Method for preparing methyl heptenone

Abstract

According to the method for preparing the methyl heptenone through the Saucy-Marbet reaction of the 2-methyl-3-butene-2-alcohol and the 2-methoxypropene, by controlling the content of the key impurities tert-amyl alcohol and water in the raw materials, the reaction conversion rate can be larger than or equal to 99.5%, and the reaction selectivity can be larger than or equal to 98.5%. The method has the advantages of cheap and easily available catalyst, mild reaction conditions, simple operation and high reaction yield, and solves the problems of more three wastes, complex side reaction, difficult product purification and the like in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing methyl heptenone by Saucy-Marbet reaction of 2-methyl-3-butene-2-ol and 2-methoxypropylene. Background Art

[0002] Methyl heptenone, with the aroma of lemongrass, isobutyl acetate and fresh fruit, is an edible flavor allowed by the national standard and can be used to prepare banana, pear and berry flavors. Methyl heptenone is also a very important synthetic intermediate and can be used in the synthesis of spices such as linalool, citral and pseudoionone. At present, the methods for preparing methyl heptenone mainly include acetylene-acetone method, isobutylene-formaldehyde method, isoprene method and Saucy-Marbet method.

[0003] The acetylene-acetone method is the earliest industrialized method for methyl heptenone (patents DE2126356, GB788301, GB888999, DE1137433, CN1218792A), which uses acetone as a starting material, adds acetylene to acetone to obtain an alkynol intermediate, and then partially hydrogenates to obtain an allyl alcohol intermediate, and the allyl alcohol intermediate and ethyl acetoacetate undergo a Carroll rearrangement reaction to obtain the methyl heptenone product. This route requires the consumption of a large amount of calcium carbide to produce acetylene, produces a large amount of calcium carbide waste residue, and the Carroll reaction produces an equivalent amount of ethanol byproducts. The atom economy of the synthetic route is poor, and the three wastes are more.

[0004] The isoprene method is a starting material with isoprene, and hydrogen chloride is added to it to obtain isopentenyl chloride, which is then condensed with acetone to obtain the methyl heptenone product. The main difficulty of this route is the condensation reaction at present. The method (patent JP40-22251, JP56-115734, JP56-61319, CN1762955A, CN1772722A, CN103664556A) of phase transfer catalysis is adopted in the literature reports. Selecting a suitable phase transfer catalyst is the key to the condensation reaction of chloroisoamylene and acetone. The prior art generally has an obvious defect, which is the recycling problem of the catalyst. In general, the selectivity of the methyl heptenone reaction prepared by the isoprene method is poor, and the yield is general, and a large amount of three wastes are produced, and the phase transfer catalyst is difficult to recycle, which is unfavorable for industrialized production, and the current technology has been eliminated.

[0005] BASF patents reported the one-pot synthesis of 6-methyl-6-heptene-2-one from isobutylene, formaldehyde and acetone, and the resulting product was further hydroisomerized to obtain methyl heptenone (patents DE1277848B, DE1267682B). Although the synthesis route is short, the first step has harsh reaction conditions, high temperature and high pressure, and the reaction selectivity is poor (40-50% product selectivity), accompanied by the generation of a large number of by-products, and the product is difficult to purify by distillation.

[0006] The Saucy-Marbet method is used to prepare methyl heptenone. 2-methyl-3-butene-2-ol and 2-methoxypropylene are used as raw materials. Saucy-Marbet rearrangement reaction occurs under the action of an acid catalyst to obtain methyl heptenone (patents DE1193490, DE19649564, CN1539 807A, CN1914143, CN108299171A, CN1228757, CN102197014). The Saucy-Marbet method is used to prepare methyl heptenone. The atomic utilization rate is high and the environment is friendly, but the reaction activity is poor when weak acid catalysis is used, and a higher reaction temperature and a longer reaction time are required to complete the reaction. The reaction activity is good when strong acid catalysts such as phosphoric acid and sulfonic acid are used, but the selectivity of the reaction is poor, and the raw material 2-methyl-3-butene-2-ol will be dehydrated to generate diene by-products, which affects separation.

[0007] In summary, there are currently a variety of methods for synthesizing methyl heptenone, and some synthetic routes have achieved industrial production. However, these synthetic routes generally have disadvantages such as more waste, complex side reactions, and difficulty in product purification. Therefore, it is still necessary to develop new methyl heptenone synthesis methods to synthesize methyl heptenone products more efficiently, environmentally friendly, and atom-economically. Summary of the invention

[0008] Aiming at the problems that the existing method for preparing methyl heptenone has more three wastes, complicated side reactions, difficult product purification, etc., the present invention provides a method for preparing methyl heptenone by Saucy-Marbet reaction of 2-methyl-3-butene-2-ol and 2-methoxypropylene. By controlling the content of tertiary amyl alcohol as an impurity in 2-methyl-3-butene-2-ol and simultaneously controlling the water content in 2-methyl-3-butene-2-ol and 2-methoxypropylene, the reaction conversion rate of ≥99.5% and the reaction selectivity of ≥98.5% can be achieved.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing methyl heptenone, comprising:

[0011] 2-Methyl-3-butene-2-ol and 2-methoxypropylene undergo Saucy-Marbet reaction in the presence of a catalyst to generate methyl heptenone.

[0012] We are surprised to find that tertiary amyl alcohol content and water content have a significant impact on the conversion rate and selectivity of the reaction in the raw material. In the described 2-methyl-3-butene-2-ol, the impurity tertiary amyl alcohol content is controlled at 200-3000ppm, and in 2-methyl-3-butene-2-ol and 2-methoxy propylene, water content is all controlled at 100-2000ppm. Impurity tertiary amyl alcohol is the main by-product generated by 2-methyl-3-butyn-2-ol hydrogenation, and is close to the boiling point of 2-methyl-3-butene-2-ol, so it can not be removed completely. In order to reduce the content of impurity tertiary amyl alcohol, usually very high theoretical plate number or very large rectification reflux ratio are needed to be separated, but also caused a significant increase in energy consumption. In addition, water and raw material 2-methyl-3-butene-2-ol, 2-methoxy propylene all have azeotropic, so they also can not be removed completely. The method for reducing the tert-amyl alcohol content may be distillation and improving the selectivity of 2-methyl-3-butyn-2-ol hydrogenation, and the method for reducing the water content may be drying, azeotropic distillation and extractive distillation, etc. As long as the relevant content is adjusted within the scope of the present invention, there is no special requirement for the method.

[0013] As a preferred embodiment, the catalyst may be one or more of an organic amine sulfonate (preferably ethanolamine sulfonate, more preferably one or more of diethanolamine methanesulfonate, triethanolamine methanesulfonate, diethanolamine p-toluenesulfonate and triethanolamine p-toluenesulfonate), a phosphoric acid diester (preferably one or more of diphenyl phosphate, binaphthol phosphate and dibenzyl phosphate) and a phosphorous acid diester (preferably one or more of dimethyl phosphite, diphenyl phosphite and diethyl phosphite);

[0014] In a specific embodiment, the molar ratio of the catalyst to 2-methyl-3-butene-2-ol is 0.005 to 0.1%, preferably 0.01 to 0.05%;

[0015] In a specific embodiment, the ethanolamine sulfonate is prepared by reacting an organic amine (diethanolamine, triethanolamine) with a sulfonic acid (methanesulfonic acid, p-toluenesulfonic acid) in a molar ratio of 1:1, and the reaction is a conventional acid-base neutralization reaction. The organic phosphate diester catalyst and the organic phosphite diester catalyst are both commercially available.

[0016] In a specific embodiment, the temperature of the Saucy-Marbet reaction is 100-200°C, preferably 140-160°C.

[0017] In a specific embodiment, the residence time of the Saucy-Marbet reaction is 2 to 6 hours, preferably 3 to 4 hours.

[0018] In a specific embodiment, the molar ratio of 2-methyl-3-butene-2-ol to 2-methoxypropylene is 1:2-5, preferably 1:2.5-3.

[0019] In a specific embodiment, the purity of 2-methyl-3-butene-2-ol and 2-methoxypropylene is above 99%, preferably above 99.5%.

[0020] In a specific embodiment, the selectivity of the Saucy-Marbet reaction is ≥98.5%, and the conversion rate is ≥99.5%.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] The method reported in the present invention controls the contents of tert-amyl alcohol and water, which are key impurities in the raw materials, and can achieve a reaction conversion rate of ≥99.5% and a reaction selectivity of ≥98.5%. The method has less three wastes, less catalyst usage, cheap and easily available catalysts, mild operating conditions, and is suitable for industrial scale-up production. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0024] The main sources of reagents in each embodiment and comparative example are as follows:

[0025] 2-Methyl-3-butene-2-ol, purity ≥99.5%; 2-methoxypropylene, purity ≥99.5%

[0026] Diethanolamine, triethanolamine, methanesulfonic acid, p-toluenesulfonic acid, diphenyl phosphate, binaphthol phosphate, and dimethyl phosphite were purchased from Aladdin Reagent with a purity of ≥99%, Aladdin Reagent.

[0027] Methanol, acetone, purity ≥99.5%, Xilong Chemical.

[0028] In the embodiment, 2-methyl-3-butene-2-ol with a tert-amyl alcohol content of 200 ppm can be obtained by optimizing the number of plates and the reflux ratio of the rectification, and then tert-amyl alcohol is additionally added to prepare 2-methyl-3-butene-2-ol with different tert-amyl alcohol contents. In addition, 2-methyl-3-butene-2-ol and 2-methoxypropylene can be dried with molecular sieves to control the water content to less than 100 ppm, and then water is additionally added to prepare 2-methyl-3-butene-2-ol and 2-methoxypropylene with different water contents.

[0029] The gas chromatography test conditions used in the present invention are as follows:

[0030] Instrument model: Agilent 8890B;

[0031] Injection volume: 0.5 μl;

[0032] Inlet temperature: 250°C;

[0033] Split ratio: 30 / 1;

[0034] Chromatographic column: Agilent INNOWAX, 30m×250μm×0.25μm;

[0035] Column flow rate: 1.5 mL / min;

[0036] Temperature program: start at 35°C, hold for 5 min, then increase to 250°C at 10°C / min, hold for 10 min;

[0037] Detector temperature: 250°C; air flow rate: 400 mL / min; hydrogen flow rate: 40 mL / min; nitrogen flow rate: 25 mL / min.

[0038] Example 1

[0039] Diethanolamine (0.0105 g, 0.1 mmol) and p-toluenesulfonic acid (0.0172 g, 0.1 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.527%, tert-amyl alcohol content 300 ppm, water content 2000 ppm) and 218.515 g (3 mol) of 2-methoxypropylene (purity 99.515%, water content 2000 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating, and the timing was started when the temperature in the autoclave rose to 140°C. The reaction was kept warm for 4 hours and samples were taken. The conversion rate of the reaction was 99.615% and the reaction selectivity was 98.531% according to GC analysis.

[0040] Example 2

[0041] Triethanolamine (0.0746 g, 0.5 mmol) and p-toluenesulfonic acid (0.0861 g, 0.5 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.525%, tert-amyl alcohol content 1000 ppm, water content 2000 ppm) and 182.096 g (2.5 mol) of 2-methoxypropylene (purity 99.517%, water content 2000 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was evacuated, and the autoclave was opened for heating. When the temperature in the autoclave rose to 100° C., the timing was started. The reaction was kept warm for 2 h and samples were taken. The conversion rate of the reaction was 99.575% and the reaction selectivity was 98.699% according to GC analysis.

[0042] Example 3

[0043] Triethanolamine (0.0746 g, 0.5 mmol) and methanesulfonic acid (0.0481 g, 0.5 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.526%, tert-amyl alcohol content 2000 ppm, water content 1000 ppm) and 145.677 g (2 mol) of 2-methoxypropylene (purity 99.516%, water content 2000 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating, and the timing was started when the temperature in the autoclave rose to 160°C. The reaction was kept warm for 3 h and samples were taken. The conversion rate of the reaction was 99.511% and the reaction selectivity was 98.513% according to GC analysis.

[0044] Example 4

[0045] Diethanolamine (0.0053 g, 0.05 mmol) and methanesulfonic acid (0.0048 g, 0.05 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.531%, tert-amyl alcohol content 500 ppm, water content 100 ppm) and 364.192 g (5 mol) of 2-methoxypropylene (purity 99.515%, water content 100 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating. When the temperature in the autoclave rose to 200° C., the timing was started. The reaction was kept warm for 6 h and samples were taken. The conversion rate of the reaction was 99.623% and the reaction selectivity was 98.897% according to GC analysis.

[0046] Example 5

[0047] Triethanolamine (0.0448 g, 0.3 mmol) and methanesulfonic acid (0.0288 g, 0.3 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.528%, tert-amyl alcohol content 2000 ppm, water content 1000 ppm) and 182.096 g (2.5 mol) of 2-methoxypropylene (purity 99.516%, water content 1000 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating, and the timing was started when the temperature in the autoclave rose to 150°C. The reaction was kept warm for 4 h and samples were taken. The conversion rate of the reaction was 99.538% and the reaction selectivity was 98.693% according to GC analysis.

[0048] Example 6

[0049] Diphenyl phosphate (0.125 g, 0.5 mmol) was added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.528%, tert-amyl alcohol content 2000 ppm, water content 2000 ppm) and 218.515 g (3.0 mol) of 2-methoxypropylene (purity 99.526%, water content 1000 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was vented, and the autoclave was opened for heating. The timing was started when the temperature in the autoclave rose to 140°C. The reaction was kept warm for 3 h and samples were taken. The conversion rate of the reaction was 99.527% and the reaction selectivity was 98.533% according to GC analysis.

[0050] Example 7

[0051] Add binaphthol phosphate (0.174g, 0.5mmol) into a 0.5L autoclave, then add 86.565g (1mol) 2-methyl-3-butene-2-ol (purity 99.531%, tert-amyl alcohol content 500ppm, water content 1000ppm) and 218.515g (3.0mol) 2-methoxypropylene (purity 99.526%, water content 1000ppm). Close the autoclave, replace the air in the autoclave with 0.5MPaG nitrogen three times, then evacuate the nitrogen in the autoclave, open the autoclave and heat it, and start timing when the temperature in the autoclave rises to 140°C. Keep the reaction for 3h and take a sample. The conversion rate of the reaction is 99.626% and the reaction selectivity is 98.554% according to GC analysis.

[0052] Example 8

[0053] Add dimethyl phosphite (0.110 g, 1 mmol) into a 0.5 L autoclave, then add 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.543%, tert-amyl alcohol content 200 ppm, water content 200 ppm) and 218.515 g (3.0 mol) of 2-methoxypropylene (purity 99.535%, water content 200 ppm). Close the autoclave, replace the air in the autoclave with 0.5 MPaG nitrogen three times, then evacuate the nitrogen in the autoclave, open the autoclave and heat it, and start timing when the temperature in the autoclave rises to 160°C. Keep the reaction for 6 hours and take a sample. The conversion rate of the reaction is 99.512% and the reaction selectivity is 98.623% according to GC analysis.

[0054] Comparative Example 1

[0055] Triethanolamine (0.0448 g, 0.3 mmol) and methanesulfonic acid (0.0288 g, 0.3 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.525%, tert-amyl alcohol content 3500 ppm, water content 1500 ppm) and 182.096 g (2.5 mol) of 2-methoxypropylene (purity 99.514%, water content 1500 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating, and the timing was started when the temperature in the autoclave rose to 150°C. The reaction was kept warm for 4 hours and samples were taken. The conversion rate of the reaction was 99.312% and the reaction selectivity was 96.165% according to GC analysis.

[0056] Comparative Example 2

[0057] Triethanolamine (0.0448 g, 0.3 mmol) and methanesulfonic acid (0.0288 g, 0.3 mmol) were added to a 0.5 L autoclave, followed by 86.565 g (1 mol) of 2-methyl-3-butene-2-ol (purity 99.531%, tert-amyl alcohol content 2000 ppm, water content 2500 ppm) and 182.096 g (2.5 mol) of 2-methoxypropylene (purity 99.515%, water content 2500 ppm). The autoclave was closed, and the air in the autoclave was replaced three times with 0.5 MPaG nitrogen, and then the nitrogen in the autoclave was emptied, and the autoclave was opened for heating, and the timing was started when the temperature in the autoclave rose to 150°C. The reaction was kept warm for 4 hours and samples were taken. The conversion rate of the reaction was 99.234% and the reaction selectivity was 96.593% according to GC analysis.

Claims

1. A method for preparing methyl heptenone, comprising: 2-methyl-3-butene-2-ol and 2-methoxypropylene undergo a Saucy-Marbet reaction under the action of a catalyst to generate methyl heptenone; the method is characterized in that the content of tert-amyl alcohol in 2-methyl-3-butene-2-ol is 200-3000 ppm, and the content of water in 2-methyl-3-butene-2-ol and 2-methoxypropylene is 100-2000 ppm.

2. The method according to claim 1, characterized in that The catalyst is selected from organic amine sulfonates (preferably ethanolamine sulfonates, more preferably one or more of diethanolamine methanesulfonate, triethanolamine methanesulfonate, diethanolamine p-toluenesulfonate and triethanolamine p-toluenesulfonate), phosphoric acid diesters (preferably one or more of diphenyl phosphate, binaphthol phosphate and dibenzyl phosphate) and phosphite diesters (preferably one or more of dimethyl phosphite, diphenyl phosphite and diethyl phosphite).

3. The method according to claim 1 or 2, characterized in that: The molar ratio of the catalyst to 2-methyl-3-butene-2-ol is 0.005 to 0.1%, preferably 0.01 to 0.05%.

4. The method according to claim 1, characterized in that: The molar ratio of 2-methyl-3-butene-2-ol to 2-methoxypropylene is 1:2-5, preferably 1:2.5-3.

5. The method according to any one of claims 1 to 4, characterized in that: The reaction temperature is 100-200°C, preferably 140-160°C.

6. The method according to any one of claims 1 to 5, characterized in that: The reaction residence time is 2 to 6 hours, preferably 3 to 4 hours.