Alkylated crown ether synthesis method

Abstract

The invention relates to an alkylated crown ether synthesis method which comprises the following steps: dissolving a benzo crown ether substrate in a solvent, adding a carbon supported Rh catalyst, and uniformly stirring; under a stirring condition, introducing hydrogen, and carrying out a hydrogenation reaction; and filtering, recovering the carbon supported Rh catalyst, and evaporating to remove the solvent to obtain the alkylated crown ether. Compared with the prior art, hydrogenation of the benzocrown ether substrate is carried out based on the carbon-supported Rh catalyst, and the method has the advantages of low reaction temperature, moderate pressure and rapid reaction, and is suitable for a large-scale production process. Meanwhile, the carbon carrier can be conveniently removed through incineration, chemical recovery of active metal is facilitated, and reduction of the synthesis cost is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of organic compound synthesis, and in particular to a method for synthesizing alkylated crown ethers. Background Art

[0002] Crown ether compounds are a type of cyclic ether compound with a coordination cavity of a specific size and have selectivity for alkali metal and alkaline earth metal ions. Alkylated crown ethers have good organic solubility and have important applications in the fields of metal ion separation and purification, isotope separation, etc. For example, alkylated cyclohexyl 18-crown-6 can highly selectively extract strontium-90 from spent fuel. The synthesis method of alkylated crown ethers is usually to use alkyl-substituted benzo crown ethers as raw materials and synthesize them by catalytic hydrogenation. Pederson used a 5% Ru / Al2O3 heterogeneous catalyst to synthesize various alkyl-substituted cyclohexyl crown ethers through a hydrogenation reaction. This reaction was carried out at 100 °C and 7-10 MPa of hydrogen, and the yield of di-tert-butylcyclohexyl crown ether was 52% (JACS, 1967, 89, 7017). US5478953A discloses a synthesis process of di-tert-butylcyclohexyl-18-crown-6, using 5% Rh / Al particles as a catalyst and adding carboxylic acid or acid anhydride as a co-catalyst. The reactants were hydrogenated under the conditions of 4-6 MPa and 60-65 °C, and the conversion rate was >90%. CN102516222A discloses a synthesis method based on a carbon-supported Ru catalyst and synthesizes alkyl-substituted cyclohexyl crown ethers. CN102336737A discloses a system for synthesizing cyclohexyl crown ethers based on a Pichler ruthenium catalyst and preferably uses a solvent with low reducibility to facilitate the recovery of the catalyst after the reaction. CN104710402A discloses a catalytic system of a Ni-Ru / γ-Al2O3 catalyst and synthesizes alkyl-substituted cyclohexyl crown ethers under the conditions of 180 °C and 8 MPa of hydrogen pressure. The catalyst recovered by filtration after the reaction can be reused once. CN114380787A discloses a Ru-based catalyst system doped with multiple metals such as Cu, Zn, and NiO, and the catalyst system can be reused multiple times when synthesizing di-tert-butylcyclohexyl-18-crown-6.

[0003] Most of the above-mentioned prior arts use Ru heterogeneous catalysts, which have the advantage of low cost. However, during the hydrogenation reaction process, the temperature is usually greater than 100 °C, the pressure is as high as 7-10 MPa, and the time consumption is long. Therefore, it is urgent to develop a synthesis method or process with milder reaction conditions. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for synthesizing alkylated crown ethers, which has a low reaction temperature, a moderate pressure, a fast reaction, and high catalytic activity.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] The present invention provides a method for synthesizing alkylated crown ethers, comprising the following steps: dissolving a benzo crown ether substrate in a solvent, adding a carbon-supported Rh catalyst, and stirring evenly; under stirring conditions, introducing hydrogen gas to carry out a hydrogenation reaction; filtering and recovering the carbon-supported Rh catalyst, and obtaining the alkylated crown ether after evaporating the solvent.

[0007] Preferably, the benzo crown ether substrate is any one of dibenzo-15-crown-5 and its alkyl compounds, dibenzo-18-crown-6 and its alkyl compounds, dibenzo-21-crown-7 and its alkyl compounds, and dibenzo-24-crown-8 and its alkyl compounds.

[0008] Preferably, the chemical formula of the benzo crown ether substrate is:

[0009]

[0010] More preferably, n = 0-3, and R includes any one of H, CH2CH2CH3, CH(CH3)2, CH2CH2CH2CH3, C(CH3)3, and C(CH3)2CH2C(CH3)3.

[0011] More preferably, the synthesis route is:

[0012]

[0013] Preferably, the solvent is any one or two of benzene, toluene, xylene, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and C2-C6 alcohols.

[0014] Preferably, the mass ratio of the carbon-supported Rh catalyst to the benzo crown ether substrate is 0.1-10%.

[0015] Preferably, the reaction temperature of the hydrogenation reaction is 30-70 °C, the reaction pressure is 2-6 MPa, and the reaction time is 0.5-4 h.

[0016] Preferably, the carbon-supported Rh catalyst includes an activated carbon carrier, Rh is loaded on the activated carbon carrier, and the loading amount of Rh element in the carbon-supported Rh catalyst is 1 wt%-5 wt%.

[0017] Preferably, the recovery of the carbon-supported Rh catalyst means that after the catalyst is deactivated, the carbon carrier therein can be incinerated to conveniently recover the active metal (Rh), which is suitable for the large-scale synthesis of alkylated crown ethers.

[0018] Preferably, the carbon-supported Rh catalyst is prepared by the following method: An aqueous Rh salt solution is added to an aqueous suspension of an activated carbon support, and the mixture is stirred and impregnated for 1 to 24 h. A precipitating agent is added to precipitate Rh ions, obtaining a mixed solution. After the mixed solution is subjected to a reduction treatment, the carbon-supported Rh catalyst is obtained.

[0019] Preferably, the concentration of the aqueous suspension of the activated carbon support is 5 wt% - 20 wt%, the Rh content in the aqueous Rh salt solution is 1 wt% - 5 wt%, the volume ratio of the aqueous suspension of the activated carbon support to the aqueous Rh salt solution is 1:1 - 100:1, and the volume ratio of the aqueous suspension of the activated carbon support to the precipitating agent is 10:1 - 100:1.

[0020] Preferably, the stirring speed is 600 - 1200 rpm.

[0021] More preferably, the activated carbon support is selected from any one of activated carbon, porous graphite, graphene, and carbon nanotubes.

[0022] More preferably, the precipitating agent is selected from any one of aqueous solutions of NH4OH, NaOH, KOH, NH4CO3, Na2CO3, and K2CO3, and the Rh salt is any one of RhCl3·3H2O, Rh(NO3)3, Rh2(SO4)3, rhodium acetate, and rhodium acetylacetonate.

[0023] More preferably, the reduction treatment includes filtering, washing with water, and drying the mixed solution to obtain a precipitate. The precipitate is calcined at a high temperature and then reduced by passing hydrogen to obtain the carbon-supported Rh catalyst.

[0024] Even more preferably, the temperature of the high-temperature calcination is 400 - 500 °C and the time is 3 - 4 h.

[0025] Even more preferably, the temperature for reduction by passing hydrogen is 100 - 300 °C and the time is 3 - 4 h.

[0026] More preferably, the reduction treatment includes adding a reducing agent to the mixed solution under continuous stirring conditions to carry out a reduction reaction, and washing with water after filtration to obtain the carbon-supported Rh catalyst.

[0027] Even more preferably, the reducing agent includes any one of NaBH4, KBH4, morpholine borane, N2H4·H2O, and aqueous HCOONa.

[0028] Even more preferably, the concentration of the reducing agent added to the mixed solution is 5 wt% - 20 wt%, and the volume ratio of the mixed solution to the reducing agent is 10:1 - 50:1.

[0029] Further preferably, the rotation speed of the continuous stirring is 600 - 1200 rpm, and the time of the reduction reaction is 3 - 4 h.

[0030] The present invention utilizes many advantages of the carbon carrier, such as large specific surface area, rich pore structure, strong adsorption capacity, and easy modulation of surface groups. Based on the Rh / carbon heterogeneous catalyst (carbon-supported Rh catalyst), the hydrogenation of the benzocrown ether substrate is carried out, which has the advantages of low reaction temperature, moderate pressure, and rapid reaction, and is suitable for large-scale production processes. At the same time, the carbon carrier can be easily removed by incineration, facilitating the chemical recovery of the active metal and helping to reduce the synthesis cost.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention synthesizes alkylated crown ethers through the catalytic hydrogenation reaction of a carbon-supported Rh catalyst, with high catalytic activity and relatively mild reaction conditions such as reaction pressure and reaction temperature.

[0033] (2) The present invention has a moderate reaction pressure (2 - 6 MPa), a relatively low reaction temperature (30 - 70 °C), and a short reaction time (0.5 - 4 h), reducing the operation difficulty and equipment requirements and improving safety.

[0034] (3) Based on the large specific surface area, rich pore structure, and strong adsorption capacity of the carbon carrier in the present invention, a carbon-supported Rh catalyst is synthesized, which has high catalytic activity for the hydrogenation reaction, with a yield of up to 96% and a purity of up to 93%.

[0035] (4) After the carbon-supported Rh catalyst in the present invention is deactivated, the carbon carrier can be incinerated to conveniently recover the active metal, which is suitable for the large-scale synthesis of alkylated crown ethers and helps to reduce the synthesis cost.

[0036] (5) After the reaction in the present invention is completed, a product with relatively high purity can be obtained through simple post-treatment steps such as filtration and solvent evaporation, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the synthesis route for the synthesis of alkylated crown ethers in the present invention;

[0038] Figure 2 is the synthesis route for Example 1 and Example 2 of the present invention;

[0039] Figure 3 is the 1H NMR spectrum of the reaction product of Example 2 of the present invention;

[0040] Figure 4 is the synthesis route for Example 3 of the present invention;

[0041] Figure 5Synthesis route for Example 4 of the present invention;

[0042] Figure 6 Synthesis route for Example 5 of the present invention. Detailed implementation manners

[0043] This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0044] An alkylated crown ether synthesis method, the reaction route is as Figure 1 shown, including the following steps: dissolving the benzo crown ether substrate in a solvent, adding a carbon-supported Rh catalyst, and stirring evenly; under stirring conditions, introducing hydrogen gas for a hydrogenation reaction; filtering and recovering the carbon-supported Rh catalyst, and obtaining the alkylated crown ether after evaporating the solvent.

[0045] Among them, the benzo crown ether substrate is any one of dibenzo-15-crown-5 and its alkyl compounds, dibenzo-18-crown-6 and its alkyl compounds, dibenzo-21-crown-7 and its alkyl compounds, dibenzo-24-crown-8 and its alkyl compounds. The solvent is any one or two of benzene, toluene, xylene, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, C2-C6 alcohols. The mass ratio of the carbon-supported Rh catalyst to the benzo crown ether substrate is 0.1-10%; the reaction temperature of the hydrogenation reaction is 30-70 °C, the reaction pressure is 2-6 MPa, and the reaction time is 0.5-4 h.

[0046] The carbon-supported Rh catalyst includes an activated carbon carrier, and Rh is supported on the activated carbon carrier.

[0047] The carbon-supported Rh catalyst is prepared by the following method: adding an Rh salt solution to an aqueous suspension of the activated carbon carrier, stirring and impregnating for 1-24 h, adding a precipitating agent to precipitate Rh ions to obtain a mixed solution; after subjecting the mixed solution to a reduction treatment, the carbon-supported Rh catalyst is obtained.

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] In addition, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. The reagents and materials used in the following examples are all commercially available.

[0050] Example 1

[0051] The synthesis route is as Figure 2As shown below, the specific preparation process is as follows: Take 100 g of the substrate 4′,4″(5″)-di-tert-butyl dibenzo-18-crown-6 and dissolve it in 500 mL of tetrahydrofuran. Add it to a 1 L high-pressure reaction kettle. Take 2 g of the Rh catalyst supported on coconut shell activated carbon and add it thereto. Start stirring. Replace the air in the reaction kettle with nitrogen 3 times and then replace the nitrogen with hydrogen 3 times. Charge 3 MPa of hydrogen, raise the reaction temperature to 50 °C, and react for 2 h. After the reaction is completed, release the pressure. Filter the reaction solution to remove the carbon-supported Rh catalyst. Distill off the solvent in the filtrate under reduced pressure to obtain 4′,4″(5″)-di-tert-butyl dicyclohexane-18-crown-6 in the form of a transparent liquid, with a purity of 92% and a yield of 96%.

[0052] The preparation method of the above-mentioned Rh catalyst supported on coconut shell activated carbon is as follows: Disperse 10 g of coconut shell activated carbon in 100 mL of water. Add 35 mL of an aqueous RhCl3 solution with an Rh content of 1 wt% thereto. After stirring for 12 h, add a 10 wt% NH4OH aqueous solution until the pH is greater than 9. Filter, wash with water, dry at 100 °C, calcine at 400 °C for 4 h, and reduce with hydrogen at 200 °C for 4 h to obtain a coconut shell activated carbon supported catalyst with an Rh loading of 3 wt%.

[0053] Example 2

[0054] The synthesis route is the same as that in Example 2. As Figure 2 shown below, the specific preparation process is as follows: Take 500 g of the substrate 4′,4″(5″)-di-tert-butyl dibenzo-18-crown-6 and dissolve it in 2000 mL of tetrahydrofuran. Add it to a 5 L high-pressure reaction kettle. Take 2 g of the Rh catalyst supported on porous graphite and add it thereto. Start stirring. Replace the air in the reaction kettle with nitrogen 3 times and then replace the nitrogen with hydrogen 3 times. Charge 3 MPa of hydrogen, raise the reaction temperature to 50 °C, and react for 2 h. After the reaction is completed, release the pressure. Filter the reaction solution to remove the carbon-supported Rh catalyst. Distill off the solvent in the filtrate under reduced pressure to obtain 4′,4″(5″)-di-tert-butyl dicyclohexane-18-crown-6 in the form of a transparent liquid. Its 1H NMR spectrum is as Figure 3 shown, with a purity of 90% and a yield of 93%.

[0055] The preparation method of the above-mentioned Rh catalyst supported on porous graphite is as follows: Disperse 10 g of porous graphite in 200 mL of water. Add 25 mL of an aqueous RhCl3 solution with an Rh content of 2 wt% thereto. After stirring for 12 h, add a 10 wt% NH4OH aqueous solution until the pH is greater than 9. Filter, wash with water, add 10 mL of a 10 wt% morpholine borane aqueous solution and reduce for 4 h. Filter, wash with water, and dry in an oven to obtain a porous graphite supported catalyst with an Rh loading of 5 wt%.

[0056] Example 3

[0057] The synthesis route is asFigure 4 As shown in the figure, the specific preparation process is as follows: Take 5 g of the substrate 4′,4″(5″)-dibutyldibenzo-18-crown-6 and dissolve it in a mixed solution of 30 mL of n-butanol and 10 mL of toluene. Add it to a 100 mL high-pressure reaction kettle, and then add 0.5 g of the bamboo charcoal activated carbon supported Rh catalyst. After replacing the air in the reaction kettle with nitrogen and hydrogen successively, charge 2 MPa of hydrogen, raise the reaction temperature to 45 °C, and after reacting for 1 h, supplement hydrogen to 2 MPa and continue to react for 1 h. After the reaction is completed, release the pressure, open the reaction kettle, and filter the black solution to remove the catalyst. Distill off the solvent under reduced pressure to obtain a transparent liquid product with a purity of 90% and a yield of 93%.

[0058] The preparation method of the above-mentioned bamboo charcoal activated carbon supported catalyst is as follows: Disperse 20 g of bamboo charcoal activated carbon in 100 mL of water, add 24 mL of an aqueous RhCl3 solution with a Rh content of 4 wt% thereto, stir for 12 h, and then gradually add 10 wt% aqueous Na2CO3 solution dropwise. Filter and wash with water, dry at 100 °C and then calcine at 450 °C for 3 h. Place it in a tubular furnace and introduce hydrogen, and reduce it at 200 °C for 4 h to obtain a bamboo charcoal activated carbon supported catalyst with a Rh loading of 4.3 wt%.

[0059] Example 4

[0060] The synthesis route is as Figure 5 As shown in the figure, the specific preparation process is as follows: Take 4 g of the substrate 4′,4″(5″)-di-tert-butyldibenzo-15-crown-5 and dissolve it in 20 mL of ethylene glycol dimethyl ether. Add it to a 100 mL high-pressure reaction kettle, add 0.4 g of the graphene supported Rh catalyst thereto, stir evenly, and seal the reaction kettle. Replace the air in the reaction kettle with nitrogen and hydrogen successively, charge 2 MPa of hydrogen, raise the reaction temperature to 55 °C, and after 2 h, release the pressure of the reaction kettle to end the reaction. Open the reaction kettle, filter the solution to remove the catalyst. Distill off the solvent under reduced pressure to obtain a transparent liquid product with a purity of 93% and a yield of 92%.

[0061] The preparation method of the above-mentioned porous graphite supported catalyst is as follows: Disperse 2 g of graphene oxide in 20 mL of water, add 3 mL of an aqueous Rh(NO3)3 solution with a Rh content of 2 wt% thereto, stir for 24 h, and then gradually add 10 wt% aqueous (NH4)2CO3 solution dropwise. Filter and wash with water, dry at 120 °C and then calcine at 400 °C for 3 h. Place it in a tubular furnace and introduce hydrogen, and reduce it at 250 °C for 3 h to obtain a graphene supported catalyst with a Rh loading of 3.1 wt%.

[0062] Example 5

[0063] The synthesis route is as Figure 6As shown below, the specific preparation process is as follows: Take 2 g of the substrate 4′,4″(5″)-di-tert-butyl dibenzo-21-crown-7 and dissolve it in 10 mL of n-butanol. Add it to a 50 mL high-pressure reactor. Take 0.05 g of the carbon nanotube-supported Rh catalyst and add it thereto. After stirring evenly, seal the reactor. Replace the air in the reactor with nitrogen and hydrogen successively three times, fill in 3 MPa of hydrogen, raise the reaction temperature to 50 °C and start the reaction. After the reaction is completed, release the pressure, open the reactor, and filter to remove the catalyst in the solution. Distill off the solvent under reduced pressure to obtain a product in the form of a transparent liquid, with a purity of 90% and a yield of 94%.

[0064] The preparation method of the above carbon nanotube-supported catalyst is as follows: Disperse 1 g of carbon nanotubes in 20 mL of water, add 2.5 mL of an aqueous solution of Rh(SO4)3 with a Rh content of 2 wt% thereto, stir for 24 h, then gradually add 10 wt% KOH dropwise, and gradually add 4 mL of a 10 wt% aqueous solution of NaBH4 and react for 3 h. Filter and wash with water, and dry in an oven to obtain a carbon nanotube-supported catalyst with a Rh loading of 4.5%.

[0065] In summary, the alkylated crown ether synthesis method provided by the present invention has high catalytic activity, and reaction conditions such as reaction pressure and reaction temperature are relatively mild, which is suitable for the industrial production of alkylated crown ethers.

[0066] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for synthesizing alkylated crown ether, characterized in that, It includes the following steps: dissolving the benzo-crown ether substrate in a solvent, adding a carbon-supported Rh catalyst, and stirring evenly; under stirring conditions, introducing hydrogen gas to carry out a hydrogenation reaction; filtering and recovering the carbon-supported Rh catalyst, and evaporating the solvent to obtain the alkylated crown ether.

2. The method for synthesizing an alkylated crown ether according to claim 1, characterized in that, The benzo-crown ether substrate is any one of dibenzo-15-crown-5 and its alkyl compounds, dibenzo-18-crown-6 and its alkyl compounds, dibenzo-21-crown-7 and its alkyl compounds, and dibenzo-24-crown-8 and its alkyl compounds.

3. The method for synthesizing an alkylated crown ether according to claim 2, wherein, The chemical formula of the benzo-crown ether substrate is: wherein, n = 0 - 3, and R includes any one of H, CH2CH2CH3, CH(CH3)2, CH2CH2CH2CH3, C(CH3)3, and C(CH3)2CH2C(CH3)3.

4. A method for synthesizing an alkylated crown ether according to claim 1, wherein, The solvent is any one or two of benzene, toluene, xylene, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and C2 - C6 alcohols; the mass ratio of the carbon-supported Rh catalyst to the benzo-crown ether substrate is 0.1 - 10%; the reaction temperature of the hydrogenation reaction is 30 - 70 °C, the reaction pressure is 2 - 6 MPa, and the reaction time is 0.5 - 4 h.

5. A method for synthesizing an alkylated crown ether according to claim 1, characterized in that, The carbon-supported Rh catalyst includes an activated carbon carrier, and Rh is loaded on the activated carbon carrier. The loading amount of Rh element in the carbon-supported Rh catalyst is 1 wt% - 5 wt%.

6. A method for synthesizing alkylated crown ether according to claim 5, characterized in that, The carbon-supported Rh catalyst is prepared by the following method: adding an Rh salt solution to an aqueous suspension of the activated carbon carrier, stirring and impregnating for 1 - 24 h, adding a precipitant to precipitate Rh ions to obtain a mixed solution; after subjecting the mixed solution to a reduction treatment, the carbon-supported Rh catalyst is obtained.

7. A method for synthesizing an alkylated crown ether according to claim 6, characterized in that, The concentration of the aqueous suspension of the activated carbon carrier is 5 wt% - 20 wt%, the Rh content in the Rh salt solution is 1 wt% - 5 wt%, the volume ratio of the aqueous suspension of the activated carbon carrier to the Rh salt solution is 1:1 - 100:1, the volume ratio of the aqueous suspension of the activated carbon carrier to the precipitant is 10:1 - 100:1, and the stirring speed is 600 - 1200 rpm.

8. A method for synthesizing an alkylated crown ether according to claim 6, characterized in that, The activated carbon carrier is selected from any one of activated carbon, porous graphite, graphene, and carbon nanotubes, the precipitant is selected from any one of aqueous solutions of NH4OH, NaOH, KOH, NH4CO3, Na2CO3, and K2CO3, and the Rh salt is any one of RhCl3·3H2O, Rh(NO3)3, Rh2(SO4)3, rhodium acetate, and rhodium acetylacetonate.

9. A method for synthesizing alkylated crown ether according to claim 6, characterized in that, The reduction treatment includes filtering, washing with water, and drying the mixed solution to obtain a precipitate; subjecting the precipitate to high-temperature calcination, and then passing hydrogen gas for reduction to obtain the carbon-supported Rh catalyst; The temperature of the high-temperature calcination is 400 - 500 °C, and the time is 3 - 4 h. The temperature for reduction by passing hydrogen gas is 100 - 300 °C, and the time is 3 - 4 h.

10. The synthesis method of an alkylated crown ether according to claim 6, characterized in that, The reduction treatment includes adding a reducing agent to the mixed solution under continuous stirring conditions for a reduction reaction, and filtering and then washing with water to obtain the carbon-supported Rh catalyst; The reducing agent includes any one of NaBH4, KBH4, morpholine borane, N2H4·H2O, and aqueous HCOONa solution; The concentration of the reducing agent added to the mixed solution is 5wt%-20wt%, and the volume ratio of the mixed solution to the reducing agent is 10:1-50:1; The rotation speed of the continuous stirring is 600-1200 rpm, and the time of the reduction reaction is 3-4 h.

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