A kind of synthesis method of 2,2-dimethoxyacetaldehyde

Abstract

The present invention discloses a method for synthesizing 2,2-dimethoxyacetaldehyde. A 40% aqueous solution of industrial glyoxal is first dehydrated using a thin-film evaporator. The solution is then reacted with methanol at a certain temperature using N-sulfonic acid saccharin as a catalyst to produce a 2,2-dimethoxyacetaldehyde reaction solution. The method has a simple operation process and a 2,2-dimethoxyacetaldehyde yield greater than 70%. The method does not require the addition of additional reagents, has a short reaction cycle, and can achieve a product yield of over 70%.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a synthesis method of 2,2-dimethoxyacetaldehyde. Background Art

[0002] 2,2-Dimethoxyacetaldehyde is a colorless, low-toxic, non-volatile aldehyde containing a highly reactive aldehyde group and an acetal group that is less reactive but can be easily converted into an aldehyde group. In synthetic chemistry, it is often used in reactions such as ring closure, extension of parent chain structure, and introduction of aldehyde groups. As an important fine intermediate, it is widely used in the resin industry, fragrance industry, and pharmaceutical industry.

[0003] The synthesis of 2,2-dimethoxyacetaldehyde is mainly prepared by acid-catalyzed dehydration with glyoxal and methanol as raw materials under certain conditions, such as patent (CN 103242145A); patent (CN 1184801A) reports the preparation of 2,2-dimethoxyacetaldehyde by the reaction of glyoxal, glyoxal diacetal and methanol under the catalysis of an acidic resin. Patent (CN

[0004] 101676252A) uses glyoxal, the corresponding ester of methanol and methanol to react under the catalysis of an acidic resin to prepare 2,2-dimethoxyacetaldehyde; and in the literature (The Monoacetalization of Glyoxal: A Direct of 2,2-dimethoxy and Diethoxy Ethanals, Synthetic Communication, 1988, 18(2), 1343-1348), Chastrette et al. describe the acetalization of glyoxal in the presence of chloroform, a constant boiling agent, using a Soxhlett apparatus filled with a desiccant to remove water generated during the preparation process. However, these methods generally have some problems, such as the need to add additional reagents, long reaction cycle, and low product yield. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for synthesizing 2,2-dimethoxyacetaldehyde to solve the problems of the existing method such as the need to add additional reagents, long reaction cycle, and low product yield.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for synthesizing 2,2-dimethoxyacetaldehyde, comprising the following steps:

[0008] Step 1, dehydration treatment of industrial 40% glyoxal aqueous solution: pumping the industrial 40% glyoxal aqueous solution into a thin film evaporator for vacuum dehydration, adding methanol to the dehydrated glyoxal when the weight ratio of glyoxal in the dehydrated glyoxal is 55-65%, and then pumping it into a thin film evaporator for vacuum dehydration, and stopping the dehydration when the weight ratio of glyoxal in the dehydrated glyoxal alcohol solution is 75-80%, thereby obtaining a qualified dehydrated glyoxal alcohol solution;

[0009] Step 2, synthesis of 2,2-dimethoxyacetaldehyde: adding methanol to a reaction kettle containing dehydrated glyoxal alcohol solution, and then adding N-sulfonic acid saccharin, and preparing 2,2-dimethoxyacetaldehyde through dehydration reaction;

[0010] The structural formula of the N-sulfonic acid saccharin is: Wherein R is hydrogen or nitro.

[0011] The present invention also includes the following technical features:

[0012] Specifically, in step 1, the operating temperature of the thin film evaporator is 50-90°C.

[0013] Specifically, in step 1, the thin film evaporator has an operating pressure of 10 to 150 mbar.

[0014] Specifically, in step 2, the molar ratio of dehydrated glyoxal, methanol and N-sulfonic acid saccharin is 1:5-20:0.001-0.05.

[0015] Specifically, in step 2, the molar ratio of dehydrated glyoxal, methanol and N-sulfonic acid saccharin is 1:8-15:0.001-0.01.

[0016] Specifically, in step 2, the synthesis reaction temperature is 40-85°C.

[0017] Specifically, in step 2, the synthesis reaction temperature is 65° C. and the reaction time is 5 h.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] The present invention is simple to operate and low in cost. Compared with patents CN 1184801A and CN 101676252A, the present invention does not require the addition of additional additives. Compared with patent CN 103242145A, the present invention uses a novel N-sulfonic acid saccharin catalyst, which significantly shortens the reaction time. Compared with the yields of the above patents, the yield of 2,2-dimethoxyacetaldehyde obtained by the method of the present invention can reach more than 70%. DETAILED DESCRIPTION

[0020] The present invention provides a method for synthesizing 2,2-dimethoxyacetaldehyde. The method comprises the following steps: first, vacuum dehydrating an industrial 40% glyoxal aqueous solution using a thin film evaporator; then, adding a certain amount of methanol to the dehydrated glyoxal solution after the dehydration is qualified; and then vacuum dehydrating the solution again; then, using the dehydrated glyoxal alcohol solution as a reaction raw material, supplementing with a required amount of methanol, and dehydrating the solution using N-sulfonic acid saccharin as a catalyst to prepare a 2,2-dimethoxyacetaldehyde reaction solution. The structural formula of 2,2-dimethoxyacetaldehyde is shown in formula (I); the structural formula of N-sulfonic acid saccharin is shown in formula (II); and in formula (II), R is hydrogen or nitro.

[0021]

[0022]

[0023] The specific steps include:

[0024] (1) Dehydration treatment of industrial 40% glyoxal aqueous solution: The industrial 40% glyoxal aqueous solution is pumped into a thin film evaporator and vacuum dehydrated at a certain temperature. When the weight ratio of glyoxal in the dehydrated glyoxal is 55-65% (glyoxal weight ratio = glyoxal / (glyoxal + water) * 100%), a certain amount of methanol is added to the dehydrated glyoxal, and then pumped into the thin film evaporator for vacuum dehydration. When the weight ratio of glyoxal in the dehydrated glyoxal alcohol solution is 75-80% (glyoxal weight ratio = glyoxal / (glyoxal + water) * 100%), dehydration is stopped to obtain a qualified dehydrated glyoxal alcohol solution; wherein, the operating temperature of the thin film evaporator is 50-90°C. The operating pressure of the thin film evaporator is 10-100 mbar.

[0025] (2) Synthesis of 2,2-dimethoxyacetaldehyde: A calculated amount of methanol is added to a reaction kettle containing a dehydrated glyoxal alcohol solution, and then N-sulfonic acid saccharin is added to obtain 2,2-dimethoxyacetaldehyde through dehydration reaction, wherein the molar ratio of glyoxal, methanol and N-sulfonic acid saccharin is 1:5-20:0.001-0.05, and the reaction temperature is 40-85°C.

[0026] Preferably, the molar ratio of glyoxal, methanol and N-sulfonic acid saccharin is 1:8-15:0.001-0.01. The synthesis reaction temperature is 50-75°C.

[0027] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0028] Example 1:

[0029] This embodiment provides a method for synthesizing 2,2-dimethoxyacetaldehyde. Check whether the thin film evaporator and the collecting kettle are normal, then start the cooling tower circulation, oil bath circulation heating, and vacuum pump in sequence. 2 When the operating temperature of the thin film evaporator reaches 65°C and the operating pressure reaches 20 mbar, 100 kg of 40% glyoxal aqueous solution is pumped into it at a certain flow rate for dehydration to obtain 69.1 kg of 57.3% glyoxal aqueous solution. 9.8 kg of methanol is added to the glyoxal aqueous solution and pumped into the thin film evaporator again for dehydration to obtain 58.5 kg of 75.3% glyoxal methanol solution.

[0030] 58.5 kg of 75.3% glyoxal methanol solution was added to a 500 L reactor, followed by 210.8 kg of methanol and 181.5 g of N-sulfonic acid saccharin. The mixture was heated to 65° C. and kept for 5 h. The yield of 2,2-dimethoxyacetaldehyde was 73.1%.

[0031] Example 2:

[0032] This embodiment provides a method for synthesizing 2,2-dimethoxyacetaldehyde. Check whether the thin film evaporator and the collecting kettle are normal, then start the cooling tower circulation, oil bath circulation heating, and vacuum pump in sequence. 2 When the operating temperature of the thin film evaporator reaches 70°C and the operating pressure reaches 20 mbar, 100 kg of 40% glyoxal aqueous solution is pumped into it at a certain flow rate for dehydration to obtain 65.6 kg of 60.7% glyoxal aqueous solution. 8.6 kg of methanol is added to the glyoxal aqueous solution and pumped into the thin film evaporator again for dehydration to obtain 56.8 kg of 75.7% glyoxal methanol solution.

[0033] 56.8 kg of 75.7% glyoxal methanol solution was added to a 500 L reactor, followed by 212.1 kg of methanol and 181.5 g of N-sulfonic acid saccharin. The mixture was heated to 65° C. and kept reacting for 5 h. The yield of 2,2-dimethoxyacetaldehyde was 74.5%.

[0034] Example 3:

[0035] This embodiment provides a method for synthesizing 2,2-dimethoxyacetaldehyde. Check whether the thin film evaporator and the collecting kettle are normal, then start the cooling tower circulation, oil bath circulation heating, and vacuum pump in sequence. 2 When the operating temperature of the thin film evaporator reached 70°C and the operating pressure reached 10 mbar, 100 kg of a 40% glyoxal aqueous solution was pumped into the thin film evaporator at a certain flow rate for dehydration to obtain 63.9 kg of a 62.1% glyoxal aqueous solution. 8.1 kg of methanol was added to the glyoxal aqueous solution and the solution was again pumped into the thin film evaporator for dehydration to obtain 53.1 kg of a 79.9% glyoxal methanol solution.

[0036] 53.1 kg of 75.7% glyoxal methanol solution was added to a 500 L reactor, followed by 212.6 kg of methanol and 181.5 g of N-sulfonic acid saccharin. The mixture was heated to 65° C. and kept reacting for 5 h. The yield of 2,2-dimethoxyacetaldehyde was 73.8%.

[0037] Example 4:

[0038] This embodiment provides a method for synthesizing 2,2-dimethoxyacetaldehyde. Check whether the thin film evaporator and the collecting kettle are normal, then start the cooling tower circulation, oil bath circulation heating, and vacuum pump in sequence. 2 When the operating temperature of the thin film evaporator reaches 65°C and the operating pressure reaches 20 mbar, 100 kg of 40% glyoxal aqueous solution is pumped into it at a certain flow rate for dehydration to obtain 69.1 kg of 57.3% glyoxal aqueous solution. 9.8 kg of methanol is added to the glyoxal aqueous solution and pumped into the thin film evaporator again for dehydration to obtain 58.5 kg of 75.3% glyoxal methanol solution.

[0039] To a 500 L reactor, 58.5 kg of 75.3% glyoxal methanol solution was added, followed by 210.8 kg of methanol and 212.6 g of 6-nitro-N-sulfonic acid saccharin. The mixture was heated to 65° C. and reacted for 5 h. The yield of 2,2-dimethoxyacetaldehyde was 79.7%.

[0040] Comparative Example:

[0041] This comparative example is a prior art patent CN 1184801A in which glyoxal, glyoxal diacetal and methanol are reacted under the catalysis of an acidic resin to prepare 2,2-dimethoxyacetaldehyde, and patent CN 101676252A in which glyoxal, an ester corresponding to methanol and methanol are reacted under the catalysis of an acidic resin to prepare 2,2-dimethoxyacetaldehyde.

[0042] Compared with the comparative example, the examples of the present invention: no additional additives are required; the novel N-sulfonic acid saccharin catalyst is used, which significantly shortens the reaction time; and the yield of the final 2,2-dimethoxyacetaldehyde can reach more than 70%.

Claims

1. A method for synthesizing 2,2-dimethoxyacetaldehyde, characterized in that: The method comprises the following steps: Step 1, dehydration treatment of industrial 40% glyoxal aqueous solution: pumping the industrial 40% glyoxal aqueous solution into a thin film evaporator for vacuum dehydration, adding methanol to the dehydrated glyoxal when the weight ratio of glyoxal in the dehydrated glyoxal is 55-65%, and then pumping it into a thin film evaporator for vacuum dehydration, and stopping the dehydration when the weight ratio of glyoxal in the dehydrated glyoxal alcohol solution is 75-80%, thereby obtaining a qualified dehydrated glyoxal alcohol solution; Step 2, synthesis of 2,2-dimethoxyacetaldehyde: adding methanol to a reaction kettle containing dehydrated glyoxal alcohol solution, and then adding N-sulfonic acid saccharin, and preparing 2,2-dimethoxyacetaldehyde through dehydration reaction; The structural formula of the N-sulfonic acid saccharin is: Wherein R is hydrogen or nitro.

2. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 1, wherein In the step 1, the operating temperature of the thin film evaporator is 50-90°C.

3. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 1, wherein In step 1, the thin film evaporator has an operating pressure of 10 to 150 mbar.

4. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 1, wherein In the step 2, the molar ratio of dehydrated glyoxal, methanol and N-sulfonic acid saccharin is 1:5-20:0.001-0.

05.

5. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 4, wherein In the step 2, the molar ratio of dehydrated glyoxal, methanol and N-sulfonic acid saccharin is 1:8-15:0.001-0.

01.

6. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 1, wherein In the step 2, the synthesis reaction temperature is 40-85°C.

7. The method for synthesizing 2,2-dimethoxyacetaldehyde according to claim 6, wherein In the step 2, the synthesis reaction temperature is 65° C. and the reaction time is 5 h.

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