JP4181297B2 - Electrolytic production method of organic compound and electrode for electrolytic production - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for efficiently producing an organic sulfur compound, and an electrode for electrolytic production that can be used in the method.
[0002]
[Prior art]
Electrolysis is a chemical synthesis method that uses clean electrical energy to perform chemistry without the use of reaction reagents. The reaction rate can be controlled by the current density, and the product can be controlled by regulating the potential. It has the feature that can be selected. In the field of electrolytic synthesis of organic compounds, many organic compound oxidation-reduction processes have been put to practical use by utilizing a non-aqueous solvent that is stable and promotes the reaction. The electrolysis method is not suitable for mass production because it is a heterogeneous phase reaction on the electrode surface, but since selective synthesis is possible, it is considered to produce a high added-value substance in a new electrosynthesis system. Has been.
Fluorine-containing organic sulfur compounds are chemical synthetic products important as pharmaceuticals and agricultural chemicals, and compounds having a wide variety of molecular structures have been developed in order to obtain desired effects. It is known that an electrolytic method is useful for selectively converting the molecular structure of a fluorine-containing compound or selectively fluorinating an organic compound to obtain a desired fluorine-containing organic sulfur compound.
[0003]
As an anode that is an electrode that performs oxidation, lead oxide, tin oxide, platinum, DSA, graphite, amorphous carbon (GC) or the like is generally used, and as a cathode that is an electrode that performs reduction, generally, lead, iron, or the like is used. Platinum, titanium, carbon, etc. are used. The material that can be used as the electrode substrate preferably has corrosion resistance in order to achieve a long life and prevent contamination of the treated surface, and the power supply for supplying power to the electrode is made of titanium or the like for the anode. It is desirable to use a valve metal or an alloy thereof, and it is desirable to use noble metals such as platinum and iridium and oxides thereof as the anode catalyst. However, even if these expensive materials are used, it is known that when energized, the materials are consumed depending on the current density and energization time and are eluted in the electrolyte solution, and an electrode with better corrosion resistance is desired. It is rare. In particular, there are few electrode materials that are resistant in organic electrolytes, and carbon-based materials are usually used. However, they are exhausted and stable operation is difficult. Precious metals such as platinum are relatively stable, but are insufficient in terms of yield and selectivity, and are expensive, which is an obstacle to practical use.
[0004]
Diamond is promising as a semiconductor device, energy conversion element, etc. because it has excellent thermal conductivity, optical transparency, high temperature and durability against oxidation, and can control electrical conductivity, especially by doping. Yes. As an electrode for electrochemistry, Swain et al. Reported the stability of diamond in acidic electrolyte [Journal of Electrochemical Society, Vol.141, p.3382 (1994)], far more than other carbon materials. Suggested to be excellent. US Pat. No. 5,399,247 suggests that organic wastewater can be decomposed using diamond as the anode material. Foti reports that the decomposition of organic matter into carbon dioxide is promoted by the decomposition mechanism different from that of platinum in electrolytic oxidative decomposition of organic matter [Electrochemical and Solid-State Letters, Vol.2, p.228-230 ( 1999)]. Furthermore, Ando reported on the electrosynthesis of organic compounds [Electrochemical and Solid-State Letters, Vol.2, p.382-384 (1999)] and pointed out that diamond electrodes are effective as fluorination electrodes. Detailed examination such as yield has not been conducted.
[0005]
Although reports on industrial applications in the high current density and high potential region are not sufficient, recently diamond electrodes are inactive against water decomposition reactions, and other than oxidation reactions, they generate oxygen and ozone. It is reported that it can be used [Japanese Journal of Applied Physics, Vol.36, L260, (1997)]. Accordingly, if the organic compound as a reactant is in a range where oxidation-reduction can proceed in terms of potential, the electrolytic reaction takes precedence, and electrolysis of the organic compound proceeds easily even in an aqueous system.
[0006]
[Problems to be solved by the invention]
Organic sulfur compounds, which are a kind of organic compounds, are also desirable targets for electrolytic synthesis, and conventionally, fluorination reactions and the like have been carried out as electrolytic synthesis reactions. However, a platinum electrode, a carbon electrode, or the like is used for this electrolytic reaction, and the platinum electrode is expensive and economically problematic, and the carbon electrode has a drawback that it is inexpensive but easily consumed and cannot have a sufficient life. .
The present invention solves the problem that the cost and operational efficiency in the conventional electrolytic production of organic sulfur compounds cannot be achieved, and the organic sulfur is produced in a yield and selectivity almost equivalent to those using noble metal electrodes. It is an object to provide a relatively inexpensive electrode capable of electrolytically producing a compound and an organic sulfur compound producing method using the electrode.
[0007]
[Means for Solving the Problems]
The present invention relates to a method for electrolytically producing an organic compound using an electrode for electrolysis containing at least a conductive diamond on its surface, wherein the raw material for the electrolytic reaction is ethyl α- phenylthioacetate, oxindole derivative, benzothiazolyl sulfide , An organic compound selected from the group consisting of sulfides having an asymmetric auxiliary group of Evans and phenyl 2,2,2-trifluoroethyl sulfide, and the organic compound to be produced is an organic sulfur compound, an electrolytic production how the organic compound.
[0008]
The present invention will be described in detail below.
The present invention is characterized in that a conductive diamond electrode is used as an electrode for electrolytic synthesis of an organic sulfur compound. This diamond electrode has a particularly marked improvement in reaction selectivity, and can synthesize the target organic sulfur compound in a relatively high yield. The reason is not clear, but it can be assumed that the adsorption behavior of the organic sulfur compound on the diamond electrode is different from that of platinum or GC.
The organic sulfur compound used as a raw material of the present invention includes ethyl α- phenylthioacetate, oxindole derivatives, benzothiazolyl sulfides, sulfides having an asymmetric auxiliary group of Evans, and phenyl 2,2,2-trifluoroethyl sulfide Selected from various sulfur compounds. The type of electrolytic reaction is not particularly limited, and the chemical structure of the organic sulfur compound to be obtained and the type of electrolytic reaction are selected in consideration of the chemical structure and application of the organic sulfur compound to be obtained. Types of reaction include halogenation, alkoxylation, carboxylation, esterification, hydrogenation, dehydrogenation and the like.
[0009]
The conductive diamond electrode to be used is desirably formed on a power feeding body such as metal. The diamond electrode can be formed by a hot filament method, a CVD method, a microwave plasma CVD method, a plasma arc jet method, a PVD method, or the like.
Depending on the diamond synthesis method, a part of the diamond component may be generated and contained in the diamond component. These non-corrosion-resistant carbon components such as non-diamond components are consumed in solution in the electrolyte solution, and thus have little practical effect. However, it is desirable to remove them by acid washing before use.
[0010]
The hot filament method, which is a typical diamond electrode manufacturing method, will be described. An organic compound such as alcohol serving as a carbon source is kept in a reducing atmosphere such as hydrogen gas, and the filament is heated to a temperature of 1800-2400 ° C. at which carbon radicals are generated. Then, a power feeder and an electrode base are arranged in the atmosphere so as to be in a temperature region (750 to 950 ° C.) where diamond is deposited. In this case, it is preferable that the concentration of the starting organic sulfur compound with respect to hydrogen is 0.1-10% by volume, the supply rate is 0.01-10 liters / minute, and the pressure is 15-760 mmHg, depending on the size of the reaction vessel. Diamond fine particles having a particle size of 0.01-1 μm are usually deposited on the electrode substrate. The thickness of the diamond layer may be adjusted by increasing / decreasing the operation time, and the thickness is preferably 0.1-50 μm and 1-10 μm for the purpose of preventing the electrolyte from entering the electrode substrate. Is particularly preferred.
[0011]
In order to obtain good conductivity, it is indispensable to add a trace amount of elements having different valences. The preferable content of boron and phosphorus is 1-100000 ppm, and the more preferable content is 100-10000 ppm. Specific compounds include boron oxide and phosphorus pentoxide which have low toxicity. DLN (diamond-like nano-composite) which is a composite material with amorphous silicon oxide can also be used.
The diamond particles thus produced may be supported on a substrate or a feeder as described above and used as a normal electrode. However, when used as a three-dimensional electrode in a fluidized bed or a fixed bed, the reaction area increases. Processing capacity is improved.
As the electrolytic cell material, glass lining material, carbon, titanium, stainless steel and PTFE resin having excellent corrosion resistance can be preferably used from the viewpoints of durability and stability against organic compounds.
The electrolysis conditions are preferably a temperature of 5 to 40 ° C. and a current density of 0.01 to 10 A / dm ² when a normal electrode is used.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of an electrolytic cell having a conductive diamond electrode for producing an organic sulfur compound of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to this.
FIG. 1 is a schematic cross-sectional view of a diaphragm type electrolytic cell that can be used in the method for electrolytically producing an organic compound of the present invention.
In the cylindrical electrolytic cell main body 1 whose upper surface is open, an anode 3 formed from diamond particles to which a dopant is added is formed on one surface of the lower end portion of the plate-like anode feeder 2, and a plate-like cathode feed. A cathode 5 made of platinum metal is suspended from one side of the lower end of the body 4 so as to be separated from each other, and the base ends of both the feeders 2 and 4 are connected via a power source 6 outside the electrolytic cell body 1. ing.
[0013]
The electrolytic cell body 1 is filled with an electrolytic solution 7 so that at least the anode 3 and the cathode 5 are immersed, and a stirring bar 8 that is rotated by magnetic force is placed on the bottom surface of the electrolytic cell body 1.
In order to perform electrolytic synthesis of organic sulfur compounds by reactions such as fluorination, methoxylation, acetoxylation using the electrolytic cell main body 1 having such a configuration, the raw material organic sulfur compound, fluorine source, methoxy When a base source, an electrolyte as an acetoxy base source, a solvent and an electrolytic solution are injected into the electrolytic cell main body 1 and a current is passed between both electrodes while rotating a stirrer, the raw material in the electrolytic solution is oxidized or oxidized on the surface of the anode or the cathode. A predetermined organic sulfur compound is synthesized by receiving a desired electrolytic reaction reductively.
[0014]
Next, examples and comparative examples of electrolytic production of organic sulfur compounds according to the present invention are described, but these do not limit the present invention.
[0015]
Example 1
Conductive diamond was deposited on both sides of a 20 mm long by 20 mm wide silicon substrate by plasma CVD so as to have a thickness of 5 μm as an anode, and a 20 mm long by 20 mm wide platinum plate was used as the cathode. Using these electrodes. The diaphragm type electrolytic cell shown in FIG. 1 was assembled.
The electrolyte used also as a fluorine source was 0.17 M of (C ₂ H ₅ ) ₃ N · 3HF, and the solvent was acetonitrile. As a substrate (raw organic sulfur compound), 50 mM ethyl α-phenylthioacetate (C ₆ H ₅ —S—CH ₂ —CO—O—C ₂ H ₅ ), which is a chain sulfide, was used. The mixture was stirred in a nitrogen atmosphere, and constant current electrolysis (current density: 0.25 A / dm ² , 2.5 F / mol) was performed at room temperature. After completion of the reaction, the solvent was filtered under reduced pressure, and the residue was analyzed using NMR. As a reaction product, a compound in which fluorine was replaced with hydrogen (C ₆ H ₅ —S—CHF—CO—O—C ₂ H ₅ ) was obtained, and the yield was 32%. The electrode was observed after electrolysis, but no consumption was observed.
[0016]
Comparative Example 1
When electrolysis was carried out under the same conditions as in Example 1 except that the anode was GC of the same area, the yield was 26%, and electrode consumption was observed after electrolysis.
[0017]
Example 2
Other than using 0.1M of (C ₂ H ₅ ) ₄ NF · 4HF as a fluorine source as an electrolyte and 50 mM of 1-phenyl-3- (phenylthio) oxindole which is a heterocyclic oxindole derivative as a substrate. Used the same diaphragmless electrolytic cell as in Example 1. The mixture was stirred in a nitrogen atmosphere, and constant current electrolysis (current density: 0.25 A / dm ² , 3.5 F / mol) was performed at room temperature. After completion of the reaction, the solvent was filtered under reduced pressure, and the residue was analyzed using NMR. As a reaction product, a compound in which fluorine was substituted with hydrogen [1-phenyl-3-fluoro-3- (phenylthio) oxindole] The yield was 66%. The electrode was observed after electrolysis, but no consumption was observed.
[0018]
Comparative Example 2
When electrolysis was performed under the same conditions as in Example 2 except that the anode was platinum, the yield was 67%.
[0019]
Comparative Example 3
When electrolysis was performed under the same conditions as in Example 2 except that the anode was GC, the yield was 31%, and consumption of the electrode was observed after electrolysis.
[0020]
Example 3
Except that (C ₂ H ₅ ) ₄ NF · 3HF is 0.1M, DME (dimethoxyethane) is used as a solvent, and 2-benzothiazolylmethylcarbonylmethyl sulfide 15mM is used as a substrate. The same diaphragm electrolyzer as in Example 1 was used. The mixture was stirred in a nitrogen atmosphere, and constant current electrolysis (current density: 0.25 A / dm ² , 3.5 F / mol) was performed at room temperature. After completion of the reaction, the solvent was filtered under reduced pressure, and the residue was analyzed using NMR. As a reaction product, a compound in which fluorine was replaced with hydrogen (methyl α-fluoro-α- (2-benzothiazolylthio) acetate ) Was obtained, and the yield was 29%.
[0021]
Comparative Example 4
When electrolysis was performed under the same conditions as in Example 3 except that the anode was GC of the same area, the yield was 23%, and consumption of the electrode was observed after electrolysis.
[0022]
Example 4
Electrolytic fluorination of the substrate using the same membrane electrolyzer as in Example 3 except that 50 mM 5-chlorobenzothiazolylmethylcarbonylmethyl sulfide was used instead of 2-benzothiazolyl methyl sulfide as the substrate. (Current density: 0.25 A / dm ² , 2.5 F / mol), a compound in which fluorine is substituted with hydrogen as a reaction product (methyl α-fluoro-α-[[2- (5-chlorobenzothiazoli L)] thio] acetate), and the yield was 53%.
[0023]
Comparative Example 5
When electrolysis was performed under the same conditions as in Example 3 except that the anode was GC of the same area, the yield was 43%, and consumption of the electrode was observed after electrolysis.
[0024]
Example 5
Same as Example 3 except that (4S) -3- (2-phenylthio-1-oxoethyl) -4-phenyl-2-oxazolidine), a sulfide having a 50 mM Evans asymmetric auxiliary group, was used as the substrate. When the substrate was electrolytically fluorinated using a non-diaphragm electrolyzer (current density: 0.5 A / dm ² , 3 F / mol), a compound in which fluorine was substituted with hydrogen as a reaction product (3- (2- Fluoro-2-phenylthio-1-oxoethyl) -4-phenyl-2-oxazolidine) was obtained, and the yield was 32%. The diastereomeric excess (de) indicating the degree of asymmetric synthesis was 24%.
[0025]
Comparative Example 6
When electrolysis was performed under the same conditions as in Example 5 except that the anode was platinum of the same area, the yield was 50% and de was 18%.
[0026]
Comparative Example 7
When electrolysis was performed under the same conditions as in Example 5 except that the anode was GC of the same area, the yield was 30% and de was 16%.
[0027]
Example 6
Other than using methanol solvent containing 0.2 M of (C ₂ H ₅ ) ₄ NO—SO ₂ —C ₆ H ₄ —CH ₃ as electrolyte and 70 mM phenyl 2,2,2-trifluoroethyl sulfide as substrate. Was subjected to electrolytic methoxylation using the same diaphragmless electrolytic cell as in Example 1. The mixture was stirred under a nitrogen atmosphere, and constant current electrolysis (current density: 0.16 A / dm ² , 5 F / mol) was performed at room temperature. After completion of the reaction, the solvent was filtered under reduced pressure, and the residue was analyzed using NMR. As a reaction product, a compound in which hydrogen was substituted with a methoxy group (phenyl 1-methoxy-2,2,2-trifluoroethyl) Sulfide) was obtained, and the yield was 68%.
[0028]
Comparative Example 8
When electrolysis was carried out under the same conditions as in Example 6 except that the anode was platinum having the same area, the yield was 70%.
[0029]
Comparative Example 9
When electrolysis was performed under the same conditions as in Example 6 except that the anode was GC of the same area, the yield was 34%.
[0030]
Example 7
Substrate of Example 5 using a non-diaphragm electrolytic cell similar to Example 5 except that 1M of (C ₂ H ₅ ) ₄ NF · 3HF was used as the electrolyte and a 1: 1 mixed solvent of methanol and acetone was used as the solvent. Was obtained (current density: 0.5 A / dm ² , 3F / mol). As a reaction product, a compound in which a methoxy group was replaced with hydrogen (3- (2-methoxy-2-phenylthio-1-oxoethyl) -4-phenyl-2-oxazolidine) was obtained with a yield of 43% and a de of 11%.
[0031]
Comparative Example 10
When electrolysis was performed under the same conditions as in Example 7 except that the anode was platinum having the same area, the yield was 78%, but de was 7%.
[0032]
Example 8
70 mM phenyl-2,2,2-trifluoro is used in the same electrolyzer as in Example 6 except that 0.1 M each of sodium acetate and sodium perchlorate are used as the electrolyte and acetic acid is used as the solvent. When ethyl sulfide electrolytic acetoxylation was performed (current density: 0.6 A / dm ² , 4.5 F / mol), a compound in which hydrogen was substituted with a methoxy group as a reaction product (phenyl 1-acetoxy-2,2,2- Trifluoroethyl sulfide) was obtained, and the yield was 45%.
[0033]
Comparative Example 11
When electrolysis was carried out under the same conditions as in Example 8 except that the anode was platinum having the same area, the yield was 52%.
[0034]
Comparative Example 12
When electrolysis was performed under the same conditions as in Example 8 except that the anode was a GC with the same area, the yield was 12% and consumption of GC was observed.
[0035]
【The invention's effect】
The present invention relates to a method for electrolytically producing an organic compound using an electrode for electrolysis containing at least a conductive diamond on its surface, wherein the raw material for the electrolytic reaction is ethyl α- phenylthioacetate, oxindole derivative, benzothiazolyl sulfide , An organic compound selected from the group consisting of sulfides having an asymmetric auxiliary group of Evans and phenyl 2,2,2-trifluoroethyl sulfide, and the organic compound to be produced is an organic sulfur compound, This is an electrolytic production method of an organic compound.
According to the method of the present invention, an organic sulfur compound can be electrolytically produced with a yield and selectivity substantially equal to that of using a noble metal electrode by using a diamond electrode that is less expensive than the noble metal electrode.
[0036]
Raw materials for the electrolytic reaction are ethyl α- phenylthioacetate, oxindole derivatives, benzothiazolyl sulfides, sulfides having an asymmetric auxiliary group of Evans, and phenyl 2,2,2-trifluoroethyl sulfide. the electrolytic reaction, the fluorinated these compounds, including the reaction of methoxylated or acetoxylation.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a diaphragmless electrolytic cell that can be used in the method for electrolytically producing an organic compound of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrolyzer main body 2 Anode feeder 3 Anode 4 Cathode feeder 5 Cathode 6 Power supply 7 Electrolyte 8 Stirrer

Claims (2)

In a method for electrolytically producing an organic compound using an electrode for electrolysis containing conductive diamond at least on its surface, the raw material for the electrolytic reaction is ethyl α- phenylthioacetate, oxindole derivatives, benzothiazolyl sulfides, Evans An organic compound selected from the group consisting of sulfides having an asymmetric auxiliary group and phenyl 2,2,2-trifluoroethyl sulfide, wherein the organic compound to be produced is an organic sulfur compound Electrolytic manufacturing method. Electrolysis reaction, electrolysis producing how according to claim 1 fluorination is methoxylated or acetoxylation.

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