-26 | 2015-07-21 | Liquid Light, Inc. | Integrated process for producing carboxylic acids from carbon dioxide |
US9090976B2 (en) | 2010-12-30 | 2015-07-28 | The Trustees Of Princeton University | Advanced aromatic amine heterocyclic catalysts for carbon dioxide reduction |
US9175409B2 (en) | 2012-07-26 | 2015-11-03 | Liquid Light, Inc. | Multiphase electrochemical reduction of CO2 |
US9222179B2 (en) | 2010-03-19 | 2015-12-29 | Liquid Light, Inc. | Purification of carbon dioxide from a mixture of gases |
US9267212B2 (en) | 2012-07-26 | 2016-02-23 | Liquid Light, Inc. | Method and system for production of oxalic acid and oxalic acid reduction products |
US9309599B2 (en) | 2010-11-30 | 2016-04-12 | Liquid Light, Inc. | Heterocycle catalyzed carbonylation and hydroformylation with carbon dioxide |
US10119196B2 (en) | 2010-03-19 | 2018-11-06 | Avantium Knowledge Centre B.V. | Electrochemical production of synthesis gas from carbon dioxide |
US10329676B2 (en) | 2012-07-26 | 2019-06-25 | Avantium Knowledge Centre B.V. | Method and system for electrochemical reduction of carbon dioxide employing a gas diffusion electrode |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3344045A (en) * | 1964-10-23 | 1967-09-26 | Sun Oil Co | Electrolytic preparation of carboxylic acids |
US3379627A (en) * | 1962-09-20 | 1968-04-23 | Pullman Inc | Process for the manufacture of oxygencontaining derivatives of olefins in an electrochemical cell |
US3864225A (en) * | 1972-11-17 | 1975-02-04 | Monsanto Co | Electrolytic Carboxylation of Substituted Olefins |
US4022673A (en) * | 1975-12-19 | 1977-05-10 | Standard Oil Company (Indiana) | Electrochemical production of 1,4-dihydro aromatic compounds |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4028201A (en) * | 1972-11-13 | 1977-06-07 | Monsanto Company | Electrolytic monocarboxylation of activated olefins |
-
1980
- 1980-10-20 DE DE8080200992T patent/DE3066199D1/en not_active Expired
- 1980-10-20 EP EP80200992A patent/EP0028430B1/en not_active Expired
- 1980-10-30 JP JP15153480A patent/JPS5675584A/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3379627A (en) * | 1962-09-20 | 1968-04-23 | Pullman Inc | Process for the manufacture of oxygencontaining derivatives of olefins in an electrochemical cell |
US3344045A (en) * | 1964-10-23 | 1967-09-26 | Sun Oil Co | Electrolytic preparation of carboxylic acids |
US3864225A (en) * | 1972-11-17 | 1975-02-04 | Monsanto Co | Electrolytic Carboxylation of Substituted Olefins |
US4022673A (en) * | 1975-12-19 | 1977-05-10 | Standard Oil Company (Indiana) | Electrochemical production of 1,4-dihydro aromatic compounds |
Non-Patent Citations (2)
Title |
---|
JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol. 123, No. 6 1976, M.M. BAIZER and R.C. HALLCHER: "Paired Electro-organic Syntheses". * |
MANUEL M. BAIZER: "Organic Electrochemistry", 1973 Marcel Dekker Inc. pages 469-471 New York US. * |
Cited By (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4582577A (en) * | 1984-12-19 | 1986-04-15 | Monsanto Company | Electrochemical carboxylation of p-isobutylacetophenone |
US8986533B2 (en) | 2009-01-29 | 2015-03-24 | Princeton University | Conversion of carbon dioxide to organic products |
US10119196B2 (en) | 2010-03-19 | 2018-11-06 | Avantium Knowledge Centre B.V. | Electrochemical production of synthesis gas from carbon dioxide |
US9970117B2 (en) | 2010-03-19 | 2018-05-15 | Princeton University | Heterocycle catalyzed electrochemical process |
US9222179B2 (en) | 2010-03-19 | 2015-12-29 | Liquid Light, Inc. | Purification of carbon dioxide from a mixture of gases |
US8845877B2 (en) | 2010-03-19 | 2014-09-30 | Liquid Light, Inc. | Heterocycle catalyzed electrochemical process |
US8845878B2 (en) | 2010-07-29 | 2014-09-30 | Liquid Light, Inc. | Reducing carbon dioxide to products |
US9309599B2 (en) | 2010-11-30 | 2016-04-12 | Liquid Light, Inc. | Heterocycle catalyzed carbonylation and hydroformylation with carbon dioxide |
US8961774B2 (en) | 2010-11-30 | 2015-02-24 | Liquid Light, Inc. | Electrochemical production of butanol from carbon dioxide and water |
US9090976B2 (en) | 2010-12-30 | 2015-07-28 | The Trustees Of Princeton University | Advanced aromatic amine heterocyclic catalysts for carbon dioxide reduction |
US8889897B2 (en) | 2011-12-23 | 2014-11-18 | Air Products And Chemicals, Inc. | Electrocarboxylation synthesis for obtaining intermediates useful for the synthesis of SPAN derivatives |
US9085827B2 (en) | 2012-07-26 | 2015-07-21 | Liquid Light, Inc. | Integrated process for producing carboxylic acids from carbon dioxide |
US9303324B2 (en) | 2012-07-26 | 2016-04-05 | Liquid Light, Inc. | Electrochemical co-production of chemicals with sulfur-based reactant feeds to anode |
US8858777B2 (en) | 2012-07-26 | 2014-10-14 | Liquid Light, Inc. | Process and high surface area electrodes for the electrochemical reduction of carbon dioxide |
US9175407B2 (en) | 2012-07-26 | 2015-11-03 | Liquid Light, Inc. | Integrated process for producing carboxylic acids from carbon dioxide |
US9175409B2 (en) | 2012-07-26 | 2015-11-03 | Liquid Light, Inc. | Multiphase electrochemical reduction of CO2 |
US8845876B2 (en) | 2012-07-26 | 2014-09-30 | Liquid Light, Inc. | Electrochemical co-production of products with carbon-based reactant feed to anode |
US9267212B2 (en) | 2012-07-26 | 2016-02-23 | Liquid Light, Inc. | Method and system for production of oxalic acid and oxalic acid reduction products |
US9080240B2 (en) | 2012-07-26 | 2015-07-14 | Liquid Light, Inc. | Electrochemical co-production of a glycol and an alkene employing recycled halide |
US8845875B2 (en) | 2012-07-26 | 2014-09-30 | Liquid Light, Inc. | Electrochemical reduction of CO2 with co-oxidation of an alcohol |
US9708722B2 (en) | 2012-07-26 | 2017-07-18 | Avantium Knowledge Centre B.V. | Electrochemical co-production of products with carbon-based reactant feed to anode |
US8821709B2 (en) | 2012-07-26 | 2014-09-02 | Liquid Light, Inc. | System and method for oxidizing organic compounds while reducing carbon dioxide |
US11131028B2 (en) | 2012-07-26 | 2021-09-28 | Avantium Knowledge Centre B.V. | Method and system for electrochemical reduction of carbon dioxide employing a gas diffusion electrode |
US10287696B2 (en) | 2012-07-26 | 2019-05-14 | Avantium Knowledge Centre B.V. | Process and high surface area electrodes for the electrochemical reduction of carbon dioxide |
US10329676B2 (en) | 2012-07-26 | 2019-06-25 | Avantium Knowledge Centre B.V. | Method and system for electrochemical reduction of carbon dioxide employing a gas diffusion electrode |
WO2014042783A1 (en) * | 2012-09-14 | 2014-03-20 | Liquid Light, Inc. | Multiphase electrochemical reduction of co2 |
Also Published As
Publication number | Publication date |
---|---|
EP0028430B1 (en) | 1984-01-18 |
DE3066199D1 (en) | 1984-02-23 |
JPS5675584A (en) | 1981-06-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0028430B1 (en) | A process for the electroreductive preparation of organic compounds | |
US4072583A (en) | Electrolytic carboxylation of carbon acids via electrogenerated bases | |
US3764492A (en) | Electrolytic preparation of esters from organo halides | |
US4917781A (en) | Process for preparing quaternary ammonium hydroxides | |
JPH01198491A (en) | Electrochemical synthesis of alpha-saturated ketone | |
US4071429A (en) | Electrolytic flow-cell apparatus and process for effecting sequential electrochemical reaction | |
US3344045A (en) | Electrolytic preparation of carboxylic acids | |
US4938854A (en) | Method for purifying quaternary ammonium hydroxides | |
US4588484A (en) | Electrochemical reduction of 3-chlorobenzo[b]thiophenes | |
US4028201A (en) | Electrolytic monocarboxylation of activated olefins | |
US4132611A (en) | Addition of organic electrophiles to carbon acids via catalysis by electrogenerated bases | |
US3193479A (en) | Electrolytic coupling of an olefinic compound with a ketone | |
JP2006037233A (en) | Preparation method of 2-alkyne-1-acetal | |
US4582577A (en) | Electrochemical carboxylation of p-isobutylacetophenone | |
US4377451A (en) | Electrochemical conversion of conjugated dienes into alkadienedioic acids | |
US4013524A (en) | Electrolytic carboxylation and dimerization of olefins | |
US3864225A (en) | Electrolytic Carboxylation of Substituted Olefins | |
US3250690A (en) | Electrolytic reductive coupling of cyano compounds | |
US4076601A (en) | Electrolytic process for the preparation of ethane-1,1,2,2-tetracarboxylate esters and related cyclic tetracarboxylate esters | |
JP4587329B2 (en) | Method for producing primary amines having a primary amino group and a cyclopropyl unit bonded to an aliphatic or alicyclic C-atom | |
Calas et al. | Change in the mechanism of the electroreduction of the perfluoro-n-hexyl iodide with varying the nature of the supporting salt Application to electrocarboxylation and sulfoxidation | |
US3980535A (en) | Process for producing sulfones | |
US3699020A (en) | Electrochemical production of 1,4-dihydro aromatic compounds | |
JP3846778B2 (en) | Method for electrolytic fluorination of organic ether compounds | |
Isse et al. | Electrochemical reduction of benzyl bromide in the presence of carbon dioxide |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Designated state(s): BE CH DE FR GB IT NL |
|
17P | Request for examination filed |
Effective date: 19811007 |
|
ITF | It: translation for a ep patent filed |
Owner name: ING. C. GREGORJ S.P.A. |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Designated state(s): BE CH DE FR GB IT LI NL |
|
REF | Corresponds to: |
Ref document number: 3066199 Country of ref document: DE Date of ref document: 19840223 |
|
ET | Fr: translation filed | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19840820 Year of fee payment: 5 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: BE Payment date: 19840930 Year of fee payment: 5 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 19841115 Year of fee payment: 5 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: CH Payment date: 19841123 Year of fee payment: 5 |
|
26N | No opposition filed | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: NL Payment date: 19871031 Year of fee payment: 8 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Effective date: 19881020 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LI Effective date: 19881031 Ref country code: CH Effective date: 19881031 Ref country code: BE Effective date: 19881031 |
|
BERE | Be: lapsed |
Owner name: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V. Effective date: 19881031 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Effective date: 19890501 |
|
NLV4 | Nl: lapsed or anulled due to non-payment of the annual fee | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19890630 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19890701 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee | ||
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |