Solvent-free synthesis method of thiacloprid

Abstract

The invention relates to a solvent-free synthesis method of thiacloprid, which comprises the following steps: adding 2-cyano imido-1, 3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid alkali into a homogenizer, and reacting while homogenizing under the condition of microwave heating to generate thiacloprid. According to the method, the limitation of chemical reaction in a solvent in the prior art is broken through, a homogenizer is initiatively adopted and matched with a microwave heating mode for reaction without a solvent, the yield and the purity of the product are greatly improved by matching with a purification process of reflux dissolution and cooling recrystallization, and due to the fact that the solvent is not adopted, the wastewater yield is low, and therefore the method is suitable for industrial production. The production cost of thiacloprid is greatly reduced, and the environmental protection pressure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of thiacloprid synthesis, and in particular to a solvent-free synthesis method of thiacloprid. Background Art

[0002] Thiacloprid technical is a chloronicotinoid insecticide developed by Bayer Agrochemicals of Germany and Bayer Agrochemicals of Japan in the 1990s. It has a broad spectrum and systemic properties, and has a good killing effect on piercing-sucking and chewing mouthparts pests. As a new type of biomimetic pesticide, Thiacloprid acts on nicotinic acid acetylcholine receptors, has no cross-resistance with conventional organophosphate, carbamate, and pyrethroid insecticides, and can be used for resistance management. The agent has excellent preventive effect on important pests on cotton, vegetables, potatoes, and pome fruits.

[0003] The molecular formula of thiacloprid is C 10 H 9 C1N 4 S, chemical name is [3-(6-chloro-3-pyridylmethyl)-thiazoline-2-ylidene] cyanamide, English common name is Thiacloprid, its structural formula is as follows:

[0004]

[0005] Thiacloprid has been industrialized for decades. Although there are many documents recording its synthesis method, such as Wu Daoxin et al.'s "Study on the Synthesis Process of High-efficiency and Low-toxic Insecticide Thiacloprid", patents CN201110389533.X, CN00104507.5, CN201711107739.2, CN201811546395.X, WO2017048628, etc., they all have the following problems: First, the solvent consumption is large and the product yield is low, resulting in high production costs and reducing its market competitiveness; second, there is a lot of wastewater, and the wastewater treatment is difficult and costly, which increases the hidden cost of its production and also brings greater environmental pressure.

[0006] Therefore, developing a solvent-free synthesis method for thiacloprid with low solvent loss, low wastewater production and low treatment difficulty, high product yield and good purity is crucial to reduce the production cost of thiacloprid and reduce environmental pressure. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a solvent-free synthesis method of thiacloprid. No solvent needs to be added during the reaction process. After the reaction is completed, only a small amount of alcohol solvent is needed for dissolution and recrystallization. The solvent can be recycled, and the processing cost is low, pollution-free, and environmental pressure is small.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0010] 2-cyano-imino-1,3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid base are added into a homogenizer, and reacted while being homogenized under microwave heating conditions to generate thiacloprid and obtain a reaction product.

[0011] As a further technical solution, the power of the microwave heating is 60-380 W, the temperature of the microwave heating is 30-60° C., the speed of homogenization is 500-4000 rpm, and the reaction time is 2-15 h.

[0012] As a further technical solution, the power of the microwave heating is 100-300W, the temperature of the microwave heating is 35-55°C, the speed of homogenization is 800-3000 rpm, and the reaction time is 2-8h.

[0013] As a further technical solution, the molar ratio of 2-cyano-imino-1,3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid base is: 1.0-1.1 mol: 1.0 mol: 1.0-1.2 mol.

[0014] As a further technical solution, the molar ratio of 2-cyanoimino-1,3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid base is: 1.0-1.05 mol: 1.0 mol: 1.0-1.1 mol.

[0015] As a further technical solution, the solid alkali is one or more of sodium carbonate, potassium carbonate, potassium hydroxide, and sodium hydroxide, preferably sodium hydroxide.

[0016] As a further technical solution, after the reaction is completed, post-treatment is required, which includes: adding a recrystallization solvent to the reaction product for reflux treatment to dissolve thiacloprid, then centrifuging while hot to obtain thiacloprid mother liquor, and then cooling and recrystallizing, washing and desalting, filtering, and drying in sequence to obtain a thiacloprid product.

[0017] As a further technical solution, the recrystallization solvent is an alcohol solvent, and the mass concentration of the alcohol solvent is ≥95%.

[0018] As a further technical solution, the alcohol solvent includes one or more of ethanol, methanol, and isopropanol, preferably ethanol with a mass concentration of 95%.

[0019] As a further technical solution, the reflux time is 2-3h.

[0020] As a further technical solution, a recrystallization solvent is added to the reaction product at a mass ratio of the reaction product to the solvent A of 94:160-200.

[0021] In the present invention, the reaction route of thiacloprid synthesis is:

[0022]

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0024] 1. The present invention utilizes the shear force of high-speed rotation and the impact force generated by forced flow during the homogenization process to cause the material to deform and break at a high frequency, and cooperates with the heating method of microwave heating, so that the material can react smoothly in the absence of solvent, solving a series of problems caused by the reaction of the material in the solvent: such as: increase in solvent cost, increase in waste liquid, etc.;

[0025] 2. After the reaction of the present invention is completed, only a small amount of solvent is needed to dissolve the product, and the cooling and recrystallization operation can be directly carried out, which further reduces the amount of solvent used. The residual salt in the crude product of the whole process needs a small amount of water to be removed, which greatly reduces the amount of wastewater and reduces the cost of wastewater treatment.

[0026] In summary, the present invention breaks the limitation of traditional chemical reactions in solvents, and innovatively adopts a homogenizer in combination with microwave heating to carry out reactions in the absence of solvents. Combined with the purification process of reflux dissolution and cooling recrystallization of the present invention, the yield and purity of the product are greatly improved. Moreover, since no solvent is used, the wastewater output is low. Therefore, the production cost of thiacloprid is greatly reduced, and the environmental pressure is reduced. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the embodiments.

[0028] In the present invention,

[0029] 2-cyano-imide-1,3-thiazolidine (purity 95.6): produced by the company;

[0030] 2-Chloro-5-chloromethylpyridine (purity 96%): purchased from Gansu Kesheng Qianyun;

[0031] Solid alkali with a purity of 96% was purchased from Jinan Feiyue Chemical Co., Ltd.

[0032] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0033] Example 1

[0034] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0035] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction solution of thiacloprid, wherein the microwave heating power is 280W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0036] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution.

[0037] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0038] In this embodiment, the yield of thiacloprid is 93%, and the purity of the obtained thiacloprid product is 97.8%.

[0039] Example 2

[0040] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0041] Step 1, homogenization reaction: add 36.5g (0.275mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0042] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0043] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0044] In this embodiment, the yield of thiacloprid is 91%, and the purity of the obtained thiacloprid product is 97.6%.

[0045] Example 3

[0046] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0047] Step 1, homogenization reaction: add 35.5 g (0.267 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5 hours until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280 W, the temperature is 45° C., and the homogenization speed is 3000 rpm;

[0048] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0049] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0050] In this embodiment, the yield of thiacloprid is 88%, and the purity of the obtained thiacloprid product is 97.1%.

[0051] Example 4

[0052] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0053] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 11.7g (0.28mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0054] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0055] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0056] In this embodiment, the yield of thiacloprid is 90%, and the purity of the obtained thiacloprid product is 97.8%.

[0057] Example 5

[0058] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0059] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 11.1g (0.267mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0060] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0061] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0062] In this embodiment, the yield of thiacloprid is 86%, and the purity of the obtained thiacloprid product is 96.3%.

[0063] Example 6

[0064] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0065] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 180W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0066] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0067] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0068] In this embodiment, the yield of thiacloprid is 92%, and the purity of the obtained thiacloprid product is 97.5%.

[0069] Example 7

[0070] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0071] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 100W, the temperature is 45°C, and the homogenization speed is 3000 rpm.

[0072] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0073] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0074] In this embodiment, the yield of thiacloprid is 92.3%, and the purity of the obtained thiacloprid product is 97.3%.

[0075] Example 8

[0076] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0077] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 100W, the temperature is 35°C, and the homogenization speed is 3000 rpm.

[0078] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0079] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0080] In this embodiment, the yield of thiacloprid is 90%, and the purity of the obtained thiacloprid product is 96.5%.

[0081] Example 9

[0082] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0083] Step 1, homogenization reaction: add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5 hours until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 100 W, the temperature is 55° C., and the homogenization speed is 3000 rpm;

[0084] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0085] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0086] In this embodiment, the yield of thiacloprid is 87%, and the purity of the obtained thiacloprid product is 96.8%.

[0087] Example 10

[0088] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0089] Step 1, homogenization reaction: add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5 hours until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280 W, the temperature is 45° C., and the homogenization speed is 2000 rpm;

[0090] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0091] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0092] In this embodiment, the yield of thiacloprid is 89%, and the purity of the obtained thiacloprid product is 97.5%.

[0093] Embodiment 11

[0094] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0095] Step 1, homogenization reaction: add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5 hours until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280 W, the temperature is 45° C., and the homogenization speed is 1500 rpm;

[0096] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0097] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0098] In this embodiment, the total yield of thiacloprid is 89%, and the purity of the obtained thiacloprid product is 97.2%.

[0099] Example 12

[0100] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0101] Step 1, homogenization reaction: add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions, react for 8 hours until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280 W, the temperature is 45° C., and the homogenization speed is 3000 rpm;

[0102] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product and refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0103] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0104] In this embodiment, the yield of thiacloprid is 93.5%, and the purity of the obtained thiacloprid product is 97.6%.

[0105] Embodiment 13

[0106] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0107] Step 1, homogenization reaction: add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine and 12.2 g (0.294 mol) of solid base into a homogenizer, and react while homogenizing under microwave heating conditions for 3 hours. At this time, the normalized content of methylpyridine is about 2.6%, and the reaction is stopped to obtain a reaction product, wherein the microwave heating power is 280 W, the temperature is 45° C., and the homogenization speed is 3000 rpm;

[0108] Step 2, post-treatment: After the reaction is completed, 180 g of 95% ethanol solvent is added to the reaction product, refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0109] Step 3, purification: cooling the thiacloprid mother liquor to 3°C for cooling recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0110] In this embodiment, the yield of thiacloprid is 91.0%, and the purity of the obtained thiacloprid product is 97.1%.

[0111] Comparative Example 1

[0112] A solvent-free synthesis method of thiacloprid comprises the following steps:

[0113] Same as Example 1, except that 100 g of 95% ethanol was added to the homogenizer;

[0114] Step 1, homogenization reaction: add 2-cyano-imino-1,3-thiazolidine 37.2g (0.28mol), 2-chloro-5-chloromethylpyridine 45.4g (0.267mol), solid base 12.2g (0.294mol) and 95% ethanol 100g into a homogenizer, and react while homogenizing under microwave heating conditions, react for 5h until the normalized content of methylpyridine is less than 1%, stop the reaction, and obtain a reaction product, wherein the microwave heating power is 280W, the temperature is 45°C, and the homogenization speed is 3000 rpm;

[0115] Step 2, post-treatment: After the reaction is completed, 80 g of 95% ethanol solvent is added to the reaction product, refluxed at 78° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0116] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0117] In this comparative example, the yield of thiacloprid was 79%, and the purity of the obtained thiacloprid product was 94.2%.

[0118] In this comparative example, due to the addition of ethanol, the side reaction of ethanol and 2-chloro-5-chloromethylpyridine was increased while the side reaction in Example 1-13 occurred. The impurities produced by the side reaction were insoluble in water and could not be removed in the recrystallization and washing steps of the post-treatment, resulting in a decrease in the yield and product purity.

[0119] Comparative Example 2

[0120] A solvent-free synthesis method of thiacloprid is the same as Example 1, except that a traditional round-bottom flask is used instead of a homogenizer, methanol is used as a solvent, and oil bath heating is used instead of microwave heating. The specific operation is as follows;

[0121] Step 1: Add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine, 12.2 g (0.294 mol) of solid base and 100 g of methanol into a round-bottom flask, and react under oil bath heating conditions for 5 h until the normalized content of methylpyridine is less than 1%, then stop the reaction to obtain a reaction product, wherein the temperature is 45° C. and the rotation speed is 380 rpm;

[0122] Step 2, post-treatment: After the reaction is completed, 80 g of methanol solvent is added to the reaction product, refluxed at 65° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0123] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0124] In this embodiment, the yield of thiacloprid is 73%, and the purity of the obtained thiacloprid product is 95.6%.

[0125] In this comparative example, the methanol solvent and the raw material methylpyridine reacted with each other; the traditional oil bath heating was not as uniform as the microwave heating, and local overheating would increase the occurrence of the above-mentioned side reactions; and the traditional flask mechanical stirring speed was too slow compared with the homogenizer, which was not conducive to material mixing. Therefore, compared with the microwave heating in comparative example 3, the yield and purity of the product were reduced.

[0126] Comparative Example 3

[0127] A solvent-free synthesis method of thiacloprid is the same as that in Example 1, except that a conventional round-bottom flask is used to replace the homogenizer in Example 1, and a conventional mechanical stirring method is used to replace the homogenization speed in Example 1. The specific operation is as follows:

[0128] Step 1: Add 37.2 g (0.28 mol) of 2-cyano-imino-1,3-thiazolidine, 45.4 g (0.267 mol) of 2-chloro-5-chloromethylpyridine, 12.2 g (0.294 mol) of solid base and 100 g of methanol into a round-bottom flask, and react while stirring under microwave heating conditions. The microwave heating power is 280 W, the temperature is 45° C., and the stirring speed is 500 rpm; react for 5 h until the normalized content of the raw material methylpyridine is less than 1%, and then stop the reaction;

[0129] Step 2, post-treatment: After the reaction is completed, 80 g of methanol solvent is added to the reaction product, refluxed at 65° C. for 2 h until the thiacloprid is dissolved, and then centrifuged while hot to obtain a thiacloprid mother solution;

[0130] Step 3, purification: cooling the thiacloprid mother solution to 3°C for recrystallization, then filtering, washing the thiacloprid wet crystals with 50 mL of water for desalination, filtering, and drying to obtain the thiacloprid product;

[0131] In this embodiment, the yield of thiacloprid is 75%, and the purity of the obtained thiacloprid product is 97%.

[0132] Comparative Example 4

[0133] The same as Example 1, except that the microwave heating function of the homogenizer is not turned on, and an oil bath is used instead of microwave for heating.

[0134] Step 1, homogenization reaction: add 37.2g (0.28mol) of 2-cyano-imino-1,3-thiazolidine, 45.4g (0.267mol) of 2-chloro-5-chloromethylpyridine and 12.2g (0.294mol) of solid base into a homogenizer, and react while homogenizing under oil bath heating conditions. The reaction temperature is 45°C and the homogenization speed is 3000 rpm. When the reaction is 5h, the area normalization method is used to control the reaction process. The normalized content of the raw material methylpyridine is about 20%.

[0135] Since no solvent is added in the reaction process of the present invention, the raw materials are all solid. In the homogenous reaction process, the materials are in a semi-solid state, the thermal conductivity of the materials is poor, the material temperature is uneven, and the reaction rate is severely reduced. Therefore, the reaction is terminated and no subsequent operations are performed.

[0136] In Examples 1-13 of the present invention and Comparative Example 4, the side reactions mainly include the following: 1) 2-chloro-5-chloromethylpyridine undergoes a decomposition reaction to generate salts, which can be removed by washing in post-treatment; 2) Impurities formed by the transformation of 2-cyano-imino-1,3-thiazolidine are insoluble in water and cannot be removed by cooling, recrystallization and washing in post-treatment, and will remain in the thiacloprid product. In Comparative Examples 1-3, in addition to the side reactions existing in Examples 1-13, the solvent ethanol / methanol and methylpyridine will also undergo a side reaction to generate impurities that are not easily dehydrated, thereby remaining in the thiacloprid product.

[0137] The occurrence of these side reactions is closely related to the control of various parameters in the reaction process, such as microwave power, reaction temperature, stirring speed, etc. Therefore, it is necessary to control the various parameters within the range required by the present invention so that the yield can be stably controlled at more than 86% and the purity of the thiacloprid product can be stably controlled at more than 96%.

[0138] The above-described embodiments are only preferred embodiments of the present invention, and are not exhaustive of the feasible implementations of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A solvent-free synthesis method of thiacloprid, characterized in that: The steps include: 2-cyano-imino-1,3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid base are added into a homogenizer, and reacted while being homogenized under microwave heating conditions to generate thiacloprid and obtain a reaction product.

2. The solvent-free synthesis method of thiacloprid according to claim 1, characterized in that: The power of the microwave heating is 60-380W, the temperature of the microwave heating is 30-60°C, the speed of homogenization is 500-4000 rpm, and the reaction time is 2-15h.

3. A solvent-free synthesis method of thiacloprid according to claim 1, characterized in that: The molar ratio of 2-cyano-imino-1,3-thiazolidine, 2-chloro-5-chloromethylpyridine and solid base is: 1.0-1.1 mol: 1.0 mol: 1.0-1.2 mol.

4. The solvent-free synthesis method of thiacloprid according to claim 1, characterized in that: The solid alkali is one or more of sodium carbonate, potassium carbonate, potassium hydroxide and sodium hydroxide.

5. The solvent-free synthesis method of thiacloprid according to claim 1, characterized in that: After the reaction is completed, post-treatment is required, which includes: adding a recrystallization solvent to the reaction product to reflux and dissolve thiacloprid, then centrifuging while hot to obtain thiacloprid mother liquor, and then cooling and recrystallizing, washing and desalting, filtering, and drying in sequence to obtain a thiacloprid product.

6. The solvent-free synthesis method of thiacloprid according to claim 5, characterized in that: The recrystallization solvent is an alcohol solvent, and the mass concentration of the alcohol solvent is ≥95%.

7. The solvent-free synthesis method of thiacloprid according to claim 6, characterized in that: The alcohol solvent includes one or more of ethanol, methanol and isopropanol.

8. The solvent-free synthesis method of thiacloprid according to claim 5, characterized in that: The reflux time is 2-3h.

9. The solvent-free synthesis method of thiacloprid according to claim 5, characterized in that: The recrystallization solvent is added to the reaction product at a mass ratio of 94:160-200.

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