Preparation method of 2, 3-dichloropyridine

Abstract

The invention discloses a preparation method of 2, 3-dichloropyridine, which is characterized in that in a solvent of C1-C4 aliphatic carboxylic acid, 2, 3, 6-trichloropyridine is dechlorinated under the catalysis of non-precious metal to obtain a target product. According to the preparation method provided by the invention, the C1-C4 aliphatic carboxylic acid which is cheap and easy to obtain is used as the solvent, and the non-precious metal is used as the catalyst, so that the reaction safety is greatly improved, and the material cost is greatly reduced.

Description

Technical Field

[0001] The present application relates to the field of organic synthesis, and in particular to a method for preparing 2,3-dichloropyridine. Background Art

[0002] As an important synthetic intermediate in pesticides and medicines, 2,3-dichloropyridine is mainly used in the synthesis of chlorantraniliprole. Therefore, with the gradual promotion of chlorantraniliprole, the demand for 2,3-dichloropyridine has increased significantly.

[0003] At present, in the known synthesis methods of 2,3-dichloropyridine, the reaction needs to be carried out under high pressure hydrogenation or using noble metals as catalysts, which is costly and has harsh synthesis conditions. For example, the synthesis methods provided by Chinese patents CN110759859A, CN112592313A and CN106518755A are to obtain 2,3-dichloropyridine by high pressure hydrogenation using 2,3,6-trichloropyridine or 2,3,4,6-tetrachloropyridine as raw materials. The above methods require the use of ligands, acid binding agents, catalysts, high pressure hydrogenation and other reaction conditions, and have the disadvantages of low reaction safety and poor selective elimination effect. Chinese patent CN106518754A provides a method for synthesizing 2,3-dichloropyridine. Although the method does not use a high-pressure hydrogenation method, it uses 2,3,6-trichloropyridine as a raw material, 10% Pd / C precious metal and menthene as catalysts, and reacts in a methanol solution to obtain a target product. This method uses precious metals for catalysis, which has the disadvantages of high cost and low selective elimination effect.

[0004] Therefore, based on the shortcomings of the above-mentioned existing 2,3-dichloropyridine synthesis method, it is very important to provide a low-cost synthesis method of 2,3-dichloropyridine with safer reaction conditions. Summary of the invention

[0005] In view of the problems existing in the prior art described above, the present application provides a method for preparing 2,3-dichloropyridine, in which 2,3,6-trichloropyridine is dechlorinated under the catalysis of non-precious metals in a solvent of C1-C4 fatty carboxylic acid to obtain the target product.

[0006] By adopting the above technical scheme, the preparation method provided by the present application uses C1-C4 fatty carboxylic acid as solvent and non-precious metal as catalyst. Compared with the high-pressure hydrogenation conditions used in the prior art, the method greatly improves the reaction safety, and compared with the prior art method using Pd / C precious metal and menthol as catalyst, the preparation method of the present application greatly reduces the material cost. Moreover, under the reaction conditions of the present application, the chlorine atom at the C-6 position of 2,3,6-trichloropyridine can be more accurately removed to accurately obtain the target product 2,3-dichloropyridine, and a higher yield is obtained, which provides a new idea for the preparation of 2,3-dichloropyridine and achieves relatively excellent results.

[0007] Preferably, the C1-C4 fatty carboxylic acid is one or more of formic acid, acetic acid, propionic acid and butyric acid.

[0008] In the above technical scheme, formic acid, acetic acid, propionic acid and butyric acid are all short-chain fatty carboxylic acids commonly found on the market. Compared with long-chain fatty carboxylic acids, short-chain fatty carboxylic acids are cheap, readily available and have stable properties. Therefore, they can save costs, achieve safe production and are particularly easy to industrialize.

[0009] Preferably, the non-precious metal is one or more of zinc powder, iron powder and copper powder.

[0010] By adopting the above technical scheme, compared with the prior art, the preparation method of the present application abandons precious metals and uses non-precious metals as catalysts. Zinc powder, iron powder and copper powder are relatively common on the market, which greatly reduces the production cost.

[0011] Preferably, the ratio of the 2,3,6-trichloropyridine, the non-precious metal and the C1-C4 fatty carboxylic acid is 4.3 g: (3-5) g: (30-50) mL.

[0012] Preferably, the reaction temperature is 130-150°C.

[0013] Preferably, the reaction time is 6 to 18 hours.

[0014] Preferably, the reaction time is 6 to 8 hours.

[0015] By adopting the above technical scheme, under the above reaction conditions, the catalytic effect can reach a better level, especially when the reaction time is 6 to 8 hours, not only the yield is higher, but the reaction process is also safer, and the short reaction time also greatly reduces the production cost.

[0016] Preferably, the non-precious metal is a mixture of copper powder and zinc powder, and the mass ratio of the copper powder to the zinc powder is (1-3):1.

[0017] Preferably, the C1-C4 fatty carboxylic acid is a mixed solvent of propionic acid and acetic acid, and the volume ratio of the propionic acid to the acetic acid is (2-3):1.

[0018] By adopting the above technical solution, under the above ratio, in a mixed acid solvent, using mixed non-precious metals as catalysts, the reaction can be made more complete, and the chlorine atom at the C-6 position of 2,3,6-trichloropyridine can be removed more accurately, thereby achieving a higher yield and accurately obtaining the target product 2,3-dichloropyridine.

[0019] In summary, this application has the following beneficial effects:

[0020] 1. The preparation method provided in the present application uses C1-C4 fatty carboxylic acid as a solvent and a non-precious metal as a catalyst. Compared with the high-pressure hydrogenation conditions used in the prior art, this method greatly improves the reaction safety, and compared with the prior art using Pd / C precious metal and menthene as a catalyst, this method greatly reduces the production cost.

[0021] 2. The preparation method provided in the present application can more accurately remove the chlorine atom at the C-6 position of 2,3,6-trichloropyridine, accurately obtain the target product 2,3-dichloropyridine, and obtain a higher yield. DETAILED DESCRIPTION

[0022] Example

[0023] The following example is a method for preparing 2,3-dichloropyridine.

[0024] Example 1

[0025] A preparation method of 2,3-dichloropyridine, in a 250mL three-necked flask, first add 30mL of formic acid, then add 4.3g of 2,3,6-trichloropyridine and 3g of zinc powder, mix, raise the temperature to 130°C, react for 6h, after the reaction is completed, add 30mL of toluene after the reaction is cooled to room temperature, stir, filter, wash the filter cake with toluene, wash until the blue-green color of the product in the filter cake disappears and turns colorless, dry the filtrate with anhydrous sodium sulfate, filter, and remove the organic solvent from the filtrate by vacuum rotary evaporation to obtain 1.71g of white powder 2,3-dichloropyridine, the yield and purity are shown in Table 1.

[0026] Example 2

[0027] The difference between Example 2 and Example 1 is that 3 g of zinc powder is replaced by 3 g of copper powder. The other steps are the same as Example 1. 1.92 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0028] Example 3

[0029] The difference between Example 3 and Example 1 is that 30 mL of formic acid is replaced by 30 mL of acetic acid. The other steps are the same as Example 1, and 2.41 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0030] Example 4

[0031] The difference between Example 4 and Example 3 is that 3 g of zinc powder is replaced by 3 g of iron powder. The other steps are the same as Example 3. 2.12 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0032] Example 5

[0033] The difference between Example 5 and Example 3 is that 3 g of zinc powder is replaced by 3 g of copper powder. The other steps are the same as Example 3, and 2.59 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0034] Example 6

[0035] The difference between Example 6 and Example 1 is that 30 mL of formic acid is replaced by 30 mL of propionic acid. The other steps are the same as Example 1, and 3.03 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0036] Example 7

[0037] The difference between Example 7 and Example 6 is that 3 g of zinc powder is replaced by 3 g of copper powder. The other steps are the same as Example 6. 3.40 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0038] Example 8

[0039] The difference between Example 8 and Example 1 is that 30 mL of formic acid is replaced by 30 mL of butyric acid. The other steps are the same as Example 1, and 2.68 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0040] Example 9

[0041] The difference between Example 9 and Example 8 is that 3 g of zinc powder is replaced by 3 g of copper powder. The other steps are the same as Example 8, and 2.89 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0042] Example 10

[0043] The difference between Example 10 and Example 7 is that 3 g of copper powder is replaced by a mixture of 1.5 g of copper powder and 1.5 g of zinc powder. The rest is the same as Example 7, and 3.43 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0044] Embodiment 11

[0045] The difference between Example 11 and Example 7 is that 3 g of copper powder is replaced by a mixture of 2 g of copper powder and 1 g of zinc powder. The rest is the same as Example 7, and 3.41 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0046] Example 12

[0047] The difference between Example 12 and Example 7 is that 3 g of copper powder is replaced by a mixture of 2.25 g of copper powder and 0.75 g of zinc powder. The rest is the same as Example 7, and 3.45 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0048] Example 13

[0049] The difference between Example 13 and Example 7 is that 30 mL of propionic acid is replaced by a mixture of 20 mL of propionic acid and 10 mL of acetic acid. The other steps are the same as Example 7, and 3.42 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0050] Embodiment 14

[0051] The difference between Example 14 and Example 7 is that 30 mL of propionic acid is replaced by a mixture of 22.5 mL of propionic acid and 7.5 mL of acetic acid. The rest is the same as Example 7, and 3.44 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0052] Embodiment 15

[0053] The difference between Example 15 and Example 7 is that the mass of the copper powder is 5 g, and the rest is the same as Example 7, and 3.39 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0054] Example 16

[0055] The difference between Example 16 and Example 7 is that the mass of the copper powder is 4 g, and the rest is the same as Example 7, and 3.43 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0056] Embodiment 17

[0057] The difference between Example 17 and Example 7 is that the amount of propionic acid is 40 mL, and the rest is the same as Example 7, to obtain 3.41 g of white powder 2,3-dichloropyridine. The yield and purity are shown in Table 1.

[0058] Embodiment 18

[0059] The difference between Example 18 and Example 7 is that the amount of propionic acid is 50 mL, and the rest is the same as Example 7, to obtain 3.39 g of white powder 2,3-dichloropyridine. The yield and purity are shown in Table 1.

[0060] Embodiment 19

[0061] The difference between Example 19 and Example 7 is that the reaction temperature is 140° C., and the other conditions are the same as Example 7, to obtain 3.46 g of white powder 2,3-dichloropyridine. The yield and purity are shown in Table 1.

[0062] Embodiment 20

[0063] The difference between Example 20 and Example 7 is that the reaction temperature is 150° C., and the other conditions are the same as Example 7, to obtain 3.38 g of white powder 2,3-dichloropyridine. The yield and purity are shown in Table 1.

[0064] Embodiment 21

[0065] The difference between Example 21 and Example 7 is that the reaction time is 18 hours. The other steps are the same as Example 7. 3.23 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0066] Embodiment 22

[0067] The difference between Example 22 and Example 7 is that the reaction time is 12 hours. The other steps are the same as Example 7. 3.31 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0068] Embodiment 23

[0069] The difference between Example 23 and Example 7 is that the reaction time is 8 hours. The other steps are the same as Example 7. 3.40 g of white powder 2,3-dichloropyridine is obtained. The yield and purity are shown in Table 1.

[0070] Table 1 Summary of yield and purity of 2,3-dichloropyridine in Examples 1-23

[0071]

[0072]

[0073] By comparing the above Examples 1-9, it can be found that when formic acid, acetic acid, propionic acid and butyric acid are used as solvents and zinc powder, iron powder and copper powder are used as catalysts, the yield reaches more than 49% and the purity reaches more than 85%. In particular, the system using propionic acid as solvent and copper powder as catalyst has a yield of 97.42% and a purity of 95.02%, which obtains relatively excellent results.

[0074] By comparing Example 7 with Examples 10-12, it can be found that when a mixed metal, copper powder and zinc powder are used in a mass ratio of (1-3):1, a better catalytic effect is obtained than a single catalyst, and the chlorine atom at the C-6 position of 2,3,6-trichloropyridine can be removed more accurately, so that the yield reaches 98.85% and the purity reaches 98.13%.

[0075] By comparing Example 7 with Examples 13-14, it can be found that when a mixed acid is used with a volume ratio of propionic acid to acetic acid of (2-3):1, a better catalytic effect is obtained than a single solvent, so that the yield reaches 98.57% and the purity reaches 97.89%.

[0076] By comparing Example 7 with Examples 15-20, it can be found that the amount of catalyst, the volume of solvent and the reaction temperature have a certain influence on the entire reaction system, and the yield and purity are improved to a certain extent. In particular, when the reaction temperature is around 140°C, the yield reaches 99.14% and the purity reaches 97.67%.

[0077] By comparing Example 7 with Examples 21-23, it can be found that the reaction time has a certain influence on the entire reaction system. When the reaction time is 12-18h, the reaction can be left overnight, but the yield and purity of the reaction have a certain degree of decrease. In order to make the reaction not only obtain a higher yield and purity, but also to ensure safe production, the present application considers a reaction time of 6-8h as a preferred reaction condition.

[0078] Through the above comparison, it can be found that the present application uses C1-C4 fatty carboxylic acid as solvent and non-precious metal as catalyst, especially mixed acid as solvent and mixed metal as catalyst, which can obtain relatively excellent reaction effect. In addition, the present application does not use precious metals, nor does it use high-pressure hydrogenation reaction conditions. The solvents and catalysts used are cheap and easy to obtain, which greatly reduces production costs. It also does not use harsh reaction conditions, which greatly improves production safety. It can also obtain relatively high yields and selectivity, accurately remove the chlorine atom at the C-6 position of 2,3,6-trichloropyridine, and accurately obtain the target product 2,3-dichloropyridine. The present application obtains very excellent results and is convenient for industrial production.

[0079] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing 2,3-dichloropyridine, characterized in that: In a solvent of C1-C4 fatty carboxylic acid, 2,3,6-trichloropyridine is dechlorinated under the catalysis of non-precious metals to obtain the target product.

2. The preparation method according to claim 1, characterized in that: The C1-C4 fatty carboxylic acid is one or more of formic acid, acetic acid, propionic acid and butyric acid.

3. The preparation method according to claim 1, characterized in that: The non-precious metal is one or more of zinc powder, iron powder and copper powder.

4. The preparation method according to claim 1, characterized in that: The ratio of the 2,3,6-trichloropyridine, the non-precious metal and the C1-C4 fatty carboxylic acid is 4.3 g: (3-5) g: (30-50) mL.

5. The preparation method according to claim 1, characterized in that: The reaction temperature is 130-150°C.

6. The preparation method according to claim 1, characterized in that: The reaction time is 6 to 18 hours.

7. The preparation method according to claim 1, characterized in that: The reaction time is 6 to 8 hours.

8. The preparation method according to claim 3, characterized in that: The non-precious metal is a mixture of copper powder and zinc powder, and the mass ratio of the copper powder to the zinc powder is (1-3):

1.

9. The preparation method according to claim 3, characterized in that: The C1-C4 fatty carboxylic acid is a mixed solvent of propionic acid and acetic acid, and the volume ratio of the propionic acid to the acetic acid is (2-3):1.

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