One-step method for preparing 2-methyl-4-acetoxy-2-butenal

Abstract

This invention provides a one-step method for preparing 2-methyl-4-acetoxy-2-butenal. The method includes: using trans-1,4-diacetoxy-2-butene as a raw material, reacting it in a syngas environment under the action of a catalyst; the resulting reaction solution is then separated to obtain 2-methyl-4-acetoxy-2-butenal; wherein the catalyst includes a homogeneous rhodium catalyst and a homogeneous ruthenium catalyst. Applying the technical solution of this invention, using trans-1,4-diacetoxy-2-butene as a raw material, under the action of a specific catalyst, a hydroformylation reaction, a decarboxylation reaction, and a double bond rearrangement reaction occur simultaneously, combining the traditional multi-step synthesis method of 2-methyl-4-acetoxy-2-butenal into a single step, shortening the production cycle, reducing the heating time of intermediates and separation steps, and significantly improving the overall yield. The use of homogeneous rhodium and ruthenium catalysts in the reaction can greatly improve the conversion rate of the raw materials.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical intermediate synthesis technology, and more specifically, to a one-step method for preparing 2-methyl-4-acetoxy-2-butenal. Background Technology

[0002] 2-Methyl-4-acetoxy-2-butenal (C5 aldehyde) is an important pharmaceutical intermediate and a key intermediate in the synthesis of vitamin A acetate. Its synthesis plays a crucial role in the overall synthesis of vitamin A and its derivatives. The quality and cost of the C5 aldehyde production process directly determine the overall quality of the synthesis route for vitamin A and its derivatives.

[0003] Since Pommer et al. of BASF first reported the industrial synthesis method of pentacarbon aldehydes in the mid-1970s, scientists from various countries have been dedicated to the research of its synthetic routes for decades. Various new synthetic routes have emerged and been continuously improved and optimized, and some processes have already achieved industrial production. In recent years, research on the synthesis of pentacarbon aldehydes has mainly focused on the synthesis of pentacarbon aldehydes using isoprene and butenediol as starting materials, which can be summarized into the following methods:

[0004] Isoprene Method: US Patent 4175204 reports the use of isoprene as a raw material, which is added to sodium hypochlorite solution to obtain 3-methyl-3-hydroxy-4-chloro-1-butene and 1-chloro-2-methyl-4-hydroxy-2-butene. These are then esterified with acetic anhydride and oxidized with DMSO to obtain 2-methyl-4-acetoxy-2-butenal. According to the patent report, this method generates a large amount of wastewater and byproducts due to the use of sodium hypochlorite solution for chlorination and DMSO oxidation, resulting in significant environmental pollution and a low yield.

[0005]

[0006] Ethylene oxide method: In US4873362, ethylene oxide and acetic acid are used as raw materials to obtain 2-acetoxyethanol through ring-opening, which is then oxidized to 2-acetoxyacetaldehyde under Ag catalysis. 2-acetoxyacetaldehyde is then condensed with propionaldehyde to obtain 2-methyl-4-acetoxy-2-butenal, as shown in formula (2). This method is prone to oxidation, resulting in a large number of by-products. In addition, propionaldehyde is prone to self-polymerization during the aldol condensation reaction, resulting in poor selectivity and low yield, making it difficult to industrialize.

[0007]

[0008] Butenyl glycol method 1: In US3732287, 1,4-butenyl glycol is acetylated to generate 1,4-butenyl glycol diacetate, which is then subjected to double bond isomerization, hydroformylation, and deacetylation to obtain 2-methyl-4-acetoxy-2-butenal. The conversion rate of the double bond isomerization reaction in the patent is only 20-30%, which requires repeated use of raw materials, resulting in an excessively long operation cycle. In addition, 25-35% of straight-chain aldehyde impurities are generated during the hydroformylation process, resulting in a low overall yield.

[0009]

[0010] CN112920047A and CN107286017A describe the preparation of pentacarbon aldehydes through a four-step reaction involving esterification, isomerization, hydroformylation, and decarboxylation. Although the use of homogeneous rhodium and ligands in hydroformylation improves the yield of the single-step reaction, the isomerization yield is still relatively low, resulting in an overall single-pass yield of less than 50%, high energy consumption, and low industrial competitiveness.

[0011] Method 2: In US4124619, 1,4-butenediol is acetylated to generate 1,4-butenediol diacetate, which is then hydroformylated and deacetylated to obtain 2-formyl-4-acetoxy-1-butene. Then, under the catalysis of metal Pd, the double bond isomerizes to generate 2-methyl-4-acetoxy-2-butenal. Each reaction in the patent requires distillation, resulting in a long production cycle. Due to the poor thermal stability of the intermediates in each reaction step, the yield loss is large. Moreover, the conversion rate of the double bond isomerization reaction is only 40-50%, and 10-20% of the double bond hydrogenation byproducts are generated, resulting in a low overall yield, which is not conducive to industrialization.

[0012]

[0013] Therefore, all of the above methods have their advantages and disadvantages. However, the butenediol method is currently the synthetic route for industrial production. However, most literature reports that this method uses a stepwise reaction, which results in a long production cycle, significant intermediate damage and loss leading to low yield, high energy consumption, and limited production. Furthermore, the stepwise reaction uses a large amount of solvent, which poses a high risk and is not safe or environmentally friendly. Summary of the Invention

[0014] The main objective of this invention is to provide a one-step method for preparing 2-methyl-4-acetoxy-2-butenal, thereby solving the problems of complex preparation processes and low conversion rates in the prior art for 2-methyl-4-acetoxy-2-butenal.

[0015] To achieve the above objectives, according to one aspect of the present invention, a one-step method for preparing 2-methyl-4-acetoxy-2-butenal is provided, the method comprising: using trans-1,4-diacetoxy-2-butene as a raw material, reacting it in a syngas environment under the action of a catalyst, and separating the resulting reaction solution to obtain 2-methyl-4-acetoxy-2-butenal; wherein the catalyst comprises a homogeneous rhodium catalyst and a homogeneous ruthenium catalyst.

[0016] Furthermore, an alkaline auxiliary agent is added to the reaction. The alkaline auxiliary agent is a strong base-weak acid salt. Preferably, the alkaline auxiliary agent includes any one or more of sodium acetate, potassium acetate, cesium acetate, sodium propionate, potassium propionate, and cesium propionate. Preferably, the amount of alkaline auxiliary agent added is 0.01% to 0.08% of the weight of the raw materials.

[0017] Furthermore, an organophosphorus ligand is added to the reaction; preferably, the organophosphorus ligand includes any one or more of 1,2-bis(diphenylphosphine)ethane, 1,3-bis(diphenylphosphine)propane, 1,4-bis(diphenylphosphine)butane, 1,5-bis(diphenylphosphine)pentane, and 2,2-bisdiphenylphosphine-1,1-naphthyl; preferably, the amount of organophosphorus ligand added is 0.5% to 2% of the weight of the raw material, more preferably 0.8% to 1.5%.

[0018] Furthermore, the amount of homogeneous rhodium catalyst added is 0.01% to 0.1% of the raw material weight, preferably 0.05% to 0.1%;

[0019] Preferably, the homogeneous rhodium catalyst is a carbonyl rhodium catalyst;

[0020] Preferably, the homogeneous rhodium catalyst includes any one or more of triphenylphosphine carbonyl rhodium, acetylacetone carbonyl rhodium, acetylacetone dicarbonyl rhodium, and acetylacetone triphenylphosphine carbonyl rhodium.

[0021] Furthermore, the amount of homogeneous ruthenium catalyst added is 0.01% to 0.1% of the raw material weight, preferably 0.05% to 0.1%;

[0022] Preferably, the homogeneous ruthenium catalyst comprises any one or more of dichloro(p-methylisopropylbenzene)ruthenium dimer, diiodo(p-cymene)ruthenium dimer, dichlorotris(1,10-phenanthroline)ruthenium hydrate, and diacetate[2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl]ruthenium.

[0023] Furthermore, the volume ratio of H2 to CO in the syngas is 1:2 to 3:1; preferably, the volume content of H2 and CO in the syngas is 99.00% to 99.99%.

[0024] Furthermore, the reaction pressure is 4–10 MPa, preferably 5–9 MPa.

[0025] Furthermore, the reaction temperature is 60–100°C, preferably 60–80°C.

[0026] Furthermore, the reaction time is 4 to 8 hours, preferably 4 to 6 hours.

[0027] Further, the above method includes: adding raw materials and catalyst into a reaction vessel, first purging the reaction vessel with inert gas for replacement, then purging the reaction vessel with syngas for replacement, stirring and heating to the reaction temperature, carrying out the reaction, after the reaction is completed, after the reaction liquid reaches room temperature, replacing the gas in the reaction vessel with inert gas, discharging the material, separating the obtained reaction liquid to obtain 2-methyl-4-acetoxy-2-butenal;

[0028] Preferably, during the reaction, synthesis gas is continuously introduced to keep the reaction pressure within any range of 4 to 10 MPa.

[0029] By applying the technical solution of this invention, using trans-1,4-diacetoxy-2-butene as a raw material, under the action of a specific catalyst, a hydroformylation reaction, a decarboxylation reaction, and a double bond rearrangement reaction occur simultaneously. This combines the traditional multi-step synthesis of 2-methyl-4-acetoxy-2-butenal into a single step, shortening the production cycle, reducing the heating time and separation steps of intermediates, and significantly improving the overall yield. The use of homogeneous rhodium and ruthenium catalysts in the reaction greatly improves the conversion rate of the raw materials. Moreover, under this catalytic system, the extremely low activity of rhodium and ruthenium metals in hydrogenating carbon-carbon double bonds, the poisoning effect of carbon monoxide on the noble metal catalyst, and the dilution effect of the hydrogen atmosphere inhibit the hydrogenation of the intermediate double bonds, resulting in fewer byproducts of double bond hydrogenation. This significantly improves the yield, reduces production costs, and is suitable for industrial production. Furthermore, since no other organic solvents are added during the reaction, the catalyst can be cooled and precipitated for recovery and reuse, making the operation convenient, generating no wastewater, and possessing safety, environmental friendliness, and reliability. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 The 1H NMR spectrum of 2-methyl-4-acetoxy-2-butenal, the product of Example 1 according to the present invention, is shown; and

[0032] Figure 2 The 13C NMR spectrum of 2-methyl-4-acetoxy-2-butenal, the product of Example 1 according to the present invention, is shown. Detailed Implementation

[0033] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] As analyzed in the background section of this application, the existing technology has the problems of multiple steps, complex process, and low conversion rate in the preparation and synthesis of 2-methyl-4-acetoxy-2-butenal. In order to solve this problem, this application provides a one-step method for preparing 2-methyl-4-acetoxy-2-butenal. The method includes: using trans-1,4-diacetoxy-2-butene as a raw material, reacting in a synthesis gas environment under the action of a catalyst, and separating the resulting reaction liquid to obtain 2-methyl-4-acetoxy-2-butenal; wherein the catalyst includes a homogeneous rhodium catalyst and a homogeneous ruthenium catalyst.

[0035] This application uses trans-1,4-diacetoxy-2-butene as a starting material. Under the action of a specific catalyst, a hydroformylation reaction, decarboxylation reaction, and double bond rearrangement reaction occur simultaneously, combining the traditional multi-step synthesis of 2-methyl-4-acetoxy-2-butenal into a single step. This shortens the production cycle, reduces the heating time and separation steps of intermediates, and significantly improves the overall yield. The use of homogeneous rhodium and ruthenium catalysts in the reaction greatly enhances the conversion rate of the starting material. Furthermore, under this catalytic system, the extremely low activity of rhodium and ruthenium metals in hydrogenating carbon-carbon double bonds, the poisoning effect of carbon monoxide on the noble metal catalyst, and the dilution effect of the hydrogen atmosphere inhibit the hydrogenation of the intermediate double bonds, resulting in fewer byproducts of double bond hydrogenation. This significantly improves the yield, reduces production costs, and makes it suitable for industrial production. In addition, since no other organic solvents are added during the reaction, the catalyst can be cooled and precipitated for recovery and reuse. The operation is convenient, generates no wastewater, and is safe, environmentally friendly, and reliable.

[0036] In some typical embodiments of this application, to further improve the conversion rate of raw materials and the yield of the target product, an alkaline auxiliary agent is added to the above reaction. The alkaline auxiliary agent can promote the decarboxylation of the hydroformylation product 2-formyl-1,4-diacetoxybutane to generate 2-methyl-4-acetoxy-1-butenal. The alkaline auxiliary agent is a strong base-weak acid salt, and the specific type of strong base-weak acid salt can be selected from the prior art without particular requirements. Exemplarily, the alkaline auxiliary agent includes any one or more of sodium acetate, potassium acetate, cesium acetate, sodium propionate, potassium propionate, and cesium propionate. Preferably, the alkaline auxiliary agent is selected from sodium acetate and / or potassium acetate, which not only has a better promoting effect on the reaction but is also relatively inexpensive and readily available. In some embodiments of this application, the amount of the above-mentioned alkaline auxiliary agent added is 0.01% to 0.08% of the weight of the raw materials, which has a better promoting effect on the reaction.

[0037] In some embodiments of this application, to further improve the yield of the target product and the reaction rate, an organophosphorus ligand is added to the reaction to promote the deacetylation of the decarboxylation product 2-methyl-4-acetoxy-1-butenal and its double bond rearrangement to generate 2-methyl-4-acetoxy-2-butenal. The organophosphorus ligand can be selected from existing technologies. Exemplarily, the organophosphorus ligand includes any one or more of 1,2-bis(diphenylphosphine)ethane, 1,3-bis(diphenylphosphine)propane, 1,4-bis(diphenylphosphine)butane, 1,5-bis(diphenylphosphine)pentane, and 2,2-bisdiphenylphosphine-1,1-naphthyl. The amount of organophosphorus ligand can be determined based on the stoichiometric ratio, referring to the amount of ruthenium and rhodium catalysts. In some embodiments of this application, the amount of organophosphorus ligand added is 0.5% to 2% of the raw material weight, preferably 0.8% to 1.5%, which has a significant promoting effect on the reaction.

[0038] In some embodiments of this application, the amount of the homogeneous rhodium catalyst added is 0.01% to 0.1% of the raw material weight, which has a significant catalytic effect on the reaction and a high utilization rate; preferably, the amount of homogeneous rhodium catalyst added is 0.05% to 0.1% of the raw material weight, which further improves the catalytic effect. Preferably, the homogeneous rhodium catalyst is a carbonyl rhodium catalyst, which has a better catalytic effect; the carbonyl rhodium catalyst can be selected from the prior art, such as any one or more of triphenylphosphine carbonyl rhodium, acetylacetone carbonyl rhodium, acetylacetone dicarbonyl rhodium, and acetylacetone triphenylphosphine carbonyl rhodium.

[0039] In some embodiments of this application, the amount of the homogeneous ruthenium catalyst added is 0.01% to 0.1% of the raw material weight, resulting in better catalytic effect. Preferably, the amount is 0.05% to 0.1%, with a more significant improvement in effect. Preferably, the homogeneous ruthenium catalyst includes any one or more of dichloro(p-methylisopropylbenzene)ruthenium dimer, diiodo(p-cymene)ruthenium dimer, dichlorotris(1,10-phenanthroline)ruthenium hydrate, and diacetate[2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl]ruthenium, which is particularly effective in improving the yield of the target product.

[0040] The syngas can be selected from existing technologies. Preferably, the volume ratio of H2 to CO in the syngas is 1:2 to 3:1, especially when the volume ratio of H2 to CO is 1:1, which is most favorable for the hydroformylation reaction. Preferably, the volume content of H2 and CO in the syngas is 99.00% to 99.99%, that is, the proportion of gases other than H2 and CO is less than 0.01% to 1%, which is beneficial to further improve the conversion rate of the feedstock trans-1,4-diacetoxy-2-butene.

[0041] To further increase the rate of the hydroformylation reaction and reduce byproducts, the pressure for the above reaction is 4–10 MPa, preferably 5–9 MPa. Since the hydroformylation reaction consumes H2 and CO, synthesis gas can be continuously introduced to maintain the required reaction pressure.

[0042] In some embodiments of this application, to further improve the yield of the target product, the reaction temperature is 60–100°C, preferably 60–80°C. In some embodiments of this application, to ensure sufficient reaction of the raw materials and further improve efficiency, the reaction time is 4–8 hours, preferably 4–6 hours, which yields higher efficiency.

[0043] In some typical embodiments of this application, the one-step method for preparing 2-methyl-4-acetoxy-2-butenal includes: adding raw materials and catalyst to a reaction vessel; first, purging the reaction vessel with an inert gas for displacement; then, purging the reaction vessel with syngas for displacement; stirring and heating to the reaction temperature; reacting; after the reaction is completed, after the reaction liquid cools to room temperature, purging the gas in the reaction vessel with an inert gas; discharging the product; separating the obtained reaction liquid to obtain 2-methyl-4-acetoxy-2-butenal; the number of gas displacements can be one or more; the inert gas can be selected from the prior art, such as any one or more of nitrogen, argon, and helium; purging the reaction vessel with inert gas before the start of the reaction and after the reaction is completed can avoid the syngas directly contacting air, thus preventing the explosion hazard and improving process safety. Preferably, during the reaction, syngas is continuously introduced to keep the reaction pressure within any range of 4 to 10 MPa.

[0044] The main components of the reaction solution are the target product 2-methyl-4-acetoxy-2-butenal, a catalyst, a small amount of unreacted raw materials, by-products, basic auxiliaries, and organophosphorus ligands. Those skilled in the art can separate and purify these components using existing techniques. The catalyst and organophosphorus ligands can be precipitated by cooling to below 10°C, filtered, and then recovered for reuse. For example, the reaction solution can be purified by vacuum distillation to obtain high-purity 2-methyl-4-acetoxy-2-butenal.

[0045] In some typical embodiments of this application, the one-step method for preparing 2-methyl-4-acetoxy-2-butenal is as follows: trans-1,4-diacetoxy-2-butene, a basic auxiliary agent, a rhodium carbonyl catalyst, a homogeneous ruthenium catalyst, and an organophosphorus ligand are sequentially added to a high-pressure reactor. The reactor is purged three times with N2 (0–0.5 MPa) and three times with syngas (0–0.5 MPa). The mixture is stirred and heated to 60–100°C, then continuously purged with syngas to 5–10 MPa, maintaining this pressure for 4–8 hours. After the reaction is complete, the gas supply is stopped, the reactor is cooled, and purged once with N2 (0–0.5 MPa). The mixture is then discharged and filtered. The reaction solution is separated to obtain 2-methyl-4-acetoxy-2-butenal. The reaction equation is shown below:

[0046]

[0047] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0048] In this invention, all raw and auxiliary materials used can be purchased from the market. The specific sources of raw materials involved in the examples and comparative examples are shown in Table 1 below.

[0049] Table 1

[0050]

[0051] Example 1

[0052] Accurately weigh 300g of trans-1,4-diacetoxy-2-butene, 30mg of sodium acetate, 150mg of triphenylphosphine carbonyl rhodium hydride, 150mg of dichloro(p-methylisopropylbenzene)ruthenium dimer, and 2.4g of 1,2-bis(diphenylphosphine)ethane ligand into a high-pressure reactor. The reactor is then purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture is stirred and heated to a reaction temperature of 60°C, and then syngas is continuously introduced. The pressure was increased to 5 MPa and maintained for 4 hours. After the reaction was complete, the gas supply was stopped, the mixture was cooled, and the mixture was purged with N2 (0.3 MPa) once. The product was discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed that the conversion rate of trans-1,4-diacetoxy-2-butene was 97.1%, and the product selectivity was 96.3% (the percentage of trans-2-methyl-4-acetoxy-2-butenal generated from the converted raw material was calculated, and the same applies below).

[0053] The 1H NMR spectrum of the product 2-methyl-4-acetoxy-2-butenal is shown below. Figure 1 As shown, the 13C NMR spectrum is as follows Figure 2The NMR data are as follows: 1H NMR (400MHz, DMSO) δ9.45 (s, 1H), 6.67 (tq, J = 5.8, 1.3Hz, 1H), 4.91 (dd, J = 5.9, 1.0Hz, 2H), 2.08 (s, 3H), 1.70 (dd, J = 2.2, 1.0Hz, 3H); 13C NMR (100MHz, DMSO) δ194.79, 170.13, 147.12, 139.32, 60.66, 40.10, 39.48, 38.85, 20.47, 8.97; consistent with the standard NMR spectrum of 2-methyl-4-acetoxy-2-butenal.

[0054] Example 2

[0055] Accurately weigh 300g of trans-1,4-diacetoxy-2-butene, 60mg of potassium acetate, 180mg of acetylacetone triphenylphosphine carbonyl rhodium, 150mg of dichloro(p-methylisopropylbenzene)ruthenium dimer, and 2.5g of 1,2-bis(diphenylphosphine)ethane ligand into a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 70℃, then continuously purged with syngas to 6MPa and maintained at this pressure for 5 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was then discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 97.6% and a product selectivity of 96.8%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0056] Example 3

[0057] 400g of trans-1,4-diacetoxy-2-butene, 120mg of cesium acetate, 280mg of rhodium carbonyl acetylacetone, 150mg of diiodo(p-cymene)ruthenium dimer, and 2.8g of 1,4-bis(diphenylphosphine)butane ligand were accurately weighed using a balance and added sequentially to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 80℃, then continuously purged with syngas to 7MPa and maintained at this pressure for 6 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was then discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 97.8% and a product selectivity of 97.1%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0058] Example 4

[0059] 400g of trans-1,4-diacetoxy-2-butene, 160mg of sodium propionate, 320mg of rhodium dicarbonyl acetylacetone, 360mg of ruthenium diiodo(p-cymene)dimer, and 2g of 1,3-bis(diphenylphosphine)propane ligand were accurately weighed using a balance and sequentially added to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 90℃, then continuously purged with syngas to 8MPa and maintained at this pressure for 7 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was then discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 98.3% and a product selectivity of 97.0%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0060] Example 5

[0061] 400g of trans-1,4-diacetoxy-2-butene, 200mg of potassium propionate, 360mg of rhodium carbonyl acetylacetone, 320mg of ruthenium diiodo(p-cymene)dimer, and 3.6g of 1,5-bis(diphenylphosphine)pentane ligand were accurately weighed using a balance and added sequentially to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 100℃, then continuously purged with syngas to 9MPa and maintained at this pressure for 8 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 99.3% and a product selectivity of 96.5%. The NMR results of the product pentacetal were consistent with those in Case Study 1.

[0062] Example 6

[0063] 400g of trans-1,4-diacetoxy-2-butene, 280mg of cesium propionate, 400mg of rhodium carbonyl acetylacetone, 400mg of dichlorotris(1,10-phenanthroline) hydrate, and 4g of 1,5-bis(diphenylphosphine)pentane ligand were accurately weighed using a balance and sequentially added to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 90℃, then continuously purged with syngas to 10MPa and maintained at this pressure for 7 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 98.5% and a product selectivity of 97.1%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0064] Example 7

[0065] Accurately weigh 500g of trans-1,4-diacetoxy-2-butene, 50mg of sodium acetate, 50mg of rhodium carbonyl acetylacetone, 50mg of ruthenium diacetate [2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl], and 7.5g of 2,2-bisdiphenylphosphine-1,1-binaphthyl] and add them sequentially to a high-pressure reactor. The reactor is purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture is stirred and heated to 90℃, then continuously purged with syngas to 10MPa and maintained at this pressure for 7 hours. After the reaction is complete, the gas supply is stopped, the reactor is cooled, and purged once with N2 (0.3MPa). The mixture is discharged and filtered. The reaction solution is degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis shows that the conversion rate of trans-1,4-diacetoxy-2-butene is 98.2%, and the product selectivity is 98.4%. The NMR results of the product pentacarbonaldehyde are consistent with those of Implementation Case 1.

[0066] Example 8

[0067] Accurately weigh 500g of trans-1,4-diacetoxy-2-butene, 80mg of sodium acetate, 100mg of rhodium carbonyl acetylacetone, 100mg of ruthenium diacetate [2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl], and 10g of 2,2-bisdiphenylphosphine-1,1-binaphthyl] and add them sequentially to a high-pressure reactor. The reactor is purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture is stirred and heated to 80℃, then continuously purged with syngas to 9MPa and maintained at this pressure for 8 hours. After the reaction is complete, the gas supply is stopped, the reactor is cooled, and purged once with N2 (0.3MPa). The mixture is then discharged and filtered. The reaction solution is degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis shows that the conversion rate of trans-1,4-diacetoxy-2-butene is 98.2%, and the product selectivity is 98.9%. The NMR results of the product pentacarbonaldehyde are consistent with those of Implementation Case 1.

[0068] Example 9

[0069] 500g of trans-1,4-diacetoxy-2-butene, 100mg of sodium acetate, 150mg of rhodium dicarbonyl acetylacetone, 150mg of dichlorotris(1,10-phenanthroline) hydrate, and 3.5g of 1,3-bis(diphenylphosphine)propane were accurately weighed using a balance and sequentially added to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 60℃, then continuously purged with syngas to 5MPa and maintained at this pressure for 6 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was then discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 97.5% and a product selectivity of 97.6%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0070] Example 10

[0071] 500g of trans-1,4-diacetoxy-2-butene, 50mg of potassium acetate, 200mg of rhodium dicarbonyl acetylacetone, 250mg of dichlorotris(1,10-phenanthroline) hydrate, and 4g of 1,3-bis(diphenylphosphine)propane were accurately weighed using a balance and sequentially added to a high-pressure reactor. The reactor was purged three times with N2 (0.3MPa) and three times with syngas (0.5MPa). The mixture was stirred and heated to 70℃, then continuously purged with syngas to 6MPa and maintained at this pressure for 6 hours. After the reaction was complete, the gas supply was stopped, the reactor was cooled, and purged once with N2 (0.3MPa). The mixture was then discharged and filtered. The reaction solution was degassed to obtain crude 2-methyl-4-acetoxy-2-butenal. GC analysis showed a trans-1,4-diacetoxy-2-butene conversion rate of 97.3% and a product selectivity of 96.6%. The NMR results of the pentacarbonaldehyde product were consistent with those in Case Study 1.

[0072] Example 11

[0073] The difference from Example 1 is that 10 mg of sodium acetate was added.

[0074] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 96.5%, and the product selectivity was 82.7%.

[0075] Example 12

[0076] The difference from Example 1 is that sodium acetate was not added.

[0077] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 85.8%, and the product selectivity was 83.1%.

[0078] Example 13

[0079] The difference from Example 1 is that the 1,2-bis(diphenylphosphine)ethane ligand was not added.

[0080] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 25.4%, and the product selectivity was 75.8%.

[0081] Example 14

[0082] The difference from Example 1 is that the synthesis gas is continuously introduced to 4 MPa.

[0083] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 65.6%, and the product selectivity was 95.1%.

[0084] Example 15

[0085] The difference from Example 1 is that the synthesis gas is continuously introduced to 2 MPa.

[0086] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 50.2%, and the product selectivity was 95.8%.

[0087] Example 16

[0088] The difference from Example 1 is that the synthesis gas is continuously introduced to 12 MPa.

[0089] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 98.5%, and the product selectivity was 84.3%.

[0090] Example 17

[0091] The difference from Example 1 is that the reaction temperature is 50°C.

[0092] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 83.2%, and the product selectivity was 95.4%.

[0093] Example 18

[0094] The difference from Example 1 is that the reaction temperature is 120°C.

[0095] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 98.9%, and the product selectivity was 85.8%.

[0096] Example 19

[0097] The difference from Example 1 is that the reaction time is 3 hours.

[0098] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 88.1%, and the product selectivity was 95.9%.

[0099] Comparative Example 1

[0100] The difference from Example 1 is that triphenylphosphine carbonyl rhodium was not added.

[0101] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 5%, and the product selectivity was 50.1%.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that ruthenium dichloro(p-methylisopropylbenzene) dimer was not added.

[0104] GC analysis showed that the conversion of trans-1,4-diacetoxy-2-butene was 97.9%, and the product selectivity was 75.8%.

[0105] Comparative Example 3

[0106] The difference from Example 1 is that the same weight of racemic 1,4-diacetoxy-2-butene is used instead of trans-1,4-diacetoxy-2-butene.

[0107] GC analysis showed that the conversion of racemic 1,4-diacetoxy-2-butene was 96.5%, with a product selectivity of 31.5%.

[0108] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: Using trans-1,4-diacetoxy-2-butene as a raw material, this application simultaneously initiates hydroformylation, decarboxylation, and double bond rearrangement reactions under the action of a specific catalyst. This combines the traditional multi-step synthesis of 2-methyl-4-acetoxy-2-butenal into a single step, shortening the production cycle, reducing the heating time and separation steps of intermediates, and significantly improving the overall yield. The use of homogeneous rhodium and ruthenium catalysts in the reaction can greatly improve the conversion rate of the raw materials. Moreover, under this catalytic system, the extremely low activity of rhodium and ruthenium metals in hydrogenating carbon-carbon double bonds, the poisoning effect of carbon monoxide on the noble metal catalyst, and the dilution effect of the hydrogen atmosphere inhibit the hydrogenation of the intermediate double bonds, resulting in fewer byproducts of double bond hydrogenation. This significantly improves the yield, reduces production costs, and is suitable for industrial production. Furthermore, since no other organic solvents are added during the reaction, the catalyst can be cooled and precipitated for recycling, making the operation convenient, generating no wastewater, and possessing safety, environmental friendliness, and reliability.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A one-step method for preparing 2-methyl-4-acetoxy-2-butenal, characterized in that, include: Using trans-1,4-diacetoxy-2-butene as a raw material, the reaction was carried out in a syngas environment under the action of a catalyst, and the resulting reaction solution was separated to obtain 2-methyl-4-acetoxy-2-butenal; The catalyst includes a homogeneous rhodium catalyst and a homogeneous ruthenium catalyst; The reaction also involves the addition of an alkaline auxiliary agent, which is a strong base-weak acid salt. The alkaline additive is any one or more of sodium acetate, potassium acetate, cesium acetate, sodium propionate, potassium propionate, and cesium propionate. The amount of alkaline additive added is 0.01% to 0.08% of the weight of the raw material; Organophosphorus ligands are also added to the reaction; The organophosphorus ligand is any one or more of 1,2-bis(diphenylphosphine)ethane, 1,3-bis(diphenylphosphine)propane, 1,4-bis(diphenylphosphine)butane, 1,5-bis(diphenylphosphine)pentane and 2,2-bisdiphenylphosphine-1,1-binaphthylene. The amount of the organophosphorus ligand added is 0.5% to 2% of the weight of the raw material; The amount of homogeneous rhodium catalyst added is 0.01~0.1% of the weight of the raw material; The homogeneous rhodium catalyst is any one or more of triphenylphosphine carbonyl rhodium, acetylacetone carbonyl rhodium, acetylacetone dicarbonyl rhodium, and acetylacetone triphenylphosphine carbonyl rhodium; The amount of homogeneous ruthenium catalyst added is 0.01~0.1% of the weight of the raw material; The homogeneous ruthenium catalyst is any one or more of the following: dichloro(p-methylisopropylbenzene)ruthenium dimer, diiodo(p-cymene)ruthenium dimer, dichlorotris(1,10-phenanthroline)ruthenium hydrate, and diacetate[2,2'-bis(di-p-tolylphosphine)-1,1'-binaphthyl]ruthenium; The reaction pressure is 4~10MPa; the reaction temperature is 60~100℃.

2. The method according to claim 1, characterized in that, The amount of the organophosphorus ligand added is 0.8% to 1.5% of the weight of the raw material.

3. The method according to claim 1, characterized in that, The amount of homogeneous rhodium catalyst added is 0.05% to 0.1% of the weight of the raw material.

4. The method according to claim 1, characterized in that, The amount of homogeneous ruthenium catalyst added is 0.05% to 0.1% of the weight of the raw material.

5. The method according to any one of claims 1 to 4, characterized in that, The volume ratio of H2 to CO in the synthesis gas is 1:2 to 3:

1.

6. The method according to claim 5, characterized in that, The volume content of H2 and CO in the synthesis gas is 99.00%~99.99%.

7. The method according to any one of claims 1 to 4, characterized in that, The reaction is carried out at a pressure of 5-9 MPa.

8. The method according to any one of claims 1 to 4, characterized in that, The reaction temperature is 60~80℃.

9. The method according to any one of claims 1 to 4, characterized in that, The reaction time is 4-8 hours.

10. The method according to claim 9, characterized in that, The reaction time is 4-6 hours.

11. The method according to any one of claims 1 to 4, characterized in that, The method includes: adding the raw materials and catalyst into a reaction vessel, first purging the reaction vessel with an inert gas for replacement, then purging the reaction vessel with syngas for replacement, stirring and heating to the reaction temperature, carrying out the reaction, after the reaction is completed, after the reaction liquid reaches room temperature, replacing the gas in the reaction vessel with an inert gas, discharging the material, separating the obtained reaction liquid to obtain 2-methyl-4-acetoxy-2-butenal.

12. The method according to claim 11, characterized in that, During the reaction process, the synthesis gas is continuously introduced to keep the reaction pressure within any range of 4 to 10 MPa.

Images