JP5228817B2 - Method for producing pyrazole compound - Google Patents

Description

  The present invention relates to a pyrazole compound having a difluoromethyl group as an intermediate for medical and agricultural chemicals and a method for producing the same.

  The difluoroacetic acid ester can be produced by reacting 1-alkoxy-1,1,2,2-tetrafluoroethane with an alcohol and difluoroacetic acid fluoride obtained by gas phase reaction in the presence of a metal oxide catalyst ( Patent Document 1).

CHF ₂ COF + ROH → CHF ₂ COOR + HF
As a method for producing a pyrazole compound, 2- (difluoroacetyl) -3- (difluoroacetyl) -3- is obtained by adding dropwise dimethylaminoacrylate in difluoroacetyl chloride dissolved in toluene at 0 ° C., then allowing to cool to room temperature and distilling off toluene. (Ethyl (dimethylamino) acrylate is obtained, and methyl hydrazine is added dropwise thereto and allowed to cool to room temperature, whereby ethyl 3- (difluoromethyl) -1-methyl-H-4-pyrazole-4-carboxylate is obtained. Is disclosed (Patent Document 2).
JP-A-8-92162 Special table 2007-509850 gazette

  The use of difluoroacetic acid halide for introducing a difluoromethyl group is described in JP-A-8-92162 and JP-T-2007-509850, and the production method of difluoroacetic acid halide is 1-alkoxy-1,1. , 2,2-tetrafluoroethane is reported to be decomposed in the presence of sulfur trioxide, fluorosulfuric acid or chlorosulfuric acid (J. Fluorine Chem., 3, 63 (1973)), and 1,1-dichloro-2 , 2-difluoroethane (HCFC-132a) and 1-chloro-1,2,2-trifluoroethane (HCFC-133) are decomposed with oxygen and chlorine under irradiation of a high-pressure mercury lamp to give difluoroacetic acid chloride and difluoroacetic acid fluoride, respectively. Production (JP-A-8-53388), 1-alkoxy-1,1,2,2-tetrafluoroethane Generating the difluoroacetate fluoride by vapor-phase reaction in the presence of a metal oxide catalyst (JP-A-8-92162) is disclosed.

  The difluoroacetic acid halide thus produced does not have sufficient stability and is converted into a difluoroacetic acid ester or iminothiazoline compound which can be used as a building block of a difluoromethyl group in the invention of the aforementioned patent publication.

  In this invention, it aims at providing the practical manufacturing method of the 2-difluoroacyl-3-aminoacrylic acid ester represented by General formula (4), and the pyrazole compound represented by General formula (6), An object is to efficiently produce an intermediate having a difluoromethyl group as a building block, and to efficiently react this intermediate with dimethylaminoacrylate.

  The present inventors do not repurify the pyrolysis product containing difluoroacetic acid fluoride obtained by pyrolyzing 1-alkoxy-1,1,2,2-tetrafluoroethane in the presence of a specific catalyst. It has been found that the reaction selectivity and the reaction rate can be maintained sufficiently high even when reacted with dimethylaminoacrylate.

That is, the thermal decomposition reaction of 1-alkoxy-1,1,2,2-tetrafluoroethane represented by CHF ₂ CF ₂ OR ¹ (R ¹ represents a monovalent organic group) according to the present invention is Is represented by the following equation:
CHF ₂ CF ₂ OR ¹ → CHF ₂ COF + R ¹ F
By-products may include difluoroacetic acid, hydrogen fluoride, R ¹ F secondary degradable organisms, and the like. However, by using a metal oxide or phosphate as the catalyst, the reaction yield of difluoroacetic acid difluoride (CHF ₂ COF) is high, and by-products can be reduced. It was found that the reaction with dimethylaminoacrylic acid ester would not be affected by the supply to 1, and the present invention was completed.
The present invention is as follows.

[1] General formula (1)
CHF ₂ CF ₂ OR ¹ (1)
(Wherein R ¹ represents a monovalent organic group) 1-alkoxy-1,1,2,2-tetrafluoroethane represented by a metal oxide or phosphate in the presence of a catalyst. in the temperature cooled pyrolysis products unpurified pyrolysis were separated at 100 to 400 ° C. as -20 ℃ ~ + 50 ℃, the general formula (3)
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms) General formula (4) comprising contacting with dimethylaminoacrylate represented by
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms), a method for producing 2-difluoroacyl-3-aminoacrylic acid ester.
[2]
The general formula (4) obtained by the production method according to claim 1.
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms) and 2-difluoroacyl-3-aminoacrylic acid ester represented by the general formula (5)
R ⁵ NHNH ₂ (5)
(In the formula, R ⁵ represents a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an alkoxyalkyl group or an aryl group, and any number of hydrogen atoms in the alkyl group and alkoxy group are halogen atoms. (The oxygen atom of the alkoxy group may be substituted with a sulfur atom.) General formula (6) comprising contacting with a hydrazine derivative represented by formula (6)
(In the formula, R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms, and R ⁵ is the same as in General Formula (5)).

  The production method of the present invention can efficiently produce an intermediate having a difluoromethyl group as a building block, and at the same time, this intermediate can be efficiently reacted with dimethylaminoacrylate to produce pyrazole in a high yield. Compounds can be produced.

  The main reaction according to the present invention can be represented by the steps (a), (b) and (c) shown in the following scheme 1. In the present specification, the display of hydrogen atoms bonded to carbon atoms is omitted in principle in accordance with the practice of the chemical field.

<Production of difluoroacetic acid fluoride>
The difluoroacetic acid fluoride according to the present invention may be produced by any method. For example, 1-alkoxy-1,1,2,2-tetrafluoroethane can be produced by thermal decomposition in the presence of a catalyst. This reaction is represented by the following formula.
CHF ₂ CF ₂ OR ¹ → CHF ₂ COF + R ¹ F
Therefore, the thermal decomposition product includes a compound represented by difluoroacetic acid fluoride and R ¹ F or a secondary decomposition product thereof. R ¹ of the alkoxy group of 1-alkoxy-1,1,2,2-tetrafluoroethane which is a starting material for this reaction is a monovalent organic group. Specific examples include a C1-C8 alkyl group or fluorine-containing alkyl group that may have a branch, a cycloalkyl group that may have an alkyl group as a substituent, an aryl group, and an aralkyl group. Among these, an alkyl group or a fluorine-containing alkyl group is preferable, an alkyl group is more preferable, and a lower alkyl group is more preferable. The lower alkyl group refers to an alkyl group having 1 to 4 carbon atoms. Specifically, among the following examples, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and an n-butyl group are preferable, but a methyl group with few secondary decomposition products is particularly preferable.

  Examples of the alkyl group having 1 to 8 carbon atoms that may have a branch include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, and n-pentyl group. An example is an isopentyl group.

  Examples of the cycloalkyl group that may have an alkyl group as a substituent include a cyclobutyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a 3-methylcyclopentyl group, a 2-ethylcyclopentyl group, a 3-ethylcyclopentyl group, a cyclohexyl group, and 2 -Methylcyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, 2-ethylcyclohexyl group, 3-ethylcyclohexyl group, 4-ethylcyclohexyl group, cycloheptyl group, 2-methylcyclohexyl group, 3-methylcyclohexane A heptyl group, 3-methylcycloheptyl group, 4-methylcycloheptyl group, etc. can be mentioned.

  As the aryl group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, 3,6-dimethylphenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, Examples include 1-naphthyl group, 2-naphthyl group and the like.

  The fluorine-containing alkyl group includes a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chlorofluoromethyl group, a chlorodifluoromethyl group, a bromofluoromethyl group, a dibromofluoromethyl group, and a 2,2,2-trifluoroethyl group. And pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, n-hexafluoropropyl group, hexafluoroisopropyl group and the like.

  Examples of the aralkyl group include phenethyl group, 2-methylphenylmethyl group, 3-methylphenylmethyl group, 4-methylphenylmethyl group, 2,3-dimethylphenylmethyl group, 2,4-dimethylphenylmethyl group, 2,5 -Dimethylphenylmethyl group, 2,6-dimethylphenylmethyl group, 3,4-dimethylphenylmethyl group, 3,5-dimethylphenylmethyl group, 3,6-dimethylphenylmethyl group, 4-ethylphenylmethyl group, 4 Examples include-(n-propyl) methylphenylmethyl group and 4- (n-butyl) methylphenylmethyl group.

1-alkoxy-1,1,2,2-tetrafluoroethane can be obtained by a known production method. For example, it can be synthesized by a method in which alcohol (R ¹ OH) and tetrafluoroethylene are reacted in the presence of a base.
Specifically, 1-methoxy-1,1,2,2-tetrafluoroethane can be synthesized by a method in which methanol and tetrafluoroethylene are reacted in the presence of potassium hydroxide (J. Am. Chem. Soc. 73, 1329 (1951)).

Specific examples of the fluorine-containing ether that can be used in the present invention include, but are not limited to, the following.
1-methoxy-1,1,2,2-tetrafluoroethane, 1-ethoxy-1,1,2,2-tetrafluoroethane, 1- (n-propoxy) -1,1,2,2-tetrafluoro Ethane, 1-isopropoxy-1,1,2,2-tetrafluoroethane, 1- (n-butoxy) -1,1,2,2-tetrafluoroethane, 1- (s-butoxy) -1,1 , 2,2-tetrafluoroethane, 1- (t-butoxy) -1,1,2,2-tetrafluoroethane, 1-trifluoromethoxy-1,1,2,2-tetrafluoroethane, 1-difluoro Methoxy-1,1,2,2-tetrafluoroethane, 1- (2,2,2-trifluoroethoxy) -1,1,2,2-tetrafluoroethane, 1-pentafluoroethoxy-1,1, 2,2-tetrafluoro Ethane, 1- (2,2,2,3,3-pentafluoropropoxy) -1,1,2,2-tetrafluoroethane, 1-hexafluoroisopropoxy-1,1,2,2-tetrafluoroethane And so on.

The catalyst according to the present invention is a solid catalyst, and metal oxides, metal fluorinated oxides and phosphates described in JP-A-8-92162 can be used as catalysts. The phosphate may be supported on a carrier.
As phosphoric acid, any of orthophosphoric acid, polyphosphoric acid, and metaphosphoric acid may be used. Examples of polyphosphoric acid include pyrophosphoric acid. Phosphate is the metal salt of these phosphoric acids. Since it is easy to handle, orthophosphoric acid is preferred. Phosphate refers to a metal salt of these phosphoric acids. In this specification, an acid in which a metal is substituted with a hydrogen atom is also referred to as a metal salt.

  Although it does not specifically limit as a phosphate, It consists of hydrogen, aluminum, boron, alkaline-earth metal, titanium, zirconium, lanthanum, cerium, yttrium, rare earth metal, vanadium, niobium, chromium, manganese, iron, cobalt, nickel And at least one metal phosphate selected from the group. Preferably, the main component is aluminum phosphate, cerium phosphate, boron phosphate, titanium phosphate, zirconium phosphate, chromium phosphate, or the like. It is also preferable that the metal of a subsidiary component is included. As specific subcomponents, cerium, lanthanum, yttrium, chromium, iron, cobalt, nickel and the like are preferable, but cerium, iron and yttrium are more preferable. Among these, more preferably, an aluminum phosphate single catalyst or a catalyst containing cerium phosphate as a minor component with aluminum phosphate as a main component can be used.

  The method for preparing the catalyst is not particularly limited, and a commercially available phosphate may be used as it is, or a general precipitation method may be used. As a specific preparation method of the precipitation method, for example, diluted ammonia water is added dropwise to a mixed aqueous solution of metal nitrate (in the case of a plurality of raw material salts, each raw material salt solution is prepared) and phosphoric acid to adjust the pH. To adjust to precipitate and leave to mature as necessary. Then, it is washed with water and it is confirmed that it has been sufficiently washed with the conductivity of the washing water. In some cases, alkali metal containing a portion of the slurry is measured. It is then filtered and dried. There is no particular limitation on the drying temperature. Preferably 80 to 150 degreeC is good. More preferably, it is 100 degreeC-130 degreeC. The obtained dried product is pulverized to uniform particle size, or further pulverized and molded. Thereafter, firing is performed in an air or nitrogen atmosphere at 200 ° C. to 1500 ° C. The firing is preferably performed at 400 to 1300 ° C, more preferably 500 to 900 ° C.

  Although depending on the temperature, the firing time is about 1 to 50 hours, preferably about 2 to 24 hours. Since the calcination treatment is a treatment necessary for stabilizing the phosphate, if the treatment is performed at a temperature lower than the above temperature range or the treatment time is short, the catalyst activity may not be sufficiently exhibited at the initial stage of the reaction. . In addition, it is not preferable to perform the calcination treatment at a temperature higher than the above temperature range or for a long time because not only excessive heating energy is required but also crystallization of the catalyst may occur.

The operation of adding a metal component other than the main component is preferably performed with a metal salt, and nitrates, chlorides, oxides, phosphates, and the like of the metal are preferable. Among them, nitrate is preferable because it is easy to prepare. Although there is no restriction | limiting in particular in addition amount, Generally it is 1 gram atom or less with respect to 1 gram atom of phosphorus, Preferably it is 0.5 gram atom or less. More preferably, it is 0.3 gram atom or less. The addition of these metal components may be performed at the time of catalyst preparation, or may be performed on the phosphate after the catalyst is calcined. The obtained catalyst has different physical properties depending on the type of metal salt and the preparation method and conditions. The catalyst may be used as it is, but it can also be used in a state of being supported on a carrier. Examples of the carrier include metal oxides such as alumina, titania, zirconia, zirconia sulfate (ZrO (SO ₄ )), silicon carbide, silicon nitride, activated carbon, and the like. preferable.

  Activated carbon carrying phosphoric acid or phosphate can be prepared by immersing it in phosphoric acid and impregnating it, or drying and coating or adsorbing it by spraying. In the case of loading a compound, it can be prepared by impregnating a solution of the compound to be loaded, or drying a coating or adsorbed by spraying. In addition, a second compound is allowed to act on activated carbon impregnated with a solution of the compound, or coated or adsorbed by spraying to cause a precipitation reaction or the like on the activated carbon surface, thereby supporting a compound different from the first compound. You can also. Further, the phosphate-carrying catalyst can also be prepared by carrying out the above-described phosphate preparation method in the presence of a support such as activated carbon. As an example, activated carbon supporting aluminum phosphate is shown in the examples.

  Activated carbon is made from plant-based, peat, lignite, lignite, bituminous coal, anthracite, etc. that are made from wood, charcoal, coconut husk, palm kernel charcoal, raw ash, etc. Any of petroleum type or synthetic resin type such as carbonized polyvinylidene chloride may be used. These commercially available activated carbons can be selected and used. For example, activated carbon produced from bituminous coal (BPL granular activated carbon manufactured by Toyo Calgon), coconut shell charcoal (granular white birch GX, SX, CX, XRC manufactured by Nippon Enviro Chemical), Toyo Calgon PCB) and the like, but is not limited thereto. 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 of the activated carbon is sufficient in a range of commercially available standards, are each 400m ² / g~3000m ² / g, preferably 800m ² / g~2000m ² / g. Furthermore, when using activated carbon as a support, it is usually immersed in a basic aqueous solution such as ammonium hydroxide, sodium hydroxide, potassium hydroxide or the like for about 10 hours or longer at room temperature or when activated carbon is used as a catalyst support. It is desirable to perform pretreatment with acid such as nitric acid, hydrochloric acid, hydrofluoric acid, etc. to activate the carrier surface and remove ash in advance.

  Further, the carrier such as an oxide of the present invention may contain a metal component and an atom other than oxygen, and the other atom is preferably a fluorine atom or a chlorine atom. For example, partially fluorinated alumina, partially chlorinated alumina, partially fluorinated chlorinated alumina, partially fluorinated zirconia, partially fluorinated titania and the like may be used. The ratio of chlorine atoms and fluorine atoms in the oxide catalyst is not particularly limited.

  In the present specification and claims, unless otherwise limited, alumina, zirconia, etc., which have been partially fluorinated or chlorinated as described above, are oxides such as “alumina” and “zirconia”. Display by name.

These supports include at least one metal oxide selected from the group consisting of alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), zirconia sulfate, and partially fluorinated oxides thereof. Catalysts are preferred, and alumina and partially fluorinated alumina are more preferred in terms of reactivity and catalyst life.

These partially fluorinated oxides can be used as a support for a difluoroacetic acid fluoride synthesis catalyst, and can also be used as a catalyst. Preparation, pretreatment, use, etc. as a catalyst are composed of a phosphate which can be applied as it is or in accordance with common general technical knowledge, with regard to preparation, pretreatment, use, etc., as a carrier in this specification. The catalyst carrying a phosphate is usually used in the form of particles or granules. The diameter of the particles or the granulated body (all may be referred to as “particle diameter”) is not particularly limited, and is usually about 20 μm to 10 mm. When the catalyst contains a chlorine atom or a fluorine atom, the chlorine atom or the fluorine atom may exist only on the surface of the metal oxide.

  The catalyst comprising the phosphate of the present invention or carrying the phosphate is also partially fluorinated by contacting with a fluorine-containing compound such as hydrogen fluoride, fluorinated hydrocarbon or fluorinated chlorinated hydrocarbon before use. In addition, it is effective to prevent changes in the composition of the catalyst during the reaction, shortening of the service life, abnormal reactions, and the like.

  In particular, treatment with hydrogen fluoride can significantly increase the activity of the reaction. The fluorination treatment with hydrogen fluoride is preferably performed by contacting with hydrogen fluoride at least at a temperature higher than the reaction temperature of the reaction according to the present invention. In the case of a phosphate simple substance, it is about 200-700 degreeC, about 250-600 degreeC is preferable and 300-550 degreeC is more preferable. On the other hand, in the case of a phosphate-carrying catalyst, the temperature is about 200 to 600 ° C, preferably about 250 to 500 ° C, and more preferably 300 to 400 ° C. In any case, if the maximum processing temperature is less than 200 ° C., it takes time for the processing, and it is not preferable to perform the processing beyond the maximum temperature range because excessive heating energy is required. The treatment time is also related to the treatment temperature and cannot be limited, but it is about 1 hour to 10 days, preferably about 3 hours to 3 days.

  In the case of activated carbon that does not carry phosphoric acid, even if it is treated with hydrogen fluoride, it shows almost no activity. However, when activated carbon treated with phosphoric acid is treated with hydrogen fluoride, the conversion rate is 96 under the same reaction conditions. The catalyst activity was 0.1% and selectivity: 98.0%. Also from this, the effect of the hydrogen fluoride treatment can be easily seen.

Furthermore, it is preferable to perform an activation treatment prior to the reaction. As the activation treatment, it is sufficiently dehydrated in a nitrogen stream at about 250 ° C. to 300 ° C., and an organic fluorine compound such as dichlorodifluoromethane or chlorodifluoromethane, or a gas or catalyst treatment such as hydrogen fluoride or chlorine trifluoride. It is preferable to activate with an inorganic fluorine compound showing a sufficient vapor pressure in the state. Of these, hydrogen fluoride is particularly preferred. By this activation treatment, it is considered that an active catalyst composed of a phosphate containing a fluorine atom is generated on the entire surface of the catalyst.
In addition, when R ^{1 of 1} -alkoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OR ¹ ) which is a reaction raw material is a group having 2 or more carbon atoms, the generated R ¹ F is reacted. It is estimated that hydrogen fluoride is generated by decomposition in the region, and this may have an effect of increasing the activity of the catalyst.

  In the method of the present invention, the gas-phase continuous flow method is recommended as the most preferable format, but is not limited thereto. The type of the reactor is preferably a fixed bed type or a fluidized bed type, and the dimensions and shape of the reactor can be appropriately changed according to the amount of the reactants and the like.

  In the reaction according to the present invention, an inert gas inert under the reaction conditions may be present. Examples of the inert gas include nitrogen or rare gases, and nitrogen or helium is preferable from the viewpoint of ease of handling and availability. The amount in the presence of the inert gas is not particularly limited, but if it is too much, there is a possibility that the recovery rate is lowered. Therefore, in the usual case, the raw material 1-alkoxy-1,1,2,2-tetrafluoro An amount less than the ethane feed rate is preferred.

  The reaction temperature in the method of the present invention varies depending on the type of catalyst and the raw material. Usually, it is 100-400 degreeC, about 150-350 degreeC is preferable and 180-280 degreeC is more preferable. If the reaction temperature is less than 100 ° C., the conversion tends to be low, which is not preferable. When the reaction temperature exceeds 400 ° C., severe heat resistance is required for the reaction apparatus, and excessive heating energy is required, which is not economically preferable.

  The reaction time (contact time) is usually 0.1 to 300 seconds, preferably 0.5 to 200 seconds, and more preferably 1 to 60 seconds. If the reaction time is too short, the conversion rate may be lowered. On the other hand, if the reaction time is too long, productivity is lowered, which is not preferable. The reaction pressure is not particularly limited and may be normal pressure, reduced pressure, or increased pressure. A pressure of about 0.05 to 0.5 MPa (0.5 to 5 atmospheres) is preferable, and usually a pressure in the vicinity of atmospheric pressure that facilitates operation is preferable.

  In the catalyst according to the present invention, coking may occur over time, and the activity of the catalyst may decrease. The catalyst having reduced activity can be easily regenerated by contacting with oxygen at 200 ° C. to 1200 ° C., preferably 400 ° C. to 800 ° C. It is convenient to perform the oxygen treatment while it is loaded in the reaction tube or in an external device. This is done by circulating oxygen there. Other gases may coexist as a method for circulating oxygen, and oxygen, air, nitrogen-diluted oxygen and the like can be used, but air or air diluted with nitrogen is economically preferable. Further, a gas having oxidizing power such as chlorine and fluorine can be used.

In the reaction according to the method of the present invention, a compound obtained by further decomposing alkyl fluoride (R ¹ F) or R ¹ F as a by-product is produced in addition to the desired difluoroacetic acid fluoride. For example, when ethyl fluoride is generated as R ¹ F, ethylene and hydrogen fluoride may be formed. However, the crude product obtained by the reaction can be used as a raw material for the reaction of the present invention (step (b)) without purification.

<Production of 2-difluoroacyl-3-aminoacrylic acid ester>
General formula (4)

2-difluoroacyl-3-aminoacrylic acid ester represented by the above formula or a known method and difluoroacetic acid fluoride and general formula (3)

It can manufacture by making it react with the dimethylamino acrylate ester represented by these.

R ^2, R ^3, R ⁴ in the general formula (3) and the general formula (4) are each independently an alkyl group having 1 to 4 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, and a t-butyl group.

  The method of the present invention is performed in a non-aqueous solvent. Aliphatic, alicyclic or aromatic hydrocarbons such as petroleum ether, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene or decalin, and halogenated hydrocarbons such as chlorobenzene, di- Examples include chlorobenzene, dichloromethane, chloroform, tetrachloromethane, dichloroethane, and trichloroethane. Use of toluene, xylene, chlorobenzene, n-hexane, cyclohexane or methylcyclohexane is preferred, and toluene or xylene is more preferred. These solvents can also be used as a mixture.

  The process according to the invention is carried out in the presence of a base. Bases are inorganic water-soluble bases, tertiary amines (tertiary amines), pyridine or pyridine derivatives, and alkaline earth metals or alkali metal hydroxides, carbonates or bicarbonates such as sodium hydroxide, water Preference is given to potassium oxide, lithium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, potassium hydrogen carbonate or sodium hydrogen carbonate. Sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, sodium carbonate or sodium bicarbonate is more preferred, and sodium hydroxide or potassium hydroxide is more preferred. The inorganic base is preferably used in a 10 to 40% aqueous solution. Examples of pyridine or pyridine derivatives include pyridine, 2-, 3- or 4-methylpyridine, 2-methyl-5-ethyl-pyridine, 2,4,6-collidine, 2- or 4-n-propylpyridine, 4 -Dimethylaminopyridine, quinoline or quinaldine, more preferably pyridine, 2-methyl-5-ethylpyridine, 2,4,6-collidine, quinoline or quinaldine can be used. Tertiary amines include trimethylamine, triethylamine, tri-n-propylamine, tri-isopropylamine, tri-n-butylamine, tri-isobutylamine, tri-sec-butylamine, tri-tert-butylamine, tri-n-amylamine. Symmetrical tertiary amines such as tri-isoamylamine, tri-sec-amylamine, tri-tert-amylamine, N-methyldi-n-butylamine, N-methyldiisobutylamine, N-methyldi-tert-butylamine, N, N- Diisopropylbutylamine, N, N-dimethyl-n-octylamine, N, N-dimethylnonylamine, N, N-dimethyldecylamine, N, N-dimethylundecylamine, N, N-dimethyldodecylamine, N-methyl Asymmetric tertiary amines such as dihexylamine Etc., and the like. Triethylamine is preferable in terms of boiling point, water solubility, and availability.

The process of the present invention is carried out at a temperature of -20 ° C to + 50 ° C, preferably -10 ° C to + 30 ° C. The reaction pressure is not particularly limited because it does not affect the reaction, but it may be carried out under a pressure of about 0.1 to 10 MPa, and usually it may be carried out at atmospheric pressure to about 1 MPa.
What is necessary is just to determine on the basis of the reduction | decrease or disappearance of a substrate, tracking reaction for about 10 minutes-10 hours of reaction time.

  In the method of the present invention, the dimethylaminoacrylic acid ester represented by the general formula (3) is added in an amount of 0.5 mol to 3 mol, preferably 0.5 mol to 1.5 mol, per mol of difluoroacetic acid fluoride. Preferably it is 0.9 mol-1 mol. The base is usually used in an equimolar amount or slightly in excess (2 mol or less) with difluoroacetic acid fluoride.

  In the method of the present invention, the dimethylaminoacrylic acid ester represented by the general formula (3) and the base are dissolved in a solvent and are generally held at a temperature equal to or lower than the reaction temperature. Although it can be performed by blowing a thermal decomposition product of 1-alkoxy-1,1,2,2-tetrafluoroethane represented, it can also be a scrubber type. The base can be appropriately added as the reaction proceeds. At this time, it is preferable to move the pyrolysis product to step (b) at a temperature lower than the pyrolysis temperature. Moreover, it is more preferable to cool the thermal decomposition product below the reaction temperature and blow it into the reaction solution. Specifically, it is about 150 ° C. or lower, preferably 100 ° C. or lower, and more preferably 50 ° C. or lower. For practical reasons, it is preferably -20 ° C to + 50 ° C, -20 ° C to + 40 ° C, and more preferably -5 ° C to + 5 ° C.

  Since the optimum temperature for the thermal decomposition reaction of 1-alkoxy-1,1,2,2-tetrafluoroethane is 200 ° C. to 250 ° C., when the product gas is blown into a solution containing a dialkyl acrylate ester without cooling. , A compound of unknown structure which is difficult to separate is produced as a by-product. In the fields of medicine and agricultural chemicals, it is avoided from the viewpoint of ensuring safety that impurities of unknown toxicity are mixed into intermediates. However, by cooling the product gas and then blowing it into a solution containing a dialkyl acrylate ester, the production of by-products is substantially suppressed. The cooling method is not limited, the cooling device is provided between the thermal decomposition device and the reaction vessel of the dialkyl acrylate, direct cooling or indirect cooling can be adopted, in indirect cooling, a method using air cooling or a refrigerant by a radiator, Direct cooling can use contact with a liquid inert to difluoroacetic acid fluoride. As the inert liquid, for example, those exemplified as the reaction solvent can be used.

At the completion of the reaction, the hydrohalide salt of the pyridine derivative can be added to the solution with water or the aqueous phase present can be removed by phase separation. In the organic phase remaining without further purification in the subsequent reaction step (step (c)), the 2-difluoroacyl-3-aminoalkyl acid ester represented by the general formula (4) is Can be used after flash distillation and drying.
HF trapped in the pyridine derivative can be easily removed by washing with water.

<Production of pyrazole compound>
General formula (4)

2-difluoroacyl-3-aminoacrylic acid ester represented by the general formula (5)
R ⁵ NHNH ₂ (5)
(In the formula, R ⁵ represents a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an alkoxyalkyl group or an aryl group, and any number of hydrogen atoms in the alkyl group and alkoxy group are halogen atoms. The oxygen atom of the alkoxy group may be substituted with a sulfur atom.) The mixture is reacted with a hydrazine derivative represented by the general formula (6):

(Wherein, R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms) can be produced.
R ⁵ in the general formula (5) and the general formula (6) is a linear, branched or cyclic alkyl group, an alkoxyalkyl group or an aryl group having 1 to 10 carbon atoms. Any number of hydrogen atoms may be substituted with a halogen atom, and the oxygen atom of the alkoxy group may be substituted with a sulfur atom. Halogen is fluorine, chlorine or chlorine.
Specifically, R ⁵ is methyl, ethyl, n-propyl, isopropyl, tert-butyl, difluoromethyl, trifluoromethyl, hydroxymethyl, hydroxyethyl, cyclopropyl, cyclopentyl, cyclohexyl or phenyl, and methyl, ethyl , Isopropyl, n-propyl or tert-butyl are preferred, and methyl is most preferred.

The ring-closing reaction to the pyrazole of the present invention is carried out in the presence of an aprotic solvent. Specifically, aliphatic, alicyclic or aromatic hydrocarbons such as petroleum ether, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene or decalin, and halogenated hydrocarbons For example, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, tetrachloromethane, dichloroethane or trichloroethane, ethers such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, methyl tert-amyl ether, dioxane, tetrahydrofuran, 1,2-dimethoxyethane 1,2-diethoxyethane or anisole; nitriles such as acetonitrile, propionitrile, n- or isobutyronitrile or benzonitrile Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone; amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone or hexamethylphosphoramide; Sulfoxides, such as dimethyl sulfoxide, or sulfones, such as sulfolane. Toluene, xylene, chlorobenzene, n-hexane, cyclohexane or methylcyclohexane are preferred, and toluene or xylene is more preferred. Moreover, it is preferable to use the same solvent as the esterification reaction in the previous stage. In the case of subjecting to the pyrazole cyclization reaction without separating or purifying the reaction product in the previous esterification reaction, it is particularly preferable to select the same solvent. These solvents can be used in combination.
The ring-closing reaction to pyrazole is preferably carried out at a low temperature, but is practically carried out at −78 ° C. to + 20 ° C., preferably −30 ° C. to 0 ° C., more preferably −20 ° C. to 0 ° C. The reaction pressure is arbitrary because it does not affect the reaction in the normal pressure range, but it may be pressurized or depressurized, and generally it may be carried out at atmospheric pressure without conscious pressure or depressurization. . Since it is not preferable that hydrazine, which is a strong reducing agent, is in contact with air, it is preferably performed in a nitrogen or argon atmosphere.

  In the ring-closing reaction to pyrazole, when the 2-difluoroacyl-3-aminoacrylic acid ester represented by the general formula (4) and the hydrazine derivative represented by the general formula (4) are mixed and brought into contact with each other, And the other is added thereto. The addition is preferably performed gradually while observing the progress of the reaction.

  The reaction product can be purified according to a general purification method. For example, the reactor contents are extracted with water, the organic phase is removed and the solvent is removed by distillation. The isomer (1-methyl-5-difluoromethylpyrazole-4-carboxylic acid) can be removed by crystallization. It is also possible to first hydrolyze the ester to an acid and then recrystallize it.

Examples will be described below, but the present invention is not limited to these examples.

[Preparation Example 1]
An aluminum phosphate catalyst made from Aldrich phosphate was formed into 5 mmφ × 5 mmL pellets and calcined at 700 ° C. for 5 hours in a nitrogen stream to prepare an aluminum phosphate catalyst.

[Difluoroacetic acid fluoride synthesis example 1]
A stainless steel reaction tube having an inner diameter of 23 mm and a length of 500 mm was charged with the aluminum phosphate catalyst (50 cc) synthesized in Preparation Example 1, and heated in an electric furnace while flowing nitrogen at 50 cc / min. When the temperature of the catalyst reached 50 ° C., hydrogen fluoride (HF) was introduced through the vaporizer while gradually increasing the feed rate (maximum 0.6 g / min). While circulating HF (0.6 g / min), the temperature was slowly raised to 350 ° C. and maintained for 24 hours. After stopping the flow of HF, increasing the nitrogen flow rate to 100 cc / min and holding it for 2 hours, 1-ethoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OC ₂ H ₅ ) was added at 1 g / min. At a rate, it was introduced through the vaporizer and the nitrogen supply was stopped. When the reactor temperature reached a steady state at 200 ° C., the product gas was analyzed by GC (FID). As a result, difluoroacetic acid fluoride (CHF ₂ COF): 14.6 area%, fluoroethane (C ₂ H ₅ F): 51.2 area%, ethylene (C ₂ H ₄ ): 32.5 area%, 1-ethoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OC ₂ H ₅ ): 0 .3 area%, other: 1.4 area%.

[Example 1]
In a gas washing bottle (500 cc) made of PFA, 28.6 g (0.2 mol) of ethyl 3-dimethylaminoacrylate ((CH ₃ ) ₂ NCH═CHCOOC ₂ H ₅ ), toluene (200 mL), 37.2 g of 2-methylpyridine (0.4 mol) was added and cooled in an ice bath with stirring. PFA coil tube (F-8024-02 manufactured by FLON INDUSTRY (tube outer diameter: 6 mmφ, wall thickness: 1 mm, coil outer diameter: 40 mm, total length: 2.4 m) is passed through a wind-cooled tube connected in series, and a synthesis example The gas synthesized in 1 was introduced into this gas washing bottle as it was without being purified, and bubbled, and the gas temperature immediately before the introduction was measured to be 43 ° C. 1-ethoxy-1,1,2, When 30 g of 2-tetrafluoroethane was supplied, the supply was stopped, and the entire contents were transferred to a 500 cc eggplant flask and stirred at room temperature for 30 minutes, and then water (100 g) was added, followed by further stirring for 15 minutes. Separated into two layers, the organic layer was recovered, the aqueous layer was extracted again with 100 mL of toluene, and the organic layer was blended with the previous organic layer, washed with 100 mL of water, separated into two layers, and organic When the solvent was distilled off with a rotary evaporator and vacuum drying (80 ° C., 0.1 kPa) was performed, oily crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate (Ethyl 2-difluoroacetyl-3 dimethylamino-acrylate) was obtained. As a result of analysis by ¹⁹ F-NMR (376 MHz), the conversion was 98% and the selectivity was 99%, and the type of impurities was obtained in Reference Example 2 using purified difluoroacetic acid fluoride. Product.
[Physical properties of ethyl 2-difluoroacetyl-3-dimethylaminoacrylate]
¹ H-NMR 1.3 ppm (t, 3 H), 2.9 ppm (s, 3 H), 3.3 ppm (s, 3 H), 4.2 ppm (q, 2 H), 6.6 ppm (t, 1 H), 7 .8 ppm (s, 1H)
¹⁹ F-NMR-126.7 ppm (d, 2F).

[Example 2]
10.2 g (0.046 mol) of crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate synthesized in Example 1 was dissolved in 40 mL of toluene and cooled to −20 ° C. with stirring in a nitrogen atmosphere. 2.6 g (0.057 mol) of methyl hydrazine was dissolved in 50 mL of toluene and added dropwise. After completion of dropping, the mixture was aged at 0 ° C. for 3 hours, and further aged at room temperature for 2 hours. 40 g of water was added to separate the two layers, and the aqueous layer was extracted with 15 mm of toluene to match the organic layer. This was washed with 25 g of water, then two layers were separated, and the organic layer was dried over magnesium sulfate. The solvent was distilled off with a rotary evaporator and further dried under vacuum at 60 ° C., and then ethyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate (Ethyl 3-difluoromethyl-1-methyl-pyrazole-4) was obtained. -Carboxylate) 8.49 g was obtained.
[Physical properties of ethyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate]
¹ H-NMR 1.2 ppm (t, 3 H), 3.9 ppm (s, 3 H), 4.2 ppm (q, 2 H), 7.0 ppm (t, 1 H), 7.8 ppm (s, 1 H)
¹⁹ F-NMR -116.4 ppm (d, 2F).

[Example 3]
1-methoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OCH ₃ ) (26 g) instead of 1-ethoxy-1,1,2,2-tetrafluoroethane (30 g), 2- Example 1 except that 18.6 g (0.2 mol) of methylpyridine was used and a 300 mm stainless steel Liebig-type cooling tube with a 0 ° C. refrigerant circulating was used instead of a PFA air-cooled tube. The same experiment was conducted. As a result, 41.2 g of oily crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate was obtained. ^When analyzed by ¹⁹ F-NMR (376 MHz), the conversion was 98% and the selectivity was 99%. The kind of impurities was the same as that of the product obtained in Reference Example 2 using purified difluoroacetic acid fluoride.

[Example 4]
The same experiment as in Example 2 was performed, except that 10.2 g (0.046 mol) of crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate obtained in Example 3 was used. As a result, 8.51-g of ethyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate was obtained.

[ Comparative Example 1]
The same experiment as in Example 3 was performed except that the pyrolysis product produced by the pyrolysis reaction was directly blown into a toluene solution of ethyl 3-dimethylaminoacrylate and 2-methylpyridine without cooling. When 42.6 g of oily crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate obtained by vacuum drying was analyzed by ¹⁹ F-NMR, other than ethyl 2-difluoroacetyl-3-dimethylaminoacrylate 7.9% of compounds with unknown structure were found. This crude ethyl 2-difluoroacetyl-3-dimethylaminoacrylate was dissolved in toluene (100 ml), washed again with water (100 cc), separated into two layers, the organic layer was evaporated using a rotary evaporator, and dried in vacuo ( What was performed at 80 ° C. and 0.1 kPa) was analyzed again by ¹⁹ F-NMR. The content of the compound with unknown structure was 7.1%, and removal by washing with water was difficult.

[Reference Example 2]
Difluoroacetic acid fluoride synthesis example 1 was collected with a dry ice strap and purified by pressure distillation, and 99.2% pure difluoroacetic acid fluoride was collected in a stainless steel container with a needle valve (50 cc). Filled. 28.6 g (0.2 mol) of ethyl 3-dimethylaminoacrylate, toluene (200 mL) and 37.2 g (0.4 mol) of 2-methylpyridine were added to a PFA gas washing bottle (500 cc), and the ice bath was stirred. And purified difluoroacetic acid fluoride (20.2 g) was introduced over 50 minutes while bubbling through the gas wash bottle. After the bubbling was completed, the entire contents were transferred to a 500 cc eggplant flask and stirred at room temperature for 30 minutes. Thereafter, water (100 g) was added and the mixture was further stirred for 15 minutes. Two layers were separated and the organic layer was recovered. The aqueous layer was extracted again with 100 mL of toluene, and the organic layer was combined with the previous organic layer. This was washed with 100 mL of water, separated into two layers, the organic layer was evaporated using a rotary evaporator, and dried under vacuum (80 ° C., 0.1 kPa). As a result, oily crude 2-difluoroacetyl-3-dimethyl was obtained. 41.6 g of ethyl aminoacrylate was obtained. ^When analyzed by ¹⁹ F-NMR, the conversion was 98% and the selectivity was 99%.

  2-Difluoroacyl-3-aminoacrylic acid ester and ethyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate obtained by the method of the present invention are useful as intermediates for medicines and agricultural chemicals.

Claims (2)

General formula (1)
CHF ₂ CF ₂ OR ¹ (1)
(Wherein R ¹ represents a monovalent organic group) 1-alkoxy-1,1,2,2-tetrafluoroethane represented by a metal oxide or phosphate in the presence of a catalyst. in the temperature cooled pyrolysis products unpurified pyrolysis were separated at 100 to 400 ° C. as -20 ℃ ~ + 50 ℃, the general formula (3)
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms) General formula (4) comprising contacting with dimethylaminoacrylate represented by
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms), a method for producing 2-difluoroacyl-3-aminoacrylic acid ester. The general formula (4) obtained by the production method according to claim 1.
(Wherein R ² , R ³ and R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms) and 2-difluoroacyl-3-aminoacrylic acid ester represented by the general formula (5)
R ⁵ NHNH ₂ (5)
(In the formula, R ⁵ represents a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, an alkoxyalkyl group or an aryl group, and any number of hydrogen atoms in the alkyl group and alkoxy group are halogen atoms. (The oxygen atom of the alkoxy group may be substituted with a sulfur atom.) General formula (6) comprising contacting with a hydrazine derivative represented by formula (6)
(In the formula, R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms, and R ⁵ is the same as in General Formula (5)).