CN120842165A - Preparation method of 5-methyl-1,3,4-oxadiazole-2-amine - Google Patents
Preparation method of 5-methyl-1,3,4-oxadiazole-2-amineInfo
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- CN120842165A CN120842165A CN202410513745.1A CN202410513745A CN120842165A CN 120842165 A CN120842165 A CN 120842165A CN 202410513745 A CN202410513745 A CN 202410513745A CN 120842165 A CN120842165 A CN 120842165A
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Abstract
本发明涉及化学合成领域，具体涉及5‑甲基‑1,3,4‑恶二唑‑2‑胺的制备方法，经过用氰化盐与卤素反应，乙酸酯与水合肼反应进而合成5‑甲基‑1,3,4‑恶二唑‑2‑胺，收率高，低成本，减小三废，利于工业化生产。The present invention relates to the field of chemical synthesis, and in particular to a method for preparing 5-methyl-1,3,4-oxadiazole-2-amine. The method comprises reacting cyanide with halogen, and reacting acetate with hydrazine hydrate to synthesize 5-methyl-1,3,4-oxadiazole-2-amine. The method has high yield, low cost, reduces three wastes, and is conducive to industrial production.
Description
Technical Field
The invention relates to the field of chemical synthesis, in particular to a preparation method of 5-methyl-1, 3, 4-oxadiazole-2-amine.
Background
5-Methyl-1, 3, 4-oxadiazol-2-amine has very broad prospects as a precursor of heterocyclic amide compounds useful as herbicides.
The process for producing 5-methyl-1, 3, 4-oxadiazole-2-amine has several industrial problems such as low yield, high cost, high risk and high yield of waste acid and waste water.
As described in the process according to document Bachkovskii, i.p.; ET AL KHIMIYA Geterotsiklicheskikh Soedinenii (1975), (11), 1493-8 and patent WO2018037223, the route is as follows:
The method takes the bromocyanides and the acethydrazide as raw materials to synthesize the 5-methyl-1, 3, 4-oxadiazole-2-amine, the raw material bromocyanides are expensive and easy to decompose, the bromocyanides are not easy to store, the yield is only 30%, the production cost is high, and the industrial production is not easy to realize.
According to the process described in patent CN 116034103a, the route is as follows:
The 5-methyl-1, 3, 4-oxadiazole-2-amine is synthesized by taking semicarbazide hydrochloride and acetic acid as raw materials and using phosphoryl chloride for dehydration, so that a large amount of phosphorus-containing wastewater can be generated, the yield is low, the production cost is high, and the industrial production is not easy.
Disclosure of Invention
The present invention aims to solve at least one of the problems of the prior art.
The invention provides a preparation method of 5-methyl-1, 3, 4-oxadiazole-2-amine, which is characterized in that cyanide reacts with halogen, acetate reacts with hydrazine hydrate to synthesize 5-methyl-1, 3, 4-oxadiazole-2-amine, the yield is high, the cost is low, three wastes are reduced, and the method is favorable for industrial production.
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following reaction route:
Wherein R 1 is lithium, sodium, potassium, copper or iron, X is fluorine, chlorine, bromine or iodine, and R 2 is C1-C8 fatty alkane.
In particular, the "C1-C8 fatty alkyl" may be branched or unbranched. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 4-methylpentyl, n-heptyl, 3-ethylpentyl, 2-ethylhexyl, 2, 3-dimethylpentyl, n-octyl, 3-propylpentyl, 6-methylheptyl.
Specifically, R 1 is sodium or potassium.
Specifically, X is bromine.
Specifically, R 2 is methyl or ethyl.
Specifically, the preparation method comprises the following steps:
Reacting a compound of formula I with a compound of formula II to form a first intermediate;
reacting a compound of formula III with a compound of formula IV to form a second intermediate;
The first intermediate is reacted with a second intermediate to produce a compound of formula V, 5-methyl-1, 3, 4-oxadiazol-2-amine.
Specifically, the reaction of a compound of formula I with a compound of formula II is carried out in the presence of a solvent. The solvent is methanol, ethanol, isopropanol, acetonitrile or water, etc. Optionally, the solvent is 1-10 times the volume of the compound of formula I.
Specifically, the reaction temperature of the compound of the formula I and the compound of the formula II is-5-25 ℃.
Specifically, the molar equivalent ratio of the compound of formula I to the compound of formula II is 1.0 (0.9-2.0), such as 1.0 (1.02-1.05).
The method for preparing the first intermediate comprises the steps of adding a compound of a formula I into a solvent, controlling the temperature to be-5-25 ℃, adding an aqueous solution of a compound of a formula II, and reacting at the temperature of-5-25 ℃ to generate the first intermediate.
Specifically, the reaction temperature of the compound of formula III and the compound of formula IV is 25 ℃ to 70 ℃, for example 40 ℃ to 60 ℃. In some embodiments, the reaction time is 1 to 6 hours.
Specifically, the molar equivalent ratio of the compound of the formula I to the compound of the formula IV to the compound of the formula III is (1.0:1.0) - (1.1:1.0) - (2.0).
Specifically, the method for preparing the second intermediate comprises the steps of controlling the temperature of the compound of the formula III to be 25-70 ℃, adding the compound of the formula IV (hydrazine hydrate), and reacting at the temperature of 25-70 ℃ to generate the second intermediate.
Specifically, the reaction temperature of the first intermediate and the second intermediate is-5 ℃ to 25 ℃, for example-5 ℃ to 0 ℃.
Specifically, the preparation method further comprises the steps of neutralizing with alkali and desolvation crystallization after the first intermediate and the second intermediate react to form the compound of the formula V. The obtained crystal is the compound of the formula V.
Specifically, the alkali is sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate or the like.
The preparation method comprises the steps of maintaining the solution of the first intermediate at a required temperature, then dropwise adding the solution of the second intermediate into a reactor until the reaction is finished, adding alkali into the reactor for neutralization, then evaporating to remove the solvent, and heating and dissolving the residual solution and then cooling for crystallization to obtain the compound of the formula V.
Specifically, the temperature of the cooling crystallization is 0 to 30 ℃, for example 25 ℃.
Compared with the process of patent WO2018037223, the invention uses halogen and cyanide salt as cyanide sources, solves the problem that the price of the bromocyanides is high, requires low-temperature transportation and preservation, and is beneficial to industrial production. Compared with the process of the patent CN116034103A, the process avoids the organophosphorus reagents such as phosphorus oxychloride, phosphorus trichloride and the like, and avoids the production of waste acid and phosphorus-containing wastewater.
Compared with the existing method, the method also has the advantage of easy processing of the reaction product, and the 5-methyl-1, 3, 4-oxadiazole-2-amine can be obtained through simple crystallization, so that the defect that the reaction product is difficult to process in the existing method is overcome.
The invention has at least one of the following beneficial effects:
1) The raw material cost is low, the yield is high, the operation is simple, and the industrial production amplification practicability is strong;
2) The reaction condition is milder, the post-treatment is simpler, and the yield is high;
3) The three wastes are less, the phosphorus-containing wastewater or waste acid is avoided, and the method is more environment-friendly.
Detailed Description
The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The amounts of reactants and products in the following examples were measured by liquid chromatography (AGILENT HPLC 1260). In the following examples, the conversion and selectivity of the reaction were calculated by the following formulas:
conversion = (molar amount of raw material charged-molar amount of raw material remaining in product)/molar amount of raw material charged ×100%
Selectivity = actual molar amount of target product/theoretical molar amount of target product x 100%
Yield = product yield/raw material molecular weight/product molecular weight x raw material feed amount x 100%
The compound of formula V is 5-methyl-1, 3, 4-oxadiazol-2-amine.
Example 1
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added methanol (197.14 g), then Br 2 (1.02 eq) was added, cooled to-5 ℃ and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃ with vigorous heat release during the addition for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Methyl acetate (1.11 eq) is added into a 100ml four-mouth bottle, 80 percent hydrazine hydrate (1.06 eq) is dripped after the temperature is raised to 40-50 ℃, the dripping process is slightly exothermic, the dripping lasts for about 30min, the temperature is raised to 50-60 ℃ after the dripping is finished, the reaction is carried out for 5-6h, and a reaction liquid B is prepared for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5 ℃, a solution of sodium hydroxide (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, and the free formula V compound was released, and the reaction solution turned from pale yellow to dark red during the dropwise addition. The solvent (methanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 25 ℃ for about 3 hours. After 3h, the reaction solution was filtered, drained and dried to give 90.08g of pale white solid with 98% content and 90.0% yield (based on sodium cyanide).
Example 2
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added ethanol (199.2 g), then Br 2 (1.05 eq) was added, cooled to-5 ℃, and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃with vigorous heat release during the dropwise addition for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Adding ethyl acetate (1.11 eq) into a 100ml four-mouth bottle, heating to 40-50 ℃, then dripping 80% hydrazine hydrate (1.06 eq.) with slight heat release in the dripping process, continuously dripping for about 30min, heating to 50-60 ℃ after dripping is completed, and reacting for 5-6h at a temperature of 50-60 ℃ after reaction is completed, thus preparing a reaction liquid B for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5 ℃, a solution of sodium hydroxide (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, and the free formula V compound was released, and the reaction solution was changed from pale yellow to dark red during the dropwise addition. The solvent (ethanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 25 ℃ for about 3 hours. After 3h, the reaction mixture was filtered, drained and dried to give 92.08g of a pale white solid, 98.1% yield 92.0% (based on sodium cyanide).
Example 3
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added methanol (197.14 g), then Br 2 (1.02 eq) was added, cooled to-5 ℃ and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃ with vigorous heat release during the addition for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Methyl acetate (1.11 eq) is added into a 100ml four-mouth bottle, 80 percent hydrazine hydrate (1.06 eq) is dripped after the temperature is raised to 40-50 ℃, the dripping process is slightly exothermic, the dripping lasts for about 30min, the temperature is raised to 50-60 ℃ after the dripping is finished, the reaction is carried out for 5-6h, and a reaction liquid B is prepared for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5℃and a solution of sodium carbonate (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, the free form V compound, and the reaction solution turned from pale yellow to dark red during the dropwise addition. The solvent (methanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 0-5 ℃ for about 3 hours. After 3h, the reaction solution was filtered, drained and dried to give 88.68g, 97.9% yield 88.68% (based on sodium cyanide).
Example 4
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added methanol (197.14 g), then Br 2 (1.02 eq) was added, cooled to-5 ℃ C. Fwith-5~0 ℃ C., a solution of potassium cyanide (65.1 g,1.0 eq) in water (155.24 mL) was slowly added dropwise, and the addition was vigorously exothermic during the dropwise addition, and continued for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Methyl acetate (1.11 eq) is added into a 100ml four-mouth bottle, 80 percent hydrazine hydrate (1.06 eq) is dripped after the temperature is raised to 40-50 ℃, the dripping process is slightly exothermic, the dripping lasts for about 30min, the temperature is raised to 50-60 ℃ after the dripping is finished, the reaction is carried out for 5-6h, and a reaction liquid B is prepared for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5 ℃, a solution of sodium hydroxide (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, and the free formula V compound was released, and the reaction solution turned from pale yellow to dark red during the dropwise addition. The solvent (methanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 25 ℃ for about 3 hours. After 3h, the reaction solution was filtered, drained and dried to give 90.08g of pale white solid with 98% yield of 90.0% (based on potassium cyanide).
Comparative example 1
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added methanol (197.14 g), then Br 2 (1.02 eq) was added, cooled to-5 ℃ and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃ with vigorous heat release during the addition for 1h. After the dripping is finished, heating to 40-45 ℃ and stirring for 3 hours to prepare a reaction solution A for later use;
(2) Methyl acetate (82.43 g) is added into a 100ml four-mouth bottle, 80 percent hydrazine hydrate (65.65 g) is dripped after the temperature is raised to 40-50 ℃, the dripping process is slightly exothermic, the dripping lasts for about 30min, the temperature is raised to 50-60 ℃ after the dripping is finished, the reaction is carried out for 5-6h, and a reaction solution B is prepared for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the temperature of the reaction solution is reduced by 0-5 ℃, a solution of sodium hydroxide (47.99 g) and water (48.18 g) is added dropwise into the reaction solution to neutralize the hydrogen bromide, and the free compound of the formula V is changed from pale yellow to dark red in the process of dropwise addition. The solvent (methanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 25 ℃ for about 3 hours. After 3h, the reaction solution was filtered, drained and dried to give 60.4g of a pale white solid with 95% yield of 61.0% (based on sodium cyanide).
As a result of comparison of comparative example 1 with example 1, it was found that when the temperature of the preparation reaction liquid A was raised to 40 to 45℃the reaction yield was lowered and the content was lowered.
Comparative example 2
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added ethanol (199.2 g), then Br 2 (1.05 eq) was added, cooled to-5 ℃, and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃with vigorous heat release during the dropwise addition for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Adding ethyl acetate (1.11 eq) into a 100ml four-mouth bottle, heating to 40-50 ℃, then dripping 80% hydrazine hydrate (1.06 eq.) with slight heat release in the dripping process, continuously dripping for about 30min, heating to 50-60 ℃ after dripping is completed, and reacting for 5-6h at a temperature of 50-60 ℃ after reaction is completed, thus preparing a reaction liquid B for standby;
(3) And (3) heating the reaction liquid B to 30-35 ℃, then controlling the temperature to 30-35 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is very intense in the dropwise adding process, and the dropwise adding time is about 2 hours. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5 ℃, a solution of sodium hydroxide (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, and the free formula V compound was released, and the reaction solution was changed from pale yellow to dark red during the dropwise addition. The solvent (ethanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. The solution was then warmed to 95 ℃ and dissolved with stirring until clear. Then slowly cooling to 25 ℃ for about 3 hours. After 3h, the reaction mixture was filtered, drained and dried to give 70.3g of a pale white solid, 94.1% strength, 71% yield (based on sodium cyanide).
As a result of comparison between comparative example 2 and example 2, it was found that when the reaction temperature of the reaction solution A and the reaction solution B was increased to 30 to 35 ℃, the heat release was severe, the risk was increased, the reaction yield was decreased, and the content was decreased.
Comparative example 3
The preparation method of the 5-methyl-1, 3, 4-oxadiazole-2-amine comprises the following steps:
(1) To a 500mL reaction flask was added methanol (197.14 g), then Br 2 (1.02 eq) was added, cooled to-5 ℃ and a solution of NaCN (49 g,1.0 eq) in water (155.24 mL) was slowly added dropwise at-5~0 ℃ with vigorous heat release during the addition for 1h. After the dripping is finished, the room temperature is restored to 20-25 ℃ and stirred for 3 hours, and a reaction solution A is prepared for standby;
(2) Methyl acetate (1.11 eq) is added into a 100ml four-mouth bottle, 80 percent hydrazine hydrate (1.06 eq) is dripped after the temperature is raised to 40-50 ℃, the dripping process is slightly exothermic, the dripping lasts for about 30min, the temperature is raised to 50-60 ℃ after the dripping is finished, the reaction is carried out for 5-6h, and a reaction liquid B is prepared for standby;
(3) And cooling the reaction liquid B to-5 ℃, controlling the temperature to-5 ℃ to 0 ℃, and dropwise adding the reaction liquid A into the reaction liquid B, wherein the heat release is obvious in the dropwise adding process, and the dropwise adding time is about 1h. After the completion of the dropwise addition, the temperature is raised to room temperature and stirred for 2 hours, and the reaction is completed.
(4) After the reaction, the reaction solution was cooled to 0-5℃and a solution of sodium carbonate (1.2 eq) in water (48.18 g) was added dropwise to the reaction solution to neutralize the hydrogen bromide, the free form V compound, and the reaction solution turned from pale yellow to dark red during the dropwise addition. The solvent (methanol) is distilled off under normal pressure or reduced pressure from the reaction solution after the completion of the dissociation to obtain an aqueous solution of the compound of formula V. Water (100 ml) was then added, and the solution was warmed to 95℃and dissolved with stirring until clear. Then slowly cooling to 0-5 ℃ for about 3 hours. After 3h, the reaction mixture was filtered, drained and dried to give 47.5g, 99.9% yield of 48% (based on sodium cyanide).
As a result of comparison between comparative example 3 and example 3, it was found that when the amount of water (100 ml) for crystallization at the end of the reaction was increased, the content of precipitated product was 99%, but the yield was reduced to 48%, so that the increase in the amount of water decreased the reaction yield and increased the content.
While the invention has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (10)
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