Method for efficiently and continuously synthesizing 1-isothiocyanate-2-chloro-2-propylene

Abstract

The invention relates to the technical field of synthesis, and provides a method for efficiently and continuously synthesizing 1-isothiocyanate-2-chloro-2-propylene, which comprises the following steps: S1, reacting 2, 3-dichloropropene and a thiocyanate compound in a first-stage reaction kettle to obtain a reaction solution; s2, upwards discharging a water phase of the reaction liquid out of the first-stage reaction kettle, enabling an oil phase of the reaction liquid and undissolved sodium chloride solid to run downwards until the oil phase separated by an oil-solid separator enters a second-stage reaction kettle, and discharging the sodium chloride solid out of the system; s3, carrying out rearrangement reaction on the oil phase in a secondary reaction kettle to obtain a mixed solution; and S4, cooling the mixed solution, adding water, mixing, standing for layering to form a first oil phase and a first water phase, and carrying out reduced pressure rectification on the first oil phase to obtain the 1-isothiocyanate-2-chloro-2-propylene. According to the technical scheme, the problems of tedious reaction steps and low production efficiency of the 1-isothiocyanate-2-chloro-2-propylene in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of synthetic technology, and more specifically, to a method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene. Background Technology

[0002] 1-Isothiocyanate-2-chloro-2-propene is an important chemical intermediate with irreplaceable applications in the pharmaceutical and agricultural fields. In the pharmaceutical field, it is a core raw material for the synthesis of chloromethylthiocyanate, a key precursor for the preparation of highly effective drugs for treating depression and asthma. These drugs, due to their significant efficacy and low side effects, have seen continuously increasing demand in clinical treatment, directly driving market demand for 1-isothiocyanate-2-chloro-2-propene. In the agricultural field, this intermediate is a core raw material for the synthesis of neonicotinoid pesticides. Neonicotinoid pesticides, with their strong systemic properties, high insecticidal efficiency, and lack of cross-resistance with traditional pesticides, have become important agricultural inputs for protecting food and cash crops from pest threats, and are of great significance to global agricultural safety.

[0003] However, the current synthesis of this compound typically employs a batch reactor process, using 1,3-dichloropropene as a starting material. This involves reacting it with thiocyanate ions to generate an intermediate, which is then further functionalized to obtain the target product. This traditional method has significant drawbacks: cumbersome reaction steps, multiple material transfers and separations, low production efficiency, and poor batch-to-batch stability, making it unsuitable for large-scale production. Therefore, developing an efficient, stable, and easily scalable continuous synthesis process is of great significance and industrial value for improving the yield and purity of this key intermediate, reducing production costs, and enhancing process safety. Summary of the Invention

[0004] This invention proposes a highly efficient continuous synthesis method for 1-isothiocyanate-2-chloro-2-propene, which solves the problems of cumbersome reaction steps and low production efficiency of 1-isothiocyanate-2-chloro-2-propene in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene, comprising the following steps: S1. After reacting 2,3-dichloropropene and thiocyanate compounds in a primary reaction vessel, a reaction solution is obtained; S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards until the oil phase, after being separated by the oil-solid separator, enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In the secondary reactor, the oil phase undergoes a rearrangement reaction to obtain a mixed liquid; S4. After cooling the mixture, water is added, the mixture is mixed, and after standing and separating into layers, a first oil phase and a first aqueous phase are formed. The first oil phase is subjected to vacuum distillation to obtain 1-isothiocyanate-2-chloro-2-propene.

[0006] As a further technical solution, step S4 involves cooling the mixture, adding water, mixing, and allowing it to stand and separate into layers to form a first oil phase and a first aqueous phase. The first aqueous phase is extracted with a solvent, and after standing and separating into layers, a second oil phase and a second aqueous phase are formed. The first oil phase and the second oil phase are mixed and then subjected to vacuum distillation to obtain 1-isothiocyanate-2-chloro-2-propene. The extraction solvent includes ethyl acetate and methyl tert-butyl ether.

[0007] In the post-processing stage, this invention further improves the yield and purity by using a mixture of ethyl acetate and methyl tert-butyl ether as the extraction solvent. This is because the polarity of the mixed solvent formed by the mixture of ethyl acetate and methyl tert-butyl ether is close to that of the target product 1-isothiocyanate-2-chloro-2-propene, thus optimizing the compatibility between the extraction solvent and the 1-isothiocyanate-2-chloro-2-propene molecule and further improving the extraction efficiency.

[0008] In step S4 of this application, the extraction solution can be removed after vacuum distillation and directly recycled for extraction operations in the subsequent batch product washing process. This reduces the production cost caused by solvent consumption and reduces waste emissions, achieving a balance between green and economical processes.

[0009] As a further technical solution, the thiocyanate compound includes sodium thiocyanate.

[0010] As a further technical solution, the thiocyanate compound is reacted in a primary reaction vessel in the form of an aqueous solution of thiocyanate compound.

[0011] As a further technical solution, the mass fraction of the aqueous solution of the thiocyanate compound is 27%~30%.

[0012] As a further technical solution, the molar ratio of sodium thiocyanate in the aqueous solution of 2,3-chloropropene and thiocyanate compounds is 1:1.01~1.1.

[0013] As a further technical solution, in step S1, the reaction temperature is 84~90℃ and the reaction time is 20~40min.

[0014] As a further technical solution, in step S3, the rearrangement reaction consists of a first stage reaction and a second stage reaction. The temperature and time of the first stage reaction and the second stage reaction are different. At this time, the secondary reactor includes a first reactor and a second reactor arranged in series. The first stage reaction is carried out in the first reactor, and the second stage reaction is carried out in the second reactor.

[0015] As a further technical solution, the temperature of the first stage reaction is 90~95℃ and the reaction time is 20~40min; the temperature of the first stage reaction is 100~105℃ and the reaction time is 100~160min.

[0016] In the rearrangement reaction stage, this invention employs a two-stage reaction condition of low temperature followed by high temperature to improve the yield and purity of the final product, 1-isothiocyanate-2-chloro-2-propene. The first stage involves a reaction at a lower temperature of 90-95°C for 20-40 minutes, aiming to gently initiate the rearrangement reaction and allow the intermediate to begin molecular structure reconstruction smoothly and orderly. This stage effectively suppresses side reactions caused by excessively vigorous initial reactions and reduces the formation of byproducts. Subsequently, the temperature is raised to 100-105°C for the second stage reaction and maintained for 100-160 minutes. This higher temperature provides sufficient activation energy for the reaction system, ensuring that the intermediate is fully and completely converted into the target product, thereby maximizing the conversion rate and final yield.

[0017] As a further technical solution, the volume ratio of ethyl acetate to methyl tert-butyl ether is 4:5~6.

[0018] As a further technical solution, in step S4, the cooling is to cool to 75~85℃, preferably 80℃.

[0019] The working principle and beneficial effects of this invention are as follows: This invention employs a continuous design combining a primary and secondary reactor, along with precise separation by an oil-solid separator, to achieve an orderly connection between reaction, separation, and rearrangement. This significantly improves production efficiency, avoids the time-consuming drawbacks of intermittent processes, and meets the needs of large-scale production. As a result, it achieves a simultaneous improvement in yield and purity, providing a strong guarantee for continuous production. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following examples and comparative examples: The mass fraction of sodium thiocyanate aqueous solution is 30%.

[0022] Example 1 A method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene includes the following steps: S1. 2,3-Dichloropropene is fed from the upper part of the primary reactor, and sodium thiocyanate aqueous solution is fed from the lower part of the primary reactor. After reacting in the primary reactor at 90°C for 60 min, a reaction solution is obtained. The molar ratio of sodium thiocyanate in the 2,3-dichloropropene and sodium thiocyanate aqueous solution is 1:1.01. S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards. After separation by the oil-solid separator, the oil phase enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In a secondary reactor, the oil phase is reacted at 100°C for 160 minutes to obtain a mixed solution. S4. Cool the mixture to 80°C, add 50mL of water, mix, and let stand to separate into layers to form a first oil phase and a first aqueous phase. Distill the first oil phase under reduced pressure to obtain 1-isothiocyanate-2-chloro-2-propene. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 92.9% and the purity was 97.1%, based on 2,3-dichloropropene.

[0023] Example 2 A method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene includes the following steps: S1. 2,3-Dichloropropene is fed from the upper part of the primary reactor, and sodium thiocyanate aqueous solution is fed from the lower part of the primary reactor. After reacting in the primary reactor at 90°C for 60 min, a reaction solution is obtained. The molar ratio of sodium thiocyanate in the 2,3-dichloropropene and sodium thiocyanate aqueous solution is 1:1.01. S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards. After separation by the oil-solid separator, the oil phase enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In a secondary reactor, the oil phase is reacted at 100°C for 160 minutes to obtain a mixed solution. S4. Cool the mixture to 80℃, add 50mL of water, mix, and let stand to separate the layers to form a first oil phase and a first aqueous phase. Take the first aqueous phase and add 50mL of ethyl acetate and methyl tert-butyl ether in a volume ratio of 4:5 for extraction. After standing to separate the layers, a second oil phase and a second aqueous phase are formed. Mix the first oil phase and the second oil phase and then distill under reduced pressure to obtain 1-isothiocyanate-2-chloro-2-propene. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 93.2% and the purity was 97.8%, based on 2,3-dichloropropene.

[0024] Example 3 A method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene, characterized by comprising the following steps: S1. 2,3-Dichloropropene is fed from the upper part of the primary reactor, and sodium thiocyanate aqueous solution is fed from the lower part of the primary reactor. After reacting in the primary reactor at 95°C for 50 min, a reaction solution is obtained. The molar ratio of sodium thiocyanate in the 2,3-dichloropropene and sodium thiocyanate aqueous solution is 1:1.05. S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards. After separation by the oil-solid separator, the oil phase enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In a secondary reactor, the oil phase is reacted at 100°C for 140 minutes to obtain a mixed solution. S4. Cool the mixture to 80℃, add 50mL of water, mix, and let stand to separate the layers to form a first oil phase and a first aqueous phase. Take the first aqueous phase and add 50mL of ethyl acetate and methyl tert-butyl ether in a volume ratio of 4:5 for extraction. After standing to separate the layers, a second oil phase and a second aqueous phase are formed. Mix the first oil phase and the second oil phase and then distill under reduced pressure to obtain 1-isothiocyanate-2-chloro-2-propene. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 93.1% and the purity was 97.6%, based on 2,3-dichloropropene.

[0025] Example 4 A method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene, characterized by comprising the following steps: S1. 2,3-Dichloropropene is fed from the upper part of the primary reactor, and sodium thiocyanate aqueous solution is fed from the lower part of the primary reactor. After reacting in the primary reactor at 100°C for 40 min, a reaction solution is obtained. The molar ratio of sodium thiocyanate in the 2,3-dichloropropene and sodium thiocyanate aqueous solution is 1:1.1. S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards. After separation by the oil-solid separator, the oil phase enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In a secondary reactor, the oil phase is reacted at 100°C for 100 minutes to obtain a mixed solution. S4. Cool the mixture to 80℃, add 50mL of water, mix, and let stand to separate the layers to form a first oil phase and a first aqueous phase. Take the first aqueous phase and add 50mL of ethyl acetate and methyl tert-butyl ether in a volume ratio of 4:5 for extraction. After standing to separate the layers, a second oil phase and a second aqueous phase are formed. Mix the first oil phase and the second oil phase and then distill under reduced pressure to obtain 1-isothiocyanate-2-chloro-2-propene. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 93.6% and the purity was 97.5%, based on 2,3-dichloropropene.

[0026] Example 5 The only difference between this embodiment and Example 2 is that the volume ratio of ethyl acetate to methyl tert-butyl ether is 4:5 in this embodiment. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 95.0% and the purity was 98.5%, based on 2,3-dichloropropene.

[0027] Example 6 The only difference between this embodiment and Example 2 is that the volume ratio of ethyl acetate to methyl tert-butyl ether is 2:3 in this embodiment. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 94.5% and the purity was 97.9%, based on 2,3-dichloropropene.

[0028] Example 7 The only difference between this embodiment and Example 4 is that in this embodiment, the oil phase is reacted at 102°C for 140 minutes to obtain a mixture. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 96.5% and the purity was 99.3%, based on 2,3-dichloropropene.

[0029] Example 8 The only difference between this embodiment and Example 4 is that in this embodiment, the oil phase is reacted at 105°C for 140 minutes to obtain a mixture. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 96.1% and the purity was 99.3%, based on 2,3-dichloropropene.

[0030] Example 9 The only difference between this embodiment and embodiment 4 is that in this embodiment, the secondary reactor includes a first reactor and a second reactor arranged in series. The oil phase is first reacted in the first reactor at 90°C for 40 minutes; then it is transferred to the second reactor and reacted at 105°C for 140 minutes. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 98.7% and the purity was 99.6%, based on 2,3-dichloropropene.

[0031] Example 10 The only difference between this embodiment and Embodiment 8 is that, in this embodiment, the secondary reactor includes a first reactor and a second reactor arranged in series. The oil phase is first reacted in the first reactor at 95°C for 20 minutes; then transferred to the second reactor and reacted at 105°C for 140 minutes. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 98.9% and the purity was 99.5%, based on 2,3-dichloropropene.

[0032] Example 11 The only difference between this comparative example and Example 2 is that ethyl acetate is replaced with an equal volume of methyl tert-butyl ether in this comparative example. Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 89.9% and the purity was 92.6%, based on 2,3-dichloropropene.

[0033] Example 12 The only difference between this comparative example and Example 2 is that methyl tert-butyl ether is replaced with an equal volume of ethyl acetate in this comparative example; Results: The yield of 1-isothiocyanate-2-chloro-2-propene was 89.1% and the purity was 92.4%, based on 2,3-dichloropropene.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene, characterized in that, Includes the following steps: S1. After reacting 2,3-dichloropropene and thiocyanate compounds in a primary reaction vessel, a reaction solution is obtained; S2. The aqueous phase of the reaction liquid is discharged upwards from the primary reaction vessel, while the oil phase and undissolved sodium chloride solids of the reaction liquid flow downwards until the oil phase, after being separated by the oil-solid separator, enters the secondary reaction vessel, and the sodium chloride solids are discharged from the system. S3. In the secondary reactor, the oil phase undergoes a rearrangement reaction to obtain a mixed liquid; S4. After cooling the mixture, water is added, the mixture is mixed, and after standing and separating into layers, a first oil phase and a first aqueous phase are formed. The first oil phase is subjected to vacuum distillation to obtain 1-isothiocyanate-2-chloro-2-propene.

2. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 1, characterized in that, Step S4 involves cooling the mixture, adding water, mixing, and allowing it to stand and separate into layers to form a first oil phase and a first aqueous phase. The first aqueous phase is extracted with a solvent, and after standing and separating into layers, a second oil phase and a second aqueous phase are formed. The first oil phase and the second oil phase are mixed and then subjected to vacuum distillation to obtain 1-isothiocyanate-2-chloro-2-propene. The extraction solvents include ethyl acetate and methyl tert-butyl ether.

3. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 1, characterized in that, The thiocyanate compounds include sodium thiocyanate.

4. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 3, characterized in that, The thiocyanate compounds are reacted in a primary reaction vessel in the form of an aqueous solution of thiocyanate compounds.

5. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 4, characterized in that, The mass fraction of the aqueous solution of the thiocyanate compound is 27% to 30%.

6. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 5, characterized in that, The molar ratio of sodium thiocyanate in the aqueous solution of 2,3-chloropropene and thiocyanate compounds is 1:1.01~1.

1.

7. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 1, characterized in that, In step S1, the reaction temperature is 84~90℃ and the reaction time is 20~40min.

8. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 1, characterized in that, In step S3, the rearrangement reaction consists of a first stage reaction and a second stage reaction, and the first stage reaction and the second stage reaction have different temperatures and times.

9. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 8, characterized in that, The temperature of the first stage reaction is 90~95℃ and the reaction time is 20~40min; the temperature of the second stage reaction is 100~105℃ and the reaction time is 100~160min.

10. The method for efficient continuous synthesis of 1-isothiocyanate-2-chloro-2-propene according to claim 2, characterized in that, The volume ratio of ethyl acetate to methyl tert-butyl ether is 4:5~6.