A method for synthesizing 1,1,1-trifluoro-2,4-pentanedione

Abstract

The present invention relates to a kind of synthesis method of 1,1,1-trifluoro-2,4-pentanedione, belong to the technical field of pesticides. The synthesis method is: toluene and TBAB are added to a reactor, and then trifluoroacetic acid ethyl ester is added. After stirring, an aqueous solution of alkali and acetone are added dropwise to the reaction system, and 1,1,1-trifluoro-2,4-pentanedione is obtained after insulation reaction; wherein, the alkali is a kind of sodium hydroxide or potassium hydroxide. The present invention adopts an inorganic base with stronger safety and operability to replace an organic base with higher danger and stronger alkalinity, and the reaction conditions are mild, the reaction yield is high, and the three wastes produced are few. The raw materials used are common raw materials, the price is cheap, the raw materials are easy to obtain, the process operation is simple, and it is easy to realize industrial conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticides, and in particular to a method for synthesizing 1,1,1-trifluoro-2,4-pentanedione. Background Art

[0002] 1,1,1-Trifluoro-2,4-pentanedione is a very important organic intermediate with a wide range of applications in many fields, such as the synthesis of pesticides, medicines, and luminescent materials. The existing methods for synthesizing 1,1,1-trifluoro-2,4-pentanedione mainly include the following routes:

[0003] (1) The more conventional synthesis method mainly uses ethyl trifluoroacetate and acetone as raw materials, and prepares 1,1,1-trifluoro-2,4-pentanedione in the presence of a strong base such as sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, or sodium hydride. A graduate thesis from Tianjin University of Science and Technology titled "Synthesis of Fluthiazolylpyrrolidone" reported that the yield was only 38%. The advantage of this method is that the raw materials are readily available, but the disadvantage is that ethyl trifluoroacetate and acetone are extremely unstable in the system and are prone to self-hydrolysis and condensation reactions. Therefore, this method has a low yield, high cost, and is not suitable for industrialization.

[0004] (2) In addition to conventional synthesis methods, some other raw materials are used for synthesis. Chinese patent CN110563568B discloses a method for preparing 1,1,1-trifluoro-2,4-pentanedione, which uses 1,1,1-trifluoro-4-hydrocarbyloxypent-3-en-2-one and carboxylic acid to obtain 1,1,1-trifluoro-2,4-pentanedione with a yield of over 90%. The reaction equation is as follows:

[0005]

[0006] The advantage of this method is that the yield is high, but the disadvantage is that the raw materials are expensive and cannot be obtained in large quantities, making industrial production impossible. Summary of the Invention

[0007] To address the low yield, high cost, and unfavorable industrial production issues of existing 1,1,1-trifluoro-2,4-pentanedione synthesis methods, the present invention provides a method for synthesizing 1,1,1-trifluoro-2,4-pentanedione. Using commonly used industrial reagents, ethyl trifluoroacetate and acetone, and sodium hydroxide or potassium hydroxide as a catalyst, the method effectively avoids hydrolysis and condensation reactions of the raw materials themselves and significantly improves the reaction yield, effectively resolving the high cost, low yield, and limited availability of raw materials issues of existing processes.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for synthesizing 1,1,1-trifluoro-2,4-pentanedione, wherein the reaction formula is as follows:

[0010]

[0011] The synthesis method comprises the following steps: adding toluene and TBAB (tetrabutylammonium bromide) to a reactor, then adding ethyl trifluoroacetate, stirring evenly, adding an aqueous alkali solution and acetone dropwise to the reaction system, and then heat-retaining the reaction to obtain 1,1,1-trifluoro-2,4-pentanedione;

[0012] The alkali is sodium hydroxide or potassium hydroxide.

[0013] Furthermore, the concentration of the aqueous alkali solution is 38% to 42%.

[0014] Furthermore, the amount of toluene used is 3-5 g / g based on the amount of ethyl trifluoroacetate used.

[0015] Furthermore, the amount of TBAB used is 0.01 to 0.03 g / g based on the amount of ethyl trifluoroacetate.

[0016] Furthermore, the amount of the base used is 1 to 3 mol / mol based on the amount of ethyl trifluoroacetate used.

[0017] Furthermore, the amount of acetone used is 1.5 to 3.5 mol / mol based on the amount of ethyl trifluoroacetate used.

[0018] Further, toluene and TBAB were added and the temperature was lowered to 5-20°C.

[0019] Furthermore, the heat preservation reaction time is 5 to 12 hours.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention adopts a dual solvent system, placing ethyl trifluoroacetate and alkali in different solvents, reducing the probability of collision between the two molecules and avoiding the self-condensation and hydrolysis reaction of ethyl trifluoroacetate;

[0022] (2) The double-drop method is adopted to reduce the time that acetone and alkali solution exist at the same time, and reduce the risk of side reactions of the raw materials themselves;

[0023] (3) Adding a phase transfer catalyst to catalyze the reaction can effectively ensure the smooth progress of the reaction;

[0024] (4) Using safer and more operable inorganic bases instead of more dangerous and alkaline organic bases, the reaction conditions are mild, the reaction yield is high, and less three wastes are generated;

[0025] (5) The raw materials used are common raw materials, which are cheap and easy to obtain. The process operation is simple and easy to achieve industrial transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 It is the gas chromatogram of the product of Example 1.

[0028] Figure 2 It is the gas chromatogram of the product of Comparative Example 1. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for synthesizing 1,1,1-trifluoro-2,4-pentanedione is as follows:

[0032] To a 250 mL four-necked flask, 60 g of toluene, 0.2 g of TBAB, and 20 g (0.14 mol) of ethyl trifluoroacetate were added in sequence, the temperature was lowered to 5 ° C, and 12.3 g (0.21 mol) of acetone and 20.63 g (0.14 mol) of 38% potassium hydroxide solution were added dropwise. After the double addition was completed, the reaction was kept at 5 ° C for 12 h. After the reaction was completed, the liquid was separated, and the pH value of the aqueous phase was adjusted to 4.0 with 10% hydrochloric acid. Then, 18.86 g of 1,1,1-trifluoro-2,4-pentanedione was distilled out. The purity of the mixture was 98.5% by GC quantitative detection, and the yield was 86.1%.

[0033] The GC test results are shown in Table 1 and Figure 1 As shown, Figure 1 The peak at around 5 min is 1,1,1-trifluoro-2,4-pentanedione, and the peak at around 7 min is the internal standard.

[0034] Table 1 GC test results of Example 1 products

[0035] Peak Retention time min Normalized area Normalized area% 1 4.875 8923.3 0.0330 2 4.972 1045.0 0.0039 3 5.045 26996775.0 99.8504 4 6.815 1065.9 0.0039 5 6.962 29415.1 0.1088

[0036] Example 2

[0037] To a 250 mL four-necked flask, 80 g of toluene, 0.4 g of TBAB, and 20 g (0.14 mol) of ethyl trifluoroacetate were added in sequence, the temperature was lowered to 12 ° C, and 20.5 g (0.35 mol) of acetone and 28 g (0.28 mol) of 40% sodium hydroxide solution were added dropwise. After the double addition was completed, the reaction was kept at 12 ° C for 9 h. After the reaction was completed, the liquid was separated, and the pH value of the aqueous phase was adjusted to 4.0 with 10% hydrochloric acid. Then, 19.84 g of 1,1,1-trifluoro-2,4-pentanedione was distilled out. The purity of the product was 98.2% by GC quantitative detection, and the yield was 90.3%.

[0038] Example 3

[0039] To a 500 mL four-necked flask, 100 g of toluene, 0.6 g of TBAB, and 20 g (0.14 mol) of ethyl trifluoroacetate were added in sequence, the temperature was lowered to 20 ° C, and 28.7 g (0.49 mol) of acetone and 40 g (0.42 mol) of 42% sodium hydroxide solution were added dropwise. After the double addition was completed, the reaction was kept at 20 ° C for 5 h. After the reaction was completed, the liquid was separated, the pH value of the aqueous phase was adjusted to 4.0 with 10% hydrochloric acid, and then 19.48 g of 1,1,1-trifluoro-2,4-pentanedione was distilled out. The purity of the product was 98.0% by GC quantitative detection, and the yield was 88.5%.

[0040] Comparative Example 1

[0041] 22.7 g (0.13 mol) of a 30% sodium methoxide methanol solution was added to a 250 mL four-necked flask, the temperature was controlled at 25°C, and the mixture was stirred with a magnetic stirrer. Then, a mixture of 20 g (0.14 mol) of ethyl trifluoroacetate and 24.4 g (0.42 mol) of acetone was dropped into the sodium methoxide. After the reaction was completed, 5 g of water was added dropwise to the system, the pH value was adjusted to 4.0 with 10% hydrochloric acid, and then 7.0 g of 1,1,1-trifluoro-2,4-pentanedione was distilled out. The purity was 90.0% by GC quantitative detection, and the yield was 32.3%.

[0042] The GC test results are shown in Table 2 and Figure 2 As shown, Figure 2 The peak at around 5 min is 1,1,1-trifluoro-2,4-pentanedione, and the peak at around 7 min is the internal standard.

[0043] Table 2 GC quantitative detection results of the product of Comparative Example 1

[0044] Peak Retention time min Normalized area Normalized area% 1 4.870 8050.6 0.0289 2 4.966 803.8 0.0029 3 5.308 25225752.0 90.4944 4 5.177 44613.8 0.1600 5 5.809 5776.2 0.0207 6 6.062 1436.6 0.0052 7 6.809 26876.2 0.0964 8 6.944 34551.3 0.1239 9 9.234 37806.9 0.1356 10 9.567 68382.9 0.2453 11 16.425 2421423.5 8.6866

[0045] In Comparative Example 1, the system has no solvent and sodium methoxide is highly alkaline. When ethyl trifluoroacetate and acetone are added to the system at the same time, most of the acetone and ethyl trifluoroacetate undergo self-condensation before they have time to react, resulting in a low yield.

[0046] Comparative Example 2

[0047] To a 500 mL four-necked flask, 100 g of toluene, 0.6 g of TBAB, and 40 g of 42% sodium hydroxide solution were added in sequence, the temperature was lowered to 20 ° C, and a mixture of 40 g of 28.7 g (0.49 mol) of acetone and 20 g (0.14 mol) of ethyl trifluoroacetate was added dropwise. After the addition was completed, the mixture was kept at 20 ° C for 5 h. After the reaction was completed, the liquid was separated, the pH value of the aqueous phase was adjusted to 4.0 with 10% hydrochloric acid, and then 14.26 g of 1,1,1-trifluoro-2,4-pentanedione was distilled out. The purity was 95.0% by GC quantitative detection, and the yield was 62.8%.

[0048] Comparative Example 2 uses two mixed solvent systems, and the base is sodium hydroxide. However, the order of adding materials is different from that of the present invention. A portion of acetone and ethyl trifluoroacetate undergoes self-condensation before reacting, resulting in a low yield.

[0049] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for synthesizing 1,1,1-trifluoro-2,4-pentanedione, characterized in that: The reaction formula is as follows: ； The synthesis method comprises the following steps: adding toluene and TBAB to a reactor, then adding ethyl trifluoroacetate, stirring evenly, adding an aqueous alkali solution and acetone dropwise to the reaction system, and then heat-retaining the reaction to obtain 1,1,1-trifluoro-2,4-pentanedione; wherein the base is one of sodium hydroxide or potassium hydroxide; The concentration of the aqueous solution of alkali is 38% to 42%; The amount of base used is 1~3 mol / mol based on the amount of ethyl trifluoroacetate used.

2. The method for synthesizing 1,1,1-trifluoro-2,4-pentanedione according to claim 1, wherein The amount of toluene used is 3-5 g / g based on the amount of ethyl trifluoroacetate used.

3. The method for synthesizing 1,1,1-trifluoro-2,4-pentanedione according to claim 1, wherein The amount of TBAB used is 0.01-0.03 g / g based on the amount of ethyl trifluoroacetate.

4. The method for synthesizing 1,1,1-trifluoro-2,4-pentanedione according to claim 1, wherein The amount of acetone used is 1.5~3.5 mol / mol based on the amount of ethyl trifluoroacetate.

5. The method for synthesizing 1,1,1-trifluoro-2,4-pentanedione according to claim 1, wherein After adding toluene and TBAB, cool to 5~20℃.

6. The method for synthesizing 1,1,1-trifluoro-2,4-pentanedione according to claim 1, wherein The heat preservation reaction time is 5~12h.

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