Preparation Process of Alkoxylated 2,5-Dihydrofuran

Abstract

The present invention relates to a process for preparing alkoxylated 2,5-dihydrofuran. This process is carried out in an electrochemical cell reactor having a vertical flow.

Description

Detailed Description of the Invention

[0001] The present invention relates to a novel process for preparing alkoxylated 2,5-dihydrofuran. This process is carried out electrochemically.

[0002] Formula (I)

Chemical formula

[0003] They can be used as such or as intermediates in organic synthesis (for example, as intermediates in carotenoid production such as intermediates for carotenoid production).

[0004] Due to the importance of these compounds, improvement in the synthesis of these compounds is always needed.

[0005] WO 2006 / 100289 discloses a process for producing 2,5-dihydrofuran derivatives by electrochemical oxidation in the presence of a C1-C6-monoalkyl alcohol.

[0006] Using an anode and a cathode made of graphite, 2,5-dimethoxy-2,5-dihydro-furan with a yield of 46% was obtained. The selectivity was 51 percent.

[0007] The alkoxylated 2,5-dihydrofuran is produced using, as starting material, a compound of formula (II) in which its Z-form is preferred, as shown in the following scheme:

Chemical formula

[0008] Surprisingly, when the process is carried out under specific conditions, it has been found that the yield of alkoxylated 2,5-dihydrofuran (the compound of formula (I)) increases significantly.

[0009] Surprisingly, when using a specific arrangement of an electrochemical reactor (cell), an increase in yield (significantly higher than that of the prior art) has been found.

[0010] When using an electrochemical reactor with a vertical flow, it has been found that increased results can be obtained. The term "vertical flow" means that the flow is from the bottom to the top, or from the top to the bottom (preferably from the bottom to the top) of the electrochemical reactor.

[0011] Accordingly, the present invention relates to a process (P) for preparing a compound of formula (I)

Chemical formula

Chemical formula

[0012] When used in the process according to the present invention, as can be seen from formula (II), it is of the Z-form.

[0013] However, a small amount of the E-form of the compound of formula (II) can also be used. The E-form can be present in an amount of less than 5% by weight, based on the total weight of the compound of formula (II) in the process.

[0014] Preferred compounds of formula (I) are those in which R is -CH3 or -CH2CH3.

[0015] More preferably, the compound of formula (I) in which R is -CH3.

[0016] Accordingly, the present invention relates to process (P1), which is process (P) in which a compound of formula (I) where R is -CH3 or -CH2CH3 is used.

[0017] Accordingly, the present invention relates to process (P1'), which is process (P) in which a compound of formula (I) where R is -CH3 is used.

[0018] The process of the present invention is usually carried out in a non-aqueous medium.

[0019] In the context of the present invention, the term "non-aqueous" means that water can be present in the non-aqueous medium in an amount of less than 50% by weight, based on the total weight of the non-aqueous medium.

[0020] Usually, the term "non-aqueous" means that water can be present in the non-aqueous medium in an amount of less than 20% by weight, based on the total weight of the non-aqueous medium.

[0021] Accordingly, the present invention relates to process (P2), which is process (P), (P1) or (P1') carried out in a non-aqueous medium.

[0022] The non-aqueous medium usually and preferably contains at least one straight-chain or branched-chain C1-C 10 ​​It is (or contains) an alcohol (preferably at least one linear or branched C1-C6 alcohol, more preferably ethanol or methanol, and most preferably methanol).

[0023] This means that the monoalcohol of formula (III) can function as a non-aqueous medium or can be a mixture of other alcohols and the monoalcohol of formula (III).

[0024] It is preferred that the monoalcohol of formula (III) is also used as a non-aqueous medium.

[0025] Therefore, the present invention relates to process (P2), process (P2') in which the non-aqueous medium is at least one linear or branched C1-C 10 alcohol.

[0026] Therefore, the present invention relates to process (P2), process (P2”) in which the non-aqueous medium is a monoalcohol of formula (III): ROH (III) (wherein R is a C1-C6 alkyl group).

[0027] Therefore, the present invention relates to process (P2), process (P2”) in which the non-aqueous medium is at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.

[0028] Therefore, the present invention relates to process (P2), process (P2”’) in which the non-aqueous medium is methanol and / or ethanol.

[0029] Therefore, the present invention relates to process (P2), process (P2””) in which the non-aqueous medium is methanol.

[0030] At least one alcohol of formula (III) is used in an amount of at least 2 molar equivalents relative to the compound of formula (II). This means that this alcohol is always present in at least that amount if it is not used as a non-aqueous medium.

[0031] Of course, the non-aqueous medium can also be at least one alcohol of the compound of formula (III).

[0032] Accordingly, the present invention relates to a process (P3), which is a process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2"") or (P2"") in which at least one alcohol of formula (III) is used in an amount of at least 2 molar equivalents relative to the compound of formula (II).

[0033] An essential feature of the present invention is that the process according to the present invention is carried out in an electrochemical reactor having a vertical flow, and better results can be obtained. This means that the flow of the reaction mixture can be from the bottom to the top or from the top to the bottom (preferably from the bottom to the top) of the electrochemical reactor. This is usually carried out by a pumping system.

[0034] The size and form / shape (and thus the volume) of the electrochemical reactor can vary. The size and form / shape (and volume) of the electrochemical reactor are not essential features.

[0035] A very common and also preferred form is a 3D rectangular shape (cuboid).

[0036] Accordingly, the present invention relates to a process (P4), which is a process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2"") or (P3) carried out in a 3D rectangular electrochemical reactor.

[0037] The flow rate of the starting material can vary. This depends on the size, form and volume of the cuboid electrochemical reactor.

[0038] The normal (vertical) flow rate is at least 10 mL / min. The normal and preferred range is 10 mL / min to 1000 mL / min.

[0039] Accordingly, the present invention relates to a process (P5) which is a process (P), (P1), (P1’), (P2), (P2’), (P2”), (P2”’), (P2””), (P3) or (P4) where the (vertical) flow rate is at least 10 mL / min.

[0040] Accordingly, the present invention relates to a process (P5’) which is a process (P), (P1), (P1’), (P2), (P2’), (P2”), (P2”’), (P2””), (P3) or (P4) where the (vertical) flow rate is 10 mL / min to 1000 mL / min.

[0041] The electrodes (cathode and anode) used in the process according to the present invention can be manufactured from only any commonly used material or from two or more materials (such as a metal on a carrier material or a metal oxide on a carrier material).

[0042] In this process, the target product is formed on the anode and hydrogen gas is generated at the cathode. Therefore, since they are more active in hydrogen generation, it is advantageous to use a metal or an alloy as the cathode instead of graphite (graphite is commonly used in the prior art). An additional advantage of using a metal or a metal alloy as the cathode is that the cell potential is significantly reduced, which results in energy savings for the process.

[0043] Examples of cathode materials that can be used are metals (iron or noble metals such as platinum, etc.), graphite or metal alloys (such as steel).

[0044] As described above in the preferred embodiment of the present invention, the cathode is not manufactured from graphite.

[0045] Materials that are stable under electrolysis conditions are used for the anode. Examples of such materials are noble metals (e.g., platinum), oxides (e.g., ruthenium dioxide on titanium), graphite, highly oriented pyrolytic graphite (HOPG), boron-doped diamond (BDD), dimensionally stable anodes (DSA), and vitreous carbon.

[0046] Accordingly, the present invention relates to process (P6), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5) or (P5'), wherein the cathode is made of a material selected from the group consisting of metals (iron or noble metals such as platinum, etc.), graphite, and metal alloys (such as steel).

[0047] Accordingly, the present invention relates to process (P6'), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5) or (P5'), wherein the cathode is not made of graphite.

[0048] Accordingly, the present invention relates to process (P6"), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5) or (P5'), wherein the cathode is made of a material selected from the group consisting of metals (iron or noble metals such as platinum, etc.) and metal alloys (such as steel).

[0049] Accordingly, the present invention relates to process (P7), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6') or (P6"), wherein the anode is made of a material selected from the group consisting of noble metals, oxides, graphite, highly oriented pyrolytic graphite (HOPG), boron-doped diamond (BDD), dimensionally stable anodes (DSA), and vitreous carbon.

[0050] The electrode can be in any normal form. Such a form can be a plate, wire, rod, cell, mesh, grid, sponge, or any other design commonly used.

[0051] Accordingly, the present invention relates to process (P8), wherein the electrode is in the form of a plate, wire, rod, cell, mesh, grid, sponge, or any other design commonly used, in processes (P), (P1), (P1'), (P2), (P2'), (P2"), (P2"'), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), or (P7).

[0052] The size of the electrode used in the process according to the present invention can vary and depends on the size, form, and structure of the electrochemical reactor (cell).

[0053] The normal size is at least 10 cm (per cell). 2 The upper limit of the electrode is not so important.

[0054] Normally (but not necessarily), the cathode and anode have the same size.

[0055] Accordingly, the present invention relates to process (P9), wherein the electrode has a size of at least 10 cm, in processes (P), (P1), (P1'), (P2), (P2'), (P2"), (P2"'), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), or (P8). 2 Accordingly, the present invention relates to process (P10), wherein the cathode and anode have the same size, in processes (P), (P1), (P1'), (P2), (P2'), (P2"), (P2"'), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), or (P9).

[0056] ​

[0057] The reaction medium usually and preferably contains at least one electrolyte. This can be added to the reaction medium in the form of a salt and / or in the form of an acid. Any generally known and commonly used electrolyte can be used, except phosphoric acid and / or any of its salts.

[0058] Suitable supporting electrolytes are, namely, HCl, H2SO4, Na2SO4, NaCl, sodium dodecyl sulfate, methyltributylammonium methyl sulfate, triethylammonium bisulfate, tetrabutylammonium bisulfate, tetramethylammonium bisulfate, tetrabutylammonium acetate (NBu4OAc), tetrabutylammonium sulfate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, methanesulfonic acid, ammonium bisulfate, tetrabutylphosphonium methanesulfonate, 1-methylimidazolium bisulfate, tetrabutylammonium perchlorate and LiClO4.

[0059] Usually, at least one electrolyte with a maximum concentration of 2M is used (preferably 0.01 - 1M, more preferably 0.1 - 0.5M, 0.2 - 0.5M).

[0060] In a preferred embodiment, the electrolyte is not phosphoric acid and / or its salts.

[0061] Accordingly, the present invention relates to a process (P11) which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2"'), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9) or (P10) carried out in the presence of at least one electrolyte.

[0062] Accordingly, the present invention relates to a process (P11') which is process (P11) where at least one electrolyte is not phosphoric acid and / or its salts.

[0063] Therefore, the present invention relates to a process (P11''), which is the process (P11) or (P11') in which at least one electrolyte is selected from the group consisting of HCl, H2SO4, Na2SO4, NaCl, sodium dodecyl sulfate, methyltributylammonium methyl sulfate, triethylammonium bisulfate, tetrabutylammonium bisulfate, tetramethylammonium bisulfate, tetrabutylammonium acetate (NBu4OAc), tetrabutylammonium sulfate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, methanesulfonic acid, ammonium bisulfate, tetrabutylphosphonium methanesulfonate, 1-methylimidazolium bisulfate, tetrabutylammonium perchlorate and LiClO4.

[0064] Therefore, the present invention relates to a process (P11'''), which is the process (P11), (P11') or (P11'') in which at least one electrolyte is used at a concentration of up to 2 M (preferably 0.01 - 1 M, more preferably 0.1 - 0.5 M).

[0065] The pH value of the reaction medium of the process according to the present invention at the start of the process is preferably 0 - 7.

[0066] Therefore, the present invention relates to a process (P12), which is the process (P), (P1), (P1'), (P2), (P2'), (P2''), (P2'''), (P2''''), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6''), (P7), (P8), (P9), (P10), (P11), (P11'), (P11'') or (P11''') in which the reaction medium has a pH value of 0 - 7 at the start of the process.

[0067] The process according to the present invention is carried out in a temperature range of 0 °C to 75 °C (preferably 10 °C to 60 °C, more preferably 15 °C to 40 °C).

[0068] Accordingly, the present invention relates to process (P13), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), or (P12), wherein the reaction is carried out in the temperature range of 0 °C to 75 °C.

[0069] Accordingly, the present invention relates to process (P13'), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), or (P12), wherein the reaction is carried out in the temperature range of 10 °C to 60 °C.

[0070] Accordingly, the present invention relates to process (P13"), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), or (P12), wherein the reaction is carried out in the temperature range of 15 °C to 40 °C.

[0071] The process according to the present invention is usually carried out under ambient pressure.

[0072] Accordingly, the present invention relates to process (P14), which is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), or (P13"), wherein the reaction is carried out under ambient pressure.

[0073] Depending on the cell, the process according to the invention can be carried out in batch or continuous mode. A continuous process is preferred.

[0074] Accordingly, the present invention relates to a process (P15) in which the reaction is carried out in batch or continuous mode, the process being (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13") or (P14).

[0075] Accordingly, the present invention relates to a process (P15') in which the reaction is carried out in continuous mode, the process being (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13") or (P14).

[0076] The current density used in the process according to the invention is preferably 1 to 1000 mA / cm 2 Preferably 10 to 1000 mA / cm 2 More preferably 20 to 1000 mA / cm 2 is.

[0077] Accordingly, the present invention relates to a reaction of 1 to 1000 mA / cm 2Regarding process (P16), which is carried out at a current density of

[0078] Therefore, the present invention relates to a process in which the reaction is carried out at a current density of 10 to 1000 mA / cm 2 Regarding process (P16'), which is carried out at a current density of

[0079] Therefore, the present invention relates to a process in which the reaction is carried out at a current density of 20 to 1000 mA / cm 2 Regarding process (P16''), which is carried out at a current density of

[0080] The potential between the anode and the cathode can be 12 V or less. A suitable range is 0.5 to 12 V, preferably 0.5 to 10 V, more preferably 0.5 to 8 V, and most preferably 1 to 8 V.

[0081] Therefore, the present invention relates to a process (P17) in which the potential between the anode and the cathode is 12 V or less, and the process is (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13"), (P14), (P15), (P15'), (P16), (P16') or (P16").

[0082] Therefore, the present invention relates to a process (P17') in which the potential between the anode and the cathode is 0.5 to 12 V, and the process is (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13"), (P14), (P15), (P15'), (P16), (P16') or (P16").

[0083] Therefore, the present invention relates to a process (P17") in which the potential between the anode and the cathode is 0.5 to 10 V, and the process is (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13"), (P14), (P15), (P15'), (P16), (P16') or (P16").

[0084] Therefore, the present invention relates to a process (P17''') which is the process (P), (P1), (P1'), (P2), (P2'), (P2''), (P2'''), (P2''''), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6''), (P7), (P8), (P9), (P10), (P11), (P11'), (P11''), (P11'''), (P12), (P13), (P13'), (P13''), (P14), (P15), (P15'), (P16), (P16') or (P16'') in which the potential between the anode and the cathode is 0.5 to 8V.

[0085] Therefore, the present invention relates to a process (P17'''') which is the process (P), (P1), (P1'), (P2), (P2'), (P2''), (P2'''), (P2''''), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6''), (P7), (P8), (P9), (P10), (P11), (P11'), (P11''), (P11'''), (P12), (P13), (P13'), (P13''), (P14), (P15), (P15'), (P16), (P16') or (P16'') in which the potential between the anode and the cathode is 1 to 8V.

[0086] The process according to the present invention can be carried out in a constant current or constant potential mode.

[0087] Therefore, the present invention relates to a process (P18) which is the process (P), (P1), (P1'), (P2), (P2'), (P2''), (P2'''), (P2''''), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6''), (P7), (P8), (P9), (P10), (P11), (P11'), (P11''), (P11'''), (P12), (P13), (P13'), (P13''), (P14), (P15), (P15'), (P16), (P16'), (P16''), (P17), (P17'), (P17''), (P17''') or (P17'''') carried out in a constant current mode.

[0088] Accordingly, the present invention relates to a process (P19) which is carried out in a potentiostatic mode and is process (P), (P1), (P1'), (P2), (P2'), (P2"), (P2'"), (P2""), (P3), (P4), (P5), (P5'), (P6), (P6'), (P6"), (P7), (P8), (P9), (P10), (P11), (P11'), (P11"), (P11'"), (P12), (P13), (P13'), (P13"), (P14), (P15), (P15'), (P16), (P16'), (P16"), (P17), (P17'), (P17"), (P17'"), (P17"") or (P18).

[0089] The reaction product (compound of formula (I)) can be isolated from the reaction medium using conventional methods.

[0090] The following examples serve to illustrate the present invention. Unless otherwise specified, all parts are given by weight and the temperatures are given in °C.

[0091] [Examples] [Example 1] The electrochemical oxidation reaction of 1M Z-2-butene-1,4-diol (compound of formula (Ia)) to 2,5-dihydro-2,5-dimethoxyfuran was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 5.6 wt% methyltributylammonium methyl sulfate was used as the electrolyte. A graphite (100 cm 2 ) electrode was used as the anode and stainless steel (100 cm 2 ) was used as the cathode. The electrolysis was carried out at 20 °C at 100 mA cm -2It was carried out galvanostatically by applying a current of

[0092] [Example 2] The electrochemical oxidation reaction of 2M Z-2-butene-1,4-diol (compound of formula (Ia)) to 2,5-dihydro-2,5-dimethoxyfuran was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 5.1 wt% methyltributylammonium methyl sulfate was used as the electrolyte. A graphite (100 cm 2 ) electrode was used as the anode, and stainless steel (100 cm 2 ) was used as the cathode. The electrolysis was carried out galvanostatically by applying a current of 100 mA cm -2 at 20 °C (the measured cell potential was 6.5 V). The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 400 mL / min. After 190 minutes, 97% conversion of Z-2-butene-1,4-diol was achieved. The reaction mixture had a DMDF content of 63% and a Faradaic efficiency of 52% was achieved.

[0093] [Example 3] The electrochemical oxidation reaction of 1M Z-2-butene-1,4-diol (compound of formula (Ia)) to 2,5-dihydro-2,5-dimethoxyfuran was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 8.2 wt% triethylammonium bisulfate was used as the electrolyte. A graphite (100 cm 2)The electrode was used as the anode, and graphite (100 cm 2 ) was used as the cathode. The electrolysis was carried out galvanostatically by applying a current of 100 mA cm -2 at 20 °C (the measured cell potential was 6.2 V). The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 400 mL / min. After 90 minutes, a conversion of 97% of Z-2-butene-1,4-diol was achieved. The reaction mixture had a DMDF content of 66%, and a Faradaic efficiency of 58% was achieved.

[0094] [Example 4] The electrochemical oxidation reaction of 1 M Z-2-butene-1,4-diol (compound of formula (Ia)) to 2,5-dihydro-2,5-dimethoxyfuran was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 8.2 wt% triethylammonium bisulfate was used as the electrolyte. Graphite (100 cm 2 ) electrodes were used as the anode, and graphite (100 cm 2 ) was used as the cathode. The electrolysis was carried out galvanostatically by applying a current of 150 mA cm -2 at 20 °C (the measured cell potential was 7.3 V). The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 400 mL / min. After 60 minutes, a conversion of 98% of Z-2-butene-1,4-diol was achieved. The reaction mixture had a DMDF content of 68%, and a Faradaic efficiency of 60% was achieved.

[0095] [Example 5] The electrochemical oxidation reaction of 1 M Z-2-butene-1,4-diol (compound of formula (Ia)) to 2,5-dihydro-2,5-dimethoxyfuran was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 8.2 wt% triethylammonium bisulfate was used as the electrolyte. Graphite (100 cm2 ) The electrode was used as the anode, and stainless steel (100 cm 2 ) was used as the cathode. The electrolysis was carried out (measured cell potential was 6.0 V) under constant current by applying a current of 150 mA cm -2 at 20 °C. The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 400 mL / min. After 60 minutes, 98% conversion of Z-2-butene-1,4-diol was achieved. The reaction mixture had a DMDF content of 65%, and a Faradaic efficiency of 57% was achieved.

[0096] [Example 6] The electrochemical oxidation reaction from 0.5 M BED (Z-2-butene-1,4-diol) to DMDF (2,5-dihydro-2,5-dimethoxyfuran) was carried out in methanol in an undivided flow cell (V = 10 mL, surface area 100 cm 2 , 1 mm electrode distance), and 3.1 wt% sodium dodecyl sulfate was used as the electrolyte. A graphite (100 cm 2 ) electrode was used as the anode, and stainless steel (100 cm 2 ) was used as the cathode. The electrolysis was carried out (measured cell potential was 5.6 V) under constant current by applying a current of 50 mA cm -2 at 20 °C. The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 400 mL / min. After 360 minutes, the total yield of DMDF was 70% and 98% conversion of BED was achieved, and a Faradaic efficiency of 61% was achieved.

[0097] [Examples 7 - 15] The electrochemical oxidation reaction from 0.5 M BED (Z-2-butene-1,4-diol) to DMDF (2,5-dihydro-2,5-dimethoxyfuran) was carried out in methanol in an undivided flow cell (V = 1 mL, surface area 10 cm 2 , 1 mm electrode distance), using various electrolytes. A graphite (10 cm 2 ) electrode was used as the anode, and various electrode materials (10 cm2 ) was used as the cathode. The electrolysis was carried out galvanostatically (with the cell potential varied) by applying a current of 17 - 50 mA cm -2 at 20 °C. The reaction mixture was pumped vertically from the bottom to the top through the flow cell at a flow rate of 50 mL / min.

[0098]

Table 1

Claims

1. A process for preparing a compound of formula (I), 【Chemical 1】 (wherein R is a linear or branched C １ -C ６ alkyl group) wherein a Z-form compound of formula (II) [Chemical 2] is electrochemically reacted with at least one monoalcohol of formula (III) ROH (III) wherein R has the same meaning as in the compound of formula (I), and the reaction is carried out in an electrochemical reactor having a vertical flow, characterized in that the process is carried out in an electrochemical reactor having a vertical flow.

2. R is -CH ３ or -CH ２ CH ３ The method according to claim 1, wherein

3. R is -CH ３ The method according to claim 1, wherein it is so.

4. The process according to any one of claims 1 to 3, which is carried out in a non-aqueous medium.

5. The process according to claim 4, wherein at least one alcohol of formula (III) is used in an amount of at least 2 molar equivalents relative to the compound of formula (II).

6. The non-aqueous medium is at least one linear or branched C １ -C １０ alcohol (or contains it), the method according to claim 4.

7. The non-aqueous medium is the formula (III) ROH (III) (wherein R is a linear or branched C １ -C ６ alkyl group), the method according to claim 4, which is a monoalcohol.

8. The process according to any one of claims 1 to 7, which is carried out in a cuboid electrochemical reactor.

9. The process according to any one of claims 1 to 8, wherein the cathode is not made of graphite.

10. The process according to any one of claims 1 to 9, wherein the cathode is made of a material selected from the group consisting of metals and metal alloys.

11. The process according to any one of claims 1 to 10, wherein the anode is made of a material selected from the group consisting of noble metals, oxides, graphite, highly oriented pyrolytic graphite (HOPG), boron-doped diamond (BDD), dimensionally stable anodes (DSA) and vitreous carbon.

12. The impressed current density is 1 to 1000 mA / cm ２ The method according to any one of claims 1 to 11, wherein the impressed current density is 1 to 1000 mA / cm

13. The process according to any one of claims 1 to 12, which is carried out in the presence of at least one supporting electrolyte.

14. The process according to claim 13, wherein at least one electrolyte is not phosphoric acid and / or its salts.

15. wherein the at least one electrolyte is HCl, H ２ SO ４ , Na ２ SO ４ , NaCl, sodium dodecyl sulfate, methyltributylammonium methyl sulfate, triethylammonium bisulfate, tetrabutylammonium bisulfate, tetramethylammonium bisulfate, tetrabutylammonium acetate (NBu ４ OAc), tetrabutylammonium sulfate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, methanesulfonic acid, ammonium bisulfate, tetrabutylphosphonium methanesulfonate, 1-methylimidazolium bisulfate, tetrabutylammonium perchlorate and LiClO ４ The method according to claim 13, selected from the group consisting of

16. The process according to any one of claims 1 to 15, which is carried out in a batch or continuous mode.

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