Preparation method of cis-2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol

Abstract

The invention discloses a preparation method of cis-2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol, and the method comprises the following steps: S1, in a hydrogen atmosphere, taking 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanedione as a raw material, and reacting under the action of a modified transition metal catalyst and an auxiliary agent to obtain a cis-2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol reaction solution; s2, an auxiliary agent is separated out, and a cis-2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol crude product is obtained; and S3, washing and drying are carried out, such that a cis-2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol product with a purity of 99.9% or more is obtained. The method is mild in reaction condition and simple in process, the catalyst can be recycled and reused, a CBDO product with a pure cis structure can be obtained, and a polymeric monomer with excellent quality is provided for downstream polyester.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for preparing cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol. Background Art

[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is an important aliphatic diol polyester monomer, mainly used to produce high-performance copolyester products to replace traditional polycarbonate (PC). The molecular formula of CBDO is C8H 16 O2 has two isomers, cis and trans, as shown in the following formula. The cis-trans ratio of CBDO (mass ratio of cis-CBDO to trans-CBDO) has an important influence on the subsequent copolyester process and even the product performance. A high ratio of cis isomers can obtain better glass transition temperature, impact strength and crystallization rate. Therefore, increasing the ratio of cis-trans isomers is what we expect to achieve.

[0003]

[0004] At present, the preparation of 2,2,4,4-tetraalkyl-1,3-cyclobutanediol from 2,2,4,4-tetramethyl-1,3-cyclobutanedione mainly adopts precious metal catalysts. For example, patent US20080132742A1 discloses the use of Cu-based catalysts to prepare CBDO with a cis-trans ratio of 0.34 to 1.68; patent US20080132738A1 discloses the use of Ni-based catalysts to prepare CBDO with a cis-trans ratio of 0.4 to 1.2; patent US8420868B2 discloses the use of Ru-based catalysts to prepare CBDO with a cis-trans ratio of 1.26 to 1.38; patent CN112023919B discloses the use of a combination catalyst composed of a main catalyst composed of various precious metals such as Ru / Ni / Pd / Pt and a co-catalyst composed of Cu / Fe / Co / Zn to prepare CBDO with a cis-trans ratio of 0.54 to 32.18; patent CN 112371192B discloses the use of a chiral ruthenium chloride precursor, which is loaded on a heterogeneous carrier ruthenium carbon to obtain a composite ruthenium catalyst. The above catalyst can be used to obtain a CBDO product with a high cis-trans ratio. However, due to the characteristics of the heterogeneous catalyst itself, when the catalyst is repeatedly used for a period of time, the catalyst performance will seriously decline, and the proportion of trans isomers in the product will increase significantly, resulting in the inability to continuously and stably produce CBDO with a high cis-trans ratio. Therefore, how to obtain a higher cis-trans isomer ratio and improve the stability of the catalyst is an urgent problem to be solved in the industry. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for synthesizing cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol. The method can directly produce CBDO with a pure cis structure, which can provide the best polymerization monomer for downstream polyester.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for synthesizing cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol comprises the following steps:

[0008] S1: In a hydrogen atmosphere, 2,2,4,4-tetramethyl-1,3-cyclobutanedione is used as a raw material, and a cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol reaction liquid is obtained under the action of a modified transition metal catalyst and an auxiliary agent;

[0009] S2: separating the auxiliary agent to obtain crude cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol;

[0010] S3: After washing and drying, the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol product with a purity of more than 99.9% is obtained.

[0011] In the present invention, the modified transition metal catalyst in S1 is a transition metal catalyst coordinated by N-heterocyclic carbene, and the structural formula is: The transition metal M is one of Pd, Cu, Ag, Au, Ru, etc.; R1-R4 are independently alkyl or phenyl, and R5-R6 are independently alkyl or Cl.

[0012] In the present invention, in the reaction system of the transition metal catalyst coordinated by N-heterocyclic carbene in S1, the N-heterocyclic carbene and the transition metal can form a very stable CM bond, and the strengthened metal active site first combines with a keto functional group of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to form an intermediate transition state of the M-alkoxy metal complex. Due to the large steric hindered benzene ring environment around the M atom (R1 to R5 are mostly alkyl substituents with benzene rings), the alkoxy intermediate formed by the keto functional group of 2,2,4,4-tetramethyl-1,3-cyclobutanedione and M is squeezed and extended in the same plane (cis structure), and finally hydrogenated to cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0013] In the present invention, the amount of the transition metal catalyst added in S1 accounts for 0.01 to 0.1% of the mass of 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0014] In the present invention, the auxiliary agent in S1 is one or more of methanol, ethanol, ethyl acetate, isobutyl acetate, butyl butyrate, octyl acetate, isobutyl isobutyrate, methyl isobutyl ketone, methyl isobutyl alcohol, diisobutyl ketone, butyl ether, and octane.

[0015] In the present invention, the mass ratio of the auxiliary agent to 2,2,4,4-tetramethyl-1,3-cyclobutanedione is 1-50.

[0016] As a preferred solution, in the present invention, the hydrogenation reaction conditions in S1 are: autoclave reactor, reaction temperature 60-120°C, reaction pressure 1.0-5.0MPa, stirring speed 500-1200rpm, reaction time 0.5-5h.

[0017] In the present invention, the separation method in S2 adopts distillation, rectification, flash evaporation or rotary evaporation to separate the auxiliary agent, and the solid crude product of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol is precipitated.

[0018] In the present invention, the detergent in S3 is one or more of hexane, heptane and cyclohexane.

[0019] In the present invention, the auxiliary agent and catalyst impurities that may be contained in the crude cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol product are washed out by a detergent, and then the detergent is removed by drying to obtain a high-purity cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0020] In the present invention, after the washing mother liquor in S3 is separated from the detergent, the catalyst is collected and can be reused.

[0021] The beneficial effects of the technical solution of the present invention are as follows: (1) by adopting the above method, the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is ≥99.99%, the yield of 2,2,4,4-tetramethyl-1,3-cyclobutanediol is ≥99.5%, and all of them are cis structures, which can provide the best polymerization monomer for downstream polyester.

[0022] (2) The modified transition metal catalyst used in the present invention can be reused, which reduces the cost and improves the economy of the overall device. DETAILED DESCRIPTION

[0023] The method provided by the present invention is described in detail below with reference to embodiments. It should be noted that the scope of the present invention includes but is not limited to such embodiments.

[0024] Sources of reagents in the embodiments and comparative examples:

[0025] 2,2,4,4-Tetramethyl-1,3-cyclobutanedione: Qingdao World Chemical Co., Ltd.;

[0026] Metal nitrogen heterocyclic carbene catalysts: NHC-Cu (Aladdin), NHC-Pd (Beijing Greenchem Technology Co., Ltd.); NHC-Ru (Shanghai Dongfan Chemical Technology Co., Ltd., Grubbs second-generation catalyst);

[0027] Additives, detergents: industrial grade, Aladdin;

[0028] The embodiments and the analytical instruments and methods used for Bili products are as follows:

[0029] Gas chromatograph: Agilent-7820:

[0030] Gas chromatography column: 0.25mm×30m HP-5 capillary column, detector FID, vaporization chamber temperature 280℃, column box temperature 280℃, FID detector temperature 280℃, hydrogen flow rate 40mL / min, air flow rate 400mL / min, tail flow rate 25mL / min, injection volume 0.2μL, split ratio 30:1. The conversion rate and product selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione were calculated using the area normalization method. Heating program: preheat to column temperature 60℃, hold for 1min, increase from 60℃ to 80℃ at a rate of 10℃ / min, hold for 1min, increase from 80℃ to 250℃ at a rate of 15℃ / min, hold for 8min.

[0031] Embodiment 1:

[0032] Accurately weigh 50 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 500 g of isobutyl isobutyrate and 0.025 g of NHC-Cu catalyst. Add to the reactor and stir to dissolve into a uniform liquid phase. After sealing the reactor, replace with nitrogen three times and start heating. When the temperature in the reactor reaches 80°C, start to introduce hydrogen, increase the pressure to 2.5MPa, adjust the stirring speed to 800rpm, and stop the experiment after 2.0h of reaction. After cooling, release the pressure, replace with nitrogen, and transfer the reaction liquid to a rotary evaporator. Heat to 76-86°C at 10KPa, and evaporate isobutyl isobutyrate to obtain solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product. Add 100mL of cyclohexane at room temperature to wash the solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product, filter and wash 4 times, and dry the filter cake at 80°C for 2h to obtain 51.3g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0033] Gas chromatography analysis of the reaction liquid after hydrogenation showed that the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was 99.99%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 99.8%. The dried product was dissolved in ethanol, and gas chromatography analysis showed that all 2,2,4,4-tetramethyl-1,3-cyclobutanediol was cis-structured.

[0034] Embodiment 2:

[0035] Accurately weigh 50 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 800 g of ethyl acetate and 0.005 g of NHC-Pd catalyst. Add to the reactor and stir to dissolve into a uniform liquid phase. After sealing the reactor, replace with nitrogen three times, start heating, and when the temperature in the reactor reaches 60°C, start introducing hydrogen, increase the pressure to 1.0MPa, adjust the stirring speed to 500rpm, and stop the experiment after 5.0h of reaction. After cooling, release the pressure, replace with nitrogen, and transfer the reaction liquid to a rotary evaporator. Heat to 77°C under normal pressure, and evaporate ethyl acetate to obtain solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product. Add 50mL of hexane at room temperature to wash the solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product, filter and wash 3 times, and dry the filter cake at 80°C for 2h to obtain 50.4g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0036] The reaction liquid after hydrogenation was analyzed by gas chromatography: the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was >99.99%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 98%. The product after drying was dissolved in ethanol, and gas chromatography analysis showed that all 2,2,4,4-tetramethyl-1,3-cyclobutanediol was cis-structure.

[0037] Embodiment 3:

[0038] Accurately weigh 80 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 300 g of methyl isobutyl alcohol and 0.08 g of NHC-Ru catalyst. Add to the reactor and stir to dissolve into a uniform liquid phase. After sealing the reactor, replace with nitrogen three times and start heating. When the temperature in the reactor reaches 120°C, start to introduce hydrogen, increase the pressure to 5.0MPa, adjust the stirring speed to 1200rpm, stop the experiment after 0.5h of reaction, release the pressure after cooling, replace with nitrogen, and transfer the reaction liquid to a rotary evaporator. Heat to 70-76°C at 8KPa, and evaporate methyl isobutyl alcohol to obtain solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product. Add 100mL of heptane at room temperature to wash the solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product, filter and wash 3 times, and dry the filter cake at 80°C for 4h to obtain 82g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0039] Gas chromatography analysis of the reaction liquid after hydrogenation showed that the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was >99.99%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 99.7%. The dried product was dissolved in ethanol, and gas chromatography analysis showed that all 2,2,4,4-tetramethyl-1,3-cyclobutanediol was cis-structured.

[0040] Embodiment 4~5:

[0041] This example illustrates the amount of catalyst added suitable for the process of the present invention.

[0042] The same preparation method as in Example 1 was used to investigate the reaction of NHC-Cu catalyst in 2,2,4,4-tetramethyl-1,3-cyclobutanedione at 0.01% and 0.1%, respectively. The results are as follows:

[0043]

[0044] Embodiment 6~9:

[0045] This example illustrates reaction temperatures suitable for use in the process of the present invention.

[0046] The same preparation method as in Example 1 was used to examine the reaction conditions at reaction temperatures of 25 / 60120 / 150°C, respectively. The results are as follows:

[0047] Example Reaction temperature / ℃ TMCB conversion rate / % CBDO yield / % Cis-trans ratio Example 6 25 2.55 ＜1 100% cis Example 7 60 99.9 99.5 100% cis Example 8 120 99.9 99.6 100% cis Example 9 150 99.9 95.4 100% cis

[0048] Embodiment 10~11:

[0049] This example illustrates the reaction pressure suitable for use in the process of the present invention.

[0050] The same preparation method as in Example 2 was used to examine the reaction conditions at reaction pressures of 3 and 5 MPa, respectively. The results are as follows:

[0051]

[0052] Embodiment 12~13:

[0053] This example illustrates the reaction time suitable for the process of the present invention.

[0054] The same preparation method as in Example 3 was used to examine the reaction conditions at reaction times of 2.5 h and 5 h, respectively. The results are as follows:

[0055] Example Reaction time / h TMCB conversion rate / % CBDO yield / % Cis-trans ratio Example 12 2.5 99.9 99.66 100% cis Example 13 5.0 99.9 99.51 100% cis

[0056] Embodiment 14:

[0057] Catalyst application: The experimental process is the same as that of Example 3, and the catalyst is applied. The application results are shown in Table 1 below:

[0058] Table 1

[0059] Number of applications TMCB conversion rate / % CBDO yield / % Cis-trans ratio 10 99.9 99.7 100% cis 20 99.9 99.6 100% cis 30 99.9 99.5 100% cis 50 99.9 99.5 100% cis

[0060] Comparative Example 1:

[0061] Accurately weigh 50g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 500g of isobutyl isobutyrate and 1.0g of chiral Ru / C catalyst (catalyst described in Example 1 of patent CN 112371192B) and add them to the reactor. After sealing the reactor, replace the nitrogen three times and start heating. When the temperature in the reactor reaches 115°C, start to introduce hydrogen, increase the pressure to 3.0MPa, adjust the stirring speed to 800rpm, stop the experiment after 4.0h of reaction, release the pressure after cooling, replace the nitrogen, and transfer the reaction liquid to a rotary evaporator. Heat to 76-86°C at 10KPa, and rotary evaporate isobutyl isobutyrate to obtain solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product. 50 mL of cyclohexane was added at room temperature to wash the solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product, which was filtered and washed three times. The filter cake was dried at 80° C. for 2 h to obtain 48 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0062] Gas chromatography analysis of the reaction liquid after hydrogenation showed that the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was >99.9%, and the yield of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 93.3%. The dried product was dissolved in ethanol and analyzed by gas chromatography: the ratio of cis-isomer to trans-isomer of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 70:30, which was not a pure cis-structure product.

[0063] Comparative Example 2:

[0064] Accurately weigh 50g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 500g of isobutyl isobutyrate and 2.5g of Ru / C heterogeneous catalyst (powdered Ru / C catalyst described in Example 1 of patent CN112047813 A), and add them to the reactor. After sealing the reactor, replace the nitrogen three times, start heating, and when the temperature in the reactor reaches 115°C, start to pass hydrogen, increase the pressure to 3.5MPa, adjust the stirring speed to 800rpm, and stop the experiment after 4.0h of reaction. After cooling, release the pressure, replace the nitrogen, and transfer the reaction solution to a rotary evaporator. Heat to 76-86°C at 10KPa, and evaporate isobutyl isobutyrate to obtain a solid crude 2,2,4,4-tetramethyl-1,3-cyclobutanediol. At room temperature, 50 mL of cyclohexane was added to wash the solid 2,2,4,4-tetramethyl-1,3-cyclobutanediol crude product, which was filtered and washed three times. The filter cake was dried at 80° C. for 2 h to obtain 49.5 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol product.

[0065] The reaction liquid after hydrogenation was analyzed by gas chromatography: the conversion rate of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was >99.9%, and the yield of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was 96.3%. The product after drying was dissolved in ethanol, and gas chromatography analysis showed that the ratio of cis-isomer to trans-isomer of 2,2,4,4-tetramethyl-1,3-cyclobutanediol was only about 50:50 to 60:40, which was not a pure cis-structure product, and the heterogeneous Ru / C had no effect on regulating the chiral diol.

Claims

1. A method for preparing cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising the following steps: S1: In a hydrogen atmosphere, 2,2,4,4-tetramethyl-1,3-cyclobutanedione is used as a raw material, and a cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol reaction liquid is obtained under the action of a modified transition metal catalyst and an auxiliary agent; S2: separating the auxiliary agent to obtain crude cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol; S3: After washing and drying, the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol product with a purity of more than 99.9% is obtained.

2. The method according to claim 1, characterized in that The modified transition metal catalyst in S1 is a transition metal catalyst coordinated by N-heterocyclic carbene, and has the structural formula: The transition metal M is one of Pd, Cu, Ag, Au and Ru; R1 to R4 are independently alkyl or phenyl, and R5 to R6 are independently alkyl or Cl.

3. The method according to claim 1 or 2, characterized in that: The modified transition metal catalyst in S1 is selected from One or more of .

4. The method according to any one of claims 1 to 3, characterized in that: The amount of the transition metal catalyst added in S1 accounts for 0.01 to 0.1% of the mass of 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

5. The method according to any one of claims 1 to 4, characterized in that: The auxiliary agent in S1 is one or more of methanol, ethanol, ethyl acetate, isobutyl acetate, butyl butyrate, octyl acetate, isobutyl isobutyrate, methyl isobutyl ketone, methyl isobutyl alcohol, diisobutyl ketone, butyl ether, and octane.

6. The method according to any one of claims 1 to 5, characterized in that: The mass ratio of the auxiliary agent to 2,2,4,4-tetramethyl-1,3-cyclobutanedione is 1-50.

7. The method according to any one of claims 1 to 6, characterized in that: The hydrogenation reaction conditions in S1 are: using a kettle reactor, a reaction temperature of 60-120° C., a reaction pressure of 1.0-5.0 MPa, and a reaction time of 0.5-5 h.

8. The method according to any one of claims 1 to 7, characterized in that: The separation method in S2 is to separate the auxiliary agent by distillation, rectification, flash evaporation or rotary evaporation, and the solid crude product of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol is precipitated.

9. The method according to any one of claims 1 to 8, characterized in that: The detergent in S3 is one or more of hexane, heptane and cyclohexane.

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