Trifluoro pyruvic acid and process for preparing trifluoro pyruvic acid from trifluoroacetone

Abstract

This invention belongs to the field of organic chemical preparation technology, specifically relating to trifluoropyruvate and a method for preparing trifluoropyruvate from trifluoroacetone. The method for preparing trifluoropyruvate from trifluoroacetone according to this invention involves: firstly, dissolving trifluoroacetone in a chlorinating solvent, then adding a catalyst, introducing chlorine gas, and sealing the reaction, controlling the reaction temperature, and cooling to room temperature after the reaction to obtain a 1,1,1-trichlorotrifluoroacetone reaction mixture. An alkaline solution is added to initiate a hydrolysis reaction. After the reaction, the aqueous phase is separated, and the chlorinating solvent is reused. Acid is added to the aqueous phase to adjust the pH to 3-4 to obtain an aqueous trifluoropyruvate solution. Finally, extraction and slurrying are performed to obtain wet trifluoropyruvate, which is then purged with air to obtain pure trifluoropyruvate. The method for preparing trifluoropyruvate from trifluoroacetone provided by this invention uses readily available raw materials, has a stable process, high yield, and low cost. This invention also provides a trifluoropyruvate product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic chemical preparation, and particularly relates to trifluoro pyruvic acid and a method for preparing trifluoro pyruvic acid from trifluoro propionone. BACKGROUND

[0002] Trifluoro pyruvic acid , with a molecular formula of CF3COCOOH and a molecular weight of 142.034, is an important fluorine-containing fine chemical and an organic synthesis intermediate. Its molecular structure contains both a highly electronegative trifluoromethyl group and a highly active alpha-keto acid functional group, making the compound have a wide application prospect in the fields of medicine, pesticide and advanced materials. In particular, trifluoro pyruvic acid is a key raw material for synthesizing a series of high-value trifluoro pyruvic acid ester compounds. Among them, trifluoro pyruvic acid methyl ester (CF3COCOOCH3) as an important derivative can be used to prepare low-temperature lithium ion battery electrolyte with excellent performance. Such electrolyte can significantly improve the ionic conductivity and cycle performance of the battery in a low-temperature environment, and is one of the hot research directions of current electrolyte development. Therefore, developing an efficient, economical and environmentally friendly synthesis process of trifluoro pyruvic acid is of great significance to meet the needs of the downstream industry, especially the new energy industry.

[0003] Currently, the synthesis route of trifluoro pyruvic acid mainly relies on multi-step conversion of trifluoro lactic acid or other high-valence fluorine-containing intermediates as raw materials. These methods generally have problems such as complicated steps, low total yield, use of expensive or toxic oxidizing agents (such as potassium permanganate, dichromate, etc.) and generation of a large amount of fluorine-containing wastewater, resulting in high production cost and great environmental pressure, which limits its large-scale industrial production.

[0004] Trifluoro propionone (CF3COCH3) as a relatively easy-to-obtain and low-cost fluorine-containing basic raw material is an ideal precursor for preparing trifluoro pyruvic acid. By oxidizing the methyl group of trifluoro propionone, the target product can be obtained in one step or simply in theory. However, due to the strong electron-withdrawing effect of the trifluoromethyl group, the C-H bond adjacent to it has high energy and the reactivity is inhibited. At the same time, under strong oxidation conditions, the target product trifluoro pyruvic acid and its alpha-keto acid structure itself are prone to over-oxidation, decarboxylation and other side reactions, leading to product decomposition and yield reduction. Therefore, developing a method that can efficiently and selectively oxidize trifluoro propionone with good atom economy and environmental friendliness has become a technical problem to be solved in the field. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a method for preparing trifluoro pyruvic acid from trifluoro propionone, which is easy to obtain, stable in process, high in yield and low in cost. The present application also provides a trifluoro pyruvic acid product.

[0006] The method for preparing trifluoroacetonic acid from trifluoroacetone comprises the following steps: firstly, dissolving trifluoroacetone into a chlorinated solvent, then adding a catalyst, passing in chlorine and sealing the reaction, controlling the reaction temperature, lowering the temperature to room temperature after the reaction is completed, obtaining a 1,1,1-trichlorotrifluoroacetone reaction mixture, adding a lye to perform a hydrolysis reaction, separating the water phase after the reaction is completed, continuously using the chlorinated solvent, continuously adding acid to the water phase to adjust the pH to 3-4 to obtain a trifluoroacetonic acid aqueous solution, and finally performing extraction and beating to obtain wet trifluoroacetonic acid, and performing air blowing to obtain pure trifluoroacetonic acid.

[0007] The chlorinated solvent is trichlorobenzene, o-dichlorobenzene, p-dichlorobenzene or m-dichlorobenzene.

[0008] The catalyst is pyridine or benzyl ethyl ammonium chloride, and the molar amount of the catalyst is 4.9%-10% of trifluoroacetone. Preferably, the catalyst is pyridine.

[0009] The chlorine is passed in to control the reaction temperature to 100-150 DEG C, and the reaction time is 8-14 h.

[0010] The molar ratio of chlorine to trifluoroacetone is 2:1-5:1.

[0011] The lye is an aqueous solution of sodium hydroxide or potassium hydroxide, and the mass concentration is 25%-35%, and the molar ratio of the lye to trifluoroacetone is 1.5:1-4:1.

[0012] The acid is added to the water phase to adjust the pH, and the acid is 2 mol / L-5 mol / L hydrochloric acid, sulfuric acid or phosphoric acid.

[0013] The extraction solvent is ethyl acetate or dichloromethane. Preferably, the extraction solvent is ethyl acetate.

[0014] The solvent for beating is n-hexane, cyclohexane or petroleum ether.

[0015] A trifluoroacetonic acid is obtained by the method for preparing trifluoroacetonic acid from trifluoroacetone.

[0016] The synthetic route of the application is as follows:

[0017] .

[0018] Specifically, the method for preparing trifluoropyruvic acid from trifluoroacetone includes the following steps: adding 200 mL of chlorinated solvent to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 3.3-6.6 mmol of catalyst, then introducing 133.4-333.5 mmol of chlorine gas and sealing the reactor for reaction, heating to 100-150°C and stirring for 8-14 hours, stopping stirring after the reaction is complete, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery. A 1,1,1-trichlorotrifluoroacetone reaction mixture was obtained. Then, a 25%-35% sodium hydroxide aqueous solution (100.05-266.8 mol of sodium hydroxide) was added to the mixture, and the mixture was subjected to a hydrolysis reaction with vigorous stirring at 40°C for 5 hours. After the reaction was completed, the aqueous phase was extracted and separated. The pH was adjusted to 3-4 by adding 2 mol / L acid to obtain an aqueous solution of trifluoropyruvate. After extraction with an extraction solvent, the chlorinating solvent was removed by evaporation, and the solution was pulped with a pulping solvent to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain pure trifluoropyruvate.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) This invention provides a novel synthetic route using inexpensive and readily available trifluoroacetone as a starting material, effectively overcoming the dependence of existing technologies on expensive fluorine-containing intermediates. Existing technical routes are vague and rely on expensive raw materials such as trifluorolactic acid, with cumbersome steps; while this invention utilizes trifluoroacetone, a relatively readily available raw material, to synthesize the target product through a simple two-step method of chlorination followed by hydrolysis, with a stable source of raw materials and significantly reduced production costs.

[0021] (2) The process design of this invention is reasonable. By precisely controlling the chlorination and hydrolysis conditions, it successfully solves the technical problems of methyl oxidation inertness caused by the strong electron-withdrawing effect of trifluoromethyl and the easy over-oxidation and decarboxylation of α-keto acids. This method has high reaction selectivity, ideal conversion rate and yield, and the chlorination solvent and catalyst used can be recycled and reused, reducing material consumption. The process is stable and more suitable for large-scale industrial production.

[0022] (3) This invention avoids the use of expensive and toxic traditional oxidants such as potassium permanganate and dichromate. It uses chlorine as the oxidation medium, which is more atom-economical. Furthermore, through process design, it achieves partial recovery of chlorine and recycling of solvents, thereby reducing the generation of fluoride-containing wastewater from the source. Its environmental friendliness is significantly better than that of the prior art. Attached Figure Description

[0023] Figure 1 The gas chromatogram of ethyl trifluoropyruvate prepared in Example 1. Detailed Implementation

[0024] The invention will be further described below with reference to specific embodiments. The calculation of material dosage and subsequent yield is based on moles.

[0025] Example 1

[0026] The method for preparing trifluoropyruvic acid from trifluoroacetone includes the following steps: adding 200 mL of trichlorobenzene to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 6.6 mmol of pyridine, then introducing 333.5 mmol of chlorine gas and sealing the reactor for reaction, heating to 150 °C and stirring for 8 hours, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery, to obtain 1,1,1-trichlorotrifluoroacetic acid. The ketone reaction mixture was then added to the mixture, followed by the addition of 35% sodium hydroxide (133.4 mmol). The mixture was stirred vigorously at 40°C for 5 hours to carry out hydrolysis. After the reaction was completed, the aqueous phase was extracted and separated. The pH was adjusted to 3-4 with 3 mol / L sulfuric acid to obtain an aqueous solution of trifluoropyruvate. After extraction with ethyl acetate, the solvent was evaporated, and the solution was slurried with cyclohexane to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain 8.902 g of trifluoropyruvate. The purity was calculated to be 99.5%, and the yield was calculated to be 93.5%.

[0027] The specific steps for the detection of trifluoropyruvate are as follows: Take 1.42 g of the prepared trifluoropyruvate and add it to a 50 mL mixture of ultra-dry dimethylformamide, HATU (10.5 mmol), and 4-dimethylaminopyridine (5.5 mmol). Add 10.1 mmol of ultra-dry ethanol and stir at room temperature for 4 h. Distill off ethyl trifluoropyruvate, and obtain 1.695 g of white solid ethyl trifluoropyruvate by vacuum drying. Then, send the obtained solid for liquid chromatography analysis; the purity is 99.8%. Figure 1 As shown, the purity and yield of trifluoropyruvate were calculated according to the following formulas. The purity was determined by derivatization: the actual molar amount of trifluoropyruvate involved = (weight of ethyl trifluoropyruvate / 170.09) × purity of ethyl trifluoropyruvate, purity = actual molar amount of trifluoropyruvate involved / theoretical molar amount of trifluoropyruvate; yield = (weight of obtained trifluoropyruvate × purity / 142.034) ÷ molar amount of trifluoroacetone.

[0028] Example 2

[0029] The method for preparing trifluoropyruvic acid from trifluoroacetone includes the following steps: adding 200 mL of o-dichlorobenzene to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 5.0 mmol of benzylethylammonium chloride, then introducing 133.4 mmol of chlorine gas and sealing the reactor for reaction, heating to 120°C and stirring for 12 h, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery, to obtain 1,1,1- The trichlorotrifluoroacetone reaction mixture was then subjected to hydrolysis with 25% potassium hydroxide (100.05 mol) for 5 hours under vigorous stirring at 40°C. After the reaction, the aqueous phase was extracted and separated. The pH was adjusted to 3-4 with 2 mol / L hydrochloric acid to obtain an aqueous solution of trifluoropyruvate. After extraction with ethyl acetate, the solvent was evaporated and the solution was slurried with cyclohexane to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain 8.777 g of trifluoropyruvate, with a purity of 99.3% and a yield of 92%. (The detection procedure for trifluoropyruvate was the same as in Example 1. 1.42 g of trifluoropyruvate sample was taken, and 1.693 g of ethyl trifluoropyruvate was obtained during the detection. The purity was measured to be 99.7% by gas chromatography.)

[0030] Example 3

[0031] The method for preparing trifluoropyruvic acid from trifluoroacetone includes the following steps: adding 200 mL of o-dichlorobenzene to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 3.3 mmol of pyridine, then introducing 133.4 mmol of chlorine gas and sealing the reactor for reaction, heating to 120°C and stirring for 14 h, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery to obtain 1,1,1-trichlorotrifluoro The acetone reaction mixture was then added to the mixture, followed by the addition of 133.4 mmol of 35% sodium hydroxide. The mixture was vigorously stirred at 40°C for 5 hours to carry out a hydrolysis reaction. After the reaction, the aqueous phase was extracted and separated. The pH was adjusted to 3-4 with 5 mol / L sulfuric acid to obtain an aqueous solution of trifluoropyruvate. This solution was extracted with dichloromethane, the solvent was evaporated, and the solution was slurried with n-hexane to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain 8.864 g of trifluoropyruvate, with a purity of 99.4% and a yield of 93%. (The detection procedure for trifluoropyruvate was the same as in Example 1. 1.42 g of trifluoropyruvate sample was taken, and 1.695 g of ethyl trifluoropyruvate was obtained during the detection. The purity was measured to be 99.7% by gas chromatography.)

[0032] Example 4

[0033] The method for preparing trifluoropyruvic acid from trifluoroacetone includes the following steps: adding 200 mL of o-dichlorobenzene to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 6.6 mmol of pyridine, then introducing 333.5 mmol of chlorine gas and sealing the reactor for reaction, heating to 100°C and stirring for 14 h, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery, to obtain 1,1,1-trichlorotrifluoroacetic acid. The ketone reaction mixture was then added to the mixture, followed by the addition of 35% sodium hydroxide (266.8 mmol). The mixture was vigorously stirred at 40°C for 5 hours to carry out a hydrolysis reaction. After the reaction, the aqueous phase was extracted and separated. 2 mol / L phosphoric acid was added to adjust the pH to 3-4, yielding an aqueous solution of trifluoropyruvate. This solution was extracted with dichloromethane, the solvent was evaporated, and the solution was slurried with petroleum ether to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain 8.704 g of trifluoropyruvate, with a purity of 98.5% and a yield of 90.5%. (The detection procedure for trifluoropyruvate was the same as in Example 1. 1.42 g of trifluoropyruvate sample was taken, and 1.677 g of ethyl trifluoropyruvate was obtained during detection. The purity was measured to be 99.85% by gas chromatography.)

[0034] Comparative Example 1

[0035] The preparation method of the aforementioned trifluoroacetic acid includes the following steps: adding 200 mL of trichlorobenzene to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 6.6 mmol of pyridine, then introducing 333.5 mmol of chlorine gas and sealing the reactor for reaction, heating to 60 °C and stirring for 8 hours, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery, to obtain 1,1,1-trichlorotrifluoroacetone. The mixture was then added with 35% sodium hydroxide (133.4 mmol), and the mixture was vigorously stirred at 40°C for 5 hours for hydrolysis. After the reaction, the aqueous phase was extracted and separated. 2 mol / L sulfuric acid was added to adjust the pH to 3-4 to obtain an aqueous solution of trifluoropyruvate. After extraction with ethyl acetate, the solvent was evaporated, and the solution was slurried with cyclohexane to obtain wet trifluoropyruvate. Finally, the solution was dried by air purging to obtain 2.6316 g of trifluoropyruvate, with a purity of 72% and a yield of 20%. (The detection procedure for trifluoropyruvate was the same as in Example 1. 1.42 g of trifluoropyruvate sample was taken, and 1.231 g of ethyl trifluoropyruvate was obtained during detection. The purity was measured to be 99.4% by gas chromatography.)

[0036] Comparative Example 2

[0037] The preparation method of the aforementioned trifluoropyruvate includes the following steps: 200 mL of trichlorobenzene is added to a 500 mL stainless steel reactor equipped with a pressure gauge, followed by 66.7 mmol of trifluoroacetone. Then, 333.5 mmol of chlorine gas is introduced and the reaction is sealed. The temperature is raised to 60 °C and the reaction is stirred for 8 h. After the reaction is completed, stirring is stopped, and the temperature inside the reactor is cooled to room temperature through an external condenser. Excess chlorine gas is introduced into another gas tank for recovery, resulting in a 1,1,1-trichlorotrifluoroacetone reaction mixture. Then, 133.4 mmol of sodium hydroxide with a mass concentration of 35% is added to the above mixture, and the mixture is subjected to a hydrolysis reaction with vigorous stirring at 40 °C for 5 h. After the reaction is completed, the aqueous phase is extracted and separated. 2 mol / L sulfuric acid is added to adjust the pH to 3-4, resulting in an aqueous solution of trifluoropyruvate. After extraction with ethyl acetate, the solvent is evaporated, and the solution is slurried with cyclohexane to obtain wet trifluoropyruvate. Finally, the solution is dried by air purging to obtain 4.521 g of pure trifluoropyruvate, with a purity of 88% and a yield of 42%. (The detection procedure for trifluoropyruvate is the same as that in Example 1. 1.42g of trifluoropyruvate sample was taken, and 1.506g of ethyl trifluoropyruvate was obtained during the detection. The purity was 99.3% as determined by gas chromatography.)

[0038] Comparative Example 3

[0039] The method for preparing trifluoroacetic acid includes the following steps: adding 200 mL of chlorinated solvent to a 500 mL stainless steel reactor equipped with a pressure gauge, then adding 66.7 mmol of trifluoroacetone and 5.0 mmol of pyridine, then introducing 66.7 mmol of chlorine gas and sealing the reactor for reaction, heating to 120 °C and stirring for 10 h, stopping stirring after the reaction, cooling the reactor to room temperature using an external condenser, and transferring excess chlorine gas to another gas tank for recovery to obtain 1,1,1-trichlorotrifluoroacetone. The reaction mixture was then added to the mixture with 25% sodium hydroxide (1.334 mol). The mixture was vigorously stirred at 40°C for 5 hours to carry out the hydrolysis reaction. After the reaction, the aqueous phase was extracted and separated. 2 mol / L sulfuric acid was added to adjust the pH to 3-4, yielding an aqueous solution of trifluoropyruvate. This solution was extracted with ethyl acetate, the solvent was evaporated, and the solution was slurried with cyclohexane to obtain wet trifluoropyruvate. Finally, it was dried by air purging to obtain 6.853 g of pure trifluoropyruvate, with a purity of 94% and a yield of 68%. (The detection procedure for trifluoropyruvate was the same as in Example 1. 1.42 g of trifluoropyruvate sample was taken, and 1.606 g of ethyl trifluoropyruvate was obtained during detection. The purity was measured to be 99.5% by gas chromatography.)

Claims

1. A method for preparing trifluoropyruvic acid from trifluoroacetone, characterized in that: First, trifluoroacetone is dissolved in a chlorinated solvent, then a catalyst is added, chlorine gas is introduced and the reaction is sealed, the reaction temperature is controlled, and after the reaction is completed, the temperature is lowered to room temperature to obtain a 1,1,1-trichlorotrifluoroacetone reaction mixture. Alkali solution is added to carry out a hydrolysis reaction. After the reaction is completed, the aqueous phase is separated, the chlorinated solvent is reused, and acid is added to the aqueous phase to adjust the pH to 3-4 to obtain an aqueous solution of trifluoropyruvic acid. Finally, the solution is extracted and slurried to obtain wet trifluoropyruvic acid, and then purified by air purging to obtain pure trifluoropyruvic acid. The chlorinated solvent is trichlorobenzene, o-dichlorobenzene, p-dichlorobenzene, or m-dichlorobenzene; The catalyst is pyridine or benzylethylammonium chloride, and the molar amount of the catalyst is 4.9% to 10% of trifluoroacetone.

2. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 1, characterized in that: Chlorine gas is introduced to control the reaction temperature at 100~150℃, and the reaction time is 8~14h.

3. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 1, characterized in that: The molar ratio of chlorine to trifluoroacetone is 2:1 to 5:

1.

4. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 1, characterized in that: The alkaline solution is an aqueous solution of sodium hydroxide and potassium hydroxide with a mass concentration of 25% to 35%, and the molar ratio of the alkali to trifluoroacetone is 1.5:1 to 4:

1.

5. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 1, characterized in that: Add acid to the aqueous phase to adjust the pH. The acid used is hydrochloric acid, sulfuric acid, or phosphoric acid with a concentration of 2 mol / L to 5 mol / L.

6. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 1, characterized in that: The extraction solvent used is ethyl acetate or dichloromethane.

7. The method for preparing trifluoropyruvic acid from trifluoroacetone according to claim 6, characterized in that: The solvent used for pulping is n-hexane, cyclohexane, or petroleum ether.

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