A method for preparing an alpha, gamma-unsaturated dienone

Abstract

The application discloses a method for preparing alpha, gamma-unsaturated dienone, which is prepared by isomerization reaction of allene ketone under the action of a catalyst, wherein the catalyst comprises a hydroxyl-functionalized quaternary ammonium salt basic ionic liquid with a structure shown in formula (I); R1, R2, R3 and R4 are independently selected from substituted or unsubstituted alkane, alkene, alkyne and aromatic hydrocarbon, and at least one of R1, R2, R3 and R4 comprises a hydroxyl substituent; and Y is a group alkaline in water. The application catalyzes the isomerization reaction of allene ketone by using the catalyst comprising the hydroxyl-functionalized quaternary ammonium salt basic ionic liquid, and then alpha, gamma-unsaturated dienone is prepared, so that the application has the advantages of small catalyst consumption, high selectivity and yield, low reaction temperature, less pollution, and high yield and selectivity of the catalyst after recycling and multiple reuse.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, and in particular to a method for preparing α, γ-unsaturated dienone. BACKGROUND

[0002] Unsaturated ketone is an important intermediate for the synthesis of fragrances, medicines, and vitamins. For example, ionone is an important raw material for the synthesis of β-ionone and other fragrances, and is also an intermediate for the synthesis of vitamin A, vitamin E, chlorophyll alcohol, and β-carotene. Ionone plays a very important role in fragrances, medicines, food additives, and synthetic chemistry. Therefore, domestic and foreign scholars have been continuously improving the synthesis process of ionone.

[0003] Currently, there are three main methods for the synthesis of ionone: 1. Dehydro-linalool undergoes rearrangement to generate citral, and then citral and acetone undergo Aldol condensation under the action of an alkaline catalyst to obtain ionone; 2. Dehydro-linalool and acetyl acetate undergo Carroll rearrangement and then isomerization to directly obtain ionone; and 3. Dehydro-linalool and methoxy propylene undergo Saucy-Marbet reaction under the action of an acid catalyst to generate a dienone, and then isomerization under the action of a base catalyst to synthesize ionone.

[0004] The most widely used method is the first method, i.e., the hydroxy aldehyde condensation method of citral and acetone. However, although this method is stable and mature (CN113429275B, CN213408648U, CN110002981B), it involves heterogeneous catalysis and generates a large amount of wastewater. In addition, citral and acetone are prone to self-condensation under alkaline conditions, resulting in a low ionone yield, generally between 80% and 90%.

[0005] The second synthesis route is that dehydro-linalool and acetyl acetate undergo Carroll rearrangement under the catalysis of isopropyl aluminum to generate a dienone, and then isomerize to generate ionone (US3860655, CN103012094A). This method is mature and stable in production, but the reaction temperature is high, carbon dioxide is generated during the reaction, the atomic economy is poor, and acetyl acetate is expensive, which increases the cost and reduces the competitiveness of this method.

[0006] The third synthesis method is that dehydrolinalool and methoxypropene undergo a Saucy-Marbet reaction under the catalysis of an acid to generate an allene ketone, and then isomerization occurs under the catalysis of a base to obtain pseudoionone. This method was first reported by Saucy and Marbet (US3029287, US6184420; G. Saucy, R. Marbet, H. Lindlar, O. Isler, Helv. Chim. Acta. 1959, 6, 1945-1955. G. Saucy, R. Marbet, Helv. Chim. Acta. 1967, 4, 1158-1167). In the reported methods, the isomerization reaction uses a basic catalyst mainly in the form of homogeneous sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, etc. There are problems such as large amount of basic catalyst, low reaction efficiency, poor selectivity, difficulty in recycling the basic catalyst and product after the reaction, and generation of excessive waste after neutralization of the base (EP1092700; CN109534977B; Huang Wei, Shanghai Chemical Industry, 2008, 12, 13-15). SUMMARY

[0007] The purpose of the present application is to overcome one or more of the deficiencies in the prior art, and to provide a new method for preparing α,γ-unsaturated dienone by catalyzing the isomerization of allene ketone using a catalyst comprising at least a hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid. The use of the catalyst makes the method of the present application not only have small amount of catalyst, high selectivity and yield, but also can reduce the reaction temperature, and has less pollution. In addition, the catalyst has high yield and selectivity after being recycled and used multiple times.

[0008] To achieve the above purpose, the technical solution adopted by the present application is:

[0009] A method for preparing α,γ-unsaturated dienone, which makes allene ketone undergo isomerization reaction under the action of a catalyst to generate α,γ-unsaturated dienone, wherein the catalyst comprises a hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid, and the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid has a structure shown in formula (I).

[0010]

[0011] In formula (I), R1, R2, R3, R4 are independently selected from substituted or unsubstituted alkane, alkene, alkyne, aromatic hydrocarbon, and at least one of R1, R2, R3, R4 contains a hydroxyl substituent, and Y is a group that is basic in water.

[0012] According to some preferred and specific aspects of the present application, in formula (I), the hydroxyl substituent is substituted at the end.

[0013] According to some preferred and specific aspects of the present application, in formula (I), Y is hydroxide, bicarbonate, formate or acetate.

[0014] According to some preferred and specific aspects of the present application, the hydroxyl-functionalized quaternary ammonium salt-based alkaline ionic liquid is in a liquid state when the temperature is greater than 20°C, and starts to be in a solid state when the temperature is less than or equal to 20°C.

[0015] In some preferred embodiments of the present application, in formula (I), R1, R2, R3, R4are each independently selected from the group consisting of substituted or unsubstituted C1-C6alkane, C2-C6alkene, C2-C6alkyne, and C6-C10aromatic hydrocarbon. 1-20 alkane, C 2-20 alkene, C 2-20 alkyne, C 6-20 aromatic hydrocarbon.

[0016] Further, in formula (I), R1, R2, R3, R4are each independently selected from the group consisting of substituted or unsubstituted C1-C6alkane, C2-C6alkene, C2-C6alkyne, and C6-C10aromatic hydrocarbon. 1-10 alkane, C 2-10 alkene, C 2-10 alkyne, C 6-10 aromatic hydrocarbon.

[0017] Further, in formula (I), R1, R2, R3, R4are each independently selected from the group consisting of substituted or unsubstituted C1-C6alkane, C2-C6alkene, C2-C6alkyne, and C6-C10aromatic hydrocarbon.

[0018] According to some preferred and specific aspects of the present application, the hydroxyl-functionalized quaternary ammonium salt-based alkaline ionic liquid is selected from the group consisting of one or more of the compounds represented by formula (I-1);

[0019]

[0020] In formula (I-1), t1, t2, t3, t4are each independently selected from 1, 2, 3, 4, 5 or 6;

[0021] A1, A2, A3, A4are each independently selected from H or OH, and are not H at the same time, and Y is as defined above.

[0022] According to some specific aspects of the present application, the hydroxyl-functionalized quaternary ammonium salt-based alkaline ionic liquid is selected from the group consisting of one or more of the mono-hydroxyl, di-hydroxyl, tri-hydroxyl and tetra-hydroxyl ionic liquids. In some specific embodiments of the present application, the hydroxyl-functionalized quaternary ammonium salt-based alkaline ionic liquid is selected from at least one of the structures represented by IL11-IL55.

[0023]

[0024] In some embodiments of the present application, the synthesis route of the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid comprises:

[0025]

[0026] In formula (III), X is chlorine, bromine or iodine; M is an alkali metal, and Y is the same as above.

[0027] In some embodiments, MY is an alkali metal hydroxide, an alkali metal bicarbonate, an alkali metal acetate or an alkali metal formate, and the alkali metal includes but is not limited to sodium, potassium and the like.

[0028] Further, the synthesis method of the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid comprises:

[0029] The compound shown in formula (III) and the compound shown in formula (IV) are reacted at 60-120°C to generate the compound shown in formula (II); in some cases, a benzene compound (including but not limited to toluene, xylene and the like) can be used as a solvent, and the reaction is carried out in the solvent, for example, the reaction can be carried out in the solvent under reflux, and after the reaction is completed, the temperature is lowered until the intermediate product shown in formula (II) is precipitated in a solid form, which is filtered, and the intermediate product shown in formula (II) can be further cleaned by washing, for example, acetone or the like can be used for cleaning, and then dried to obtain the pure compound shown in formula (II);

[0030] The compound shown in formula (II) is reacted with an alkali metal hydroxide in water under heating to generate the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid shown in formula (I); in some cases, the temperature of the heating condition is controlled to be 30-50°C, after the reaction is completed, the temperature is lowered until the solid is precipitated, which is filtered and dried to obtain the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid; wherein, if the drying is followed by cooling to a certain temperature, the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid can be obtained in a solid form, and if the temperature is higher than 20°C or room temperature, the hydroxyl-functionalized quaternary ammonium salt-based basic ionic liquid can exist in a liquid form.

[0031] According to the present application, the catalyst of the present application can greatly reduce the amount of the catalyst, for example, in some embodiments of the present application, the molar ratio of the catalyst to the dienone is 0.001-0.01:1, and further 0.001-0.003:1.

[0032] According to the present application, the catalyst of the present application can greatly reduce the reaction temperature of the isomerization, for example, in some embodiments of the present application, the isomerization reaction is controlled to be carried out at 5-60°C, and further at 20-40°C.

[0033] According to the present invention, the catalyst of the present invention can greatly reduce the reaction time of isomerization, and the reaction time of the isomerization reaction can be controlled to be 0.2-2h, and more specifically 0.3-1h.

[0034] In some preferred and specific embodiments of the present invention, allenones represented by formula (V) are used as raw materials, and α,γ-unsaturated diene ketones represented by formula (VI) are generated by isomerization reaction under the action of a catalyst.

[0035]

[0036] In formula (V) or formula (VI), R5, R6, R7, R8, and R9 are each independently selected from hydrogen, or independently selected from the following groups, whether substituted or unsubstituted: alkanes, alkenes, alkynes, and aromatic hydrocarbons.

[0037] Furthermore, in formula (V) or formula (VI), R5, R6, R7, R8, and R9 are each independently selected from hydrogen, or independently selected from substituted or unsubstituted groups of the following: C 1-20 Alkanes, C 2-20 Olefins, C 2-20 Alkynes, C 6-20 Aromatic hydrocarbons.

[0038] Furthermore, in formula (V) or formula (VI), R5, R6, R7, R8, and R9 are each independently selected from hydrogen, or independently selected from the following substituted or unsubstituted groups: C 1-10 Alkanes, C 2-10 Olefins, C 2-10 Alkynes, C 6-10 Aromatic hydrocarbons.

[0039] In some specific embodiments, the α,γ-unsaturated diene represented by formula (VI) can be pseudoionone, 6-methyl-3,5-heptadien-2-one, or 6,10,14-trimethyl-3,5-pentadedien-2-one.

[0040] In this invention, after the isomerization reaction is completed, the reaction mixture can be simply washed with water. The hydroxyl-functionalized quaternary ammonium salt basic ionic liquid is soluble in water, and the product can be separated from the ionic liquid using phase separation technology, so that it can be recycled.

[0041] In some preferred and specific embodiments of the present invention, during the synthesis of α,γ-unsaturated diene, after the isomerization reaction is completed, the reaction mixture is dissolved in water, the aqueous phase is separated, and then the aqueous phase is cooled until the hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid precipitates in solid form.

[0042] According to certain aspects of the invention, allenones are commercially available (e.g., from Energie Chemicals) or synthesized in the laboratory, for example, by means of prior art (US3029287, US6184420; G. Saucy, R. Marbet, H. Lindlar, O. Isler, Helv. Chim. Acta. 1959, 6, 1945-1955; G. Saucy, R. Marbet, Helv. Chim. Acta. 1967, 4, 1158-1167).

[0043] For example, in some embodiments, the preparation method of allenone includes: synthesizing allenone using alkynols or enols and alkoxyolefins as raw materials; wherein the alkynols or enols in the synthesis step are dehydrolinalool, 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-2-ol or dehydroneryl alcohol, and the alkoxyolefins are 2-alkoxypropenes, including 2-methoxypropenes, 2-ethoxypropenes, 2-propoxypropenes or 2-isopropoxypropenes.

[0044] For example, weigh and measure the raw materials, solvent, and catalyst, mix them to ensure the catalyst is completely dissolved, add them to a high-pressure reactor with a stirrer, cover the reactor, tighten the bolts, maintain the pressure with N2 to 1.0 MPa, and heat while stirring until it reaches about 90°C. Stir and maintain the temperature for several hours until the reaction is complete, and then distill to separate allenone (Saucy, G.; Marbet, R. Helv. Chim. Acta 1967, 50, 1158).

[0045] In some embodiments of the present invention, the alkynol or enol is dehydrolinalool, and the alkoxyolefin is 2-methoxypropene, thereby preparing allenone 1, the reaction formula is as follows:

[0046]

[0047] Allenone 1 (6,10-dimethyl-4,5,9-trien-2-undecanone, CAS No.: 16647-05-5) is commercially available or prepared by existing methods.

[0048] This allenone 1 can be used to prepare pseudoionones; the isomerization reaction process is as follows:

[0049]

[0050] Because pseudoionone (pseudo-violet) contains a non-rotating carbon-carbon double bond functional group, it exists as isomers: pseudo-violet 1, pseudo-violet 2, and pseudo-violet 3 are isomers of each other. Pseudo-violet is subsequently used in the production of vitamin A, undergoing cyclization and Darzens reactions. Pseudo-violet 1 isomers cyclize to yield cis-β-ketones, which do not undergo Darzens reactions; therefore, this isomer is usually considered an impurity when calculating yields. Pseudo-violet 3, due to steric hindrance, slightly affects the subsequent Darzens reaction, mainly in the elimination process to form α,β-epoxy esters. Therefore, a lower concentration of pseudo-violet 1 and higher selectivity for pseudo-violet 2 in the product are beneficial for subsequent reactions.

[0051] In some embodiments of the present invention, the reaction formula for preparing allenone 2 by reacting 2-methyl-3-butyn-2-ol with 2-methoxypropylene is as follows:

[0052]

[0053] Allenone 2 (6-methyl-4,5-diene-2-heptanone, CAS No.: 16647-01-1) can be prepared by this route or is commercially available.

[0054] In some embodiments of the present invention, the reaction formula for preparing allenone 3 by reacting dehydroneryl alcohol with 2-methoxypropylene is as follows:

[0055]

[0056] Allenone 3 (6,10,14-trimethyl-4,5,9,13-tetraen-2-pentadecanone, CAS No.: 16647-09-9) can be prepared by this route or is commercially available.

[0057] Another technical solution provided by this invention: the application of a hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid with the structure shown in formula (Ⅰ) as a catalyst in the preparation of α,γ-unsaturated diene. In formula (Ⅰ), R1, R2, R3, and R4 are independently selected from the following groups, whether substituted or unsubstituted: alkanes, alkenes, alkynes, and aromatic hydrocarbons, and at least one of R1, R2, R3, and R4 contains a hydroxyl substituent, and Y is a group that is basic in water.

[0058] Another technical solution provided by the present invention is a method for synthesizing pseudoionones, which adopts the above-mentioned method for preparing α,γ-unsaturated diene ketones.

[0059] Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art:

[0060] Based on extensive experimental research, the inventors unexpectedly discovered that hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquids with the structure shown in Formula (I) can activate allenones, thereby significantly reducing the amount of catalyst required and exhibiting extremely high selectivity and yield, resulting in high reaction efficiency. Analysis suggests that the hydroxyl groups in this functionalized ionic liquid can form hydrogen bonds with the oxygen atoms in allenones, thus activating the allenone. Furthermore, its liquid state during the reaction allows for excellent contact with allenones, facilitating catalysis. Its unique structure also enhances catalytic efficiency and selectivity. In addition, after the reaction, the functionalized ionic liquid can be converted back to a solid state by temperature control, facilitating separation from the reaction liquid for recycling. Even after multiple recycling cycles, it maintains a high conversion rate and yield. Practical application shows that using the hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid of this invention as a catalyst can achieve a reaction yield of over 99.98%, with minimal pollution, aligning with the development concept of green chemistry. It also reduces reaction temperature and energy consumption, making it suitable for industrial production. Attached Figure Description

[0061] Figure 1 The gas chromatogram of allenone used in Example 1 of this invention shows that the peak time is 8.510 min, the purity is 98.03%, and the substances with peak times of 9.048, 9.390 and 10.113 min are, in order, the three isomers of allenone: false purple 1, false purple 2 and false purple 3.

[0062] Figure 2 The gas chromatogram of pseudoionone generated after isomerization in Example 1 of the present invention is shown. Pseudo-ionone 1 was completely converted to generate pseudo-ionone 2 and pseudo-ionone 3.

[0063] Figure 3 The present invention prepares ionic liquid IL11 in DMSO-d6 1 H NMR spectrum;

[0064] Figure 4 The present invention prepares ionic liquid IL44 in DMSO-d6 1 H NMR spectrum. Detailed Implementation

[0065] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0066] The gas chromatography test conditions of this invention are as follows: Instrument model: Thermo Trace1300; Column: SE-30 (30m×0.32mm×0.25μm); Column temperature: initial temperature 45℃, hold for 4 min, then increase to 160℃ at 50℃ / min, hold for 24 min; Injector temperature: 280℃; Detector type: FID; Detector temperature: 280℃; Split injection, split ratio 80:1; Injection volume: 0.26μL; H2 flow rate: 30mL / min; Air flow rate: 400mL / min; Carrier gas N2 flow rate: 2mL / min.

[0067] The ionic liquid IL11 was prepared using the following method:

[0068] Triethylamine and 2-bromoethanol were reacted with toluene as solvent in an oil bath at 110°C under stirring and reflux for 12 hours (reagents purchased from Anaiji Chemical). After the reaction was completed, the mixture was cooled to room temperature, and a white solid was observed to form in the mixture. The solid obtained after filtration was washed with acetone and dried under vacuum at 80°C for 12 hours to obtain the intermediate. (CHENGW.,XIAO B.,SUN J.,et al.Tetrahedron Letters,2015,56:1416-1419);

[0069] A certain mass of potassium hydroxide aqueous solution (mass concentration of 10%) and the intermediate were added to a three-necked flask, and the mixture was stirred in an oil bath at 40°C for 12 hours. After the reaction was completed, the mixture was cooled to about 20°C, and a solid precipitated. The mixture was filtered through a sintered glass funnel, and the solid sample was dried in an oven at (103±2)°C until completely dry. After cooling to about 20°C, the solid form of the hydroxyl-functionalized quaternary ammonium salt basic ionic liquid IL11 was obtained. (SUN J., LU B., WANGX., et al. Fuel Processing Technology, 2013, 115: 233-237).

[0070] The ionic liquid IL22 is prepared by the following method: the preparation process is basically the same as that of the ionic liquid IL11, except that triethylamine is replaced with diethylethanolamine.

[0071] The ionic liquid IL33 is prepared by the following method: the preparation process is basically the same as that of the ionic liquid IL11, except that triethylamine is replaced with triethanolamine and 2-bromoethanol is replaced with 2-bromoethane.

[0072] The ionic liquid IL44 is prepared by the following method: the preparation process is basically the same as that of the ionic liquid IL11, except that triethylamine is replaced with triethanolamine.

[0073] The ionic liquid IL55 is prepared by the following method: the preparation process is basically the same as that of the ionic liquid IL11, except that 2-bromoethanol is replaced with 3-bromo-1-propanol.

[0074] IL66 (structural formula) The preparation process is basically the same as that of ionic liquid IL11, except that potassium hydroxide aqueous solution is replaced with potassium acetate aqueous solution.

[0075] Ionic liquid IL77 (structural formula) The preparation method is basically the same as that of ionic liquid IL11, except that potassium hydroxide aqueous solution is replaced with potassium formate aqueous solution.

[0076] IL88 (structural formula) The preparation method is basically the same as that of ionic liquid IL11, except that potassium hydroxide aqueous solution is replaced with potassium bicarbonate aqueous solution.

[0077] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0078] Example 1

[0079] This example provides a method for preparing pseudoionones. Under a nitrogen atmosphere at room temperature, allenone 1 (294.25 g, 1.5 mol, 6,10-dimethyl-4,5,9-trien-2-undecanone, CAS No.: 16647-05-5) was added to a 500 mL three-necked flask. The flask was then placed in a 20°C constant-temperature bath, and stirring was started. Ionic liquid IL11 (0.50 g, 0.003 mol) was added, resulting in a pale yellow solution. The temperature was kept constant, and the reaction was rapidly stirred for 0.5 hours. The sample was then removed, and gas chromatography analysis showed that the conversion rate of allenone was 100%, with a pseudoionone selectivity of 0.42%, a pseudoionone selectivity of 64.15%, and a pseudoionone selectivity of 35.43% (details are shown in Table 1 below). After the reaction, the reaction solution was dissolved in water, and the aqueous phase was separated using phase separation technology. The solution was then cooled to below 20°C to precipitate a solid ionic liquid, allowing for catalyst recovery.

[0080] The gas chromatogram of the raw material allenone is shown below. Figure 1 As shown, this indicates that these three isomers are generated during the preparation of the raw material allenone, with pseudo-ionone being the main product; the gas chromatogram of the pseudoionone generated after the isomerization reaction in this example is shown below. Figure 2 As shown, it indicates that Fake 1 has been almost completely transformed, generating Fake 2 and Fake 3.

[0081] Examples 2-10

[0082] Referring to the synthesis method in Example 1 above, different reaction conditions were screened, mainly focusing on the effects of different feed molar ratios, different temperatures, and different reaction times on the reaction. The specific results are shown in Table 1 below.

[0083] Table 1

[0084]

[0085]

[0086] Examples 11-14

[0087] Following the synthesis method of Example 1, the effects of different hydroxyl-functionalized quaternary ammonium salt basic ionic liquids on the reaction were investigated, and the specific results are shown in Table 2 below.

[0088] Table 2

[0089] Example Ionic liquid Conversion / % Pseudo 1 selectivity / % Pseudo 2 selectivity / % Pseudo 3 selectivity / % 11 IL22 100 0.41％ 64.18％ 35.41％ 12 IL33 100 0.40％ 63.17％ 36.43％ 13 IL44 100 0.38％ 64.65％ 34.97％ 14 IL55 100 0.42％ 64.53％ 35.05％

[0090] Example 15

[0091] In this example, allenone 2 (6-methyl-4,5-diene-2-heptanone, CAS No.: 16647-01-1) was used as the starting material for the isomerization reaction, otherwise the same as in Example 1. Gas chromatography analysis of the reaction solution showed that the conversion rate of allenone 2 was 100%, with pseudoselectivity of 0.44% for pseudo-1, 64.16% for pseudo-2, and 35.4% for pseudo-3.

[0092] Example 16

[0093] In this example, allenone 3 (6,10,14-trimethyl-4,5,9,13-tetraen-2-pentadecanone, CAS No.: 16647-09-9) was used as the starting material for the isomerization reaction, otherwise the same as in Example 1. Gas chromatography analysis of the reaction solution showed that the conversion rate of allenone 3 was 100%, with pseudoselectivity of 0.43% for pseudo-1, 64.14% for pseudo-2, and 35.43% for pseudo-3.

[0094] Example 17

[0095] Reuse of ionic liquid catalysts. IL11 was selected. After the reaction, the reaction solution was dissolved in water, and the product was separated from the ionic liquid using phase separation technology. Subsequently, the temperature was lowered to below 20°C to precipitate the solid form of the ionic liquid from the water for recycling. The specific results are shown in Table 3 below.

[0096] Table 3

[0097]

[0098]

[0099] Examples 18-20

[0100] Following the synthesis method of Example 1, the effects of different hydroxyl-functionalized quaternary ammonium salt basic ionic liquids on the reaction were investigated, and the specific results are shown in Table 4 below.

[0101] Table 4

[0102] Example Ionic liquid Conversion / % Pseudo 1 selectivity / % Pseudo 2 selectivity / % Pseudo 3 selectivity / % 18 Ionic liquid IL66 98.2 0.52％ 64.13％ 35.35％ 19 Ionic liquid IL77 97.6 0.57％ 64.38％ 35.05％ 20 Ionic liquid IL88 98.7 0.49％ 64.14％ 35.37％

[0103] Comparative Example 1

[0104] The reaction was essentially the same as in Example 1, except that the ionic liquid IL11 was replaced with 1-butyl-3-methyl-imidazolium acetate. After the reaction, the conversion rate of allenone 1 was 96.3%, with pseudo-selectivity of 0.82%, pseudo-selectivity of 50.3%, and pseudo-selectivity of 48.88%.

[0105] Comparative Example 2

[0106] The reaction was basically the same as in Example 1, except that the ionic liquid IL11 was replaced with N,N-diethylethanolamine. After the reaction, the conversion rate of allenone 1 was 91.7%, with pseudo-selectivity of 0.97%, pseudo-selectivity of 47.36%, and pseudo-selectivity of 51.67%.

[0107] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0108] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing α,γ-unsaturated diene, characterized in that, This method uses allenone as a raw material and generates α,γ-unsaturated diene as shown in formula (VI) through isomerization reaction under the action of a catalyst. ， In equations (V) and (VI), R5, R6, R7, R8, and R9 are independently selected from hydrogen, C, and C, respectively. 1-20 Alkanes, C 2-20 Olefins, C 2-20 Alkynes, C 6-20 Aromatic hydrocarbons; The catalyst is a hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid, which has the structure shown in formula (Ⅰ). ， In equation (Ⅰ), R1, R2, R3, and R4 are each independently selected from C. 1-20 Alkane, wherein at least one of R1, R2, R3, and R4 contains a hydroxyl substituent, and Y is a group that is basic in water; When the temperature is above 20°C, the hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid transforms into a liquid or is in a liquid state; when the temperature is below or equal to 20°C, it begins to transform into a solid or is in a solid state.

2. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, In formula (I), the hydroxyl substituent is substituted at the end; and / or, in formula (I), Y is hydroxide, bicarbonate, formate or acetate.

3. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, In equation (Ⅰ), R1, R2, R3, and R4 are each independently selected from C. 1-10 Alkanes.

4. The method for preparing α,γ-unsaturated diene according to claim 3, characterized in that, In formula (I), R1, R2, R3, and R4 are each independently selected from one or more hydroxyl groups that replace the following groups: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, or hexyl.

5. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid is selected from one or more compounds shown in formula (Ⅰ-1); ， In equation (Ⅰ-1), t1, t2, t3, and t4 are independently selected from 1, 2, 3, 4, 5, or 6, respectively; A1, A2, A3, and A4 are each independently selected from H or OH, and are not all H at the same time. Y is the same as in claim 1.

6. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The synthetic route for the hydroxyl-functionalized quaternary ammonium salt basic ionic liquid includes: ， In formula (Ⅲ), X is chlorine, bromine or iodine; M is an alkali metal; and Y is the same as in claim 1.

7. The method for preparing α,γ-unsaturated diene according to claim 6, characterized in that, The method for synthesizing the hydroxyl-functionalized quaternary ammonium salt basic ionic liquid includes: The compound shown in formula (III) and the compound shown in formula (IV) are reacted at 60-120℃ to produce the compound shown in formula (II); The compound shown in formula (II) is reacted with an alkali metal hydroxide in water under heating conditions to generate the hydroxyl-functionalized quaternary ammonium salt alkaline ionic liquid having the structure shown in formula (I).

8. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The molar ratio of the catalyst to the allenone is 0.001 to 0.01:

1.

9. The method for preparing α,γ-unsaturated diene according to claim 8, characterized in that, The molar ratio of the catalyst to the allenone is 0.001 to 0.003:

1.

10. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The isomerization reaction is controlled to be carried out at 5-60°C.

11. The method for preparing α,γ-unsaturated diene according to claim 10, characterized in that, The isomerization reaction is controlled to be carried out at 20-40°C.

12. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The reaction time for the isomerization reaction is controlled to be 0.2-2 h.

13. The method for preparing α,γ-unsaturated diene according to claim 12, characterized in that, The reaction time for the isomerization reaction is controlled to be 0.3-1 h.

14. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, In formula (V) or formula (VI), R5, R6, R7, R8, and R9 are independently selected from hydrogen, C, and C, respectively. 1-10 Alkanes, C 2-10 Olefins, C 2-10 Alkynes, C 6-10 Aromatic hydrocarbons.

15. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, The α,γ-unsaturated diene shown in formula (VI) is pseudoionone, 6-methyl-3,5-heptadien-2-one or 6,10,14-trimethyl-3,5-pentadedien-2-one.

16. The method for preparing α,γ-unsaturated diene according to claim 1, characterized in that, In the preparation of α,γ-unsaturated diene, after the isomerization reaction is completed, the reaction mixture is dissolved in water, the aqueous phase is separated, and then the aqueous phase is cooled until the hydroxyl-functionalized quaternary ammonium salt basic ionic liquid precipitates in solid form.

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