A preparation method of 4-acetoxy-2-methyl-2-buten-1-al

Abstract

The present invention relates to the technical field of organic chemical industry. The present invention discloses a preparation method of 4-acetoxy-2-methyl-2-buten-1-al, which comprises the following steps: S1. Mix a chloride, hexamine and water, react at a certain temperature for 8 hours, and after the reaction is completed, let it stand for stratification, and separate the unreacted chloride to obtain a quaternary ammonium salt solution; S2. Add a certain amount of acid to the quaternary ammonium salt solution to adjust the pH; S3. Add an organic phase solvent to the quaternary ammonium salt solution, and add a certain amount of copper catalyst, and carry out hydrolysis at a certain temperature. After the reaction is completed, separate the organic phase; S4. Add sodium carbonate with a concentration of 1% to the product of S3 to adjust it to neutral, recover the organic phase, and obtain pentanal through vacuum distillation. In the present invention, a quaternary ammonium salt is obtained by mixing a chloride, hexamine and water, and pentanal is obtained by adding an organic phase and a copper catalyst to the quaternary ammonium salt. By copper-catalyzed hydrolysis of the carbon-nitrogen bond, the reaction temperature can be reduced, and the selectivity and yield of hydrolysis can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical industry, and specifically relates to a preparation method of 4-acetoxy-2-methyl-2-buten-1-aldehyde. Background Art

[0002] 4-acetoxy-2-methyl-2-buten-1-aldehyde, abbreviated as pentanaldehyde, is a chemically synthesized product and is an intermediate of vitamin A. The storage condition is at room temperature and sealed storage. Pentanaldehyde is stable at room temperature and under sealed conditions, but it should be avoided to be stored together with strong oxidants, strong acids, and strong alkalis. It has irritating effects on eyes, skin, and respiratory tract, and is toxic if swallowed.

[0003] Generally, when preparing aromatic aldehydes through the Sommelet reaction, there is a good yield. However, when preparing aliphatic aldehydes, the yield is generally not high. Patent GB736488 (1955) reported that hydrolyzing formula 3 in an aqueous solution to obtain the target product formula 1, and the yield was only about 20%; Patent US5471004A, in order to improve the yield, carried out the hydrolysis reaction in two phases, and at the same time adopted acid catalysis and reacted at a higher temperature, and the yield was significantly improved. However, the product was hydrolyzed at a higher temperature under acidic conditions, and the products were complex. It was necessary to adopt column chromatography purification or purification with sodium bisulfite to remove impurities, which was inconvenient for industrialization and had a large loss; Patent CN1919825A reported that the hydrolysis yield could be improved through a microwave reactor, but the microwave catalytic reaction could not be realized in large-scale industrial production. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of 4-acetoxy-2-methyl-2-buten-1-aldehyde. By copper-catalyzed hydrolysis of the carbon-nitrogen bond, the reaction temperature can be reduced, and the selectivity and yield of hydrolysis can be improved; in addition, the product has high purity, and high-purity product can be obtained only by simple distillation.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the present invention provides the following technical solutions: A preparation method of 4-acetoxy-2-methyl-2-buten-1-aldehyde, comprising the following steps:

[0008] S1. Mix the chloride, hexamine, and an aqueous phase, react at a certain temperature for 8 hours, and after the reaction is completed, let it stand for stratification, and separate the unreacted chloride to obtain a quaternary ammonium salt solution.

[0009] S2. Add a certain amount of acid to the quaternary ammonium salt solution to adjust the pH.

[0010] S3. Add an organic phase solvent to the quaternary ammonium salt solution, add a certain amount of copper catalyst, and perform hydrolysis at a certain temperature for 6 hours. After the reaction, separate the organic phase.

[0011] S4. Add sodium carbonate with a concentration of 1% to the product of S3 to adjust it to neutral, recover the organic phase, and obtain pentanal through vacuum distillation.

[0012] As a preferred embodiment, in S1, the molar ratio of the chloride to hexamine is 1:1 - 1.5.

[0013] As a preferred embodiment, in S1, the reaction temperature of the chloride and hexamine in the aqueous phase is 25°C - 80°C, and the better temperature is between 30°C - 45°C.

[0014] As a preferred embodiment, in S1, the amount of water used is 1 - 10 times the mass of the chloride, and the better amount is 2 - 4 times.

[0015] As a preferred embodiment, in S3, the organic phase used is one of toluene, xylene, n - heptane, n - hexane, cyclohexane, ethyl acetate, ethyl propionate, methyl tert - butyl ether, and diethane, and the amount of the organic phase is 1 - 3 times the volume of the aqueous phase.

[0016] As a preferred embodiment, in S2, adjust the pH = 2 - 6 with an acid, and the better pH = 2.5 - 3.0.

[0017] As a preferred embodiment, in S3, the copper catalyst used is one of copper sulfate, copper acetate, cuprous chloride, and copper chloride. The better copper catalyst is copper acetate, and the concentration (m / v) of the copper catalyst in the aqueous phase is between 0.5% - 5%, and the better concentration is between 0.8% - 1.5%.

[0018] As a preferred embodiment, in S3, the reaction temperature is 20°C - 60°C, and the better temperature is between 25°C - 35°C.

[0019] (III) Beneficial Effects

[0020] The present invention provides a preparation method of 4 - acetoxy - 2 - methyl - 2 - buten - 1 - aldehyde, and the beneficial effects are as follows:

[0021] In the present invention, a quaternary ammonium salt is obtained by mixing a chloride, hexamine, and an aqueous phase at a certain temperature, and then the quaternary ammonium salt is hydrolyzed. During the hydrolysis process, an organic phase and a copper catalyst are added to obtain pentanal. By copper - catalyzed hydrolysis of the carbon - nitrogen bond, the reaction temperature can be reduced, the selectivity and yield of hydrolysis can be improved. In addition, the product has high purity, and a high - purity product can be obtained only by simple distillation. Specific Embodiments

[0022] To better understand the purpose, structure and function of the present invention, a further detailed description is given of a method for preparing 4-acetoxy-2-methyl-2-buten-1-al of the present invention.

[0023] A method for preparing 4-acetoxy-2-methyl-2-buten-1-al comprises the following steps:

[0024] S1. Mix a chloride, hexamine and water, react at a certain temperature for 8 hours, and after the reaction is completed, let it stand for stratification, separate the unreacted chloride to obtain a quaternary ammonium salt solution.

[0025]

[0026] S2. Add a certain amount of acid to the quaternary ammonium salt solution to adjust the pH.

[0027] S3. Add an organic phase solvent to the quaternary ammonium salt solution, and add a certain amount of copper catalyst, and carry out hydrolysis at a certain temperature for 6 hours. After the reaction is completed, separate the organic phase.

[0028]

[0029] S4. Add sodium carbonate with a concentration of 1% to the product of S3 to adjust it to neutral, recover the organic phase, and obtain pentanal through vacuum distillation.

[0030] As a preferred embodiment, in S1, the molar ratio of the chloride to hexamine is 1:1 to 1.5.

[0031] As a preferred embodiment, in S1, the reaction temperature of the chloride and hexamine in the aqueous phase is 25°C to 80°C, and the better temperature is between 30°C and 45°C.

[0032] As a preferred embodiment, in S1, the amount of water used is 1 to 10 times the mass of the chloride, and the better amount is 2 to 4 times.

[0033] As a preferred embodiment, in S3, the organic phase used is one of toluene, xylene, n-heptane, n-hexane, cyclohexane, ethyl acetate, ethyl propionate, methyl tert-butyl ether and diethane, and the amount of the organic phase used is 1 to 3 times the volume of the aqueous phase.

[0034] As a preferred embodiment, in S2, the pH is adjusted to 2 to 6 with an acid, and the better pH is 2.5 to 3.0.

[0035] As a preferred embodiment, in S3, the copper catalyst used is one of copper sulfate, copper acetate, cuprous chloride, and copper chloride. A better copper catalyst is copper acetate, and the concentration (m / v) of the copper catalyst in the aqueous phase is between 0.5% and 5%, preferably between 0.8% and 1.5%.

[0036] As a preferred embodiment, in S3, the reaction temperature is between 20°C and 60°C, preferably between 25°C and 35°C.

[0037] Example 1

[0038] Take 65 g (0.4 mol) of chloride, 84 g (0.6 mol) of hexamine, add 195 g of water, react at 30°C for 8 hours, then let it stand for stratification, separate 6.2 g of unreacted chloride, adjust the pH of the aqueous phase to 3.5 with 3 g of 50% hydrochloric acid, add 0.98 g of cuprous chloride, then add 390 ml of n-heptane, react at 35°C for 6 hours. After the reaction, separate the organic phase, adjust it to neutral with 1% sodium carbonate, recover the organic phase, and then distill the crude product under reduced pressure to obtain 41.62 g of 4-acetoxy-2-methyl-2-buten-1-al, with a gas phase content of 97.71%. The yield calculated based on the actually reacted chloride is 81%;

[0039] 1H-NMR data of 4-acetoxy-2-methyl-2-buten-1-al: 1 1H-NMR(CDCl 3 , 300 MHz): δ 9.48 (s, -CHO); 6.51 (t, H, -CH=);

[0040] 4.91 (d, 2H, -CH2-); 2.15 (s, 3H, -CH3); 1.80 (s, 3H, =C-CH3);

[0041] Example 2

[0042] Take 65 g (0.4 mol) of chloride, 67.2 g (0.48 mol) of hexamine, add 240 g of water, react at 30°C for 8 hours, then let it stand for stratification, separate 6.5 g of unreacted chloride, adjust the pH of the aqueous phase to 3.0 with 4 g of acetic acid, add 2.4 g of copper acetate, then add 300 ml of toluene, react at 30°C for 6 hours. After the reaction, separate the organic phase, adjust it to neutral with 1% sodium carbonate, recover the organic phase, and then distill the crude product under reduced pressure to obtain 43.45 g of 4-acetoxy-2-methyl-2-buten-1-al, with a gas phase content of 97.65%. The yield calculated based on the actually reacted chloride is 85%.

[0043] It will be understood that the present invention is described by way of some embodiments, and those skilled in the art will know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A preparation method of 4-acetoxy-2-methyl-2-buten-1-al, characterized in that, it comprises the following steps: S1. Mix the chloride, hexamine and water phase, react at a certain temperature for 8 hours, after the reaction ends, let it stand for layering, separate the unreacted chloride to obtain a quaternary ammonium salt solution, S2. Add a certain amount of acid to the quaternary ammonium salt solution to adjust the pH; S3. Add an organic phase solvent to the quaternary ammonium salt solution, and add a certain amount of copper catalyst. The copper catalyst used is one of copper sulfate, copper acetate, cuprous chloride, and copper chloride. Hydrolysis is carried out at a temperature of 25°C to 35°C for 6 hours. After the reaction ends, separate the organic phase, S4. Add sodium carbonate with a concentration of 1% to the product of S3 to adjust it to neutral, recover the organic phase, and obtain pentanal through vacuum distillation.

2. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S1, the molar ratio of the chloride to hexamine is 1:1 to 1.

5.

3. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S1, the reaction temperature of the chloride and hexamine in the water phase is 25°C to 80°C.

4. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S1, the amount of water used is 1 to 10 times the mass of the chloride.

5. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S3, the organic phase used is one of toluene, xylene, n-heptane, n-hexane, cyclohexane, ethyl acetate, ethyl propionate, and methyl tert-butyl ether, and the amount of the organic phase used is 1 to 3 times the volume of the water phase.

6. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S2, the pH is adjusted to 2 to 6 by the acid.

7. The preparation method of 4-acetoxy-2-methyl-2-buten-1-al according to claim 1, characterized in that: in S3, the concentration of the copper catalyst in the water phase is 0.5% to 5% (m / v).

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