A preparation method of ethyl 4-(diethoxyphosphoryl)-2-butenoate

Abstract

The invention provides a method for obtaining C5 phosphate by using ethyl pyruvate, 1,2-dichloroethane and triethyl phosphite to undergo a Wittig-Horner reaction under the action of a catalyst. The process is green and pollution-free, has a low preparation cost, and can realize industrial production.

Description

Technical Field

[0001] The present invention relates to the field of organic chemical intermediate synthesis, and in particular to a method for preparing an apoester intermediate C5 phosphate by utilizing a byproduct ethyl pyruvate. Background Art

[0002] Apocarotene, also known as apocarotene ethyl ester, is an oxygen-containing carotenoid. It is widely used in coloring products such as jelly, beverages, and edible cream. It has antioxidant and immune-enhancing functions.

[0003] Ethyl 4-(diethoxyphosphoryl)-2-butenoate (abbreviated as C5 phosphate) is a key intermediate in the synthesis of apo esters via the C25+C5 route characterized by the Wittig reaction.

[0004] At present, the preparation of ethyl 4-(diethoxyphosphoryl)-2-butenoate is mainly divided into three categories:

[0005] 1) Using acetone ether as the starting material has the main disadvantages of a long reaction route and a large amount of wastewater generated during the process;

[0006] 2) Using methyl vinyl ketone as the starting material, the main disadvantage is the use of highly toxic raw materials such as hydrocyanic acid, which limits industrialization to a certain extent.

[0007] 3) Using butadiene as the starting material has the main disadvantage that it also uses highly toxic raw materials such as hydrocyanic acid, which limits its industrialization to a certain extent.

[0008] Patent CN 109851633 mentions that ethyl 2-methyl-3-oxopropionate and tetraethyl methylene diphosphate undergo HWE reaction in an aprotic solvent to prepare C5 phosphate. The raw material ethyl 2-methyl-3-oxopropionate is expensive and difficult to purchase.

[0009] CN110655533A mentions the use of pyruvic acid aqueous solution to prepare C5 phosphate through a five-step reaction, which has a long process and produces a large amount of high COD salt.

[0010] In the process of producing ethyl acrylate, ethyl pyruvate is produced as a byproduct. After being treated by rectification or distillation, the content of ethyl pyruvate in the bottom of the tower increases continuously, accounting for more than 80%. The bottom of the tower is dark in color and has high viscosity, and usually needs to be incinerated, which not only wastes resources, but also has adverse effects on environmental protection.

[0011] At present, the difficulty in preparing apo ester intermediates using ethyl pyruvate as raw material lies in the complex composition of the raw materials in the distillation tower kettle, which affects the selectivity of the reaction. At the same time, the product is difficult to purify, which places high requirements on the reaction conversion rate and selectivity. Summary of the invention

[0012] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for preparing ethyl 4-(diethoxyphosphoryl)-2-butenoate. The method can use ethyl pyruvate, a byproduct produced in the process of producing ethyl acrylate, as a starting material, thereby achieving green and highly selective preparation of C5 phosphate.

[0013] The technical solution adopted by the present invention includes:

[0014] Ethyl pyruvate reacts with 1,2-dichloroethane and triethyl phosphite in the presence of a catalyst to produce C5 phosphate.

[0015]

[0016] Wherein, the ethyl pyruvate can come from the product distillation tower bottom liquid of propylene oxidation to prepare ethyl acrylate, which is usually composed of ethyl pyruvate, ethyl 3-methoxypropionate, ethyl acryloxypropionate, and the rest is polymer impurities. This material is a viscous liquid. When directly subjected to the Wittig-Horner reaction, its polymer will deactivate the catalyst. It is necessary to control the mass fraction of ethyl pyruvate to 50-99%, preferably 75-99%; when the polymer impurities in the raw material are higher than 1%, the raw material needs to be pretreated to remove the polymer.

[0017] In the present invention, the raw material can be diluted with a solvent, the solvent is a non-polar solvent such as toluene, n-heptane, n-hexane, etc., and the amount of the solvent is 1 to 10 times that of ethyl pyruvate, preferably 2 to 7 times;

[0018] The molar ratio of ethyl pyruvate to 1,2-dichloroethane and triethyl phosphite is 1:1.1-1.5:1.1-2;

[0019] The reaction temperature is -10 to 70°C, preferably 10 to 50°C, and the reaction time is 0.5 to 20 hours, preferably 2 to 6 hours.

[0020] The amount of the catalyst is 0.5-5% of the mass of ethyl pyruvate;

[0021] In the present invention, the catalyst is a supported alkaline catalyst, which comprises a carrier, an alkali metal salt, and a modifier;

[0022] The carrier is an inert inorganic material, preferably one or more of silicon dioxide, activated carbon, and ZSM-5 molecular sieve;

[0023] The alkali metal salt is one or more of a titanate or cuprate of a metal such as potassium or magnesium, preferably potassium titanate, magnesium cuprate, magnesium titanate, or potassium cuprate, wherein the mass percentage of the alkali metal salt to the mass percentage of the catalyst is 0.1 to 20%, preferably 5 to 15%;

[0024] The modifier is a soluble salt of a metal element, the metal element is selected from iron, zinc, and copper, and the salt is preferably one or more of ferric acetate, zinc sulfate, and copper chloride;

[0025] In the catalyst, the amount of the modifier added is 0.1 to 10% of the catalyst mass, preferably 1 to 10%.

[0026] The preparation method of the catalyst comprises:

[0027] Weigh a certain mass of alkali metal salt and modifier and place them in a solvent (acetone, water or alkaline solution). After stirring for a certain period of time, add the carrier and continue stirring to mix them thoroughly. Wash them with n-heptane for 3-4 times and dry them in an oven at 100-150°C in a nitrogen atmosphere to obtain the catalyst.

[0028] The beneficial effects of the present invention are:

[0029] The present invention can use the tower bottom liquid as raw material. Due to its complex composition, it has a great influence on the life and selectivity of the catalyst. The catalyst of the present invention is conducive to improving the product selectivity, and the reaction conditions are mild; the by-product ethyl pyruvate is fully utilized, and the environmental pressure is reduced. A green synthesis process of apo ester intermediate is provided. DETAILED DESCRIPTION

[0030] The ethyl pyruvate bottom liquid is the bottom liquid obtained after removing the product in the preparation of ethyl acrylate. The material is a viscous liquid composed of ethyl pyruvate, ethyl 3-methoxypropionate, ethyl acryloyloxypropionate, and the rest are polymer impurities.

[0031] Unless otherwise specified, all reagents used were not specially treated.

[0032] The gas chromatography analysis conditions in the present invention are as follows:

[0033] Chromatographic column: Agilent WAX (specifications: 30m×0.32mm×0.25mm)

[0034] Inlet temperature: 230°C

[0035] Split ratio: 30:1

[0036] Column flow rate: 1.5ml / min

[0037] Column temperature: Start from 180℃, increase to 230℃ at 5℃ / min, maintain for 15min

[0038] Detector temperature: 280°C, H2 flow rate: 35ml / min, air flow rate: 350ml / min

[0039] Example 1

[0040] Preparation process of catalyst A: Weigh 0.1g potassium titanate and 0.5g zinc sulfate (as a modifier), place in acetone, stir for 1h, add 99.4g activated carbon as a carrier, continue stirring for 2h to mix thoroughly, wash with n-heptane 3 times, place in an oven at 100℃ in nitrogen atmosphere for 2h, and set aside.

[0041] Example 2

[0042] Preparation process of catalyst B: Weigh 5.0g of magnesium cuprate and 5.0g of ferric acetate (as a modifier), place in 30%wt sodium hydroxide solution, stir for 1h, add 90g of silica as a carrier, continue stirring for 2h to mix thoroughly, wash with n-heptane 3 times, place in an oven under nitrogen atmosphere at 130°C for 2h, and set aside.

[0043] Example 3

[0044] Preparation process of catalyst C: 10.0g magnesium titanate and 1.0g copper chloride (as a modifier) ​​were weighed and placed in a 30%wt sodium hydroxide solution. After stirring for 1h, 40g ZSM-5 molecular sieve was added as a carrier and stirred for 2h to mix thoroughly. The catalyst was washed with n-heptane for 3 times and dried in an oven at 150°C in a nitrogen atmosphere for 2h before use.

[0045] Example 4

[0046] Preparation process of catalyst D: Weigh 0.5g potassium cuprate and 0.2g zinc sulfate (as a modifier) ​​in 30%wt potassium hydroxide solution, stir for 1h, add 100g activated carbon as carrier, continue stirring for 2h to mix thoroughly, wash with n-heptane 4 times, dry in an oven at 120℃ under nitrogen atmosphere for 2h, and set aside.

[0047] Example 5

[0048] Take 1000g of the bottom liquid, the composition is: w(ethyl acrylate)=12.5%, w(ethyl pyruvate)=74.1%, w(ethyl 3-methoxypropionate)=7.4%, w(ethyl acryloxypropionate)=4.8%, and the other main components are polymer impurities. The vacuum degree of reduced pressure distillation is 200Pa, the bottom temperature is 165°C, and a total of 910g of ethyl pyruvate with a purity of 81.2% is obtained at the top of the tower, wherein the content of ethyl acrylate is 13.2%, the content of ethyl 3-methoxypropionate is 4.2%, the content of ethyl acryloxypropionate is 1.2%, and the polymer content is less than 0.2%.

[0049] Add 100g of toluene and 1g of catalyst A into a three-necked flask, 120g of ethyl pyruvate with a purity of 81.2% after pretreatment, 100g of 1,2-dichloroethane, and 170g of triethyl phosphite, and keep the temperature in the three-necked flask at 60°C for 2h. After stopping stirring, add 100g of water for phase separation, and take the organic phase for desolventizing and concentration. Take a small amount of liquid for gas chromatography analysis of product composition. The conversion rate is 92.6% and the selectivity is 89.3%.

[0050] Example 6

[0051] Add 500g of n-heptane and 2g of catalyst B into a three-necked flask. After pretreatment, add 180g of ethyl pyruvate, 140g of 1,2-dichloroethane, and 270g of triethyl phosphite with a purity of 78.5%. Keep the temperature in the three-necked flask at 30°C and react for 10 hours. After stopping stirring, add 500g of water for phase separation, and take the organic phase for desolventizing and concentration. Take a small amount of liquid for gas chromatography analysis of product composition. The conversion rate is 91.3% and the selectivity is 82.7%.

[0052] Example 7

[0053] Add 1000g of n-hexane and 5g of catalyst C into a three-necked flask. After pretreatment, add 130g of ethyl pyruvate, 117g of 1,2-dichloroethane, and 230g of triethyl phosphite with a purity of 76.4%. Keep the temperature in the three-necked flask at 0°C and react for 20 hours. After stopping stirring, add 500g of water for phase separation, and take the organic phase for desolventizing and concentration. Take a small amount of liquid for gas chromatography analysis of product composition. The conversion rate is 84.3% and the selectivity is 91.8%.

[0054] Example 8

[0055] Add 500g toluene, 3g catalyst D, 100g ethyl pyruvate, 115g 1,2-dichloroethane, and 190g triethyl phosphite into a three-necked flask, and keep the temperature in the three-necked flask at 60°C for 0.5h. After stopping stirring, add 500g water for phase separation, and take the organic phase for desolventizing and concentration. Take a small amount of liquid for gas chromatography analysis of product composition. The conversion rate is 95.3% and the selectivity is 95.8%.

Claims

1. A method for preparing ethyl 4-(diethoxyphosphoryl)-2-butenoate, characterized in that: Ethyl pyruvate is reacted with 1,2-dichloroethane and triethyl phosphite in the presence of a catalyst at 0-70°C for 0.5-20h to obtain ethyl 4-(diethoxyphosphoryl)-2-butenoate; The catalyst is a supported alkaline catalyst, which is composed of a carrier, an alkali metal salt, and a modifier; The carrier is one or more of silicon dioxide, activated carbon, and ZSM-5 molecular sieve; The alkali metal salt is one or more of potassium and magnesium titanates and cuprates; The modifier is one or more of acetate, sulfate and chloride of iron, zinc and copper.

2. The method according to claim 1, wherein: The molar ratio of ethyl pyruvate to 1,2-dichloroethane and triethyl phosphite is 1:1.1-1.5:1.1-2.

3. The method according to claim 1 or 2, wherein: The reaction temperature is 10-50°C; the reaction time is 2-6h.

4. The method according to any one of claims 1 to 2, wherein: A non-polar solvent is also used, selected from one or more of toluene, n-heptane, and n-hexane.

5. The method according to claim 4, wherein: The mass of the non-polar solvent is 1 to 10 times that of ethyl pyruvate.

6. The method according to claim 1, wherein: The amount of the catalyst used is 0.5-5% of the mass of ethyl pyruvate.

7. The method according to claim 1, wherein: The alkali metal salt is one or more of potassium titanate, magnesium cuprate, magnesium titanate and potassium cuprate.

8. The method according to claim 7, wherein: The alkali metal salt accounts for 0.1 to 20% of the catalyst mass.

9. The method according to claim 7, wherein: The alkali metal salt accounts for 5 to 15% of the catalyst mass.

10. The method according to claim 1, wherein: The amount of modifier added is 0.1 to 10% of the catalyst mass.

11. The method according to claim 1, wherein: The amount of modifier added is 1 to 10% of the catalyst mass.

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