CN114751807A - Novel efficient preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol - Google Patents
Novel efficient preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol Download PDFInfo
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Abstract
The invention discloses a novel efficient preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol, and belongs to the technical field of fine chemical engineering. The pentafluorobenzonitrile is subjected to Pd/C catalytic reaction in a 85% formic acid and sodium formate system to generate 2,3,5, 6-tetrafluorobenzonitrile, then stannous dichloride Stephen is reduced to obtain 2,3,5, 6-tetrafluorobenzaldehyde, and finally sodium borohydride/potassium borohydride is reduced to generate 2,3,5, 6-tetrafluorobenzyl alcohol, wherein the purity of the product is over 99.5%. The preparation process of the 2,3,5, 6-tetrafluorobenzyl alcohol has the advantages of high yield, low cost, good safety and high product purity.
Description
Technical Field
The invention relates to a novel high-efficiency preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol, belonging to the technical field of fine chemical engineering.
Background
2,3,5, 6-tetrafluorobenzyl alcohol is a key intermediate for preparing transfluthrin. Transfluthrin belongs to a broad-spectrum pesticide, has extremely low acute and chronic toxicity, is widely applied to sanitary insecticidal products, and is an environment-friendly green pesticide. The literature reports that the preparation process of the 2,3,5, 6-tetrafluorobenzyl alcohol mainly has six routes.
Route one: 2,3,5, 6-tetrafluorobenzyl alcohol is prepared by taking 2,3,5, 6-tetrafluoro terephthalic acid dimethyl ester as a raw material. 2,3,5, 6-tetrafluoro terephthalic acid dimethyl ester is reduced by sodium borohydride in glycol dimethyl ether solvent, and after hydrolysis of the off-white solid obtained by reduction, 2,3,5, 6-tetrafluoro p-hydroxymethyl benzoic acid (yield 82.6%) and 2,3,5, 6-tetrafluoro p-benzhydrol (yield 11.57%) are obtained. Decarboxylation of 2,3,5, 6-tetrafluoro-p-hydroxybenzoic acid in DMSO to give 2,3,5, 6-tetrafluorobenzyl alcohol. The raw material 2,3,5, 6-tetrafluoro terephthalic acid methyl ester is prepared by hydrolyzing and methyl esterifying 2,3,5, 6-tetrafluoro terephthalonitrile. If the route is calculated by 2,3,5, 6-tetrafluoroterephthalonitrile, the route is actually completed by five steps of reaction, and the route is long and poor in economy. Representative document is CN 201711008251.
And a second route: 2,3,5, 6-tetrafluorobenzyl alcohol is prepared by taking 2,3,5, 6-tetrafluorobenzoic acid as a raw material. DE3714602 uses sodium borohydride as reducing agent/dimethyl sulfate as activating agent to obtain 2,3,5, 6-tetrafluorobenzyl alcohol by one-step reduction. CN1900037 uses sodium borohydride as a reducing agent and zinc chloride as an activating agent to obtain tetrafluorobenzyl alcohol by one-step reduction. In the processes, a large amount of expensive reducing agent sodium borohydride is needed, and in some processes, even 10 equivalents of sodium borohydride is used, so that the production cost is high.
And a third route: 2,3,5, 6-tetrafluorobenzyl alcohol is prepared by taking 2,3,5, 6-tetrafluorobenzoyl chloride as a raw material. CN2006101010646 and CN109293478 etc. 2,3,5, 6-tetrafluorobenzoyl chloride is used as raw material glycol dimethyl ether as solvent, sodium borohydride is reduced to obtain 2,3,5, 6-tetrafluorobenzyl alcohol. The 2,3,5, 6-tetrafluorobenzoyl chloride is prepared by reacting 2,3,5, 6-tetrafluorobenzoic acid with thionyl chloride, and the process steps are more than one step of directly using the 2,3,5, 6-tetrafluorobenzoic acid as a raw material.
And a fourth route: 2,3,5, 6-tetrafluorobenzyl alcohol is prepared by taking 2,3,5, 6-tetrafluoro methyl benzoate as a raw material. In organic synthesis 2005,25,1125, sodium borohydride is used as a raw material to reduce methyl 2,3,5, 6-tetrafluorobenzoate under the catalysis of elemental iodine to obtain 2,3,5, 6-tetrafluorobenzyl alcohol. The reaction conditions are mild, but besides a large amount of sodium borohydride, a large amount of expensive iodine simple substance is used.
Route five: 1,2,4, 5-tetrafluorobenzene is used as a raw material to prepare 2,3,5, 6-tetrafluorobenzyl alcohol. CN113292399 reports that 1,2,4, 5-tetrafluorobenzene and carbon tetrachloride are subjected to Friedel-crafts reaction to obtain 2,3,5, 6-tetrafluorotrichlorotoluene, then the 2,3,5, 6-tetrafluorotrichlorotoluene is subjected to catalytic hydrolysis to obtain 2,3,5, 6-tetrafluorobenzoyl chloride, the 2,3,5, 6-tetrafluorobenzoyl chloride is subjected to Rosenmend reduction to obtain 2,3,5, 6-tetrafluorobenzaldehyde, and then the 2,3,5, 6-tetrafluorobenzaldehyde is subjected to Pt/MgAl treatment2O4Hydrogenating and reducing the catalyst to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol. The route uses the carbon tetrachloride which is difficult to obtain in the market and has higher market-scale yieldThe small 1,2,4, 5-tetrafluorobenzene uses expensive catalysts Pd and Pt, and hydrogen is used in the two reactions of the RosenMond reduction and the aldehyde reduction to alcohol, so that the large potential safety hazard exists. Thus, this route has advantages in terms of both cost and safety control.
Route six: the pentafluorophenylnitrile is used as a raw material to prepare the 2,3,5, 6-tetrafluorobenzyl alcohol. CN101462928 reports that pentafluorobenzonitrile is defluorinated under the action of active metal to obtain 2,3,5, 6-tetrafluorobenzonitrile, then the 2,3,5, 6-tetrafluorobenzylamine is obtained through high-pressure catalytic hydrogenation, and the 2,3,5, 6-tetrafluorobenzylamine is subjected to diazotization hydrolysis to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol. Or the pentafluorobenzonitrile is firstly subjected to catalytic hydrogenation to obtain pentafluorobenzylamine, the pentafluorobenzylamine is subjected to diazotization hydrolysis to obtain pentafluorobenzyl alcohol, and the pentafluorobenzyl alcohol is subjected to defluorination by using an active metal to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol. According to the method, the pentafluorophenylnitrile is used as a raw material, and the 2,3,5, 6-tetrafluorobenzyl alcohol is obtained through three-step reaction, however, the conversion of cyano-group into benzylamine can be realized only through catalytic hydrogenation under a high-pressure condition, and the hydrogen pressure is as high as 10-20 atm. The high-pressure hydrogenation has great potential safety hazard. The second conversion of benzylamine to benzyl alcohol is achieved under diazotization conditions, which results in a large volume of high salinity wastewater. In addition, when the active metal is used for defluorinating the pentafluorobenzyl alcohol, a large amount of active metal reacts with acid to generate hydrogen, so that explosion and fire easily occur.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a safe, controllable, green and environment-friendly preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol with low cost and high purity. The technical scheme of the invention is as follows:
a preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol is characterized by comprising the following steps:
step one, para-defluorination of pentafluorophenylnitrile: reacting pentafluorobenzonitrile serving as a raw material in a formic acid and sodium formate system in the presence of a catalyst to obtain 2,3,5, 6-tetrafluorobenzonitrile;
second step, Stephen reduction: reducing 2,3,5, 6-tetrafluorobenzonitrile in an ether solvent containing hydrogen chloride in the presence of tin dichloride to obtain 2,3,5, 6-tetrafluorobenzaldehyde;
thirdly, borohydride reduction: 2,3,5, 6-tetrafluorobenzaldehyde is reduced by borohydride in an alcohol-containing solvent to obtain 2,3,5, 6-tetrafluorobenzyl alcohol.
The reaction equation is expressed as:
further, in the technical scheme, the first step is to add pentafluorobenzonitrile and sodium formate dihydrate into 85% formic acid, heat the mixture, and then add a catalyst for reaction; after the reaction, recovering the catalyst and formic acid; adding water and extracting water phase with chlorine-containing solvent; the organic phase is subjected to reduced pressure distillation after recovering the chlorine-containing solvent at normal pressure to obtain the 2,3,5, 6-tetrafluoronitrile.
Further, in the technical scheme, in the first step, the catalyst is selected from Pd/C or Pt/C, and the content is 0.1-20%; the mass ratio of the catalyst to the pentafluorophenylnitrile is 0.01-1: 1.
further, in the above technical scheme, in the first step, the mass ratio of formic acid to pentafluorophenylnitrile is 5-50: 1; the mass ratio of sodium formate to pentafluorophenylnitrile is 1-20: 1; the reaction temperature is 50-80 ℃.
Further, in the above technical scheme, the second step is to introduce dry hydrogen chloride gas into the ether solvent cooled to-10 ℃ to 10 ℃ and saturate the hydrogen chloride gas; adding stannous dichloride, and then adding 2,3,5, 6-tetrafluorobenzonitrile in batches for reduction; after the reaction is finished, extracting by using a chlorine-containing solvent; recovering the chlorine-containing solvent from the organic phase at normal pressure, and then carrying out vacuum rectification to obtain the 2,3,5, 6-tetrafluorobenzaldehyde.
Further, in the above technical solution, in the second step, the ether solvent is selected from methyltetrahydrofuran, cyclopentyl methyl ether, ethylene glycol dimethyl ether or tert-butyl methyl ether; the mass ratio of the ether solvent to the 2,3,5, 6-tetrafluorobenzonitrile is 1-50: 1; the reaction temperature is 0-50 ℃.
Further, in the technical scheme, the third step of operation is that 2,3,5, 6-tetrafluorobenzaldehyde is dissolved in an alcohol-containing solvent, and borohydride is added in batches at the temperature of 0-50 ℃; after the reaction is finished, decompressing and recovering the solvent, adding water for acidification, and extracting feed liquid by using a chlorine-containing solvent; and recovering the chlorine-containing solvent from the organic phase at normal pressure, and carrying out vacuum rectification to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol.
Further, in the above technical scheme, in the third step, the borohydride is sodium borohydride, potassium borohydride or lithium borohydride; the molar ratio of borohydride to 2,3,5, 6-tetrafluorobenzaldehyde is 0.25-10: 1.
further, in the above technical solution, in the third step, the alcohol solvent is selected from methanol, ethanol or isopropanol, and the alcohol-containing solvent is an alcohol solvent or a mixed solvent of the alcohol solvent and toluene, dichloromethane.
Further, in the above technical solution, the chlorine-containing solvent is selected from dichloromethane, chloroform or 1, 2-dichloroethane.
Advantageous effects of the invention
The invention provides a preparation process of high-efficiency 2,3,5, 6-tetrafluorobenzyl alcohol, which takes pentafluorophenylnitrile as an initial material, and aldehyde is reduced into alcohol through palladium-carbon para-defluorination, Stephen reduction and sodium borohydride to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol. Pentafluoronitrile is available in the market and has already formed a large production scale. The pentafluorobenzonitrile is subjected to para-position defluorination in a formic acid and sodium formate system by adopting 5 percent Pd/C to obtain the 2,3,5, 6-tetrafluorobenzonitrile, and has better selectivity. Stephen reduction refers to the conversion of a cyano group to an aldehyde group by reduction with stannous dichloride in methyltetrahydrofuran hydrogen chloride solution. The tin salt used in the Stephen reduction can be recovered in the form of a tin oxide precipitate, thereby reducing environmental pollution. And reducing the 2,3,5, 6-tetrafluorobenzaldehyde in methanol by using sodium borohydride or potassium borohydride to obtain tetrafluorobenzyl alcohol. The sodium borohydride is less in dosage when the aldehyde is converted into the alcohol by the sodium borohydride, so that the process has a strong cost advantage.
The preparation process of the efficient 2,3,5, 6-tetrafluorobenzyl alcohol provided by the invention has the advantages of easily obtained starting materials, short steps, minimum consumption of sodium borohydride, small environmental pollution and no high-risk reaction.
Detailed Description
Example 1
A3L reactor was charged with 2000g of 85% formic acid and 100g of pentafluorophenylnitrile (0.518 mol). 539g of sodium formate dihydrate were added with stirring. Heating to 50-60 deg.C and adding 6.3g 5% Pd/C (dry basis); heating to 70-80 ℃ for reaction for 5 hours. The end point of the reaction is defined when the starting material remains less than 1.0%. Cooling to 20-30 deg.C, and filtering. The filtrate was concentrated under reduced pressure by means of a water pump. Concentrate to dryness, add 500g of water to the kettle and stir. The aqueous phase was extracted 2 times with 400g of dichloromethane. The organic phase was freed from dichloromethane at normal pressure and distilled under reduced pressure to give 78.9g of 2,3,5, 6-tetrafluorobenzonitrile in 87% yield and 99.4% purity.
Example 2
A3L reactor was charged with 2000g of 85% formic acid and 100g of pentafluorophenylnitrile (0.518 mol). 539g of sodium formate dihydrate were added with stirring. Heating to 50-60 deg.C and adding 3.2g 10% Pd/C (dry basis); the temperature is increased to 70-80 ℃ for reaction for 6 hours. The end point of the reaction is when the starting material remains less than 1.0%. Cooling to 20-30 deg.C, and filtering. The filtrate was concentrated under reduced pressure by means of a water pump. Concentrate to dryness, add 500g of water to the kettle and stir. The aqueous phase was extracted 2 times with 400g of dichloromethane. The organic phase was subjected to normal pressure recovery of methylene chloride and vacuum distillation to give 77.1g of 2,3,5, 6-tetrafluorobenzonitrile in 85% yield and 99.0% purity.
Example 3
250g of 2-methyltetrahydrofuran was added to the dry reactor and stirred. And cooling the ice water to 0-10 ℃, and introducing dry hydrogen chloride gas. And (5) detecting the bottle opening by using a wet pH test paper, and stopping introducing the hydrogen chloride when the pH test paper rapidly turns red. 81.2g of stannous dichloride (0.428mol) are added and stirred for 1 hour. 50g of 2,3,5, 6-tetrafluorobenzonitrile (0.2856mol) were added in portions and the reaction was incubated for 5 hours. The end point of the reaction is when the starting material remains less than 1.0%. Adding water for hydrolysis. The organic phase was washed with water. After recovering 2-methyltetrahydrofuran from the organic phase at normal pressure, carrying out reduced pressure distillation to obtain 48.2g of 2,3,5, 6-tetrafluorobenzaldehyde, wherein the purity is 98.3 percent, and the yield is 94.7 percent.
Example 4
400g of tert-butyl methyl ether was added to the dry reaction vessel and stirred. And cooling the ice water to-10 ℃, and introducing dry hydrogen chloride gas. And (5) detecting the bottle opening by using a wet pH test paper, and stopping introducing the hydrogen chloride when the pH test paper rapidly turns red. 81.2g of stannous dichloride (0.428mol) are added and stirred for 1 hour. 50g of 2,3,5, 6-tetrafluorobenzonitrile (0.2856mol) were added in portions and the reaction was incubated for 5 hours. The end point of the reaction is when the starting material remains less than 1.0%. Adding water for hydrolysis. The organic phase was washed with water. After recovering tert-butyl methyl ether from the organic phase at normal pressure, carrying out reduced pressure distillation to obtain 46.3g of 2,3,5, 6-tetrafluorobenzaldehyde, wherein the purity is 98.8 percent, and the yield is 91 percent.
Example 5
400g of methanol was added to a 1L reactor, and stirring was started. 200g of 2,3,5, 6-tetrafluorobenzaldehyde (1.123mol) are added. 17.85g of sodium borohydride (0.47mol) are added in portions, the temperature being controlled between 30 and 40 ℃. After the addition of sodium borohydride, the reaction was continued with stirring for 1 hour. The reaction solution was examined, and the reaction was completed when 1.0% of the starting material remained. After recovering methanol under reduced pressure, the temperature is reduced to 15-25 ℃, and hydrochloric acid is added to adjust the pH value to 3-4. When the material is pasty and the internal temperature is 35-40 ℃, stopping distilling. 200g of water were added to the reaction kettle. Cooling to 10-20 deg.C, adding 400g dichloromethane, and extracting. Standing for layering, recovering dichloromethane from the organic phase at normal pressure, and distilling under reduced pressure to obtain 184g of 2,3,5, 6-tetrafluorobenzyl alcohol, wherein the yield is 91.0%, and the purity is 99.2%.
Example 6
400g of methanol was added to a 1L reactor, and stirring was started. 200g of 2,3,5, 6-tetrafluorobenzaldehyde (1.123mol) are added. 32.4g of potassium borohydride (0.6mol) are added in portions at a temperature of between 30 and 40 ℃. After the addition of potassium borohydride, the reaction was continued for 1 hour with stirring. The reaction solution was examined, and the reaction was completed when 1.0% of the starting material remained. After recovering methanol under reduced pressure, the temperature is reduced to 15 to 25 ℃, and hydrochloric acid is added to adjust the pH to 3-4. When the material is pasty and the internal temperature is 35-40 ℃, stopping distilling. 200g of water were added to the reaction kettle. Cooling to 10-20 deg.C, adding 400g dichloromethane, and extracting. Standing and layering. The organic phase recovers the dichloromethane under normal pressure, and is distilled under reduced pressure to obtain 183g of 2,3,5, 6-tetrafluorobenzyl alcohol, the yield is 90.0 percent, and the purity is 99.3 percent.
Example 7
A3000L reactor was charged with 1800kg of 85% formic acid and 100kg of pentafluorophenylnitrile (518 mol). 539kg of sodium formate dihydrate were added with stirring. Heating to 50-60 deg.C, 6.3kg of 5% Pd/C (dry basis) was added. The temperature is increased to 70-80 ℃ for reaction for 5 hours. The end point of the reaction is when the starting material remains less than 1.0%. Cooling to 20-30 deg.C, and filtering. The filtrate was concentrated under reduced pressure by means of a water pump. Concentrating to dryness, adding 500kg of water into the kettle, and stirring. The aqueous phase was extracted 2 times with 400kg of dichloromethane. The organic phase was subjected to normal pressure recovery of methylene chloride and vacuum distillation to give 80.1kg of 2,3,5, 6-tetrafluorobenzonitrile in a yield of 88.3% and a purity of 99.3%.
Example 8
220kg of 2-methyltetrahydrofuran was added to the dry reaction vessel and stirred. Cooling the ice water to 0-10 ℃, and introducing dry hydrogen chloride gas. And (5) detecting the bottle opening by using a wet pH test paper, and stopping introducing the hydrogen chloride when the pH test paper rapidly turns red. 81.2kg of stannous dichloride (428mol) were added and stirred for 1 hour. 50kg of 2,3,5, 6-tetrafluorobenzonitrile (285.6mol) were added in portions and the reaction was incubated for 5 hours. The end point of the reaction is when the starting material remains less than 1.0%. Hydrolysis was carried out with water and the organic phase was washed with water. The organic phase is decompressed and distilled after recovering 2-methyltetrahydrofuran under normal pressure to obtain 48.6kg of 2,3,5, 6-tetrafluorobenzaldehyde. Purity 98.3% and yield 95.5%.
Example 9
780kg of methanol was added to a 2000L reactor, and stirring was started. 400kg of 2,3,5, 6-tetrafluorobenzaldehyde (2.246kmol) are added. 64.8kg of potassium borohydride (1.2kmol) are added in portions, the temperature being controlled between 30 and 40 ℃. After the potassium borohydride is added, the reaction is continued to be stirred for 2 hours. The reaction solution was examined, and the reaction was completed when 1.0% of the starting material remained. After recovering methanol under reduced pressure, the temperature was reduced to 15 to 25 ℃ and hydrochloric acid was added to adjust the pH to 3 to 4. When the material is pasty and the internal temperature is 35-40 ℃, stopping distillation. 380kg of water was added to the reaction kettle. Cooling to 10-20 deg.C, and extracting with 800kg dichloromethane. Standing for layering, recovering dichloromethane from the organic phase at normal pressure, and distilling under reduced pressure to obtain 369.5kg of 2,3,5, 6-tetrafluorobenzyl alcohol, wherein the yield is 90.9%, and the purity is 99.2%.
The foregoing embodiments have described the general principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the present invention, and that various changes and modifications may be made without departing from the scope of the principles of the present invention, and the invention is intended to be covered by the appended claims.
Claims (10)
1. A preparation process of 2,3,5, 6-tetrafluorobenzyl alcohol is characterized by comprising the following steps:
Step one, para-defluorination of pentafluorophenylnitrile: reacting pentafluorobenzonitrile serving as a raw material in a system of formic acid and sodium formate in the presence of a catalyst to obtain 2,3,5, 6-tetrafluorobenzonitrile;
second step, Stephen reduction: reducing 2,3,5, 6-tetrafluorobenzonitrile in an ether solvent containing hydrogen chloride in the presence of tin dichloride to obtain 2,3,5, 6-tetrafluorobenzaldehyde;
thirdly, borohydride reduction: 2,3,5, 6-tetrafluorobenzaldehyde is reduced by borohydride in an alcohol-containing solvent to obtain 2,3,5, 6-tetrafluorobenzyl alcohol.
2. The process for preparing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1, wherein: the first step is that the pentafluorobenzonitrile and the sodium formate dihydrate are added into 85 percent formic acid and then heated, and then the catalyst is added for reaction; after the reaction, recovering the catalyst and formic acid; adding water and extracting water phase with chlorine-containing solvent; the organic phase is subjected to reduced pressure distillation after recovering the chlorine-containing solvent at normal pressure to obtain the 2,3,5, 6-tetrafluoronitrile.
3. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1 or 2, characterized in that: in the first step, the catalyst is selected from Pd/C or Pt/C, and the content is 0.1% -20%; the mass ratio of the catalyst to the pentafluorophenylnitrile is 0.01-1: 1.
4. the process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1 or 2, characterized in that: in the first step, the mass ratio of formic acid to pentafluorophenylnitrile is 5-50: 1; the mass ratio of sodium formate to pentafluorophenylnitrile is 1-20: 1; the reaction temperature is 50-80 ℃.
5. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1, wherein: the second step is that dry hydrogen chloride gas is introduced into the ether solvent cooled to-10 ℃ to 10 ℃ and is saturated; adding stannous dichloride, and then adding 2,3,5, 6-tetrafluorobenzonitrile in batches for reduction; after the reaction is finished, extracting by using a chlorine-containing solvent; recovering the chlorine-containing solvent from the organic phase at normal pressure, and then carrying out vacuum rectification to obtain the 2,3,5, 6-tetrafluorobenzaldehyde.
6. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1 or 5, characterized in that: in the second step, the ether solvent is selected from methyltetrahydrofuran, cyclopentyl methyl ether, ethylene glycol dimethyl ether or tert-butyl methyl ether; the mass ratio of the ether solvent to the 2,3,5, 6-tetrafluorobenzonitrile is 1-50: 1; the reaction temperature is 0-50 ℃.
7. The process for preparing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1, wherein: dissolving 2,3,5, 6-tetrafluorobenzaldehyde in an alcohol-containing solvent, and adding borohydride in batches at the temperature of 0-50 ℃; after the reaction is finished, decompressing and recovering the solvent, adding water for acidification, and extracting feed liquid by using a chlorine-containing solvent; and recovering the chlorine-containing solvent from the organic phase at normal pressure, and carrying out vacuum rectification to obtain the 2,3,5, 6-tetrafluorobenzyl alcohol.
8. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1 or 7, characterized in that: in the third step, the borohydride is sodium borohydride, potassium borohydride or lithium borohydride; the molar ratio of borohydride to 2,3,5, 6-tetrafluorobenzaldehyde is 0.25-10: 1.
9. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 1 or 7, wherein: in the third step, the alcohol solvent is selected from methanol, ethanol or isopropanol, and the alcohol-containing solvent is an alcohol solvent or a mixed solvent of the alcohol solvent and toluene and dichloromethane.
10. The process for producing 2,3,5, 6-tetrafluorobenzyl alcohol according to claim 2, 5 or 7, characterized in that: the chlorine-containing solvent is selected from dichloromethane, chloroform or 1, 2-dichloroethane.
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| US6624336B1 (en) * | 1999-05-07 | 2003-09-23 | Showa Denko K.K. | Process for producing tetrafluorobenzenemethanols |
| CN101462928A (en) * | 2008-12-01 | 2009-06-24 | 浙江中欣化工股份有限公司 | Preparation of 2,3,5,6-tetrafluorobenzyl alcohol |
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| CN1349484A (en) * | 1999-05-07 | 2002-05-15 | 昭和电工株式会社 | Process for producing tetrafluoro benzenemethanols |
| US6624336B1 (en) * | 1999-05-07 | 2003-09-23 | Showa Denko K.K. | Process for producing tetrafluorobenzenemethanols |
| CN101462928A (en) * | 2008-12-01 | 2009-06-24 | 浙江中欣化工股份有限公司 | Preparation of 2,3,5,6-tetrafluorobenzyl alcohol |
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