Novel synthesis method of bromelain

Abstract

The invention discloses a novel synthesis method of bromelain, which belongs to the field of fine chemical engineering and flavors and fragrances, and comprises the following steps: by taking cyclohexane as a raw material, in the presence of di-tert-butyl peroxide, adding an acidic catalyst A to react with methyl acrylate to obtain methyl cyclohexyl propionate, and reacting with methyl acrylate to obtain methyl cyclohexyl propionate; then carrying out ester exchange reaction on the bromelain and allyl alcohol in the presence of a basic catalyst B to obtain bromelain; the acidic catalyst A is one of fumaric acid, tartaric acid and boric acid. The method has the advantages of low raw material price, high yield, high product purity, simple reaction conditions, simple process route and potential industrial application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals and flavors and fragrances, and in particular to a new method for synthesizing pineapple ester. Background Art

[0002] Pineapple ester, also known as allyl cyclohexylpropionate, is widely used in the food industry and is also used as a flavoring agent. It has a strong sweet pineapple-like fruit aroma. Therefore, the efficient and simple synthesis of pineapple ester has always been widely valued. The main synthesis method is to use cinnamic acid as a raw material to generate phenylpropionic acid, which is then hydrogenated to generate cyclohexylpropionic acid, and then esterified with allyl acid to form pineapple ester.

[0003] Chinese patent CN116102420A discloses a method for synthesizing pineapple esters: cinnamic acid is hydrogenated to obtain sodium cyclohexylpropionate, which is then reacted with allyl chloride to produce pineapple esters. Cinnamic acid is cheap and easy to obtain, so this method has certain market prospects. However, the working conditions of hydrogenation are harsh, and allyl chloride is highly toxic, which requires high quality of operators.

[0004] Chinese patent CN85102572A discloses a method for synthesizing pineapple ester from 4-vinylcyclohexene: using 4-vinylcyclohexene, a byproduct of petrochemical industry, as raw material, β-cyclohexene methyl propionate is prepared by hydrogenation esterification reaction, and then pineapple ester is prepared by hydrogenation ester exchange reaction. The octacarbonyl dicobalt catalyst used in the hydrogenation esterification reaction has great environmental pollution and is not conducive to industrial production. Summary of the invention

[0005] The invention aims at the disadvantages of the prior art and provides a novel preparation method of pineapple ester. Cyclohexane is used as a raw material, and a free radical reaction is carried out with methyl acrylate which is easily available as a raw material under the catalysis of di-tert-butyl peroxide to generate methyl cyclohexylpropionate, and then an ester exchange reaction is carried out with allyl alcohol to obtain pineapple ester. The invention has the advantages that the raw materials for synthesis are low in price, the yield is high, the product purity is high, the reaction conditions are simple, the process route is simple, and the invention has the current industrial application prospect.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A novel method for synthesizing pineapple ester comprises the following steps:

[0008] Cyclohexane is used as a raw material, and an acidic catalyst A is added in the presence of di-tert-butyl peroxide to react with methyl acrylate to obtain methyl cyclohexylpropionate, which is then subjected to an ester exchange reaction with allyl alcohol in the presence of a basic catalyst B to obtain pineapple ester.

[0009] The synthetic principle of described pineapple ester is as follows:

[0010]

[0011] As a further embodiment of the present invention: the acidic catalyst A is one of fumaric acid, tartaric acid and boric acid, preferably boric acid.

[0012] As a further solution of the present invention: the molar ratio of methyl acrylate to cyclohexane is 1:1-4, preferably 1:100.

[0013] As a further embodiment of the present invention: the mass ratio of the acidic catalyst A to cyclohexane is 1:50-200, preferably 1:2.5.

[0014] As a further embodiment of the present invention: the alkaline catalyst B is one of sodium carbonate, potassium carbonate and potassium iodide, preferably potassium carbonate.

[0015] As a further embodiment of the present invention: the mass ratio of the alkaline catalyst B to methyl cyclohexylpropionate is 1:20-100, preferably 1:50.

[0016] As a further embodiment of the present invention: the molar ratio of methyl cyclohexylpropionate to allyl alcohol is 1:1-2, preferably 1:1.5.

[0017] The invention has the following beneficial effects: the synthetic raw materials are cheap and widely available, the reaction yield is high, the reaction conditions are mild, the process route is simple, and the invention has potential industrial application prospects. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1: Preparation of methyl cyclohexylpropionate

[0020] Add 126.4g (1.5mol) of cyclohexane and 2.1g of boric acid to a 1000ml four-necked flask equipped with a stirrer, a thermometer, a spherical condenser and a constant pressure funnel, start stirring, slowly heat up to 80°C until the cyclohexane refluxes, and then start dripping a mixture of 86g (1mol) of methyl acrylate, 84g (1mol) of cyclohexane and 4.4g (0.03mol) of di-tert-butyl peroxide, maintain the dripping temperature at 80°C, and drip for 5-6h. After the dripping is completed, keep the temperature for 4h and take samples for analysis until the methyl acrylate content is less than 1%. Then transfer to a flash evaporator to evaporate cyclohexane and tert-butyl alcohol at normal pressure. After distillation, the contents of the kettle were washed twice with saturated brine, and water was removed by atmospheric distillation. The component fractions at 85-100° C. were collected under reduced pressure using a fractionating column to obtain 125 g (0.735 mol) of methyl cyclohexylpropionate with a purity of 93.6% and a yield of 68.8%.

[0021] Example 2: Preparation of methyl cyclohexylpropionate

[0022] Add 252.8g (3mol) of cyclohexane and 4.3g of boric acid to a 2000ml four-necked flask equipped with a stirrer, a thermometer, a spherical condenser and a constant pressure funnel, start stirring, slowly heat up to 80°C until cyclohexane refluxes, and then start dripping a mixture of 172g (2mol) of methyl acrylate, 168g (2mol) of cyclohexane and 9g (0.06mol) of di-tert-butyl peroxide, maintain the dripping temperature at 80°C, and drip for 5-6h. After the dripping is completed, keep the temperature for 4h and take samples for analysis until the methyl acrylate content is less than 1%. Then transfer to a flash evaporator to evaporate cyclohexane and tert-butyl alcohol at normal pressure. After distillation, the contents of the kettle were washed twice with saturated brine, and water was removed by atmospheric distillation. The component fractions at 85-100°C were collected under reduced pressure using a fractionating column to obtain 267 g (1.44 mol) of methyl cyclohexylpropionate with a purity of 91.7% and a yield of 72.0%.

[0023] Example 3: Preparation of pineapple ester

[0024] In a 500 three-necked flask with a stirrer and a thermometer, 125 g of methyl cyclohexylpropionate synthesized in Example 1 (GC: 93.6%, 0.688 mol), 60 g of allyl alcohol (1.03 mol), and 2 g of potassium carbonate were added. A 400 mm long distillation tower was connected to the three-necked flask, and the temperature was slowly raised to 98° C. When material was discharged from the top of the tower, full reflux was performed. When the top temperature of the tower stabilized at about 60° C., extraction began. The fraction (methanol) with a top temperature between 60 and 70° C. was extracted. When the top of the tower rose to above 70° C., the reaction was stopped. The contents of the kettle were transferred to a suction filter, and the filter cake potassium carbonate was used for the next batch. The filtrate was transferred to a flash kettle to recover allyl alcohol at normal pressure, and then transferred to a fractionating column to collect the component fractions at 95-105° C. under reduced pressure to obtain 118 g (0.598 mol) of pineapple ester with a content of 99.61%, a reaction yield of 87%, and a two-step total yield of 59.85%.

[0025] Example 4: Preparation of pineapple ester

[0026] In a 1000 three-necked flask with a stirrer and a thermometer, 267 g of methyl cyclohexylpropionate synthesized in Example 2 (GC: 91.7%, 1.44 mol), 125 g of allyl alcohol (2.16 mol), and 5 g of potassium carbonate were added. A 400 mm long distillation tower was connected to the three-necked flask, and the temperature was slowly raised to 98°C. When material was discharged from the top of the tower, full reflux was performed. When the top temperature of the tower stabilized at about 60°C, extraction began. The fraction (methanol) with a top temperature between 60 and 70°C was extracted. When the top of the tower rose to above 70°C, the reaction was stopped. The contents of the kettle were transferred to a suction filter, and the filter cake potassium carbonate was used for the next batch. The filtrate was transferred to a flash kettle to recover allyl alcohol at normal pressure, and then transferred to a fractionating column to collect the component fractions at 95-105° C. under reduced pressure to obtain 258 g (1.31 mol) of pineapple ester with a content of 99.27%, a reaction yield of 91%, and a two-step total yield of 65.52%.

[0027] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A novel method for synthesizing pineapple ester, characterized in that, The following steps are involved: Cyclohexane is used as a raw material, and an acidic catalyst A is added in the presence of di-tert-butyl peroxide to react with methyl acrylate to obtain methyl cyclohexylpropionate, which is then subjected to an ester exchange reaction with allyl alcohol in the presence of a basic catalyst B to obtain pineapple ester.

2. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The acidic catalyst A is one of fumaric acid, tartaric acid and boric acid.

3. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The molar ratio of the methyl acrylate to the cyclohexane is 1:1-4.

4. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The mass ratio of the acidic catalyst A to cyclohexane is 1:50-200.

5. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The alkaline catalyst B is one of sodium carbonate, potassium carbonate and potassium iodide.

6. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The mass ratio of the alkaline catalyst B to methyl cyclohexylpropionate is 1:20-100.

7. A novel method for synthesizing pineapple ester according to claim 1, characterized in that: The molar ratio of the methyl cyclohexylpropionate to the allyl alcohol is 1:1-2.

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