A process for the preparation of cycloxazolidinone intermediates using acidic alumina as catalyst

Abstract

The application discloses a method for preparing a cycloxazolidinone intermediate by using acidic aluminum oxide as a catalyst, relates to the technical field of cycloxazolidinone preparation, and is characterized in that, under the condition of no additional solvent, by using acidic aluminum oxide as a catalyst, N-methyl cyanoaminoformic acid ethyl ester and a dimethylamine hydrochloride aqueous solution are heated to a set temperature under the catalysis of the acidic aluminum oxide, and then a cycloxazolidinone intermediate, guanidine hydrochloride, can be efficiently and highly selectively synthesized. The method reduces the unit consumption of the dimethylamine hydrochloride, improves the product yield, and does not need to introduce chloroform to extract the product, and is more green and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of cycloazinone preparation technology, and specifically to a method for preparing cycloazinone intermediates using acidic alumina as a catalyst. Background Technology

[0002] Cycloazolinone, also known as Lincaojing, Wilbur, and 3-cyclohexyl-6-dimethylamino-1-methyl-1,3,5-triazine-2,4-dione, is a systemic, selective, post-emergence contact herbicide developed by DuPont in 1974. It is a highly effective, low-toxicity, and selective herbicide widely used in forestry weed control worldwide. It has a broad spectrum of weed control, long residual effect, low toxicity, good solubility in water, and high leaching solubility in soil, thus avoiding cumulative pollution. This meets my country's environmental protection requirements and gives it a significant position in the Chinese herbicide market.

[0003] Since the 1980s, my country has made some progress in the research of cycloazinones. However, due to the long synthetic route and high technical difficulty, certain problems still exist in the industrial production process. Currently, the synthetic method of cycloazinones in industrial production mainly refers to US patents US4178448 and US4150225. This method involves reacting a mixture of dimethylamine aqueous solution and dimethylamine hydrochloride aqueous solution with methyl N-methylcyanocarbamate to generate methyl N-methyl-NNNN-dimethylamidinecarbamate. The methyl N-methyl-NNNN-dimethylamidinecarbamate is then extracted multiple times with chloroform to obtain a chloroform solution of methyl N-methyl-NNNN-dimethylamidinecarbamate, which is then removed by distillation. This method requires solvent replacement and distillation operations, making it relatively complex. The utilization rate of dimethylamine is low (requiring 1.4 equivalents of methyl N-methylcyanocarbamate), and approximately 2% of the product is lost in the aqueous solution after extraction. The single-step yield is only about 93%, and energy consumption is high.

[0004] Based on this, the production process of cycloazinone was optimized, and a new method with "simple production process, low cost, high yield and low energy consumption" was developed, which has certain application value and is expected to promote the application of cycloazinone products. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing cycloazinone intermediates using acidic alumina as a catalyst. By optimizing the synthetic process route, the cycloazinone intermediate can be prepared with high efficiency and selectivity. The intermediate is then added to cyclohexyl isocyanate and cyclized to obtain cycloazinone.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing cycloazinone intermediates using acidic alumina as a catalyst, comprising: using ethyl N-methylcyanocarbamate and dimethylamine hydrochloride to efficiently and selectively generate guanidine hydrochloride under the catalysis of acidic alumina.

[0007] Preferably, the method for preparing acidic alumina includes the following steps: Weigh out 50 grams of industrial activated alumina (morphology shown in the appendix). Figure 1 The alumina was soaked in 0.1 M dilute nitric acid for 12 h. After being removed and washed with water until neutral, it was dried at 100 °C for 2 h, and then calcined at 800 °C for 5 h in air to obtain acidic alumina (morphology shown in Appendix). Figure 2 The catalyst prepared by this method exhibits a change in morphology, with a spherical morphology resulting in an increased specific surface area and more activation sites, thus leading to better catalytic activity. Preferably, 0.1 M dilute nitric acid can be replaced with other acidic solutions.

[0008] Preferably, the novel method for synthesizing guanidine hydrochloride includes the following steps: Add an aqueous solution of N-methylcyanocarbamate and dimethylamine hydrochloride to a reaction vessel, then add acidic alumina and stir; then heat to 90-100 ℃ and keep warm until the N-methylcyanocarbamate reaction is complete; filter, wash the filter cake with process water, combine the filtrate and washing liquid, dehydrate under negative pressure to obtain guanidine hydrochloride.

[0009] Preferably, the acidic alumina catalyst can be reused more than 5 times.

[0010] Preferably, the concentration of N-methylcyanocarbamate is above 90%.

[0011] Preferably, the concentration of the dimethylamine hydrochloride aqueous solution is 70%.

[0012] Preferably, the amount of the dimethylamine hydrochloride aqueous solution added is 1.05 times the molar amount of N-methylcyanocarbamate.

[0013] Compared with the prior art, the beneficial effects of the present invention are: The acidic alumina used in this invention has a higher specific surface area and more acidic sites compared to traditional industrial alumina. The method used in this invention improves the utilization rate of dimethylamine hydrochloride; The method used in this invention replaces the distillation step with simple atmospheric distillation, making the operation more convenient; The method used in this invention directly separates guanidine hydrochloride solid without the need to introduce other solvents, thus reducing production costs; The method used in this invention directly separates guanidine hydrochloride solid without the need for chloroform extraction, thereby increasing yield and reducing production costs. The method used in this invention separates guanidine hydrochloride with a content of 98.5% and a yield of over 95%. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is a SEM image of traditional commercial alumina; Figure 2 This is a SEM image of alumina after acid treatment. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0017] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0018] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0019] Example 1 Weigh 50 g of industrial activated alumina and soak it in 0.1 M dilute nitric acid for 12 h. After removing it and washing it with water until neutral, dry it at 100 ℃ for 2 h, and then calcine it at 800 ℃ for 5 h in air atmosphere to obtain acidic alumina.

[0020] Example 2 Weigh 50 g of industrial activated alumina and soak it in 0.1 M dilute hydrochloric acid for 12 h. After washing with water until neutral, dry it at 100 ℃ for 2 h, and then calcine it at 800 ℃ for 5 h in air atmosphere to obtain acidic alumina.

[0021] Example 3 Weigh 50 g of industrial activated alumina and soak it in 0.1 M acetic acid solution for 12 h. After washing with water until neutral, dry it at 100 ℃ for 2 h, and then calcine it at 800 ℃ for 5 h in air atmosphere to obtain acidic alumina.

[0022] Example 4 Weigh 50 g of industrial activated alumina and soak it in 0.1 M formic acid for 12 h. After washing with water until neutral, dry it at 100 ℃ for 2 h, and then calcine it at 800 ℃ for 5 h in air atmosphere to obtain acidic alumina.

[0023] Example 5 Weigh 50 g of industrial activated alumina and soak it in 0.1 M acetic acid for 12 h. After washing with water until neutral, dry it at 100 °C for 2 h, and then calcine it at 800 °C for 5 h in air to obtain acidic alumina.

[0024] Example 6 Weigh 50 g of industrial activated alumina and soak it in 0.1 M citric acid for 12 h. After washing with water until neutral, dry it at 100 ℃ for 2 h, and then calcine it at 800 ℃ for 5 h in air atmosphere to obtain acidic alumina.

[0025] Example 7 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 1 were added to a 500 mL four-necked flask. Stirring was started, and the temperature was raised to 95 °C and maintained for 8 h. After confirming complete reaction of N-methylcyanocarbamate, the mixture was cooled to room temperature, filtered, and the filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and washing liquid were mixed, and the solvent was removed under negative pressure. After drying the white solid, 187.47 g of product, namely the cycloazinone intermediate-guanidine hydrochloride, was obtained, with a purity of 98.5% and a yield of 95.6%. The catalyst prepared under these experimental conditions, when used in conjunction with the reaction process conditions, yielded good product content and yield.

[0026] Example 8 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 2 were added to a 500 mL four-necked flask. The mixture was stirred and heated to 95 °C and kept at that temperature for 8 h. The reaction of N-methylcyanocarbamate was detected to be complete. The mixture was then cooled to room temperature and filtered. The filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and the washing liquid were mixed and the solvent was removed under negative pressure. The white solid was dried and weighed to obtain 187.25 g of product, namely cycloazinone intermediate-guanidine hydrochloride, with a purity of 98.2% and a yield of 89.6%.

[0027] Example 9 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 3 were added to a 500 mL four-necked flask. Stirring was started, the temperature was raised to 95 °C, and kept at that temperature for 8 h. The reaction of N-methylcyanocarbamate was detected to be complete. The mixture was cooled to room temperature, filtered, and the filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and the washing liquid were mixed, and the solvent was removed under negative pressure. After drying the white solid, 187.17 g of product, namely cycloazinone intermediate-guanidine hydrochloride, was obtained, with a purity of 98.1% and a yield of 91.6%.

[0028] Example 10 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 4 were added to a 500 mL four-necked flask. The mixture was stirred and heated to 95 °C and kept at that temperature for 8 h. The reaction of N-methylcyanocarbamate was detected to be complete. The mixture was then cooled to room temperature and filtered. The filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and the washing liquid were mixed and the solvent was removed under negative pressure. The white solid was dried and weighed to obtain 186.47 g of product, namely cycloazinone intermediate-guanidine hydrochloride, with a purity of 98.1% and a yield of 75.6%.

[0029] Example 11 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 5 were added to a 500 mL four-necked flask. The mixture was stirred and heated to 95 °C and kept at that temperature for 8 h. The reaction of N-methylcyanocarbamate was detected to be complete. The mixture was then cooled to room temperature and filtered. The filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and the washing liquid were mixed and the solvent was removed under negative pressure. The white solid was dried and weighed to obtain 186.47 g of product, namely cycloazinone intermediate-guanidine hydrochloride, with a purity of 98.5% and a yield of 82.6%.

[0030] Example 12 118 g (0.922 mol) of N-methylcyanocarbamate, 111.66 g (70%, 0.959 mol) of dimethylamine hydrochloride aqueous solution, and 9.38 g (99%, 0.092 mol) of acidic alumina prepared in Example 6 were added to a 500 mL four-necked flask. The mixture was stirred and heated to 95 °C and kept at that temperature for 8 h. The reaction of N-methylcyanocarbamate was detected to be complete. The mixture was then cooled to room temperature and filtered. The filter cake was washed with 100 g of process water. The filter cake was dried and recovered. The filtrate and the washing liquid were mixed and the solvent was removed under negative pressure. The white solid was dried and weighed to obtain 187.37 g of product, namely cycloazinone intermediate-guanidine hydrochloride, with a purity of 98.2% and a yield of 92.3%.

[0031] Example 13 The specific implementation method of this example is the same as that of Example 7, except that the acidic alumina used is alumina that has been recovered and dried once, and finally a white dried product weighing 188.3 g is obtained with a content of 98.02% and a yield of 95.56%.

[0032] Example 14 The specific implementation method of this example is the same as that of Example 7, except that the acidic alumina used is alumina that has been recycled and dried twice. The final product obtained is white, dried and weighed to 185.01 g, with a content of 98.86% and a yield of 94.69%.

[0033] Example 15 The specific implementation method in this example is the same as in Example 7, except that the acidic alumina used is alumina that has been recycled and dried three times. The final product obtained is white, dried, and weighed to 187.86 g, with a content of 98.36% and a yield of 95.66%.

[0034] Example 16 The specific implementation method of this example is the same as that of Example 7, except that the acidic alumina used is alumina that has been recycled and dried six times. Finally, a white product with a content of 98.04% and a yield of 95.13% is obtained after drying.

[0035] Example 17 The specific implementation method in this example is the same as in Example 7, except that the heat preservation temperature is 85 ℃, and a white product weighing 151.54 g after drying is finally obtained, with a content of 92.45% and a yield of 72.53%.

[0036] Comparative Example 1 The specific implementation method of this example is the same as that of Example 7, except that the alumina used is alkaline alumina. The final product obtained after drying is white and weighs 167.01 g, with a content of 93.14% and a yield of 80.53%.

[0037] Comparative Example 2 The specific implementation method of this example is the same as that of Example 7, except that the alumina used is commercial alumina, and the final product obtained after drying is 165.01 g with a content of 91.14% and a yield of 75.53%.

[0038] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing cycloazinone intermediates using acidic alumina as a catalyst, characterized in that, Guanidine hydrochloride can be synthesized efficiently and selectively by heating an aqueous solution of N-methylcyanocarbamate and dimethylamine hydrochloride to a set temperature under the catalysis of acidic alumina without the addition of additional solvents.

2. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The acidic alumina can be obtained by treatment with alkaline alumina or neutral alumina.

3. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The acidic alumina can be reused more than 5 times.

4. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The concentration of the dimethylamine hydrochloride aqueous solution is 70%.

5. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The temperature is 50-100℃.

6. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 5, characterized in that, The temperature is 90-100 ℃.

7. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The raw material contains more than 90% ethyl N-methylcyanocarbamate.

8. The method for preparing cycloazinone intermediates using acidic alumina as a catalyst according to claim 1, characterized in that, The reaction formula for the synthesis of guanidine hydrochloride from N-methylcyanocarbamate and dimethylamine hydrochloride aqueous solution under the catalysis of alumina is as follows: 。

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