A method for preparing dichlorvos quick-acting salt

Abstract

This invention belongs to the field of fine chemicals and discloses a method for preparing dichlorvos. The method includes: reacting 2,2'-bipyridine with a haloalcohol compound of formula I to generate a bipyridine monosalt compound of formula I; after the reaction, separating the bipyridine monosalt compound from the haloalcohol compound; using water as the reaction solvent, reacting the bipyridine monosalt compound with a hydrohalic acid under the action of a catalyst to obtain a reaction solution containing dichlorvos; adjusting the pH of the reaction solution to 4-6 to obtain a dichlorvos solution. This invention provides a novel method for preparing dichlorvos, with a simple synthetic route, high overall yield, lower total cost, and less waste generation, making it more environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals, specifically relating to a method for preparing dichlorvos quick-acting salt. Background Technology

[0002] Diquat is a high-performance non-selective herbicide, ranking third globally after glyphosate and paraquat. It can also be used to causative the withering of potato and sweet potato stems and leaves, and its market demand has been increasing in recent years. Generally speaking, diquat refers to diquat dibromo salt, obtained by the cyclization reaction of 2,2'-bipyridine and 1,2-dibromoethane. In this reaction, 1,2-dibromoethane serves as both the substrate and the solvent, requiring a large amount of 1,2-dibromoethane, which is expensive, resulting in high production costs (US2823987A).

[0003] Existing data indicate that the herbicidal activity of diquat dibromide is due to its cationic portion, not the bromide anion (GB815348, The dipyridylium herbicides, paraquat and diquat, p. 99, J. Sci. Food Agric., 11, June, 1960, 309-315). From an atom economy perspective, diquat dichloride is the most suitable. The method used is to first prepare diquat dibromide, and then convert it into diquat dichloride through a series of methods (CN106220629A, CN106279166A, CN107573342A, CN106220628A). However, the preparation process is somewhat complex, and the presence of bromine or bromides during preparation causes significant corrosion to equipment. Therefore, continuing to seek new preparation methods for diquat dibromide and diquat dichloride to reduce process difficulty and production costs is of great significance.

[0004] In 1964, ICI (later Syngenta) proposed using chloroethanol as a solvent and reactant to react with bipyridine to prepare dichlorvos dichlorophosphate (GB1087052A). The inventors discovered the following drawbacks through verification: firstly, the yield was low (≤60%), and ethylene glycol was produced as a byproduct, making separation difficult; secondly, at reaction temperatures above 125°C, the loss rate of bipyridine and chloroethanol was significant, making it unsuitable for industrial application.

[0005] Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the above-mentioned process and provide a new method for preparing dichlorvos. This preparation method has a simple synthesis route, high overall reaction yield, low "three wastes" generated by the reaction, and low synthesis cost.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing dichlorvos salt, the synthetic route is as follows:

[0009]

[0010] X is selected from Cl and Br; Nu is selected from OH and SH.

[0011] Includes the following steps:

[0012] Step (1), 2,2'-bipyridine and formula The haloalcohol compound shown reacts to produce the bipyridine monosalt compound shown in Formula I; after the reaction is complete, the bipyridine monosalt compound is separated from the haloalcohol compound.

[0013] Step (2): Using water as the reaction solvent, under the action of a catalyst, the bipyridine monosalt compound and hydrohalic acid react to obtain a reaction solution containing dichlorvos salt. Adjust the pH of the reaction solution to 4-6 to obtain a dichlorvos salt solution.

[0014] In step (1), the reaction solvent is one of the following: haloalcohol compound, toluene, xylene, tetrahydronaphthalene, nitrobenzene, etc., preferably haloalcohol compound, toluene or xylene; when the reaction solvent is haloalcohol compound, the haloalcohol is used as both solvent and reactant.

[0015] When the reaction solvent is a haloalcohol compound, the reaction includes: mixing 2,2'-bipyridine and the haloalcohol compound, heating the mixture to react, and synthesizing a bipyridine monochloride compound; after the reaction is complete, removing part of the reaction solvent by solvent removal, adding water and an extractant, separating the liquid to obtain an aqueous phase containing the bipyridine monochloride. The extractant is one of dichloromethane, chloroform, toluene, 1,2-dichloroethane, xylene, etc., preferably 1,2-dichloroethane or toluene.

[0016] When the reaction solvent is one of toluene, xylene, tetrahydronaphthalene, nitrobenzene, etc., the reaction includes: dissolving 2,2'-bipyridine in the reaction solvent, adding a haloalcohol compound, heating the reaction to synthesize a bipyridine monosalt compound; after the reaction is complete, removing part of the solvent by solvent removal, adding water, separating the liquid, and obtaining an aqueous phase containing the bipyridine monochloride. The removed solvent (the mixture of the reaction solvent and the haloalcohol compound) accounts for 40-70% of the mass of the reaction solvent and the haloalcohol compound.

[0017] The molar ratio of the reaction solvent to 2,2'-bipyridine is 4:1 to 20:1, preferably 7:1 to 15:1, and more preferably 8:1 to 10:1.

[0018] The haloalcohol compound is one of 2-chloroethanol, 2-bromoethanol, 2-chloroethanethiol, 2-bromoethanethiol, etc. Considering that when Nu is selected from OH, water is produced as a byproduct, making the process more environmentally friendly, the haloalcohol compound is preferably 2-chloroethanol or 2-bromoethanol.

[0019] The molar ratio of the haloalcohol compound to 2,2'-bipyridine is 1.1:1 to 20.0:1, preferably 3:1 to 10:1.

[0020] The reaction temperature is 60℃~150℃, preferably 100~130℃.

[0021] In step (2), the halogen in the hydrohalic acid is the same as the halogen in the haloalcohol compound.

[0022] Preferably, the hydrohalic acid is hydrogen chloride, hydrogen bromide, etc., and correspondingly, the diquat salt is diquat dichloride or diquat dibromide.

[0023] The molar ratio of the hydrohalic acid to 2,2'-bipyridine is 1.2:1 to 8.0:1.

[0024] This invention improves the conversion rate and reaction rate by adding a small amount of catalyst. The mass ratio of the catalyst to 2,2'-bipyridine is 0.1:10 to 0.2:10.

[0025] The catalyst is one of concentrated sulfuric acid, zinc chloride, aluminum chloride, p-toluenesulfonic acid, etc., preferably zinc chloride.

[0026] The reaction temperature is 80–150℃ or reflux reaction.

[0027] Specifically, a bipyridine monosalt compound is dissolved in an aqueous solution of hydrohalic acid, or a mixture of an aqueous solution of a bipyridine monosalt compound and an aqueous solution of hydrohalic acid is added, a catalyst is added, and the reaction is heated to obtain a reaction solution containing dichlorvos. The pH of the reaction solution is adjusted to 4-6 to obtain a dichlorvos solution.

[0028] The aqueous solution of the hydrohalic acid is hydrochloric acid or hydrobromic acid; the concentration of the aqueous solution of the hydrohalic acid is 10% to 48%.

[0029] 2,2'-Bipyridine reacts with haloalcohol compounds to form a bipyridine monosalt compound as shown in Formula I. Intramolecular dehydration then achieves CN-C coupling to form a new onium salt, ultimately forming diquat salt. Taking the preparation of diquat dichlorosalt as an example, 2,2'-bipyridine reacts with 2-chloroethanol. At the reaction temperature, neither 2,2'-bipyridine nor 2-chloroethanol is lost during the reaction, producing a bipyridine monosalt compound. This bipyridine monosalt compound then reacts with hydrogen chloride to form a compound as shown in Formula II, which further undergoes intramolecular dehydration to form an onium salt, i.e., diquat dichlorosalt. Similarly, diquat dibromosalt, etc., can also be obtained using this method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention provides a novel method for preparing dichlorvos quick-acting salt, with a simple synthetic route, high overall reaction yield, lower total cost, and less waste generation, making it more environmentally friendly. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0033] Example 1

[0034] Synthesis of dichlorvos dichloride

[0035] 10.00 g (0.064 mol) of 2,2'-bipyridine was added to 51.2 g (0.64 mol) of 2-chloroethanol, and the temperature was slowly raised to 120 °C. During the reaction, the reaction was monitored by HPLC until the 2,2'-bipyridine was completely converted. The reaction was then stopped, and part of the 2-chloroethanol was recovered by vacuum distillation to obtain a chloroethanol solution of bipyridine monochloro salt. 30 g of water and 30 mL of toluene were added to this solution, and the mixture was extracted and separated. The aqueous phase was the bipyridine monochloro salt solution.

[0036] The above-mentioned bipyridine monochloro salt solution, 5.0 g of 36% hydrochloric acid (HCl 0.50 mol) and 0.1 g of zinc chloride were added to a 100 mL four-necked flask. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to reflux. During the reaction, the reaction was monitored by HPLC until the bipyridine monochloro salt reaction was complete. The reaction was then stopped to obtain an aqueous solution of dichlorvos dichloro salt. An appropriate amount of ammonia was added to adjust the pH to 5.6, yielding 33.6 g of a solution with a dichlorvos cation content of 31.5%, and a yield of 90% based on bipyridine.

[0037] Example 2

[0038] Synthesis of dibromodibromide

[0039] 10.0 g (0.064 mol) of 2,2'-bipyridine and 67.7 g of xylene were added to a 150 mL four-necked flask. A magnetic stir bar was added, an internal temperature thermometer was inserted, and a spherical condenser was attached. Then, 23.99 g (0.192 mol) of 2-bromoethanol was added, and the temperature was slowly raised to 130 °C. During the reaction, the reaction was monitored by HPLC until the 2,2'-bipyridine reacted completely. The reaction was stopped, and the mixture of 2-bromoethanol and xylene was recovered by vacuum distillation, yielding a total of 60.5 g. The remaining liquid was extracted with 30 g of water by stirring thoroughly. The mixture was separated to obtain an aqueous phase containing bipyridine monobromide.

[0040] The aqueous phase containing bipyridine monobromide was added to a 200 mL autoclave along with 86.4 g of 12% hydrobromic acid (HBr 0.128 mol) and 0.15 g of zinc chloride. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to 140 °C. During the reaction, the reaction was monitored by HPLC until the bipyridine monobromide was completely reacted. The reaction was then stopped, and the pH was adjusted to 5.0 with ammonia water to obtain 60.4 g of dichlorvos dibromide aqueous solution. The purity of the dichlorvos cation content was 18.1%, and the yield was 93%.

[0041] Example 3

[0042] Synthesis of dichlorvos dichloride

[0043] 10.00 g (0.064 mol) of 2,2'-bipyridine and 67.94 g (0.64 mol) of xylene were added to a 250 mL four-necked flask. A magnetic stir bar was added, an internal temperature thermometer was inserted, and a spherical condenser was attached. Then, 20.61 g (0.256 mol) of 2-chloroethanol was added, and the temperature was slowly raised to 140 °C. During the reaction, the reaction was monitored by HPLC until the reactant 2,2'-bipyridine was completely reacted. The reaction was then stopped, and 50.5 g of the xylene and 2-chloroethanol mixture was recovered by vacuum distillation. The remaining liquid was extracted with 30.1 g of water and separated to obtain an aqueous phase containing bipyridine monochloro salt.

[0044] The aqueous phase containing bipyridine monochloride, 10.1 g of 36% hydrochloric acid (HCl 0.10 mol), and 0.1 g of zinc chloride were added to a 100 mL autoclave. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to 130 °C. During the reaction, the reaction was monitored by HPLC until the bipyridine monochloride reacted completely. The reaction was then stopped, and the pH was adjusted to 5.5 with ammonia water to obtain 29.68 g of diquat dichloride aqueous solution with a diquat cation content of 37.3% and a yield of 94%.

[0045] Example 4

[0046] Synthesis of dibromodibromide

[0047] 10.00 g (0.064 mol) of 2,2'-bipyridine and 47.18 g (0.512 mol) of toluene were added to a 100 mL four-necked flask. A magnetic stir bar was added, an internal thermometer was inserted, and a spherical condenser was attached. Then, 23.99 g (0.192 mol) of 2-bromoethanol was added, and the temperature was slowly raised to 110 °C. During the reaction, the reaction was monitored by HPLC until the starting material 2,2'-bipyridine reacted completely. The reaction was then stopped, and 30.5 g of the toluene and 2-bromoethanol mixture was recovered by vacuum distillation. The remaining liquid was extracted with 25.3 g of water and separated to obtain an aqueous phase containing bipyridine monobromide.

[0048] The aqueous phase containing bipyridine monobromide, 67.50 g of 12% hydrobromic acid (HBr 0.10 mol), and 0.15 g of zinc chloride were added to a 200 mL autoclave. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to 100 °C. During the reaction, the reaction was monitored by HPLC until the bipyridine monobromide reacted completely. The reaction was then stopped, and the pH was adjusted to 5.7 with ammonia water to obtain 78.05 g of dichlorvos dibromide aqueous solution with a dichlorvos cation content of 14.5% and a yield of 96%.

[0049] Example 5

[0050] Synthesis of dichlorvos dichloride

[0051] 10.00 g (0.064 mol) of 2,2'-bipyridine and 67.94 g (0.64 mol) of xylene were added to a 250 mL four-necked flask. A magnetic stir bar was added, an internal temperature thermometer was inserted, and a spherical condenser was attached. Then, 24.72 g (0.256 mol) of 2-chloroethanethiol was added, and the temperature was slowly raised to 140 °C. During the reaction, the reaction was monitored by HPLC until the 2,2'-bipyridine reacted completely. The reaction was then stopped, and 50.9 g of the xylene and 2-chloroethanethiol mixture was recovered by vacuum distillation. The remaining liquid was extracted with 30.6 g of water and separated to obtain an aqueous phase containing bipyridine monochloro salt.

[0052] The aqueous phase containing bipyridine monochloro salt, 16.22 g of 36% hydrochloric acid (HCl 0.16 mol), and 0.1 g of zinc chloride were added to a 100 mL autoclave. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to 130 °C. During the reaction, the reaction was monitored by HPLC until the bipyridine monochloro salt reacted completely. The reaction was then stopped, and the pH was adjusted to 5.2 with ammonia water to obtain 36.47 g of diquat dichloro salt aqueous solution with a diquat cation content of 28.7% and a yield of 89%.

[0053] Example 6

[0054] Synthesis of dibromodibromide

[0055] 10.00 g (0.064 mol) of 2,2'-bipyridine and 47.18 g (0.512 mol) of toluene were added to a 100 mL four-necked flask. A magnetic stir bar was added, an internal thermometer was inserted, and a spherical condenser was attached. Then, 27.08 g (0.192 mol) of 2-bromoethanethiol was added, and the temperature was slowly raised to 110 °C. During the reaction, the reaction was monitored by HPLC until the starting material 2,2'-bipyridine reacted completely. The reaction was then stopped, and 33.5 g of the toluene and 2-bromoethanethiol mixture was recovered by vacuum distillation. The remaining liquid was extracted with 23.1 g of water and separated. The aqueous phase yielded the bipyridine monobromide.

[0056] The aqueous phase containing bipyridine monobromide, 62.31 g of 13% hydrobromic acid (HBr 0.10 mol), and 0.2 g of zinc chloride were added to a 150 mL autoclave. A magnetic stir bar was added, and a polytetrafluoroethylene stopcock was fitted. The temperature was slowly raised to 100 °C. During the reaction, the reaction was monitored by HPLC until the bipyridine monobromide reacted completely. The reaction was then stopped, and the pH was adjusted to 5.4 with ammonia water to obtain 73.75 g of dichlorvos dibromide aqueous solution with a dichlorvos cation content of 13.7% and a yield of 86%.

[0057] Comparative Example 1

[0058] Synthesis of dichlorvos dichloride

[0059] 10.00 g (0.064 mol) of 2,2'-bipyridine was added to 51.2 g (0.64 mol) of 2-chloroethanol, and the temperature was slowly raised to 120 °C. During the reaction, the reaction was monitored by HPLC until the 2,2'-bipyridine was completely converted. The reaction was then stopped, and 30.2 g of 2-chloroethanol was recovered by vacuum distillation. The remaining liquid was extracted with 33.2 g of water and 30.5 g of toluene, and the liquid was separated. The aqueous phase was a solution of bipyridine monochloro salt.

[0060] The above-mentioned bipyridine monochloro salt solution and 5.0 g of 36% hydrochloric acid (HCl 0.50 mol) were added to a 100 mL four-necked flask. A magnetic stir bar was added, a polytetrafluoroethylene stopcock was attached, and the temperature was slowly raised to reflux. The reaction was monitored by HPLC. After 5 hours of reaction, the bipyridine monochloro salt no longer decreased significantly, and the reaction was stopped to obtain an aqueous solution of diquat dichloro salt. An appropriate amount of ammonia was added to adjust the pH to 5.5, yielding 25.3 g of a solution with a diquat cation content of 20.9%, and a yield of 45.1% based on bipyridine.

Claims

1. A method for preparing dichlorvos quick-acting salt, characterized in that: The synthesis route is as follows: X is selected from Cl and Br; Nu is selected from OH and SH. Includes the following steps: Step (1), 2,2'-bipyridine and formula The haloalcohol compound shown reacts to generate the bipyridine monosalt compound shown in Formula I; after the reaction is complete, the bipyridine monosalt compound is separated from the haloalcohol compound; wherein, Formula I... The molar ratio of the haloalcohol compound to 2,2'-bipyridine shown is 1.1:1 to 20.0:1; the reaction temperature is 60℃ to 150℃. Step (2): Using water as the reaction solvent, under the action of a catalyst, the bipyridine monosalt compound and hydrohalic acid react to obtain a reaction solution containing diquat salt. The pH of the reaction solution is adjusted to 4-6 to obtain a diquat salt solution. The diquat salt is diquat dichlorosalt or diquat dibromide. The molar ratio of the hydrohalic acid to 2,2'-bipyridine is 1.2:1 to 8.0:

1. The catalyst is zinc chloride.

2. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (1), the reaction solvent is of formula [formula missing]. One of the following: haloalcohol compound, toluene, xylene, tetrahydronaphthalene, and nitrobenzene.

3. The method for preparing dichlorvos quick-acting salt according to claim 1 or 2, characterized in that: In step (1), the reaction solvent is of formula [formula missing]. The haloalcohol compound shown is toluene or xylene.

4. The method for preparing dichlorvos quick-acting salt according to claim 2, characterized in that: In step (1), when the reaction solvent is of formula... The process for obtaining the haloalcohol compound includes: mixing 2,2'-bipyridine with the haloalcohol compound, heating the mixture to react, and synthesizing a bipyridine monosalt compound; after the reaction is complete, removing part of the reaction solvent by solvent removal, adding water and an extractant, separating the liquid to obtain an aqueous phase containing the bipyridine monochloro salt; wherein the extractant is one of dichloromethane, chloroform, toluene, 1,2-dichloroethane, and xylene; When the reaction solvent is one of toluene, xylene, tetrahydronaphthalene, or nitrobenzene, the reaction includes: dissolving 2,2'-bipyridine in the reaction solvent and adding the following formula: The haloalcohol compound shown was reacted at elevated temperature to synthesize a bipyridine monosalt compound. After the reaction was completed, some solvent was removed by solvent removal, water was added, and the mixture was separated to obtain an aqueous phase containing bipyridine monochloride. The solvent removed was 40-70% of the total mass of the reaction solvent and the haloalcohol compound.

5. The method for preparing dichlorvos quick-acting salt according to claim 4, characterized in that: In step (1), when the reaction solvent is of formula... When the haloalcohol compound shown is used, the extractant is 1,2-dichloroethane or toluene.

6. The method for preparing dichlorvos quick-acting salt according to claim 2, characterized in that: In step (1), the molar ratio of the reaction solvent to 2,2'-bipyridine is 4:1 to 20:

1.

7. The method for preparing dichlorvos quick-acting salt according to claim 6, characterized in that: In step (1), the molar ratio of the reaction solvent to 2,2'-bipyridine is 7:1 to 15:

1.

8. The method for preparing dichlorvos quick-acting salt according to claim 7, characterized in that: In step (1), the molar ratio of the reaction solvent to 2,2'-bipyridine is 8:1 to 10:

1.

9. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (1), the molar ratio of the haloalcohol compound to 2,2'-bipyridine is 3:1 to 10:

1.

10. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (1), the reaction temperature is 100-130℃.

11. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (2), the halogen in the hydrohalic acid is the same as the halogen in the haloalcohol compound.

12. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (2), the hydrogen halide is hydrogen chloride or hydrogen bromide.

13. The method for preparing dichlorvos quick-acting salt according to claim 1, characterized in that: In step (2), the mass ratio of the catalyst to 2,2'-bipyridine is 0.1:10 to 0.2:10.

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