阅读说明：本技术 一种2,4,6-三氟苄胺的合成方法 (Synthetic method of 2,4, 6-trifluorobenzylamine ) 是由 袁其亮 钱捷 赖鑫 陈海峰 陈寅镐 王超 于 2018-07-05 设计创作，主要内容包括：本发明公开了一种2,4,6-三氟苄胺的合成方法,属于化学合成技术领域,包括以下步骤：(1)、以五氯苯腈作为原料,以2,4,6-三氟-3,5-二氯苯腈作为溶剂,与氟化剂发生氟化反应,得到2,4,6-三氟-3,5-二氯苯腈；(2)、步骤(1)得到的2,4,6-三氟-3,5-二氯苯腈,在有机羧酸存在下,以钯炭作为催化剂,经氢气氢化还原,得到2,4,6-三氟-3,5-二氯苄胺；(3)、步骤(2)得到的2,4,6-三氟-3,5-二氯苄胺,在溶剂中,在催化剂作用下,经氢气氢化还原,得到2,4,6-三氟苄胺。该合成方法具有原料成本低、反应步骤短、反应收率高、产品纯度好、操作简单等优点,适合工业化生产应用。(The invention discloses a synthetic method of 2,4, 6-trifluorobenzylamine, belonging to the technical field of chemical synthesis and comprising the following steps: (1) the method comprises the following steps of taking pentachlorobenzonitrile as a raw material, taking 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile as a solvent, and carrying out fluorination reaction with a fluorinating agent to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile; (2) in the presence of organic carboxylic acid, palladium-carbon is used as a catalyst, and the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile obtained in the step (1) is subjected to hydrogen hydrogenation reduction to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzylamine; (3) and (3) carrying out hydrogen hydrogenation reduction on the 2,4, 6-trifluoro-3, 5-dichlorobenzylamine obtained in the step (2) in a solvent under the action of a catalyst to obtain the 2,4, 6-trifluorobenzylamine. The synthesis method has the advantages of low raw material cost, short reaction steps, high reaction yield, good product purity, simple operation and the like, and is suitable for industrial production and application.)

1. A synthetic method of 2,4, 6-trifluorobenzylamine is characterized by comprising the following steps:

(1) the method comprises the following steps of taking pentachlorobenzonitrile as a raw material, taking 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile as a solvent, and carrying out fluorination reaction with a fluorinating agent to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile;

(2) in the presence of organic carboxylic acid, palladium-carbon is used as a catalyst, and the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile obtained in the step (1) is subjected to hydrogen hydrogenation reduction to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzylamine;

(3) and (3) carrying out hydrogen hydrogenation reduction on the 2,4, 6-trifluoro-3, 5-dichlorobenzylamine obtained in the step (2) in a solvent under the action of a catalyst to obtain the 2,4, 6-trifluorobenzylamine.

2. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (1), the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile used as the solvent is 1-15 times of the mass of pentachlorobenzonitrile.

3. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (1), the fluorinating agent is selected from one or two of the following: the mass ratio of sodium fluoride, potassium fluoride, fluorinating agent and pentachlorobenzonitrile is: 3: 1-6: 1.

4. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (1), the reaction temperature is 170-240 ℃.

5. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (2), the organic carboxylic acid is selected from one or more of the following: formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid and isovaleric acid, wherein the organic carboxylic acid is used as an acid and a solvent, and the dosage of the organic carboxylic acid is 1-20 times of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile.

6. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (2), the hydrogenation pressure is 0.01 to 3.0 MPa.

7. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (2), the reaction temperature is 0-70 ℃.

8. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (3), the solvent is selected from one or more of the following: the solvent amount is 1-15 times of the mass of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine.

9. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (3), the catalyst is selected from one or two of the following: palladium carbon, sponge nickel.

10. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (3), the hydrogenation pressure is 0.01 to 3.0 MPa.

11. The method for synthesizing 2,4, 6-trifluorobenzylamine according to claim 1, wherein: in the step (3), the reaction temperature is 0-100 ℃.

The technical field is as follows:

the invention belongs to the technical field of chemical synthesis, and particularly relates to a synthetic method of 2,4, 6-trifluorobenzylamine.

Background art:

2,4, 6-trifluorobenzylamine is an important fine chemical, has wide application prospect in the fields of drug synthesis and the like, and is a key intermediate for synthesizing Bictegravir (GS-9883).

The synthesis methods of the 2,4, 6-trifluorobenzylamine disclosed at present mainly comprise the following three methods:

(1) and patent CN104610068 discloses synthesis of 2,4, 6-trifluorobenzylamine by using 1,3, 5-trifluorobenzene as raw material and carrying out lithiation, formylation, reduction, chlorination, ammoniation and other reactions.

The synthesis method has long reaction steps, complex operation conditions, expensive raw and auxiliary materials and large amount of three wastes in the synthesis process, thereby lacking industrial application value.

(2) And patent CN106349083 discloses that 2,4, 6-trifluorobenzonitrile is used as a raw material and subjected to one-step hydrogenation reduction to synthesize 2,4, 6-trifluorobenzylamine.

Although the synthesis method only has one-step reaction, the raw material 2,4, 6-trifluorophenylnitrile is expensive and not easy to obtain, so that the synthesis method cannot be applied in a large scale.

(3) And patent CN107778183 discloses the synthesis of 2,4, 6-trifluorobenzylamine by using pentachlorobenzonitrile as a raw material and performing steps of fluorination, reduction and the like.

The synthesis method has the advantages of cheap and easily-obtained raw materials and short reaction steps, but has complex operation process, more side reactions and unsatisfactory reaction yield, thereby limiting the industrial application of the synthesis method.

The invention content is as follows:

the invention aims to provide a synthetic method of 2,4, 6-trifluorobenzylamine, which has the advantages of low raw material cost, short reaction steps, high reaction yield, good product purity, simple operation and suitability for industrial production.

The technical scheme adopted by the invention is as follows:

a synthetic method of 2,4, 6-trifluorobenzylamine is characterized by comprising the following steps:

(1) the method comprises the following steps of (1) taking pentachlorobenzonitrile (I) as a raw material and 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile as a solvent to perform fluorination reaction with a fluorinating agent to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile (II);

(2) in the presence of organic carboxylic acid, palladium carbon is used as a catalyst, and the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile (II) obtained in the step (1) is subjected to hydrogen hydrogenation reduction to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzylamine (III);

(3) and (3) carrying out hydrogen hydrogenation reduction on the 2,4, 6-trifluoro-3, 5-dichlorobenzylamine (III) obtained in the step (2) in a solvent under the action of a catalyst to obtain the 2,4, 6-trifluorobenzylamine (IV).

The synthetic route adopted by the invention can be represented by the following reaction formula:

the invention further provides that:

in the step (1):

the reaction in the step belongs to halogen exchange fluorination reaction, and the selection of the solvent has important influence on the smooth proceeding of the reaction. Most of the common solvents used for halogen exchange fluorination are polar aprotic solvents, mainly comprising the following solvents: n, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, dimethyl sulfone, sulfolane, and the like. However, the introduction of the solvent not only increases the types of materials, but also requires additional operations such as solvent removal and solvent recovery, which complicates the operation process and increases the synthesis cost. Considering that the product 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile of step (1), which is also a polar aprotic compound, is a liquid at normal temperature and has a boiling point of about 230 ℃, the thermal stability thereof was measured by a differential scanning calorimeter, and it was confirmed that it is chemically stable within 300 ℃, meets the requirements as a solvent of step (1), and excellent results were obtained after studies on its use as a reaction solvent. Therefore, 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is used as a reaction solvent, and the dosage of the reaction solvent is 1-15 times of the mass of the compound (I).

The fluorinating agent refers to alkali metal fluoride salt, such as lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride and the like, and combines the factors of fluorinating agent activity, cost and the like, and the preferable fluorinating agent is one or two of the following: sodium fluoride and potassium fluoride. The ratio of the amount of fluorinating agent to the amount of material of compound (I) is: 3: 1-6: 1.

In the fluorination reaction process, a proper amount of single or composite catalyst is added, which is beneficial to improving the fluorination reaction rate and reducing the fluorination temperature. There are many kinds of catalysts to be used, for example, quaternary ammonium salt catalysts such as tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium fluoride, benzyltriethylammonium chloride and hexadecyltrimethylammonium chloride, quaternary phosphonium salt catalysts such as triphenylmethylphosphonium bromide, triphenylethylphosphonium bromide and tetraphenylphosphonium bromide, and crown ether catalysts such as 18-crown-6 and 15-crown-5. The dosage of the catalyst is 0-0.5 times of the mass of the compound (I).

The fluorination reaction system composed of different fluorinating agent types and dosage, different catalyst types and dosage and different solvent dosage has different reactivity, so the fluorination reaction temperature is also different. Generally, when the fluorination reaction temperature is lower than 150 ℃, the fluorination reaction speed is slow, which is not beneficial to improving the synthesis efficiency; when the fluorination reaction temperature is higher than 250 ℃, the over-fluorination side reaction increases rapidly with the increase of the reaction temperature, and the pyrolysis side reaction of the fluorinated product and the intermediate compound also increases, which results in a complicated reaction system and rapid decrease of the reaction yield and product purity. Therefore, in order to obtain an appropriate reaction rate and suppress the occurrence of side reactions such as over-fluorination and pyrolysis as much as possible, the fluorination reaction temperature is usually selected to be 150 to 250 ℃, and a preferable fluorination reaction temperature is 170 to 240 ℃.

After the fluorination reaction is finished, the reaction system can be post-treated by various methods to obtain the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile (comprising a fluorination product and an added reaction solvent, wherein the two are the same compound), and the optional post-treatment methods comprise the following steps: 1. evaporating the compound (II) out of the system by adopting a reduced pressure distillation method until the compound (II) is completely evaporated to dryness, wherein the obtained fraction is 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile; 2. separating the compound (II) from inorganic salt by adopting a filtering method to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile; 3. firstly, adding water to dissolve inorganic salt, and then obtaining 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile by a standing and layering mode; 4. firstly adding a proper amount of organic solvent to dilute the system, then separating inorganic salt from the system by adopting a filtering mode, and distilling the filtrate to remove the solvent to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile; 5. firstly, adding water to dissolve inorganic salt, then extracting with a proper organic solvent, drying the extract liquor, distilling to remove the solvent and the like to obtain the 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile. Of course, other suitable workup procedures may be employed to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile. The preferable post-treatment method is 1-3, and no new organic solvent is introduced, so that the method is favorable for reducing the types of materials used in the synthesis process, simplifying the operation process and reducing the synthesis cost.

In the step (2):

the organic carboxylic acid refers to straight chain or branched chain mono-or dibasic alkyl carboxylic acid with 1-10 carbon atoms, mono-or dibasic aryl carboxylic acid and the like, and specifically comprises the following components: formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, benzoic acid, p-toluic acid, phthalic acid, terephthalic acid, and the like. Based on the factors such as the overall cost, the preferred organic carboxylic acid is a linear or branched monocarboxylic acid having 1 to 10 carbon atoms, and the following concrete examples are: formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, and the like. Most preferably the organic carboxylic acid is selected from one or more of the following: formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid. The main function of the organic carboxylic acid in the reaction process is to generate corresponding carboxylate with the reduction product 2,4, 6-trifluoro-3, 5-dichlorobenzylamine, so as to avoid the side reaction of similar reductive amination with the reduction intermediate 2,4, 6-trifluoro-3, 5-dichlorobenzylimine.

The reaction is carried out in a suitable solvent, and the solvent can be selected from ester solvents such as methyl acetate, ethyl acetate, propyl acetate, etc., ether solvents such as tetrahydrofuran, 2-methyltetrahydrofuran, etc., alcohol solvents such as methanol, ethanol, isopropanol, etc., and water. When one or more of formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid and isovaleric acid is/are used as organic carboxylic acid, the organic carboxylic acid can also be used as a reaction solvent, and when the organic carboxylic acid and the reaction solvent are the same compound, the material types are reduced, the production operation is simplified, the solvent recovery is convenient, and the like, so that the preparation method has great advantages in production. Therefore, one or more of formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, and isovaleric acid are preferably used as the organic carboxylic acid and the reaction solvent in an amount of 1 to 20 times the mass of the compound (II).

The palladium-carbon is an activated carbon dispersion of palladium obtained by supporting metal palladium on activated carbon, and has an activity of catalyzing a hydrogenation reaction. The palladium carbon can be prepared by self or can adopt commercial products with different specifications. The palladium carbon is classified into various specifications such as 10% dry palladium carbon, 10% wet palladium carbon (moisture content of about 50%), 5% dry palladium carbon, 5% wet palladium carbon (moisture content of about 50%), 1% dry palladium carbon, 1% wet palladium carbon (moisture content of about 50%), and the like, depending on the effective content of palladium, whether water is contained or not. The palladium carbon is not specifically limited in specification as long as the catalytic activity satisfies the requirement. The dosage of the palladium carbon is related to the effective content of palladium in the palladium carbon, and if 10 percent of the palladium carbon is used as the catalyst, after water is deducted (i.e. dried), the dosage is 0.001-0.15 times of the mass of the compound (II); if 5% palladium carbon is used as the catalyst, after water is subtracted (i.e. dried), the dosage of the palladium carbon is 0.001-0.2 times of the mass of the compound (II); when 1% palladium-carbon is used as the catalyst, the amount of the catalyst is 0.001 to 0.25 times the mass of the compound (II) after water is subtracted (i.e., dried). If other effective palladium contents of palladium carbon are used, the amount of the palladium carbon is changed, and the specific amount needs to be confirmed through experiments.

The hydrogenation pressure refers to the sum of the partial pressures of various gases in the reaction kettle under certain hydrogenation conditions, such as a certain feeding ratio and reaction temperature, and includes the sum of the partial pressure of hydrogen, the partial pressure of raw material vapor, the partial pressure of solvent vapor and the like under the conditions. Under fixed conditions, the hydrogenation pressure can indirectly represent the partial pressure of hydrogen in the reaction vessel. The hydrogenation pressure has a significant influence on the hydrogenation reduction rate and the type of hydrogenation equipment. The hydrogenation pressure is low, the hydrogenation speed is slow, but the requirement on hydrogenation equipment is low; the hydrogenation pressure is high, the hydrogenation speed is high, but the requirements on hydrogenation equipment and safe operation are increased. The preferable hydrogenation pressure is 0.01 to 3.0 MPa.

The hydrogenation temperature is selected in consideration of not only the hydrogenation reduction reaction rate but also suppression of the occurrence of side reactions. Although the hydrogenation reduction reaction is carried out at a high temperature, and even a part of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine is subjected to hydrogenation dechlorination reaction to produce 2,4, 6-trifluoro-3-chlorobenzylamine and 2,4, 6-trifluorobenzylamine, a series of side reactions such as amidation of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine with organic carboxylic acid, amidation of 2,4, 6-trifluoro-3-chlorobenzylamine with organic carboxylic acid, and amidation of 2,4, 6-trifluorobenzylamine with organic carboxylic acid may occur. Therefore, the hydrogenation temperature is not preferably too high, and the preferable range of the hydrogenation temperature is 0 to 70 ℃.

After the hydrogenation reaction is finished, the reaction solution is subjected to simple post-treatment operations such as filtration and recovery of palladium-carbon, distillation and recovery of a solvent and the like to obtain a crude product of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine, which can be directly used for the reaction in the step (3), and can also be subjected to appropriate purification operation on the obtained crude product of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine to obtain 2,4, 6-trifluoro-3, 5-dichlorobenzylamine with higher purity, and then the reaction in the step (3) is carried out. The following post-processing methods can be selected: 1. filtering the reaction liquid in the step (2) to recover palladium carbon, distilling the filtrate to recover the solvent, and distilling the concentrate to perform the reaction in the step (3); 2. filtering the reaction liquid obtained in the step (2) to recover palladium-carbon, distilling the filtrate to recover a solvent, carrying out alkali adjustment, layering, extraction, concentration and other operations on a distillation concentrate to obtain a crude product of 2,4, 6-trifluoro-3, 5-dichlorobenzylamine, and carrying out the reaction in the step (3); 3. filtering the reaction liquid in the step (2) to recover palladium-carbon, distilling the filtrate to recover a solvent, carrying out operations such as alkali adjustment, layering, extraction, concentration, rectification and the like on a distillation concentrate to obtain a pure 2,4, 6-trifluoro-3, 5-dichlorobenzylamine, and carrying out the reaction in the step (3); 4. distilling the reaction liquid in the step (2) to recover the solvent, dissolving the distillation concentrate by using the reaction solvent in the step (3), filtering and recovering palladium-carbon, and using the filtrate for the reaction in the step (3); 5. and (3) distilling the reaction liquid in the step (2) to recover the solvent, and directly carrying out the reaction in the step (3) without recovering palladium-carbon from the distillation concentrate. Of course, other suitable post-treatment methods may be used. The palladium carbon and the solvent obtained by post-treatment and recovery can be reused in the step (2) after proper treatment.

In the step (3):

the solvent is selected from one or more of the following: ester solvents such as methyl acetate, ethyl acetate, and propyl acetate, ether solvents such as tetrahydrofuran and 2-methyltetrahydrofuran, alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol, and water. The preferred solvent is an alcohol solvent and water, and is selected from one or more of the following: water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol. The dosage of the solvent is 1-15 times of the mass of the compound (III).

The catalyst is selected from one or two of the following: palladium carbon, sponge nickel. The palladium-carbon catalyst refers to an activated carbon dispersion of palladium obtained by loading metal palladium on activated carbon, and is classified into various specifications according to the effective content of palladium, whether water is contained, and the like, such as 10% dry palladium-carbon, 10% wet palladium-carbon (water content of about 50%), 5% dry palladium-carbon, 5% wet palladium-carbon (water content of about 50%), 1% dry palladium-carbon, 1% wet palladium-carbon (water content of about 50%), and the like. The spongy nickel catalyst, also called skeleton nickel or Raney nickel, is prepared by treating nickel-aluminum alloy with concentrated alkali, such as concentrated sodium hydroxide solution, concentrated potassium hydroxide solution, etc., dissolving aluminum therein, and leaving microporous metal nickel which is active and burns when exposed to air, thus being soaked in water for storage. The catalyst can be prepared by self or can be commercial products with different specifications. The catalyst is selected without specific limitation on the specification as long as the catalytic activity satisfies the requirements. The dosage of the palladium-carbon catalyst is related to the effective content of palladium in the palladium-carbon, and if 10 percent of palladium-carbon is used as the catalyst, after water is deducted (i.e. dried), the dosage is 0.001-0.15 times of the mass of the compound (III); if 5% palladium carbon is used as the catalyst, after water is subtracted (i.e. dried), the dosage of the palladium carbon is 0.001-0.2 times of the mass of the compound (III); when 1% palladium-carbon is used as the catalyst, the amount of the catalyst is 0.001 to 0.25 times the mass of the compound (III) after water is subtracted (i.e., dried). If other palladium-carbon catalysts with effective palladium content are used, the dosage of the palladium-carbon catalysts is changed, and the specific dosage needs to be confirmed through experiments. The sponge nickel catalyst is used as an aqueous paste in an amount of 0.01 to 0.3 times the mass of the compound (III).

The reaction in this step is aromatic ring hydrogenation dechlorination, and hydrogen chloride is generated in the reaction process. As most hydrogenation equipment used for production is made of stainless steel materials, the catalyst cannot resist corrosion of hydrogen chloride, and in addition, sponge nickel of the catalyst can also react with the hydrogen chloride to generate nickel chloride, so that the catalyst fails. Therefore, in order to avoid the adverse effect of the generated hydrogen chloride on hydrogenation equipment and the sponge nickel catalyst, a proper amount of acid-binding agent is preferably added in the reaction process to neutralize the hydrogen chloride generated in the reaction. Of course, if the reaction equipment with anti-corrosion capability is selected and palladium carbon is selected as the catalyst, the reaction can be carried out without using an acid-binding agent. The acid-binding agent can be hydroxide, oxide, phosphate, carbonate, etc. of alkali metal and alkaline earth metal, and can also be organic tertiary amine compound. The preferable acid-binding agent is one or more of the following: lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium oxide, lithium phosphate, sodium phosphate, potassium phosphate, lithium carbonate, sodium carbonate, potassium carbonate, triethylamine, tri-N-propylamine, tri-N-butylamine, diethylisopropylamine, diisopropylethylamine, triethylenediamine, N-methylmorpholine, N-dimethylpiperazine, pyridine. The dosage of the acid-binding agent is determined according to the acid-binding capacity of the acid-binding agent molecules, the hydrogen chloride generated by the complete neutralization reaction is taken as a standard, and the preferable ratio of the acid-binding agent to the compound (III) is as follows: 0.5:1 to 4: 1.

The hydrogenation pressure refers to the sum of the partial pressures of various gases in the reaction kettle under certain hydrogenation conditions, such as a certain feeding ratio and reaction temperature, and includes the sum of the partial pressure of hydrogen, the partial pressure of raw material vapor, the partial pressure of solvent vapor and the like under the conditions. Under fixed conditions, the hydrogenation pressure can indirectly represent the partial pressure of hydrogen in the reaction vessel. The hydrogenation pressure has a significant influence on the hydrogenation reduction rate and the type of hydrogenation equipment. The hydrogenation pressure is low, the hydrogenation speed is slow, but the requirement on hydrogenation equipment is low; the hydrogenation pressure is high, the hydrogenation speed is high, but the requirements on hydrogenation equipment and safe operation are increased. The preferable hydrogenation pressure is 0.01 to 3.0 MPa.

The selection of the hydrogenation temperature is related to the hydrogenation system, such as reaction solvent, the type and amount of catalyst, hydrogenation pressure and the like. The preferable range of the hydrogenation temperature is 0 to 100 ℃.

Compared with the prior art, the invention has the beneficial effects that:

(1) in the fluorination reaction step, the fluorination product 2,4, 6-trifluoro-3, 5-dichlorobenzonitrile is used as a reaction solvent, so that the use of other solvents is avoided, the operation of removing the solvent from the product after the fluorination reaction is finished is eliminated, the production process is simplified, and the production cost is reduced.

(2) Compared with the technical scheme of firstly hydrogenating and reducing cyano groups into aminomethyl groups and then hydrogenating and dechlorinating aromatic rings, or the technical scheme of simultaneously carrying out hydrogenation and dechlorinating reaction and cyano group reduction reaction by one-pot method, the technical scheme can effectively avoid the side reaction of reduction-like reduction amination between cyano group reduction products and cyano group reduction intermediate states in the process of reducing cyano groups into aminomethyl groups, and greatly improve the reaction yield.

(3) Pentachlorobenzonitrile is used as a raw material, and is subjected to three steps of fluorination, cyano reduction and reductive dechlorination to synthesize 2,4, 6-trifluorobenzylamine, the total reaction yield is over 80 percent, the product purity is over 99 percent, and the method has obvious advantages compared with the prior art.

The present invention will be further described with reference to the following embodiments. The following embodiments are only for the purpose of facilitating understanding of the present invention and do not limit the present invention. The present invention is not intended to be limited to the specific embodiments, and all the features mentioned in the description may be combined with each other to constitute a new embodiment as long as the features do not conflict with each other.

The specific implementation mode is as follows: