Specification
Title of the Invention: Process for producing 1,2,2,2-tetrafluoroethyl difluoromethyl ether (desflurane)
Technical field
[0001]
　The present invention relates to a method for producing 1,2,2,2-tetrafluoroethyl difluoromethyl ether (desflurane).
Background
[0002]
　1,2,2,2-Tetrafluoroethyl difluoromethyl ether is an important inhalation anesthetic known as desflurane. The inhalation anesthetic has a very low in vivo metabolic rate and is widely used as a safe and gentle drug for the living body. Production examples for desflurane include its precursors 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether (CF 3 CHClOCHF 2 ; isoflurane), 2,2,2-trifluoroethyl difluoromethyl ether ( CF 3 CH 2 OCHF 2 ) and 1,2,2,2-tetrafluoroethyl dichloromethyl ether (CF 3 CHFOCHCl 2 ) are fluorinated. As a halogen exchange fluorination reaction of isoflurane, a method using an alkali metal fluoride (Patent Document 1), a method using bromine trifluoride (Patent Document 2 and Patent Document 3), a method using hydrogen fluoride (Patent Document 1) Document 4, Patent Document 5, Patent Document 6, and Patent Document 7) are known. As a reaction for directly fluorinating 2,2,2-trifluoroethyldifluoromethyl ether, a method using a fluorine gas (Patent Document 8), a method using a higher-order metal fluorine compound (Patent Document 9 and Patent Documents) 10) is known. As a fluorination reaction for 1,2,2,2-tetrafluoroethyldichloromethyl ether, a method using hydrogen fluoride is known (Patent Document 11).
Prior art documents
Patent Literature
[0003]
Patent Document 1: US Pat. No. 4,874,901
Patent Document 2: US Pat. No. 4,762,856
Patent Document 3: US Pat. No. 5,157,781
Patent Document 4: JP-A-2-279646
Patent Document 5: US Patent the 6800786 Pat
Patent Document 6: International Publication No. 2006-076324
Patent Document 7: JP-T 2010-533211 Patent Publication
Patent Document 8: U.S. Patent No. 3,897,502 Pat
Patent Document 9: JP-a 4-273839 JP
Patent Document 10: Japanese Patent Laid-Open No. 6-192154
Patent Document 11: German Patent No. 2361058
Summary of the Invention
Problems to be solved by the invention
[0004]
　Regarding the method for producing desflurane, when a fluorination reaction is performed under severe conditions due to the physical properties of a compound having an ether moiety (“—O—”) such as desflurane, the decomposition product accompanying the cleavage of the ether moiety By-product comes into question. The conventional method is not an efficient method because the conversion rate is poor for employing an expensive starting substrate.
[0005]
　Since the method described in Patent Document 1 is a fluorination reaction under conditions of high temperature and high pressure, it is difficult to employ industrially and has a low yield. The methods described in Patent Document 2 and Patent Document 3 are also highly toxic and corrosive reagents and are difficult to handle. The methods described in Patent Literature 4 and Patent Literature 5 are intended to achieve a medium yield by performing liquid phase fluorination using hydrogen fluoride in the presence of an antimony pentachloride catalyst in the vicinity of room temperature. You're getting a deathful run. However, hydrogen fluoride itself is an acidic substance, and antimony pentachloride, which is generally considered to have a high reaction activity, is used, so that it can cleave the ether moiety of isoflurane as the raw material and desflurane as the target product. Many by-products of derived impurities were generated. Although the method described in Patent Document 6 performs a gas phase fluorination reaction in the presence of a chromia catalyst, the conversion rate is moderate and satisfactory results are not obtained. Although the method described in Patent Document 7 performs a gas phase fluorination reaction in the presence of an antimony catalyst supported on activated carbon, the conversion rate is not necessarily high.
[0006]
　On the other hand, the method described in Patent Document 8 has a risk of explosion and is inconvenient to handle. Furthermore, the conversion rate is low (30%), and the target product is also low in yield, so that it is difficult to adopt as industrial production. The methods described in Patent Document 9 and Patent Document 10 require a large excess of higher-order metal fluorine compound in order to carry out the reaction smoothly, which is not preferable from an economical viewpoint. In addition, any of the methods described in Patent Document 11 has a low yield to a medium yield, and is difficult to employ as a production method as an inhalation anesthetic, and any method still has problems. In particular, Patent Document 11 discloses a reaction example in which liquid phase fluorination of 1,2,2,2-tetrafluoroethyldichloromethyl ether using hydrogen fluoride is performed in the presence of an antimony pentachloride catalyst near room temperature. However, the yield of the intended desflurane was low (21%).
[0007]
　As described above, there has been a strong demand for a method for efficiently producing desflurane using a readily available starting material and using a safe fluorination reagent.
Means for solving the problem
[0008]
　In view of the above problems, the present inventors have conducted intensive studies. As a result,
　2,2,2-trichloroacetaldehyde (chloral, sometimes referred to simply as “chloral” in this specification) represented by the formula [1] is continuously fluorinated with hydrogen fluoride. Thus, 2,2,2-trifluoroacetaldehyde represented by the formula [2] (fluoral, sometimes referred to simply as “fluoral” in this specification) was obtained, and
　then the obtained 2,2,2 By reacting 2-trifluoroacetaldehyde with trimethyl orthoformate, 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3] is selectively obtained, and
　then the obtained 1,1 , 2,4,2-Tetrafluoroethyl methyl ether is subjected to chlorination in the presence of a radical initiator or in the presence of light to form a precursor of desflurane, which is represented by the formula [4 In represented by 1,2,2,2-induced to tetrafluoroethyl dichloromethyl ether,
　further, by reacting hydrogen fluoride in the obtained 1,2,2,2-tetrafluoroethyl dichloromethyl ether The inventors have newly found knowledge that can efficiently produce desflurane represented by the formula [5], and have completed the present invention.
[Chemical 1]

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5]

[0009]
　Although the fluorination process of 1,2,2,2-tetrafluoroethyl dichloromethyl ether corresponds to the reaction example of Patent Document 11, chloral which can be obtained industrially at a very low cost is used as a starting material, and four production processes are performed. By adopting it, impurities that are difficult to separate are hardly generated in each step, and the intended desflurane can be manufactured much more advantageously than before. The production method of the present invention can be said to be a particularly preferable method for industrial production.
[0010]
　As described above, 2,2,2-trifluoroacetaldehyde disclosed in the present invention is obtained by performing a fluorination reaction in a gas phase using 2,2,2-trichloroacetaldehyde as a starting material. Thus, a method for producing desflurane by efficiently converting to 1,2,2,2-tetrafluoroethyl methyl ether, followed by a chlorination reaction and a fluorination reaction has not been known.
[0011]
　That is, the present invention provides a method for producing 1,2,2,2-tetrafluoroethyl difluoromethyl ether (desflurane) described in the following [Invention 1] to [Invention 22].
[0012]
　[Invention 1]
　A process for producing 1,2,2,2-tetrafluoroethyldifluoromethyl ether (desflurane) represented by the formula [5], comprising the following four steps.
First step: 2,2,2-trichloroacetaldehyde represented by the formula [1] is reacted with hydrogen fluoride in the gas phase in the presence of a catalyst to produce 2,2 represented by the formula [2]. , 2-trifluoroacetaldehyde.
Second step: 1,2,2,2 represented by the formula [3] by reacting 2,2,2-trifluoroacetaldehyde obtained in the first step with hydrogen fluoride and trimethyl orthoformate. Obtaining tetrafluoroethyl methyl ether;
Third step: By reacting 1,2,2,2-tetrafluoroethyl methyl ether obtained in the second step with chlorine (Cl 2 ) in the presence of a radical initiator or under light irradiation , A step of obtaining 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4].
Step 4: By reacting 1,2,2,2-tetrafluoroethyldichloromethyl ether obtained in Step 3 with hydrogen fluoride, 1,2,2 represented by the formula [5] Obtaining 2,2-tetrafluoroethyldifluoromethyl ether (desflurane);
[0013]
　[Invention 2]
　The metal compound containing at least one metal selected from the group consisting of chromium, titanium, manganese, iron, nickel, cobalt, magnesium, zirconium, and antimony as the catalyst in the first step is a metal oxide or activated carbon. The production method according to invention 1, which is a metal compound-supported catalyst supported on a catalyst.
[0014]
　[Invention 3] The
　metal compound is at least one metal halide or metal oxyhalogen selected from the group consisting of metal fluoride, chloride, fluoride chloride, oxyfluoride, oxychloride, and oxyfluoride chloride. The manufacturing method of the invention 2 which is a compound.
[0015]
　[Invention 4]
　The production method according to Invention 2 or 3, wherein the metal oxide is at least one selected from the group consisting of alumina, zirconia, titania, chromia, and magnesia.
[0016]
　[Invention 5]
　The production according to any one of Inventions 1 to 4, wherein 2,2,2-trifluoroacetaldehyde obtained in the first step is used as it is as a starting material in the second step without performing a purification operation. Method.
[0017]
　[Invention 6]
　The production method according to any one of Inventions 1 to 5, wherein the reaction in the second step is performed without using an organic solvent.
[0018]
　[Invention 7]
　The production according to any one of Inventions 1 to 6, wherein in the third step, the radical initiator or light irradiation is at least one selected from the group consisting of an organic peroxide and an azo radical initiator. Method.
[0019]
　[Invention 8] Inventions 1 to 6 wherein in
　the third step, the radical initiator or light irradiation is at least one selected from the group consisting of a mercury lamp, an ultraviolet LED, an organic EL, an inorganic EL, an ultraviolet laser, and a halogen lamp. The manufacturing method in any one of.
[0020]
　[Invention 9]
　The production method according to any one of Inventions 1 to 8, wherein the reaction in the third step is performed in the presence of a fluoride ion scavenger.
[0021]
　[Invention 10]
　Fluoride ion scavenger is alkali metal halide, alkali metal sulfate, alkaline earth metal hydroxide, alkaline earth metal halide, alkaline earth metal sulfate, periodic table The production according to invention 9, which is at least one selected from the group consisting of a hydroxide of a metal belonging to Group 13, a metal halide belonging to Group 13 of the periodic table, and a sulfate of a metal belonging to Group 13 of the periodic table. Method.
[0022]
　[Invention 11]
　The production method according to any one of Inventions 1 to 10, wherein the reaction in the third step is performed in the presence of a reaction solvent.
[0023]
　[Invention 12] In
　the third step, by reacting chlorine, 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by Formula [4] and 1,2 represented by Formula [7] The production method according to any one of inventions 1 to 11, which is obtained as a mixture containing 2,2,2-tetrafluoroethyl chloromethyl ether.
[Chemical 6]

[0024]
　[Invention 13] The
　method further includes a step of separating and removing 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] from the mixture by subjecting the mixture to distillation purification. The manufacturing method of the invention 12.
[0025]
　[Invention 14] In
　the third step, 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] separated and removed by distillation purification is recovered, and chlorine in the third step is recovered. The production method according to invention 13, which is used as a starting material in a chemical reaction.
[0026]
　[Invention 15]
　The production method according to any one of Inventions 1 to 14, wherein the reaction is carried out in a gas phase in the fourth step.
[0027]
　[Invention 16]
　The production method according to any one of Inventions 1 to 15, wherein in the fourth step, the reaction is carried out in the presence of a catalyst.
[0028]
　[Invention 17] In
　the fourth step, the catalyst is selected from the group consisting of tin tetrachloride, tin dichloride, tin tetrafluoride, tin difluoride, titanium tetrachloride, antimony trichloride, antimony pentachloride, and antimony pentafluoride. The production method according to invention 16, which is at least one selected.
[0029]
　[Invention 18]
　The production method according to any one of Inventions 1 to 15, wherein the reaction in the fourth step is carried out in the absence of a catalyst.
[0030]
　[Invention 19]
　The production method according to any one of Inventions 1 to 14, wherein the reaction is carried out in a liquid phase in the fourth step.
[0031]
　[Invention 20] In
　the fourth step, the reaction in the liquid phase is carried out at a temperature range of −10 ° C. to + 150 ° C. and 0.1 MPa to 2.0 MPa (absolute pressure, hereinafter the same in this specification). The manufacturing method of the invention 19 performed in a pressure range.
[0032]
　[Invention 21] In
　the fourth step, the reaction of 1,2,2,2-tetrafluoroethyldichloromethyl ether with hydrogen fluoride is carried out in the liquid phase by “a salt or complex comprising an organic base and hydrogen fluoride”. The manufacturing method in any one of invention 1 thru | or 14 performed by making it react.
[0033]
　[Invention 22] The
　organic base in the “salt or complex comprising an organic base and hydrogen fluoride” is triethylamine, diisopropylethylamine, tri-n-butylamine, pyridine, and 2,6-lutidine and 1,8-diazabicyclo [5.4. 0.0] The production method according to invention 21, which is at least one selected from the group consisting of undec-7-ene.
[0034]
　According to the present invention, 1,2,2,2-tetrafluoroethyldifluoromethyl is obtained by using the easily described chloral as a starting material and passing through the steps described above using various reagents that are safe to handle. The effect is that ether (desflurane) can be produced efficiently.
BEST MODE FOR CARRYING OUT THE INVENTION
[0035]
　Hereinafter, the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be appropriately implemented based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.
[0036]
　The present invention is a manufacturing method including the four steps described above, and the relationship between each step is illustrated as follows.
[Chemical 7]

[0037]
　[First Step]
　First, the first step will be described. In the first step, 2,2,2-trichloroacetaldehyde represented by the formula [1] is reacted with hydrogen fluoride in the presence of a catalyst in the gas phase, whereby 2, In this step, 2,2-trifluoroacetaldehyde is obtained.
[0038]
　As the 2,2,2-trichloroacetaldehyde represented by the formula [1] of the starting material used in this step, a commercially available product (Tokyo Chemical Industry Co., Ltd.) can be used. (Tetrahedron Letters, 56 (24), 3758-3761, 2015).
[0039]
　This step is performed by using a reactor made of a material substantially inert to hydrogen fluoride and introducing chloral into the reaction zone filled with the catalyst under temperature control. The reaction vessel used in the present process, usually, be of tubular, stainless steel, Hastelloy TM , those or metal such as platinum, tetrafluoroethylene resin, chlorotrifluoroethylene resin, vinylidene fluoride resin, It is preferable to use a reaction vessel in which a PFA resin or the like is lined, and can sufficiently react even under normal pressure or under pressure.
[0040]
　The catalyst used in this step is a metal compound in which a metal compound containing at least one metal selected from the group consisting of chromium, titanium, manganese, iron, nickel, cobalt, magnesium, zirconium and antimony is supported on a metal oxide or activated carbon. It is a supported catalyst. The metal compound may be at least one metal halide or metal oxyhalide selected from the group consisting of fluoride, chloride, fluoride chloride, oxyfluoride, oxychloride, and oxyfluoride chloride. is there. Furthermore, the metal oxide is at least one selected from the group consisting of alumina, zirconia, titania, chromia, and magnesia. A fluorinated carrier (for example, fluorinated alumina) can also be used as a catalyst. Among these catalysts, a catalyst in which a chromium compound is supported on a metal oxide or activated carbon is preferable.
[0041]
　When a catalyst in which the metal compound is supported on a carrier is used as a catalyst, the supported metal compound is 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass with respect to 100 parts by mass of the carrier. As will be described in detail in Preparation Example 1 described later, alumina used as a metal oxide is generally alumina obtained by molding and dehydrating a precipitate generated from an aluminum salt aqueous solution using ammonia or the like. Usually, γ-alumina commercially available for catalyst support or for drying is preferably used.
[0042]
　The method for preparing the catalyst (metal compound-supported catalyst) is not limited, but a soluble compound of at least one metal selected from chromium, manganese, nickel, cobalt, and iron is added to the aluminum oxide such as γ-alumina. The impregnated solution is impregnated or sprayed and then dried. Thereafter, the catalyst is prepared by partially or completely fluorinating the support with a fluorinating agent such as hydrogen fluoride to obtain fluorinated alumina. In the final stage of the preparation of the catalyst, it is preferable to distribute hydrogen fluoride at a temperature equal to or higher than the reaction temperature of the fluorination reaction. Therefore, it is normally treated at 200 to 500 ° C., particularly 300 to 400 ° C.
[0043]
　The soluble compound is not particularly limited as long as it is an oxide or salt of a corresponding metal that dissolves in a solvent such as water, ethanol, and acetone, and examples thereof include nitrates, chlorides, sulfates, carbonates, and acetates. Specifically, chromium nitrate, chromium trichloride, chromium trioxide, potassium dichromate, manganese nitrate, manganese chloride, manganese dioxide, nickel nitrate, nickel chloride, cobalt nitrate, cobalt chloride, iron nitrate, iron chloride, etc. are used. Is preferred. These compounds may be hydrates, and the metal valence may be any valence. It is effective to treat the catalyst prepared by any method in advance with a fluorinating agent such as hydrogen fluoride at a temperature equal to or higher than a predetermined reaction temperature before use to prevent a change in the composition of the catalyst during the reaction.
[0044]
　Activated carbon used as a carrier is plant based on wood, charcoal, coconut shell charcoal, palm kernel charcoal, bare ash, etc., coal based on peat, lignite, lignite, bituminous coal, anthracite, etc., petroleum residue, oil carbon And other synthetic resin systems such as petroleum-based or carbonized polyvinylidene chloride. These activated carbons can be selected and used. For example, activated carbon manufactured from bituminous coal (BPL granular activated carbon manufactured by Mitsubishi Chemical Calgon), coconut shell charcoal (G2c, G2x, GS3c, GS3x, C2c, C2x manufactured by Nippon Environmental Chemicals) , X2M, Mitsubishi Chemical Calgon PCB), and the like. The shape and size are usually used in a granular form, but can be used within a normal knowledge range as long as it is suitable for a reactor such as a sphere, fiber, powder, or honeycomb. The activated carbon used in the present invention is preferably activated carbon having a large specific surface area. The specific surface area and pore volume of the activated carbon are sufficient within the range of the specifications of commercially available products, but are desirably larger than 400 m 2 / g and larger than 0.1 cm 3 / g , respectively . Further , they may be 800 to 3000 m 2 / g and 0.2 to 1.0 cm 3 / g, respectively . Furthermore, when using activated carbon as a support, it is immersed in a basic aqueous solution such as ammonium hydroxide, sodium hydroxide or potassium hydroxide for about 10 hours or more at normal temperature or when activated carbon is used as a catalyst support. It is preferable to perform pretreatment with acid such as nitric acid, hydrochloric acid, hydrofluoric acid, etc., to activate the carrier surface and remove ash in advance.
[0045]
　In addition, supplying oxygen, chlorine, fluorinated or chlorinated hydrocarbons into the reactor during the reaction is effective for extending the catalyst life, improving the reaction rate, and the reaction yield. When the catalyst according to the present invention loses activity due to the reaction, it can be activated again. That is, the deactivated catalyst can be reactivated by contacting it with an oxidizing substance such as oxygen, air, chlorine, etc. at an elevated temperature. The treatment temperature at that time is 200 to 550 ° C., among which 300 to 500 ° C. is preferable. If it is less than 200 ° C., it remains in an inactivated state.
[0046]
　The reaction temperature in this step is not particularly limited, but is 100 to 500 ° C, preferably 100 to 400 ° C, and more preferably 100 to 350 ° C. Even when the reaction temperature exceeds 500 ° C., the reaction rate is not particularly improved, and a decomposition product is generated, which lowers the selectivity of the fluoral represented by the formula [2].
[0047]
　In this step, the molar ratio of chloral: hydrogen fluoride supplied to the reaction zone is affected by the reaction temperature, but is usually from 1: 2 to 1:50, preferably from 1: 4 to 1:20. : 6 to 1:15 are more preferable. When there is little hydrogen fluoride, the conversion rate of reaction may fall and the yield of a target object may fall.
[0048]
　In this step, chloral supplied to the reaction region can be supplied together with a gas such as nitrogen, helium, or argon that is not involved in the reaction. Similarly, hydrogen fluoride can coexist. Such a gas has a ratio of 100 mol or less per mol of the raw material composed of chloral or a mixture containing the same, and preferably 20 mol or less. Gases that do not participate in the reaction may not be used.
[0049]
　The reaction pressure in this step is usually in the range of 0.1 to 6.0 MPa, but the preferable pressure range in this step is preferably 0.1 to 3.0 MPa, more preferably 0.1 to 1.MPa. The range is 5 MPa. When setting the pressure, it is desirable to select conditions such that organic substances such as raw materials existing in the system do not liquefy in the reaction system.
[0050]
　The contact time in the method of the first step is usually 0.1 to 200 seconds, preferably 3 to 100 seconds in the standard state. If the contact time is short, the reaction rate decreases, and if the contact time is too long, side reactions occur, which is not preferable.
[0051]
　In this step, the fluorination reaction proceeds by circulating hydrogen fluoride in the gas phase. In such a flow format, the catalyst retention method can be any type such as fixed bed, fluidized bed, moving bed, etc. Although it does not matter, it is convenient and preferable to carry out on a fixed bed.
[0052]
　The product mainly composed of fluoral that is fluorinated by the method of this step and flows out of the reactor can be used in the next step after being purified by a known method. The purification method is not particularly limited, but since fluoral is a water-soluble compound, a deoxidation operation such as washing with water is not preferable.
[0053]
　In this step, the product mainly composed of fluoral that flows out from the reactor contains hydrogen fluoride, but even if it exists, the fluorinating agent is used in the subsequent second step. Therefore, it is not always necessary to positively remove hydrogen fluoride from the reaction system in this step. Therefore, as shown in the below-mentioned Example, it can be said that it is one of the preferable aspects that the fluoral obtained by this process is used for the next process as it is, without performing special refinement | purification operation.
[0054]
　[Second Step]
　Next, the second step will be described. The second step is represented by the formula [3] by reacting the 2,2,2-trifluoroacetaldehyde obtained in the first step with hydrogen fluoride and trimethyl orthoformate. , 2,2,2-Tetrafluoroethyl methyl ether.
[0055]
　Although hydrogen fluoride is used in this process, the product obtained in the previous process and containing fluoral as a main component out of the reactor contains hydrogen fluoride. It can utilize as a fluorinating agent in a process (refer the below-mentioned Example). In this case, since it is substantially synonymous with the embodiment in which hydrogen fluoride is added in this step, even the embodiment using hydrogen fluoride derived from the previous step is included in the scope of this step. .
[0056]
　The amount of hydrogen fluoride used in this step is usually 1 equivalent or more with respect to the fluoral obtained in the first step, and using 2 to 10 equivalents is preferable because the reaction proceeds smoothly. Considering the post-treatment surface, 3 to 6 equivalents are particularly preferable. When the amount of hydrogen fluoride used in the first step is small, it is necessary to newly add hydrogen fluoride, but sufficient hydrogen fluoride is contained in the organic matter recovered in the first step. If it is, it can be used as it is.
[0057]
　Trimethyl orthoformate used in this step can be added to the reaction system, so that the conversion rate of the fluorination reaction can be improved. As trimethyl orthoformate, a commercially available product (Nichiho Chemical Co., Ltd.) can be used. As shown in the following formula, the fluorination reaction with respect to the fluoroal generates water molecules in addition to the target product as the reaction proceeds. Trimethyl orthoformate is considered to function as a scavenger (scavenger) for water molecules. That is, trimethyl orthoformate is promptly promoted to undergo hydrolysis under the acidic condition of hydrogen fluoride, and is converted into one molecule of methyl formate and two molecules of methanol. Thus, alcohol (methanol) is produced by the reaction of orthoester (trimethyl orthoformate) and water (functions as a dehydrating agent), and at the same time, the ester (methyl formate) obtained is reacted with the desired product (formula It can be easily separated from 1,2,2,2-tetrafluoroethyl methyl ether represented by [3].
[Chemical 8]

[0058]
　In order for trimethyl orthoformate to function as a dehydrating agent, the amount of trimethyl orthoformate used is 0.2 equivalents or more, usually 1 equivalent of 2,2,2-trifluoroacetaldehyde represented by the formula [2]. It is preferable to use 0.5 to 1.5 equivalents. However, when an amount exceeding 1.5 equivalents of trimethyl orthoformate is used, it is affected by the alcohol (methanol) by-produced by hydrolysis, and the hemi of 2,2,2-trifluoroacetaldehyde, which is an equilibrium compound with fluoral. An acetal form (2,2,2-trifluoroacetaldehyde methyl hemiacetal form) or dimethylacetal (1,1-dimethoxy-2,2,2-trifluoroethane) is produced, and is represented by the target formula [3]. Since the reaction to 1,2,2,2-tetrafluoroethyl methyl ether may be hindered, the use of an amount in the above-mentioned range is one preferred embodiment.
[0059]
　As the reaction solvent in this step, a solvent having high hydrogen fluoride resistance can be suitably used. Aliphatic hydrocarbon type, aromatic hydrocarbon type, halogenated hydrocarbon type, ether type, ester type, amide type, nitrile type, sulfoxide type and the like can be mentioned. Specific examples include n-hexane, cyclohexane, n-heptane, benzene, toluene, ethylbenzene, xylene, mesitylene, methylene chloride, chloroform, 1,2-dichloroethane, diethyl ether, tetrahydrofuran, diisopropyl ether, tert-butyl methyl ether, Examples include ethyl acetate, n-butyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, propionitrile, dimethyl sulfoxide and the like. It is done. These reaction solvents can be used alone or in combination.
[0060]
　In the present invention, the reaction can be carried out without using a reaction solvent. This embodiment is more preferable because the purification operation after the reaction is simple and there is an advantage that the high-purity target product can be obtained only by a washing operation.
[0061]
　The temperature condition may be in the range of −50 to + 100 ° C., usually −20 to + 50 ° C. is preferable, and 0 to + 20 ° C. is particularly preferable.
[0062]
　The pressure condition may be in the range of 0.1 MPa to 0.9 MPa, but usually 0.1 MPa to 0.5 MPa is preferable, and 0.1 MPa to 0.2 MPa is more preferable. Therefore, a pressure-resistant reaction vessel made of a material such as stainless steel (SUS) or a resin such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE) having corrosion resistance against hydrogen fluoride. The reaction is preferably performed using a container. For example, when the reaction is performed at a temperature higher than the boiling point of hydrogen fluoride (+ 19.54 ° C.), it is preferable to use a pressure resistant reaction vessel such as stainless steel (SUS).
[0063]
　Although the reaction time is usually within 12 hours, the progress of the fluorination reaction is traced by analytical means such as gas chromatography, thin layer chromatography, liquid chromatography, nuclear magnetic resonance, and the starting substrate is almost lost. It is preferred that the time point be the end point of the reaction.
[0064]
　In the post-treatment, the target liquid 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3] can be easily obtained by washing the reaction completion solution, which is a normal purification operation. Can be obtained. The target product can be purified to a higher chemical purity product by activated carbon treatment, distillation, recrystallization, column chromatography and the like, if necessary.
[0065]
　[Third Step]
　Next, the third step will be described. In the third step, the 1,2,2,2-tetrafluoroethyl methyl ether obtained in the second step is reacted with chlorine in the presence of a radical initiator or under light irradiation to obtain the formula [4 ] 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by
[0066]
　When this step is performed, the supply amount of chlorine is from 1.00 equivalent to 4.4 with respect to 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3] obtained in the second step. It may be carried out in the range of 00 equivalents, among which 1.25 equivalents to 3.00 equivalents are preferred, with 1.50 equivalents to 2.50 equivalents being particularly preferred.
[0067]
　The degree of chlorination of the reaction substrate proceeds according to the amount of chlorine supplied, but by appropriately controlling the amount of chlorine supplied, the target product (1,2,2,2-tetra Byproduct of 1,2,2,2-tetrafluoroethyltrichloromethyl ether (higher chlorinated product) represented by formula [6], which is difficult to separate from (fluoroethyldichloromethyl ether), can be minimized. Obtained knowledge.
[Chemical 9]

[0068]
　On the other hand, in addition to the target product (formula [4]), 1,2,2,2-tetrafluoroethylchloromethyl ether of formula [7], which is a low-order chlorinated product, is also produced as a mixture with the target product However, this mixture can be separated by a normal distillation operation. Further, low-order chlorinated products can be recovered and reused as a raw material for the chlorination reaction.
[Chemical 10]

[0069]
　When chlorine is supplied to the reactor, the chlorine may be either a gas or a liquid, but is preferably a gas from the viewpoint of ease of handling. The method for supplying chlorine is not particularly limited as long as it can supply chlorine into the reaction solution. For example, a method of charging chlorine into the reaction vessel in a batch before starting the chlorination reaction, a method of supplying chlorine sequentially during the chlorination reaction, and a continuous supply of chlorine during the chlorination reaction There are methods. If the reaction is too intense, an inert gas such as argon or nitrogen may be introduced while being mixed with chlorine (that is, “diluting” chlorine with an inert gas).
[0070]
　In this step, in order to further improve the selectivity of the chlorination reaction with respect to 1,2,2,2-tetrafluoroethyl methyl ether, a radical initiator can coexist. Specific examples include organic peroxides and azo radical initiators. Examples of the organic peroxide include benzoyl peroxide, ketone peroxide, peroxy ketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxy ester, and peroxy dicarbonate. As the azo radical initiator, 2,2′-azobis (2-methylpropionitrile) (abbreviation “AIBN”), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate), 2,2′-azobis (2-methylbutyronitrile), 2,2 '-Azobis (2- (2-imidazolin-2-yl) propane) dihydrochloride, 2,2'-azobis (2- (2-imidazolin-2-yl) propane) disulfate, 2,2'- An example is azobis (2-methylpropionamidine) dihydrochloride.
[0071]
　When a radical initiator is used, the amount of the radical initiator used is usually 0.01 to 20 mol with respect to 1.0 mol of 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3]. %, Preferably 0.1 to 10 mol%, more preferably 0.5 to 5 mol%. Further, the radical initiator can be added as appropriate by observing the progress of the reaction. If the amount of the radical initiator is less than 0.01 mol% with respect to 1 mol of the raw material, the reaction is likely to stop during the process, and the yield may be lowered. .
[0072]
　On the other hand, when light irradiation is performed in this step, the light source is at least one selected from the group consisting of a mercury lamp, an ultraviolet LED, an organic EL, an inorganic EL, an ultraviolet laser, and a halogen lamp. Among these, a mercury lamp is used. Is preferred.
[0073]
　In this step, a reaction solvent can be used (the reaction can also be performed without using the reaction solvent, as shown in Examples below). Examples of the reaction solvent include water, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, esters, amides, nitriles, and sulfoxides. Specific reaction solvents include water, n-hexane, cyclohexane, n-heptane, benzene, toluene, ethylbenzene, xylene, mesitylene, methylene chloride, chloroform, 1,2-dichloroethane, diethyl ether, tetrahydrofuran, diisopropyl ether, tert -Butyl methyl ether, ethyl acetate, n-butyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, propionitrile and Examples thereof include dimethyl sulfoxide, and these reaction solvents can be used alone or in combination of one or more.
[0074]
　When water is used as the reaction solvent, the compound having a high vapor pressure, 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3] or a low-order chlorinated product, the formula [7 The volatilization of 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by Since improvement of reaction efficiency is also expected, it is one of the preferred embodiments.
[0075]
　The amount of the reaction solvent used in this step may be in the range of 10 parts by weight to 1000 parts by weight with respect to 100 parts by weight of 1,2,2,2-tetrafluoroethyl methyl ether. Mass parts are preferred, and a use amount of 25 to 250 parts by mass is particularly preferred. In this step, when water is used as the reaction solvent, the amount of water used may be in the range of 10 to 1000 parts by mass with respect to 100 parts by mass of 1,2,2,2-tetrafluoroethyl methyl ether. Of these, 10 to 500 parts by mass are preferable, and 25 to 250 parts by mass is particularly preferable.
[0076]
　Further, in this step, fluoride ions generated during the reaction can be efficiently collected by adding a fluoride ion scavenger into the reaction system. Alkali metal halides, alkali metal sulfates, alkaline earth metal hydroxides, alkaline earth metal halides, alkaline earth metal sulfates, metal hydroxides belonging to Group 13 of the periodic table, periodicity It is at least one selected from the group consisting of metal halides belonging to Group 13 and sulfates of metals belonging to Group 13 of the periodic table. Specific examples of the fluoride ion scavenger include sodium fluoride, sodium sulfate, calcium hydroxide, calcium chloride, calcium sulfate, aluminum hydroxide, aluminum chloride and aluminum sulfate. Among these, calcium chloride is easy to handle and has high solubility in water, so that it can be suitably used. As the calcium chloride, at least one kind of calcium chloride selected from the group of anhydride, monohydrate, dihydrate, tetrahydrate, and hexahydrate may be used. The fluoride ion scavenger may be added to the reaction system in the form of a solid, but it is more preferable to dissolve it in a solvent such as water because an effective trap action of fluoride ions is expected.
[0077]
　The amount of the fluoride ion scavenger used may be in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of 1,2,2,2-tetrafluoroethyl methyl ether, and in particular 0.5 mass Part to 50 parts by weight is preferable, and a use amount of 1 part to 25 parts by weight is particularly preferable.
[0078]
　The reaction temperature in this step may be usually in the range of −50 to + 80 ° C., and is usually preferably −20 to + 50 ° C., and particularly preferably −10 to + 25 ° C. The lower the reaction temperature, the better the chlorine regioselectivity. Therefore, it is preferable to carry out the reaction at room temperature or lower.
[0079]
　The pressure condition in this step may be in the range of 0.05 MPa to 5.0 MPa, and usually a slight pressure range of about 0.1 MPa to 0.3 MPa is more convenient and preferable. The reaction can be carried out at a pressure exceeding 5.0 MPa. However, since the equipment is loaded under excessive pressure conditions, the reaction in the pressure range and atmospheric pressure is preferred. Therefore, glass containers such as quartz glass and borosilicate glass having corrosion resistance against chlorine and by-product hydrogen chloride, or resins such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) and polytetrafluoroethylene (PTFE) A container can be used suitably.
[0080]
　1,2,2,2-Tetrafluoroethyldichloromethyl ether represented by the formula [4], which is the object of this step, is a precursor of desflurane, which is a useful inhalation anesthetic. On the other hand, when fluorination was attempted with respect to 1,2,2,2-tetrafluoroethyltrichloromethyl ether represented by the formula [6] with reference to the methods described in Patent Document 2 and Patent Document 3, Proceeds partially to obtain 1,2,2,2-tetrafluoroethyl chlorodifluoromethyl ether (see Reference Example 1 described later). However, since the ether can be a difficult-to-separate impurity when producing desflurane, when considering the production process of desflurane as an inhalation anesthetic, it is represented by the formula [6] at the time of photochlorination of the present invention. 1,2,2,2-tetrafluoroethyl trichloromethyl ether is preferably reduced as much as possible.
[0081]
　The reaction time of this step is usually within 12 hours, but the progress of the reaction is traced by analytical means such as gas chromatography, thin layer chromatography, liquid chromatography, nuclear magnetic resonance, etc. After confirmation, the reaction was completed so that the selectivity of 1,2,2,2-tetrafluoroethyltrichloromethyl ether represented by the formula [6], which is a high-order chlorinated product that is difficult to separate, was approximately 10% or less. It is preferable to make it.
[0082]
　The post-treatment operation after the completion of the reaction is carried out by subjecting the reaction-terminated liquid to a normal distillation operation, whereby the desired 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4] is used. Is obtained. If necessary, it is possible to obtain a target product with higher purity by activated carbon treatment, silica gel column chromatography, or the like.
[0083]
　On the other hand, 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7], which is a low-order chlorinated product, can be easily separated and recovered, and the recovered 1,2,2,2-tetrafluoroethyl is recovered. Chloromethyl ether can be derived into 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by the formula [4], which is the target product, by chlorinating again. When the 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by [7] is reused, the 1,2,2,2-tetrafluoroethyl methyl ether represented by the formula [3] is used. The chlorination reaction can be repeated by re-adding.
[0084]
　[Fourth Step]
　Next, the fourth step will be described. In the fourth step, 1,2,2,2-tetrafluoroethyldichloromethyl ether obtained in the third step is reacted with hydrogen fluoride to give 1,2 represented by the formula [5]. , 2,2-tetrafluoroethyldifluoromethyl ether (desflurane).
[0085]
　In this step, the fluorination reaction can be carried out in the liquid phase or in the gas phase, but the reaction conditions differ depending on the difference in the liquid phase or the gas phase. Therefore, the case where the fluorination reaction is performed in the liquid phase or in the gas phase will be described step by step.
[0086]
　[When fluorination reaction is carried out
　in the liquid phase ] In this step, a catalyst can be used when the fluorination reaction is carried out in the liquid phase. Specifically, at least one selected from the group consisting of tin tetrachloride, tin dichloride, tin tetrafluoride, tin difluoride, titanium tetrachloride, antimony trichloride, antimony pentachloride, and antimony pentafluoride. A catalyst is available. These catalysts can be used alone or in combination. Among these, the use of tin tetrachloride, tin dichloride, tin tetrafluoride and tin difluoride is preferable, and tin tetrachloride is particularly preferably used.
[0087]
　The amount of the catalyst used is 0.01 to 50 parts by mass with respect to 100 parts by mass of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4]. Preferably it is 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass. When the amount of the catalyst exceeds 50 parts by mass, the amount of tar generated from the high boiling point compound increases, which is not preferable. In addition, about the fluorination reaction in a liquid phase, it can also react without using a catalyst (after-mentioned Example).
[0088]
　The amount of hydrogen fluoride used in the fluorination reaction in the liquid phase is from 0.1 mol to 1 mol of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4]. 100 moles, preferably 0.5 moles to 50 moles, more preferably 1 moles to 25 moles. When the amount of hydrogen fluoride is less than 0.1 mol, the conversion rate in the reaction is poor. Moreover, it is not preferable from the viewpoint of use and an economical viewpoint that the amount of hydrogen fluoride exceeds 100 mol.
[0089]
　In this step, when the fluorination reaction is carried out in the liquid phase, hydrogen fluoride is converted to “a salt or complex comprising an organic base and hydrogen fluoride with respect to 1,2,2,2-tetrafluoroethyldichloromethyl ether. It is also possible to produce desflurane which is the target product. The “salt or complex comprising an organic base and hydrogen fluoride” can be prepared by mixing an organic base and hydrogen fluoride. In addition, “complex composed of 1 mol of triethylamine and 3 mol of hydrogen fluoride” or “complex composed of 30% of pyridine and 70% of hydrogen fluoride” commercially available from Aldrich (Aldrich, 2012-2014 catalog) Can also be used.
[0090]
　The organic base in the “salt or complex comprising an organic base and hydrogen fluoride” is triethylamine, diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, pyridine, 2,6-lutidine, 2,4,6-collidine, Preferred examples include 4-dimethylaminopyridine, 1,5-diazabicyclo [4.3.0] non-5-ene and 1,8-diazabicyclo [5.4.0] undec-7-ene. However, it is not limited to these, The organic base generally used in organic synthesis can also be employ | adopted. Among them, triethylamine, diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, pyridine, 2,6-lutidine, 1,5-diazabicyclo [4.3.0] non-5-ene and 1,8-diazabicyclo [ 5.4.0] undec-7-ene is preferred, and triethylamine, diisopropylethylamine, tri-n-butylamine, pyridine, 2,6-lutidine and 1,8-diazabicyclo [5.4.0] undec-7-ene are preferred. Particularly preferred. The organic bases can be used alone or in combination.
[0091]
　The “salt or complex comprising an organic base and hydrogen fluoride” means that hydrogen fluoride present in the salt or complex reacts with 1,2,2,2-tetrafluoroethyl dichloromethyl ether to generate fluorine. The hydrogenation reaction proceeds (that is, hydrogen fluoride contained in the salt or complex serves as a fluorine source for substituting a chlorine atom for a fluorine atom as in the case of single hydrogen fluoride). Therefore, in this step, the embodiment of “reacting a salt or complex comprising an organic base and hydrogen fluoride with 1,2,2,2-tetrafluoroethyldichloromethyl ether” It is treated as being included in the embodiment of “reacting hydrogen fluoride with 1,2,2,2-tetrafluoroethyldichloromethyl ether”.
[0092]
　The molar ratio of the organic base to hydrogen fluoride in the “salt or complex comprising an organic base and hydrogen fluoride” may be used in the range of 100: 1 to 1: 100. A ratio of 25: 1 to 1:25 is particularly preferable.
[0093]
　The amount of hydrogen fluoride contained in the “salt or complex comprising an organic base and hydrogen fluoride” is 1 mol of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [1]. The amount is 0.1 to 200 mol, preferably 0.5 to 100 mol, and more preferably 1 to 50 mol. When the amount of hydrogen fluoride is less than 0.1 mol, the conversion rate in the reaction is poor. Also, the use of an amount of hydrogen fluoride exceeding 200 mol is not preferable from an economical viewpoint.
[0094]
　In this step, when the fluorination reaction is performed in the liquid phase, a solvent can be used. Examples of the solvent include ether solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ester solvents, amide solvents, nitrile solvents, sulfoxide solvents, and the like.
[0095]
　Specific examples of these reaction solvents include diethyl ether, diisopropyl ether, dibutyl ether, tert-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, cyclopentyl methyl ether, n-hexane, n-heptane, and n-pentane. , N-nonane, n-decane, toluene, xylene, mesitylene, ethylbenzene, methylene chloride, chloroform, 1,2-dichloroethane, ethyl acetate, n-butyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, Examples thereof include N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, propionitrile, dimethyl sulfoxide and the like.
[0096]
　Among these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, acetonitrile, propionitrile and dimethyl sulfoxide are preferable, and tetrahydrofuran, N, N-dimethyl is preferred. Particularly preferred are formamide and acetonitrile. These reaction solvents can be used alone or in combination.
[0097]
　The amount of the solvent used is not particularly limited, but 0.05 L (liter) or more is used with respect to 1 mol of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the general formula [1]. Usually, 0.1 to 20 L is preferable, and 0.1 to 10 L is more preferable.
[0098]
　The reaction temperature for carrying out the fluorination reaction in the liquid phase may be in the range of −20 ° C. to + 200 ° C., usually −10 to + 150 ° C., and particularly preferably 0 to + 100 ° C.
[0099]
　The pressure condition for performing the fluorination reaction in the liquid phase may be in the range of 0.1 MPa to 4.0 MPa, preferably 0.1 MPa to 2.0 MPa, and particularly preferably 0.1 MPa to 1.5 MPa. More preferred.
[0100]
　When performing the fluorination reaction in the liquid phase of this step, the temperature range and the pressure range are 0 ° C. to + 50 ° C. and 0.1 MPa to 1.0 MPa so that the fluorination can be performed at a high conversion rate. In addition to the progress of the reaction, it is possible to avoid the formation of decomposition products generated by cleavage of the ether sites of the reaction substrate and product (desflurane). This means that desflurane is obtained with high selectivity, and adopting this reaction condition is a very preferable embodiment.
[0101]
　In the case of using a “salt or complex comprising an organic base and hydrogen fluoride” for carrying out the fluorination reaction in the liquid phase, the temperature range and pressure range are −10 ° C. to + 150 ° C., and By setting the pressure to 1 MPa to 2.0 MPa, the fluorination reaction similarly proceeds with a high conversion rate, and desflurane can be obtained with a high selectivity (see Example 14 described later).
[0102]
　[When fluorination reaction is carried out
　in the gas phase ] In this step, a catalyst can be used when the fluorination reaction is carried out in the gas phase. Specifically, a metal compound-supported catalyst in which a metal compound containing at least one metal selected from the group consisting of chromium, titanium, manganese, iron, nickel, cobalt, magnesium, zirconium and antimony is supported on a metal oxide or activated carbon. (The specific types and preparation methods of these catalysts can be the same as the catalysts described in the first step, and the description is omitted here.)
[0103]
　The reaction temperature when performing the fluorination reaction in the gas phase is not particularly limited, but is 100 to 500 ° C, preferably 100 to 400 ° C, and more preferably 100 to 350 ° C. When the reaction temperature exceeds 500 ° C., a decomposition product is generated, and the selectivity of the target product may be lowered, which is not preferable.
[0104]
　The molar ratio of 1,2,2,2-tetrafluoroethyldichloromethyl ether: hydrogen fluoride supplied to the reaction zone when performing the fluorination reaction in the gas phase is affected by the reaction temperature, but usually 1 : 2 to 1:50, preferably 1: 4 to 1:20, more preferably 1: 5 to 1:15. When there is little hydrogen fluoride, the conversion rate of reaction may fall and the yield of a target object may fall.
[0105]
　The 1,2,2,2-tetrafluoroethyldichloromethyl ether supplied to the reaction zone when performing the fluorination reaction in the gas phase can be supplied together with a gas such as nitrogen, helium, or argon that does not participate in the reaction. it can. Similarly, hydrogen fluoride can coexist. Such a gas has a ratio of 100 mol or less per mol of 1,2,2,2-tetrafluoroethyl dichloromethyl ether, and preferably 20 mol or less. Gases that do not participate in the reaction may not be used.
[0106]
　The reaction pressure when performing the fluorination reaction in the gas phase is usually in the range of 0.1 to 6.0 MPa, but the preferred pressure range in this step is preferably 0.1 to 3.0 MPa, more The range is preferably from 0.1 to 1.5 MPa. When setting the pressure, it is desirable to select conditions such that organic substances such as raw materials existing in the system do not liquefy in the reaction system.
[0107]
　The contact time for carrying out the fluorination reaction in the gas phase is usually 0.1 to 200 seconds, preferably 3 to 100 seconds, in the standard state. If the contact time is short, the reaction rate decreases, and if the contact time is too long, side reactions occur, which is not preferable. In addition, it is possible to advance the fluorination reaction by circulating hydrogen fluoride in the gas phase, but in such a circulation format, the catalyst holding method may be any of fixed bed, fluidized bed, moving bed, etc. However, it is convenient and preferable to use a fixed bed.
[0108]
　Regarding the reaction vessel in this step, a pressure resistant reaction vessel made of a material such as stainless steel (SUS), a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) having a corrosion resistance against hydrogen fluoride, or polytetrafluoro The reaction is preferably carried out using a pressure-resistant reaction vessel whose interior is lined with a resin such as ethylene (PTFE).
[0109]
　The reaction time in this step is usually within 12 hours, but it was caused by the amount of hydrogen fluoride used with 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4]. Depending on the reaction conditions, the progress of the reaction may be traced by analytical means such as gas chromatography, thin layer chromatography, liquid chromatography, nuclear magnetic resonance, etc., and the end point of the reaction may be the end point of the reaction. preferable.
[0110]
　In the post-treatment, the target desflurane can be obtained in a high yield by carrying out a normal purification operation on the reaction end solution. The target product can be purified to a higher chemical purity product by activated carbon treatment, distillation, recrystallization, column chromatography and the like, if necessary.
[0111]
　In addition, the fluorination reaction of 1,2,2,2-tetrafluoroethyl dichloromethyl ether in this step is performed using 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether ( Compared to the fluorination reaction (comparative examples 1 to 4) for isoflurane), it is possible to produce desflurane with high conversion and high selectivity. This result is presumed to be influenced by the specific properties of the substrate itself, but by using this process through the first to third steps described above, It is possible to produce desflurane efficiently.
Example
[0112]
　EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not restricted to these embodiments. Here, “%” of the composition analysis value represents “area%” of the composition obtained by measuring the raw material or the product by gas chromatography (the detector is FID unless otherwise specified).
[0113]
　[Preparation Example 1: Preparation Example of Catalyst with Chromium Chloride Supported on Alumina]
　896 g of a special grade reagent CrCl 3 .6H 2 O was dissolved in pure water to make 3.0 L. In this solution, 400 g of granular alumina was immersed and left for a whole day and night. Next, the alumina was removed by filtration, kept at 100 ° C. in a hot air circulating dryer, and further dried overnight. The obtained chromium-supported alumina was filled in a cylindrical SUS316L reaction tube having a diameter of 4.2 cm and a length of 60 cm equipped with an electric furnace, and the temperature was raised to 300 ° C. while flowing nitrogen gas at a flow rate of about 20 mL / min. When the outflow of water was not observed, hydrogen fluoride was accompanied by nitrogen gas, and the concentration was gradually increased. When the hot spot due to fluorination of the packed chromium-supported alumina reached the outlet end of the reaction tube, the reactor temperature was raised to 350 ° C., and this state was maintained for 5 hours to prepare a catalyst.
[0114]
　[Preparation Example 2; Preparation Example of Complex
Consisting of Pyridine and Hydrogen Fluoride] Weigh 158.2 g (2 mol, 1 equivalent) of pyridine in a 1000 mL stainless steel (SUS) autoclave reactor equipped with a stirrer and a pressure gauge. Cooled with dry ice. Thereafter, 200.0 g (10 mol, 5 equivalents) of hydrogen fluoride was slowly added dropwise at an internal temperature of 20 ° C. or less while paying attention to heat generation. After completion of the dropwise addition, the mixture was stirred at room temperature for 1 hour to prepare a pyridine / hydrogen fluoride complex (molar ratio, pyridine: hydrogen fluoride = 1: 5).
[0115]
　[Example 1]
[Chemical Formula 11]

　125 mL of the catalyst prepared in Preparation Example 1 was charged as a catalyst in a gas phase reactor (made of SUS316L, diameter 2.5 cm, length 40 cm) including a cylindrical reaction tube equipped with an electric furnace. did. While flowing air at a flow rate of about 100 mL / min, the temperature of the reaction tube was raised to 305 ° C., and hydrogen fluoride was introduced at a rate of about 0.32 g / min over 1 hour. Next, the supply of chloral as a raw material to the reaction tube was started at a rate of about 0.38 g / min (contact time 15 seconds). Since the reaction was stable 1 hour after the start of the reaction, the gas flowing out from the reactor was collected in a cylinder with a blow tube cooled with dry ice over 3 hours. When the hydrogen fluoride content, the hydrogen chloride content, and the organic matter content are calculated by titration with respect to 70.4 g of the fluoral-containing collected liquid, the hydrogen fluoride content is 41 mass%, the hydrogen chloride content is 11 mass%, and the organic matter content is 49 mass%. The organic matter recovery rate was 90% (based on the number of moles of feedstock chloral). In addition, after adding anhydrous calcium chloride for the purpose of removing hydrogen fluoride to a part of the collected organic matter, the degree of fluorination is confirmed by 19 F-NMR. It was confirmed.
[0116]
　[Example 2]
[Chemical

　Formula 12] A polytetrafluoroethylene (PTFE) stirrer was placed in a 250 ml tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) reactor equipped with a thermometer and a condenser for condenser. 70.4 g (the number of moles of fluoral: 352 mmol) obtained in Example 1 was quickly charged and cooled. Next, 37.4 g (352 mmol) of trimethyl orthoformate was added while paying attention to the exotherm. Thereafter, after stirring at room temperature for 2 hours, 60 g of water was added to stop the reaction. The organic substance obtained by separating the reaction solution into two layers was washed with 30 g of a 16% by mass aqueous potassium hydroxide solution, and 25.7 g of organic matter was recovered again by separating into two layers. The two-stage reaction yield from Example 1 was 50%. When the collected organic substance was subjected to GC analysis, the amount of 1,2,2,2-tetrafluoroethyl methyl ether represented by the above formula was 91.1%.
[0117]
　[Example 3]
[Chemical 13]

　A stirrer of polytetrafluoroethylene (PTFE) was placed in a reaction vessel of borosilicate glass equipped with a condenser and a thermometer, and 1,2,2,2-tetrafluoroethylmethyl was added. 40.0 g of ether (303 mmol, 1.00 equiv) and 40 g of water were weighed out. In addition, a water trap that absorbs hydrogen chloride by-produced by the reaction and a dry ice strap for the purpose of recovering volatile organic substances were connected to the outlet of the condenser condenser. Under cooling, 37.5 g (529 mmol, 1.75 equivalents) of chlorine was heated for 4 hours while irradiating UV light from the outside of the reactor with a 400 W high pressure mercury lamp (USHIO INC.). Introduced. After the introduction of chlorine, unreacted chlorine was purged with nitrogen, and the aqueous layer was removed by two-layer separation to obtain 59.0 g of a crude reaction product. When the obtained reaction crude product was subjected to analysis by gas chromatography, 1,2,2,2-tetrafluoroethyl methyl ether represented by the above formula was not detected, and 1,2,2 represented by formula [7] , 2-tetrafluoroethyl chloromethyl ether, 38.9%, 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by the above formula is 48.2%, 1,2 represented by formula [6] 2,2-tetrafluoroethyltrichloromethyl ether was 2.7%, and the others were 10.2%. On the other hand, the organic matter collected by the dry eye strap was 0.3 g, which was a trace amount.
[Physical property data]
1,2,2,2-tetrafluoroethyl methyl ether:
1 H-NMR (400 MHz, CDCl 3) Δ (ppm): 3.72 (3H, s), 5.28 (1H, dq, J = 60.0, 3.2 Hz)
19 F-NMR (400 MHz, CDCl 3 , CFCl 3 ) δ (ppm) : −84.33 (3F, s), −146.04 (1F, d, J = 60.7 Hz)
1,2,2,2-tetrafluoroethyldichloromethyl ether:
1 H-NMR (400 MHz, CDCl 3 ) Δ (ppm): 6.05 (1H, dq, J = 54.2, 3.2 Hz), 7.27 (1H, s)
19 F-NMR (400 MHz, CDCl 3 , CFCl 3 ) δ (ppm) : -83.68 (3F, s), -148.66 (1F, d, J = 54.8 Hz)
1,2,2,2-tetrafluoroethyl chloromethyl ether:
1 H-NMR (400 MHz, CDCl 3 ) Δ (ppm): 5.57 (2H dd, J = 9.5,9.9Hz), 5.73 (IH, dq, J = 59.4,3.2Hz)
19 F-NMR (400 MHz, CDCl 3 , CFCl 3) Δ (ppm): −83.91 (3F, s), −152.60 (1F, d, J = 57.7 Hz)
1,2,2,2-tetrafluoroethyltrichloromethyl ether:
1 H-NMR (400 MHz, CDCl 3 ) δ (ppm): 6.10 (1H, dq, J = 52.7, 3.2 Hz)
19 F-NMR (400 MHz, CDCl 3 , CFCl 3 ) δ (ppm): −83 . 38 (3F, s), -148.06 (1F, d, J = 52.2 Hz)
[0118]
　[Example 4]
[Chemical 14]

　A stirrer of polytetrafluoroethylene (PTFE) was placed in a borosilicate glass reaction vessel equipped with a condenser and a thermometer, and 1,2,2,2-tetrafluoroethylmethyl was added. 30 g of ether (227 mmol, 1.00 equivalent), 15 g of water, and 1.5 g of anhydrous calcium chloride were weighed out. Under cooling, 33 g (465 mmol, 2.00 equivalents) of chlorine was introduced over 4 hours while irradiating UV light from the outside of the reactor with a 400 W high-pressure mercury lamp (USHIO INC.) While paying attention to heat generation. did. After the introduction of chlorine, unreacted chlorine was purged with nitrogen to obtain 39 g of a crude reaction product. When the obtained reaction crude product was subjected to analysis by gas chromatography, 1,2,2,2-tetrafluoroethyl methyl ether represented by the above formula was not detected, and 1,2,2 represented by formula [7] , 2-tetrafluoroethyl chloromethyl ether is 26.9%, 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by the above formula is 58.3%, 1,2 represented by formula [6] , 2,2-tetrafluoroethyltrichloromethyl ether was 6.4%, and the others were 8.4%. Moreover, when the fluoride ion in this reaction crude body was measured by the ion electrode method, it was 3 ppm.
[0119]
　[Example 5]
[Chemical 15]

　A stirrer of polytetrafluoroethylene (PTFE) was placed in a reaction vessel of borosilicate glass equipped with a condenser and a thermometer, and 1,2,2,2-tetrafluoroethylmethyl was added. 30 g of ether (227 mmol, 1.00 equivalent) and 1.5 g of anhydrous calcium chloride were weighed out. Under cooling, 33 g (465 mmol, 2.00 equivalents) of chlorine was introduced over 4 hours while irradiating UV light from the outside of the reactor with a 400 W high-pressure mercury lamp (USHIO INC.) While paying attention to heat generation. did. After the introduction of chlorine, unreacted chlorine was purged with nitrogen to obtain 39 g of a crude reaction product. When the obtained reaction crude product was subjected to analysis by gas chromatography, 1,2,2,2-tetrafluoroethyl methyl ether represented by the above formula was not detected, and 1,2,2 represented by formula [7] 1,2-tetrafluoroethyl chloromethyl ether is 18.7%, 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by the above formula is 61.2%, 1,2 represented by formula [6] , 2,2-tetrafluoroethyltrichloromethyl ether was 8.9%, and the others were 11.2%. Moreover, when the fluoride ion in this reaction crude body was measured by the ion electrode method, it was 5 ppm.
[0120]
　[Example 6]
[Chemical

　Formula 16] A stirrer of polytetrafluoroethylene (PTFE) was placed in a borosilicate glass reaction vessel equipped with a condenser and a thermometer, and 1,2,2,2-tetrafluoroethyl methyl ether was added. 400 g (3.03 mol, 1.00 equivalent), 285 g of water, and 15 g of anhydrous calcium chloride were weighed out. While cooling, 379 g (5.35 mol, 1.76 equivalents) of chlorine was heated for 5 hours while irradiating UV light from the outside of the reactor with a 400 W high pressure mercury lamp (USHIO INC.). Introduced. After the introduction of chlorine, the unreacted chlorine was purged with nitrogen to obtain 510 g of a crude reaction product. When the obtained reaction crude product was subjected to analysis by gas chromatography, 1,2,2,2-tetrafluoroethyl methyl ether represented by the above formula was not detected, and 1,2,2 represented by formula [7] , 2-tetrafluoroethyl chloromethyl ether is 33.5%, 1,2,2,2-tetrafluoroethyl dichloromethyl ether represented by the above formula is 52.6%, 1,2 represented by formula [6] 2,2-tetrafluoroethyltrichloromethyl ether was 4.4%, and the others were 9.5%. Moreover, when the fluoride ion in this reaction crude body was measured by the ion electrode method, it was 5 ppm. When this reaction crude product was subjected to fractional distillation using a distillation column having 10 theoretical plates, 1,7.2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] was obtained as the initial fraction by 97.2%. 148 g of a fraction containing was obtained, and 226 g of a fraction containing 96.8% of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the above formula as a main fraction was obtained. The main fraction contained 1.0% or less of 1,2,2,2-tetrafluoroethyltrichloromethyl ether represented by the formula [6]. From the reaction of the low-order chlorinated product contained in the first fraction, the recovery rate was 29%, and the recovery rate of the target product contained in the main fraction was 37%.
[0121]
　[Example 7]
[Chemical

　Formula 17] A polytetrafluoroethylene (PTFE) stirrer was placed in a reaction vessel of borosilicate glass equipped with a condenser condenser and a thermometer, and the formula [7] recovered in Example 6 was used. 20 g (120 mmol, 1.00 equivalent) of 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the following formula and 10 g of water were weighed out. Under cooling, 8 g (113 mmol, 0.95 equivalents) of chlorine was introduced over 1 hour while paying attention to heat generation while irradiating UV light from the outside of the reactor with a 400 W high pressure mercury lamp (USHIO INC.). did. After the introduction of chlorine, the unreacted chlorine was purged with nitrogen to obtain 22 g of a crude reaction product. When the obtained reaction crude product was subjected to analysis by gas chromatography, 27.9% of 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] was obtained. The 2,2,2-tetrafluoroethyl dichloromethyl ether is 64.7%, the 1,2,2,2-tetrafluoroethyl trichloromethyl ether represented by the formula [6] is 5.3%, and the others are 2. 1%.
[0122]
　[Example 8]
[Chemical

　Formula 18] A stirrer of polytetrafluoroethylene (PTFE) was placed in a borosilicate glass reaction vessel equipped with a condenser and a thermometer, and 1, 2, 2, 2- 150 g (1.14 mol, 1.00 equivalent) of tetrafluoroethyl methyl ether was weighed out. Then, under cooling, irradiate ultraviolet rays from the outside of the reactor with a 400 W high-pressure mercury lamp (USHIO Co., Ltd.) and take 178 g (2.51 mol, 2.20 equivalents) of chlorine over 5 hours while paying attention to heat generation. Introduced. After the introduction of chlorine, the unreacted chlorine was purged with nitrogen to obtain 199 g of a crude reaction product. When this reaction crude product was subjected to fractional distillation using a distillation column having 10 theoretical plates, 114 g of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the above formula was obtained as a fraction with a 92.9% GC purity. It was. The yield from the reaction in this case was 50%.
[0123]
　[Example 9]
[Chemical

　Formula 19] A polytetrafluoroethylene (PTFE) stirrer was placed in a borosilicate glass reaction vessel equipped with a condenser and a thermometer, and 1, 2, 2, 2- 50 g (379 mmol, 1.00 equivalent) of tetrafluoroethyl methyl ether and 1.2 g (7.6 mmol, 2 mol%) of AIBN were weighed out. After heating the oil bath temperature to 40 ° C., introduction of 107 g (1.52 mol, 4.00 equivalents) of chlorine was started while paying attention to heat generation. During the reaction, the oil bath temperature was raised with the progress of the degree of chlorination of the substrate, and finally the internal temperature was raised to 66 ° C. After introducing chlorine, the unreacted chlorine was purged with nitrogen, and the reaction solution was subjected to GC analysis. As a result, 59.7 GC% of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the above formula was obtained. 15.0 GC% for low-order chlorinated products (1,2,2,2-tetrafluoroethyl chloromethyl ether) and 16.5 for high-order chlorinated products (1,2,2,2-tetrafluoroethyl trichloromethyl ether). It was 9 GC% and the others were 8.4%.
[0124]
　[Example 10]
[Chemical

　formula 20] A stirrer of polytetrafluoroethylene (PTFE) was placed in a 100 mL autoclave reaction vessel (manufactured by SUS316L) equipped with a pressure gauge and a cooling condenser, and 1, 2, 2, 2 shown in the above formula. 10 g (49.8 mmol, 1.00 equivalent) of tetrafluoroethyl dichloromethyl ether and 1.3 g (4.99 mmol, 10 mol%) of tin tetrachloride were weighed out. After cooling in an ice bath, 20.0 g (1.00 mol, 20.0 equivalents) of hydrogen fluoride is charged all at once, the temperature is raised to 80 ° C., and a reaction pressure of 1.0 MPa is maintained. The hydrogen was stirred with heating for 8 hours while removing it from the system through a condenser. Then, reaction was stopped by making all the reaction liquids absorb to ice water. The organic matter obtained by the two-layer separation was 7.8 g, and the organic matter recovery rate was 93%. Moreover, the purity of the obtained desflurane (the above formula) was 98.0%.
[0125]
　[Example 11]
[Chemical

　Formula 21] To a 500 mL autoclave reaction vessel (manufactured by SUS316L) equipped with a stirrer, a pressure gauge, and a cooling condenser, 201 g of 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the above formula (1 0.000 mol, 1.00 equivalent) and 2.61 g (10.0 mmol, 1.0 mol%) of tin tetrachloride were weighed out. After cooling in an ice bath, 49.8 g (2.49 mol, 2.5 equivalents) of hydrogen fluoride was charged all at once, and the temperature was gradually raised to 20 ° C. while paying attention to sudden heat generation. Next, in order to maintain the reaction pressure in the vicinity of 0.1 MPa (atmospheric pressure), hydrogen chloride produced as a by-product was reacted for 12 hours while being removed from the system through a cooling condenser. Then, reaction was stopped by making all the reaction liquids absorb to ice water. The organic matter obtained by the two-layer separation was 163 g, and the organic matter recovery rate was 97.0%. Moreover, the purity of the obtained desflurane (the above formula) was 93.3%.
[0126]
　[Example 12]
[Chemical

　Formula 22] A stirrer of polytetrafluoroethylene (PTFE) was placed in a 100 mL autoclave reaction vessel (manufactured by SUS316L) equipped with a pressure gauge and a cooling condenser, and 1, 2, 2, 2 shown in the above formula -20 g (99.5 mmol, 1.00 equiv) of tetrafluoroethyldichloromethyl ether and 0.36 g (1.20 mmol, 1.2 mol%) of antimony pentachloride were weighed out. After cooling in an ice bath, 8.8 g (440 mmol, 4.4 equivalents) of hydrogen fluoride was charged all at once, and the temperature was gradually raised to 15 ° C. while paying attention to sudden heat generation. Next, in order to maintain the reaction pressure in the vicinity of 0.1 MPa (atmospheric pressure), the by-produced hydrogen chloride was reacted for 6 hours while being removed from the system through a cooling condenser. Then, reaction was stopped by making all the reaction liquids absorb to ice water. The organic matter obtained by the two-layer separation was 12.1 g, and the organic matter recovery rate was 72.4%. Moreover, the purity of the obtained desflurane (the above formula) was 96.9%.
[0127]
　[Example 13]
[Chemical

　Formula 23] A stirrer of polytetrafluoroethylene (PTFE) was placed in a 100 mL autoclave reaction vessel (manufactured by SUS316L) equipped with a pressure gauge and a cooling condenser, and 1, 2, 2, 2 shown in the above formula -10 g (49.8 mmol, 1.00 equiv) of tetrafluoroethyl dichloromethyl ether were weighed out. After cooling in an ice bath, 20.0 g (1.00 mol, 20.0 equivalents) of hydrogen fluoride is charged all at once, the temperature is raised to 80 ° C., and a reaction pressure of 1.0 MPa is maintained. The hydrogen was heated and stirred for 8 hours while being removed from the system through a cooling condenser. Then, reaction was stopped by making all the reaction liquids absorb to ice water. The organic matter obtained by the two-layer separation was 7.7 g, and the organic matter recovery rate was 92%. Moreover, the purity of the obtained desflurane (the above formula) was 71.3%. The collected organic matter contained 26.1% of 1,2,2,2-tetrafluoroethylfluorochloromethyl ether represented by the formula [8] (note that this compound contains 1,1 2,2,2-tetrafluoroethyl dichloromethyl ether is a monofluorinated reaction intermediate).
[Chemical 24]

[0128]
　[Example 14]
[Chemical

　Formula 25] To a 500 mL stainless steel (SUS) autoclave reactor equipped with a stirrer, a pressure gauge, and a condenser, 1,2,2,2-tetrafluoroethyldichloromethyl ether 39. 9 g (199 mmol, 1 equivalent) was weighed and cooled with dry ice. After cooling, 71.0 g (396 mmol, 1.99 equivalents) of the pyridine-hydrogen fluoride complex obtained in Preparation Example 2 (molar ratio, pyridine: hydrogen fluoride = 1: 5) was introduced while paying attention to heat generation. The reaction was started by raising the temperature to 120 ° C. In order to control the reaction pressure at 1.8 MPa after the temperature rise, the reaction was carried out for 15 hours while removing by-produced hydrogen chloride out of the system through a condenser. After the reaction, the reaction was stopped by absorbing all the reaction liquid into ice water. The organic matter obtained by the two-layer separation was 27.1 g, and the organic matter recovery rate was 81.1%. In addition, desflurane (the above formula) as a target product was 90.2%.
[0129]
　[Examples 15 to 17]
[Chemical Formula 26] The

　catalyst prepared in Preparation Example 1 was used as a catalyst in a gas phase reactor (made of SUS316L, diameter 2.5 cm, length 40 cm) including a cylindrical reaction tube equipped with an electric furnace. Filled with 100 mL. While flowing nitrogen gas at a flow rate of about 10 mL / min, the temperature of the reaction tube was raised to 180 ° C., and hydrogen fluoride was introduced at a rate of about 0.1 g / min over 1 hour. Next, the raw material 1,2,2,2-tetrafluoroethyl dichloromethyl ether (91.9 GC%) was fed into the reaction tube at a rate of about 0.1 g / min (contact time 25 seconds). Since the reaction was stable 1 hour after the start of the reaction, the gas flowing out from the reactor was blown into water to remove the acidic gas, and then the product was analyzed by gas chromatography.
　Thereafter, the temperature of the reaction tube was changed as shown in Table 1 (Examples 16 and 17). After the reaction was stabilized, the gas flowing out from the reactor was blown into water to remove the acid gas, The product was analyzed by gas chromatography.
[0130]
　The results of Examples 15 to 17 are also shown in Table 1.
[table 1]

[0131]
　[Example 18] Using the
　same gas phase reactor as in Examples 15 to 17, the temperature of the reaction tube was set to 180 ° C, and hydrogen fluoride was introduced at a rate of about 0.1 g / min over 1 hour. Next, 1,2,2,2-tetrafluoroethyl dichloromethyl ether (94.6 GC%) as a raw material was introduced into the reaction tube at a rate of 0.1 to 0.2 g / min (contact time 20 to 25 seconds). Feeding took place over 4.5 hours. After the gas flowing out from the reactor was blown into water to remove the acidic gas, the organic matter slipped through was collected with a dry ice strap to obtain 23.3 g of organic matter. When this organic substance was subjected to GC analysis, desflurane was produced at 96.8%. Further, the yield of the obtained organic substance was 91% (based on the number of moles of the feedstock 1,2,2,2-tetrafluoroethyldichloromethyl ether).
[0132]
　Reference Example 1
[Chemical

　Formula 27] A polytetrafluoroethylene (PTFE) stirrer was placed in a 100 mL stainless steel (SUS) autoclave reactor equipped with a pressure gauge under dry ice cooling. , 2,2-tetrafluoroethyltrichloromethyl ether 5.0 g (21.2 mmol), hydrogen fluoride 8.5 g (425 mmol), and antimony pentachloride 329 mg (1.1 mmol) were each weighed and allowed to warm to room temperature. To 80 ° C. for 8 hours. After the reaction, the reaction pressure of 0.90 MPa was released, the reaction solution was washed with water, and the organic substance obtained by the two-layer separation was measured by gas chromatography. As a result, 1,2,2,2-tetrafluoro represented by the above formula was obtained. Ethyl difluorochloromethyl ether was obtained at 90 GC%.
[Physical property data]
1,2,2,2-tetrafluoroethyldifluorochloromethyl ether:
1 H-NMR (400 MHz, CDCl 3 ) δ (ppm): 5.96 (1H, dq, J = 53.4, 2 .8 Hz)
19 F-NMR (400 MHz, CDCl 3 , CFCl 3 ) δ (ppm): −28.93 (1F, d, J = 86.8 Hz), −29.95 (1F, d, J = 92. 8 Hz), −83.41 (3 F, s), −146.75 (1 F, d, J = 54.8 Hz)
[0133]
　[Comparative Example 1-4]
[Chemical Formula 28] The

　catalyst prepared in Preparation Example 1 was used as a catalyst in a gas phase reactor (made of SUS316L, diameter 2.5 cm, length 40 cm) including a cylindrical reaction tube equipped with an electric furnace. Filled with 100 mL. While flowing nitrogen gas at a flow rate of about 10 mL / min, the temperature of the reaction tube was raised to 180 ° C., and hydrogen fluoride was introduced at a rate of about 0.1 g / min over 1 hour. Next, supply of the raw material 1-chloro-2,2,2-trifluoroethyldifluoromethyl ether (isoflurane, 99.9 GC%) to the reaction tube at a rate of about 0.1 g / min (contact time 25 seconds) was started. did. Since the reaction was stable 1 hour after the start of the reaction, the gas flowing out from the reactor was blown into water to remove the acidic gas, and then the product was analyzed by gas chromatography.
　Thereafter, the temperature of the reaction tube was changed as shown in Table 2 (Comparative Examples 2, 3, and 4), and after the reaction was stabilized, the gas flowing out from the reactor was blown into water to remove the acid gas and generate The product was analyzed by gas chromatography.
[0134]
　The results of Comparative Examples 1 to 4 are shown in Table 2.
[Table 2]

[Chemical 29]

Industrial applicability
[0135]
　The 1,2,2,2-tetrafluoroethyl difluoromethyl ether (desflurane) targeted in the present invention can be used as an inhalation anesthetic.
The scope of the claims
[Claim 1]
A process for producing 1,2,2,2-tetrafluoroethyldifluoromethyl ether (desflurane) comprising the following four steps.
First step: 2,2,2-trichloroacetaldehyde represented by the formula [1] is reacted with hydrogen fluoride in the gas phase in the presence of a catalyst to produce 2,2 represented by the formula [2]. , 2-trifluoroacetaldehyde.
[Chemical Formula 30]

[Chemical

Formula 31] Second step: 2,2,2-trifluoroacetaldehyde obtained in the first step is reacted with hydrogen fluoride and trimethyl orthoformate, and represented by the formula [3]. Obtaining 1,2,2,2-tetrafluoroethyl methyl ether.
[Chemical

step 32] Third step: 1,2,2,2-tetrafluoroethyl methyl ether obtained in the second step is reacted with chlorine (Cl 2 ) in the presence of a radical initiator or under light irradiation. To obtain 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4].
[Chemical

Formula 33] Fourth step: 1,2,2,2-tetrafluoroethyldichloromethyl ether obtained in the third step is reacted with hydrogen fluoride to be represented by the formula [5] A step of obtaining 1,2,2,2-tetrafluoroethyl difluoromethyl ether (desflurane).
[Chemical 34]

[Claim 2]
The metal in which the catalyst in the first step carries a metal compound containing at least one metal selected from the group consisting of chromium, titanium, manganese, iron, nickel, cobalt, magnesium, zirconium, and antimony on a metal oxide or activated carbon The production method according to claim 1, which is a compound-supported catalyst.
[Claim 3]
The metal compound is at least one metal halide or metal oxyhalide selected from the group consisting of metal fluoride, chloride, fluorinated chloride, oxyfluoride, oxychloride, and oxyfluoride chloride, The manufacturing method according to claim 2.
[Claim 4]
The production method according to claim 2 or 3, wherein the metal oxide is at least one selected from the group consisting of alumina, zirconia, titania, chromia, and magnesia.
[Claim 5]
The production method according to any one of claims 1 to 4, wherein 2,2,2-trifluoroacetaldehyde obtained in the first step is directly used as a starting material in the second step without performing a purification operation.
[Claim 6]
The production method according to claim 1, wherein the reaction in the second step is performed without using an organic solvent.
[Claim 7]
The production method according to any one of claims 1 to 6, wherein in the third step, the radical initiator or the light irradiation is at least one selected from the group consisting of an organic peroxide and an azo radical initiator.
[Claim 8]
In the third step, the radical initiator or light irradiation is at least one selected from the group consisting of mercury lamp, ultraviolet LED, organic EL, inorganic EL, ultraviolet laser, and halogen lamp. The manufacturing method as described in.
[Claim 9]
The production method according to claim 1, wherein the reaction in the third step is performed in the presence of a fluoride ion scavenger.
[Claim 10]
Fluoride ion scavenger belongs to alkali metal halide, alkali metal sulfate, alkaline earth metal hydroxide, alkaline earth metal halide, alkaline earth metal sulfate, periodic table group 13 The production method according to claim 9, which is at least one selected from the group consisting of a metal hydroxide, a metal halide belonging to Group 13 of the periodic table, and a metal sulfate belonging to Group 13 of the periodic table.
[Claim 11]
The production method according to any one of claims 1 to 10, wherein the reaction in the third step is performed in the presence of a reaction solvent.
[Claim 12]
In the third step, by reacting chlorine, 1,2,2,2-tetrafluoroethyldichloromethyl ether represented by the formula [4] and 1,2,2,2 represented by the formula [7] The method according to any one of claims 1 to 11, which is obtained as a mixture containing 2-tetrafluoroethyl chloromethyl ether.
[Chemical 35]

[Claim 13]
The method further comprises a step of separating and removing 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] from the mixture by subjecting the mixture to distillation purification. The manufacturing method as described.
[Claim 14]
In the third step, 1,2,2,2-tetrafluoroethyl chloromethyl ether represented by the formula [7] separated and removed by distillation purification is recovered, and the starting in the chlorination reaction of the third step The manufacturing method of Claim 13 used as a raw material.
[Claim 15]
The production method according to claim 1, wherein in the fourth step, the reaction is performed in a gas phase.
[Claim 16]
The production method according to claim 1, wherein in the fourth step, the reaction is performed in the presence of a catalyst.
[Claim 17]
In the fourth step, the catalyst is at least one selected from the group consisting of tin tetrachloride, tin dichloride, tin tetrafluoride, tin difluoride, titanium tetrachloride, antimony trichloride, antimony pentachloride, and antimony pentafluoride. The manufacturing method of Claim 16 which is a seed.
[Claim 18]
The production method according to any one of claims 1 to 15, wherein the reaction in the fourth step is carried out in the absence of a catalyst.
[Claim 19]
The production method according to claim 1, wherein the reaction is performed in a liquid phase in the fourth step.
[Claim 20]
The production method according to claim 19, wherein in the fourth step, the reaction in the liquid phase is performed in a temperature range of -10 ° C to + 150 ° C and a pressure range of 0.1 MPa to 2.0 MPa.
[Claim 21]
In the fourth step, the reaction of 1,2,2,2-tetrafluoroethyldichloromethyl ether with hydrogen fluoride is carried out by reacting “a salt or complex comprising an organic base and hydrogen fluoride” in the liquid phase. The manufacturing method in any one of Claims 1 thru | or 14 performed.
[Claim 22]
The organic base in “a salt or complex comprising an organic base and hydrogen fluoride” is triethylamine, diisopropylethylamine, tri-n-butylamine, pyridine, and 2,6-lutidine and 1,8-diazabicyclo [5.4.0] undeca. The production method according to claim 21, which is at least one selected from the group consisting of -7-enes.