A method for synthesizing 2-methyl-3-tetrahydrofuran thiol

Abstract

The application discloses a synthesis method of 2-methyl-3-tetrahydrofuran thiol, and the 2-methyl-3-tetrahydrofuran thiol is synthesized by 2-methyl tetrahydrofuran-3-alcohol and thiourea hydrochloride; the conversion rate of 2-methyl tetrahydrofuran-3-alcohol and thiourea hydrochloride is high, by-products are few, three-waste pollution is little, and the excessive 2-methyl tetrahydrofuran-3-alcohol can be reused. The raw material ratio, the reaction temperature and the reaction pressure are simultaneously discussed, so that the reaction obtains a high yield, the safety and stability of the test are effectively ensured, and an unexpected technical effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, in particular to a method for synthesizing 2-methyl-3-tetrahydrofuranthiol. Background Art

[0002] 2-Methyltetrahydrofuran-3-thiol (FEMA No. 3787) is an important sulfur-containing spice. It was first found in broth and is a degradation product of vitamin B1. After dilution, the product has a strong meaty and barbecued aroma. It has high added value and is widely used. It is one of the most commonly used spices in various meat flavoring formulas. It can be used to prepare a variety of edible flavors [3]. GB2760-1997 No. I1895.

[0003] The main domestic production process for 2-methyl-3-tetrahydrofuranthiol currently uses 2-methyltetrahydrofuran-3-ol as the main raw material. 2-methyltetrahydrofuran-3-ol reacts with p-toluenesulfonyl chloride to produce 2-methyl-3-p-toluenesulfonyl tetrahydrofuran, which then undergoes a substitution reaction with potassium thioacetate to produce 2-methyltetrahydrofuran-3-thioacetate. 2-methyltetrahydrofuran-3-thioacetate then reacts with aqueous sodium hydroxide to produce 2-methyltetrahydrofuran-3-sodium sulfonate and 2-methyltetrahydrofuran-3-sodium sulfonate, which is then acidified with hydrochloric acid to produce 2-methyltetrahydrofuran-3-thiol. This process is complex and produces a large amount of sodium p-toluenesulfonate as a by-product, which places significant pressure on environmental protection. The present invention optimizes the raw material ratio and reaction temperature of the reaction simultaneously, thereby achieving a high reaction yield and effectively ensuring the safe and stable operation of the experiment, thereby achieving unexpected results. The present invention improves the preparation process of 2-methyl-3-tetrahydrofuranthiol, has excellent product quality, reduces three waste pollution, and the only by-product urea can be sold as a by-product after dehydration, crystallization, centrifugation and recovery. Summary of the Invention

[0004] The object of the present invention is to provide a kind of synthetic method of 2-methyl-3-tetrahydrofuran mercaptan, to solve the problems of the technologies described above.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0006] A method for synthesizing 2-methyl-3-tetrahydrofuranthiol comprises the following steps: mixing 2-methyltetrahydrofuran-3-ol, thiourea hydrochloride, ether, and hydroquinone, adding zinc chloride as a catalyst, immediately sealing the kettle mouth to prevent gasification and leakage, stirring and reacting for 2.5-3.5 hours at a pressure of 1.3-1.6 MPa and a temperature of 130-150° C., cooling and releasing the pressure, discharging the reaction liquid, neutralizing it with a sodium carbonate solution to neutrality, performing static layer separation, removing the solvent and unreacted 2-methyltetrahydrofuran-3-ol, and then performing rectification to obtain high-purity 2-methyl-3-tetrahydrofuranthiol.

[0007] As a further embodiment of the present invention, the molar ratio of the 2-methyltetrahydrofuran-3-ol to thiourea hydrochloride is 1 to 2.5:1.

[0008] As a further embodiment of the present invention, the reaction pressure is 1.0-1.6 MPa.

[0009] As a further embodiment of the present invention, the mass ratio of the 2-methyltetrahydrofuran-3-ol to the diethyl ether is 1:3.

[0010] As a further embodiment of the present invention, the mass ratio of the 2-methyltetrahydrofuran-3-ol to zinc chloride is 7-10:1.

[0011] As a further embodiment of the present invention, the mass ratio of 2-methyltetrahydrofuran-3-ol to hydroquinone is 200:1.

[0012] Reaction equation of the present invention is as follows:

[0013]

[0014] Compared with the prior art, the present invention has the following advantages: 2-methyl-3-tetrahydrofuranthiol is synthesized by a synthesis method using 2-methyltetrahydrofuran-3-ol and thiourea hydrochloride. The conversion rate of 2-methyltetrahydrofuran-3-ol and thiourea hydrochloride is high, by-products are small, and three wastes pollution is reduced. Furthermore, excess 2-methyltetrahydrofuran-3-ol can be reused. The raw material ratio, reaction temperature, and pressure of the reaction are simultaneously studied to achieve a high reaction yield. Furthermore, the safe and stable operation of the experiment is effectively ensured, achieving unexpected technical results. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Example 1

[0018] 2-methyltetrahydrofuran-3-alcohol 300g, thiourea hydrochloride 120g, ether 900g, Resorcinol 1.5g are mixed in a 2000ml pressure reactor, and then 43g of zinc chloride is added. The still mouth is immediately sealed to prevent gasification and the mixture is heated to 150°C. The reaction mixture is stirred for 3h under a pressure of about 1.6mpa. The reaction mixture is cooled and depressurized, and the reaction solution is discharged. The mixture is neutralized to neutrality with sodium carbonate solution, and then static layering is performed. The organic phase is desorbed from the solvent and unreacted 2-methyltetrahydrofuran-3-alcohol, and then high-purity 2-methyl-3-tetrahydrofuran mercaptan is obtained by rectification. 423g of 2-methyl-3-tetrahydrofuran mercaptan is obtained, with a content of 99.1% and a productive rate of 73%.

[0019] Example 2

[0020] Under the conditions of Example 1, the consumption of zinc chloride was changed. It was found that even if the catalyst level was increased by 2 times, the yield of 2-methyl-3-tetrahydrofuran mercaptan changed very little; The catalyst level was reduced by 1 times, and the yield of 2-methyl-3-tetrahydrofuran mercaptan reduced significantly. We speculate that the mass ratio of 2-methyltetrahydrofuran-3-alcohol and zinc chloride is 7-10:1 and is advisable.

[0021] A 2000ml medium-pressure reactor was added with 300g of 2-methyltetrahydrofuran-3-ol, 120g of thiourea hydrochloride, 900g of ether, and 1.5g of hydroquinone. 43g, 80g, and 20g of zinc chloride were added, respectively. The reactor was immediately sealed to prevent gasification and the temperature was raised to 150°C. At this time, the pressure was about 1.6 MPa and the reaction was stirred for 3h. After cooling, the pressure was released and the reaction liquid was discharged. It was neutralized with sodium carbonate solution to neutrality and then subjected to static stratification. The organic phase was freed of the solvent and unreacted 2-methyltetrahydrofuran-3-ol, and then distilled to obtain high-purity 2-methyl-3-tetrahydrofuranthiol.

[0022] Experimental results

[0023] 2-Methyl-3-tetrahydrofuranthiol g content Group A: Add 43g zinc chloride 423 99.1％ Group B: add 80g zinc chloride 415 99.0％ Group C: add 20g zinc chloride 361 99.12％

[0024] Example 3

[0025] Under the conditions of Example 1, the consumption of ether was changed, and it was found that the consumption of ether improved by 1.2 times, and the yield of 2-methyl-3-tetrahydrofuran mercaptan changed very little; the consumption of ether was reduced to 0.5 times, and the yield of 2-methyl-3-tetrahydrofuran mercaptan decreased sharply; we speculate that the mass ratio of 2-methyltetrahydrofuran-3-alcohol and ether was 1:3 and was advisable.

[0026] A 2000ml medium-pressure reactor was added with 300g of 2-methyltetrahydrofuran-3-ol, 120g of thiourea hydrochloride, 900g, 1080g, 450g of ether, and 1.5g of hydroquinone. 43g, 80g, and 20g of zinc chloride were added, respectively. The reactor was immediately sealed to prevent gasification and the temperature was raised to 150°C. At this time, the pressure was about 1.6 MPa and the reaction was stirred for 3h. After cooling, the pressure was released and the reaction liquid was discharged. It was neutralized with sodium carbonate solution to neutrality and then subjected to static stratification. The organic phase was freed from the solvent and unreacted 2-methyltetrahydrofuran-3-ol, and then distilled to obtain high-purity 2-methyl-3-tetrahydrofuranthiol.

[0027] Experimental results:

[0028] 2-Methyl-3-tetrahydrofuranthiol g content Group A: Add 900g of ether 423 99.1％ Group B: add 1080g ether 418 99.06％ Group C: add 450g ether 330 99.11％

[0029] Example 4

[0030] Under the conditions of Example 1, the temperature and pressure were changed (the pressure was approximately the saturated vapor pressure of ether at the corresponding temperature). It was found that when the temperature was lower than 130°C and the pressure was 8.5 MPa, the reaction rate was significantly slow. When the temperature was higher than 150°C and the pressure was higher than 1.6 MPa, the reaction rate was no longer significantly accelerated, the by-products increased, and the yield decreased. We speculate that it is appropriate to control the reaction temperature at 130-150°C and the pressure at 1.0-1.6 MPa.

[0031] 300 g of 2-methyltetrahydrofuran-3-ol, 120 g of thiourea hydrochloride, 900 g of ether, and 1.5 g of hydroquinone were added to a 2000 ml medium-pressure reactor. 43 g of zinc chloride was added and the reactor mouth was immediately sealed to prevent gasification leakage. The temperature was raised to 130 ° C, 140 ° C, 150 ° C, and 160 ° C, respectively. The mixture was kept warm and stirred for 3 h. After cooling, the pressure was released and the reaction liquid was discharged. It was neutralized with sodium carbonate solution to neutrality, and then static stratification was performed. The organic phase was freed from the solvent and unreacted 2-methyltetrahydrofuran-3-ol, and then distilled to obtain high-purity 2-methyl-3-tetrahydrofuran thiol.

[0032] Experimental results:

[0033] 2-Methyl-3-tetrahydrofuranthiol g content Group A: temperature 130°C, pressure 8.5 MPa 352 99.1％ Group B: Temperature: 140°C, pressure 1.2 MPa 418 99.06％ Group C: Temperature: 150°C, Pressure 1.6 MPa 423 99.11％ Group D: Temperature: 160°C, pressure 1.9 MPa 416 99.02％

[0034] Example 5

[0035] Under the conditions of Example 1, the reaction time was changed to 2h, 3h, and 4h, respectively. It was found that the reaction of thiourea hydrochloride was incomplete after 2h and the conversion rate was significantly reduced; it was found that the side reactions increased significantly after 4h and the product yield was reduced. We speculate that it is appropriate to control the reaction time to 2.5-3h.

[0036] 300 g of 2-methyltetrahydrofuran-3-ol, 120 g of thiourea hydrochloride, 900 g of ether, and 1.5 g of hydroquinone were added to a 2000 ml medium-pressure reactor, and 43 g of zinc chloride was added. The reactor was immediately sealed to prevent gasification leakage, and the temperature was raised to 150 ° C. The reaction was kept warm and stirred for 2 h, 3 h, and 4 h, respectively. After cooling, the pressure was released, the reaction solution was discharged, and the solution was neutralized with sodium carbonate solution to neutrality. The solution was then allowed to stand for stratification, and the organic phase was freed of the solvent and unreacted 2-methyltetrahydrofuran-3-ol, which was then distilled to obtain high-purity 2-methyl-3-tetrahydrofuranthiol.

[0037] Experimental results

[0038] 2-Methyl-3-tetrahydrofuranthiol g content Group a: Keep warm and stir for 2 hours 302 99.03％ Group B: Keep warm and stir for 3 hours 423 99.1％ Group C: Keep warm and stir for 4 hours 413 99.02％

[0039] The above is a preferred embodiment of the present invention. For ordinary technicians in this field, based on the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the scope of protection of the present invention.

Claims

1. a synthetic method for 2-methyl-3-tetrahydrofuran mercaptan, is characterized in that, The method comprises the following steps: mixing 2-methyltetrahydrofuran-3-ol, thiourea hydrochloride, ether and hydroquinone, adding zinc chloride as a catalyst, immediately sealing the kettle mouth to prevent gasification and leakage, stirring and reacting for 2.5-3.5 hours at a pressure of 1.3-1.6 MPa and a temperature of 130-150° C., cooling and releasing the pressure, releasing the reaction liquid, neutralizing it with a sodium carbonate solution to neutrality, performing static stratification, removing the solvent and unreacted 2-methyltetrahydrofuran-3-ol, and then performing rectification to obtain high-purity 2-methyl-3-tetrahydrofuranthiol.

2. the synthetic method of a kind of 2-methyl-3-tetrahydrofuran mercaptan as claimed in claim 1, is characterized in that, The molar ratio of the 2-methyltetrahydrofuran-3-ol to thiourea hydrochloride is 1-2.5:

1.

3. the synthetic method of a kind of 2-methyl-3-tetrahydrofuran mercaptan as claimed in claim 1, is characterized in that, The reaction pressure is 1.0-1.6 MPa.

4. the synthetic method of a kind of 2-methyl-3-tetrahydrofuran mercaptan as claimed in claim 1, is characterized in that, The mass ratio of the 2-methyltetrahydrofuran-3-ol to diethyl ether is 1:

3.

5. the synthetic method of a kind of 2-methyl-3-tetrahydrofuran mercaptan as claimed in claim 1, is characterized in that, The mass ratio of the 2-methyltetrahydrofuran-3-ol to zinc chloride is 7-10:

1.

6. the synthetic method of a kind of 2-methyl-3-tetrahydrofuran mercaptan as claimed in claim 1, is characterized in that, The mass ratio of the 2-methyltetrahydrofuran-3-ol to hydroquinone is 200:1.

Images