Application of a two-component metal complex and method for catalyzing carbonylation of epoxides to prepare beta-lactones

Abstract

The present invention provides an application of a two-component metal complex in catalyzing the carbonylation of epoxides to prepare beta-lactones, the two-component metal complex including a complex A and a complex B, wherein the structure of complex A is as shown in formula (I) or formula (II), and the structure of complex B is as shown in formula (III) or formula (IV): the present invention also discloses a method for preparing beta-lactones by catalyzing the carbonylation of epoxides using the above-mentioned two-component metal complex: alkylene oxide and carbon monoxide CO are subjected to a ring amplification reaction under the catalytic action of the two-component metal complex to prepare a four-membered ring beta-lactone compound. The two-component metal complex is a catalytic system with good thermal stability and high reaction activity, which can achieve efficient preparation of beta-lactones.

Description

Technical Field

[0001] The invention belongs to the technical field of carbonylation reaction of epoxy compounds, and particularly relates to an application of a two-component metal complex and a method for catalyzing the carbonylation of epoxy compounds to prepare beta-lactone. Background Art

[0002] The carbonylation reaction of epoxides and carbon monoxide, which undergoes ring expansion in the presence of a catalyst, to produce β-lactones has garnered significant attention. From a raw material perspective, carbon monoxide, as a C1 source, is already widely used as a feedstock for many commodity chemicals, such as methanol and phosgene. Epoxides can be efficiently prepared in a single step via the oxidation of alkenes. This broad availability of raw materials offers cost advantages for the carbonylation reaction. From a product perspective, four-membered ring β-lactones are not only synthetic precursors for complex chemicals, but their high ring tension also facilitates ring-opening polymerization to produce polyhydroxylated fatty acids. These polymers have been extensively studied for their superior mechanical properties, biocompatibility, and biodegradability. Therefore, the carbonylation reaction of epoxides, which uses inexpensive raw materials to produce high-value-added β-lactones, holds significant research value in large-scale chemical production.

[0003] The key to achieving carbonylation reaction lies in the development of efficient catalysts. To date, a variety of catalytic systems have been developed. Among them, the [Lewisacid] developed by Coates of Cornell University in the United States + [Co(CO)4] - Research on catalytic systems is particularly prominent. This catalytic system boasts high catalytic efficiency and simple metal ligand synthesis, enabling the carbonylation of various epoxides with carbon monoxide (J.Am.Chem.Soc.2002,124,7,1174–1175; J.Am.Chem.Soc.2005,127,32,11426–11435). Furthermore, Dong Kaiwu et al. achieved efficient carbonylation of propylene oxide and ethylene oxide using the TPPAlCl / Co2(CO)8 system (CN 114656426A). Applicants have developed a catalytic system combining a tetradentate metal complex and a metal carbonyl compound, achieving efficient ring-expansion carbonylation of alkylene oxides under mild reaction conditions (CN 115710241 A).

[0004] However, the catalytic systems developed so far all involve Co2(CO)8 or [Co(CO)4] - On the one hand, these two compounds are light sensitive and need to be stored away from light. On the other hand, during the carbonylation reaction, Co2(CO)8 and [Co(CO)4] -The high dosage increases the production cost of the carbonylation reaction, and both will decompose at high temperatures and lose their catalytic activity, making it impossible to increase the carbonylation reaction rate by raising the reaction temperature. Therefore, the development of a catalytic system with good thermal stability and high catalytic efficiency is an urgent problem to be solved in the current epoxide carbonylation reaction. Summary of the Invention

[0005] The present invention aims to provide an application of a two-component metal complex and a method for preparing β-lactone by catalyzing the carbonylation of epoxide. The two-component metal complex is a catalytic system with good thermal stability and high reaction activity, which can achieve efficient preparation of β-lactone.

[0006] The technical solution provided by the present invention is:

[0007] A two-component metal complex is used to catalyze the carbonylation of epoxides to prepare β-lactones, comprising a complex A consisting of a metal center and its corresponding ligand, with a structure shown in formula (I) or formula (II):

[0008]

[0009] And a complex B comprising another metal center and its corresponding ligand, the structure of which is shown in formula (III) or formula (IV):

[0010]

[0011] Wherein, M1 and M2 are metal centers, each independently selected from any same or different metal atoms of Al, Cr, Mn, Fe, Co, Ni, and In;

[0012] represents a single bond or a double bond;

[0013] X1 and X2 are each independently selected from N or S atoms; X3, X4, and X5 are each independently selected from N or P atoms;

[0014] Y is selected from Cl, Br, I, CH3COO, NO3, Co(CO)4, ClO4, BF4;

[0015] R1 is selected from C2-C6 alkylene, C3-C10 cycloalkylene, C6-C10 substituted or unsubstituted arylene;

[0016] Among them, R1 is preferably but not limited to the following structure:

[0017]

[0018] in, For a single bond.

[0019] R2-R4 are one or more of H, halogen, nitro, substituted or unsubstituted C1-C10 alkyl, C1-C10 cycloalkyl, C1-C10 alkenyl, C1-C10 alkynyl, C1-C10 alkoxy, C1-C10 aromatic, C1-C10 heterocyclic, and C1-C10 heteroaryl;

[0020] R2 to R4 are preferably but not limited to the following structures:

[0021]

[0022] R5 is selected from C2-C6 alkylene;

[0023] R6~R9、R 11 ~R 13 is one or more of H, halogen, nitro, substituted or unsubstituted C1-C10 alkyl, C1-C10 cycloalkyl, C1-C10 alkenyl, C1-C10 alkynyl, C1-C10 alkoxy, C1-C10 aromatic, C1-C10 heterocyclic, and C1-C10 heteroaryl; wherein R6 and R7, R8 and R9 may form a bond to form a ring, and R 11 ~R 13 Any two can form a bond to form a ring;

[0024] R 10 It is a substituted or unsubstituted C1-C6 alkyl group with or without branches, wherein the branches and the main chain are substituted by one or more atoms of O, S, and N.

[0025] R6~R9、R 11 ~R 13 The following structures are preferred but not limited to:

[0026]

[0027] The complex A is preferably but not limited to the following structure:

[0028]

[0029] The complex B is preferably but not limited to the following structure:

[0030]

[0031] The technical concept of the present invention is that the metal center and the ligand in the structures of formula (I) and formula (II) in complex A jointly form a planar conjugated structure, and the formulas (III) and (IV) in complex B are both composed of the metal center + CO + acyl group + organic ligand. The planar structures of formula (I) and formula (II) enable the metal centers in complex A and complex B to coordinate with the epoxy substrate during the reaction process, thereby activating the epoxy substrate; at the same time, the metal centers in formula (III) and formula (IV) can attack the activated epoxy substrate to cause it to open its ring; after the ring opening, the coordinated CO in formula (III) and formula (IV) can be dislocated and inserted into the opened epoxide to achieve carbonylation; in addition, the acyl group in the structure also plays an important role in stabilizing the catalyst and the intermediates in the carbonylation process.

[0032] Furthermore, the complex A is prepared by the following method:

[0033] (1) Preparation of ligand

[0034] Under nitrogen, the salicylaldehyde compound represented by Formula a and the diamine compound represented by Formula b were dissolved in anhydrous methanol at a molar ratio of 2:1. The mixture was heated under reflux for 4 hours, and the resulting reaction solution was filtered to produce the ligand represented by Formula c. C was dispersed in anhydrous methanol, and sodium borohydride was added (the equivalent ratio of C to sodium borohydride was 1:25). The solution was stirred until clear, and then extracted with a dichloromethane / water system. The organic phase was removed from the solvent to produce the ligand represented by Formula d.

[0035]

[0036] Under nitrogen protection, the thiolamino compound or its salt compound represented by formula e is dissolved in anhydrous tetrahydrofuran, and then 1.25 equivalents of triethylamine is added. After stirring, a tetrahydrofuran solution of the salicylaldehyde compound represented by formula a is added, and the mixture is heated under reflux for 2 hours. The solid is removed by filtration under nitrogen protection, and 1.25 equivalents of triethylamine is added to the filtrate again. Then, a tetrahydrofuran solution of the 6-bromomethylphenol compound represented by formula f is added dropwise, and stirred at room temperature for 2 hours. The resulting reaction solution is post-treated to obtain a ligand represented by formula g; the ligand g is further reduced with sodium borohydride to obtain a ligand represented by formula h; the molar ratio of the thiolamino compound or its salt compound represented by formula e, the salicylaldehyde compound represented by formula a, and the 6-bromomethylphenol compound represented by formula f is 1:1.25:1;

[0037]

[0038] Under nitrogen atmosphere, the dithiol compound represented by formula i was dissolved in anhydrous tetrahydrofuran, and triethylamine was subsequently added. After stirring evenly, a tetrahydrofuran solution of the 6-bromomethylphenol compound represented by formula f was added dropwise. The mixture was stirred at room temperature for 4 hours. The resulting reaction solution was post-treated to obtain a ligand represented by formula j. The reaction formula is shown below. The molar ratio of the dithiol compound represented by formula i, triethylamine, and the 6-bromomethylphenol compound represented by formula f is 1:2.5:2.

[0039]

[0040] Pyrrole (Formula K) and the aldehyde (Formula I) were added to a flask, followed by propionic acid. The reaction mixture was refluxed for 45 minutes. The equivalent ratio of pyrrole, aldehyde, and propionic acid was 1:1:6. After the reaction, the mixture was filtered and washed with methanol to obtain the ligand (Formula M).

[0041]

[0042] (2) Preparation of complex A

[0043] Under nitrogen atmosphere, the ligands represented by formula c, d, g, h, j, and m were dissolved in tetrahydrofuran solvent respectively, and then reacted with the metal organic compound M1Y s (R alkyl ) v Stir the reaction at room temperature, or with metal salt M1Y w After stirring the reaction at room temperature, oxygen is introduced for oxidation, and the resulting reaction solution is post-treated to obtain the corresponding metal complex A. Wherein, M1 and Y are as defined above, and R alky It is a C1-C5 alkyl group, and s, v, and w are integers of 1-4.

[0044] The complex B was prepared by the following method:

[0045] In a nitrogen atmosphere, NaM2(CO)4 and the ligand represented by Formula N or P are dissolved in ether. Stir under ice water for 10 minutes and purge with CO gas for several minutes. Under a CO environment, add the ether solution of the iodine reagent represented by Formula O dropwise into the flask, react under ice water for 1 hour and then at room temperature for 4 hours. After the reaction is completed, vacuum filter the solution. Concentrate the filtrate under vacuum and slowly add pentane with stirring. Cool the mixture in a refrigerator at -20°C overnight, filter it, and wash with pentane to obtain the complex represented by Formula (III) or (IV).

[0046]

[0047] The present invention also provides a method for preparing β-lactone by carbonylation of epoxides catalyzed by a two-component metal complex. The method comprises: an alkylene oxide represented by formula (V) and carbon monoxide (CO) are subjected to a ring expansion reaction under the catalytic action of the two-component metal complex to prepare a four-membered ring β-lactone compound represented by formula (VI), which is represented by:

[0048]

[0049] Among them, in formula (V) and (VI), R a 、R b Each is independently H, C1-C10 alkyl, C1-C10 alkoxy, or C6-C10 aromatic;

[0050] The H on the C1-C10 alkyl group or C1-C10 alkoxy group is not substituted or is substituted with one or more substituents D, and the substituent D is a C6-C10 aromatic group, a C1-C5 alkyl group, a C1-C5 alkoxy group or a halogen;

[0051] The H on the C6-C10 aromatic group is not substituted or is substituted with one or more substituents E, and the substituent E is a C1-C5 alkyl, a C1-C5 alkoxy or a halogen;

[0052] The R a 、R b It can form a bond to form a ring, and together with the two carbon atoms on the epoxy group, it can form a C4-C8 cycloalkyl group or a heterocyclic group containing one or more of O, N, and S atoms in the carbon chain; the H on the cycloalkyl or heterocyclic group is not substituted or is substituted with one or more substituents C, and the substituent C is a C1-C5 alkyl group, a C1-C5 alkoxy group or a halogen.

[0053] Furthermore, the molar ratio of the two-component metal complex to the alkylene oxide is 1:100 to 200,000; preferably 1:100 to 100,000;

[0054] Furthermore, in the two-component metal complex, the molar ratio of complex A to complex B is 1:1-4.

[0055] Furthermore, the method can be carried out without a solvent or in the presence of an organic solvent, wherein the organic solvent is any one of tetrahydrofuran, ethylene glycol dimethyl ether, toluene, benzene, and dichloromethane.

[0056] The reaction temperature of the ring amplification reaction is 60-180° C., the reaction time is 0.1-170 hours, and the carbon monoxide pressure is 0.1-10 MPa.

[0057] Furthermore, the method further comprises: after completion, placing the reaction mixture in a -10°C cold bath for cooling for 30 minutes to slowly release carbon monoxide, and performing reduced pressure distillation to obtain the β-lactone represented by formula (VI); after separating the product by reduced pressure distillation, continuing to add the epoxide represented by formula (V) and carbon monoxide into the system, and the carbonylation reaction can still be carried out.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention adopts a two-component metal complex catalytic system to catalyze the carbonylation of epoxides to prepare β-lactones. The catalytic system solves the problem of the traditional Co2(CO)8 or [Co(CO)4] - The components have issues such as high catalyst dosage and high temperature resistance (instability at high temperatures), which are not conducive to reducing industrial production costs. At the same time, this catalytic system requires low dosage, has high catalytic efficiency, and good thermal stability. The substrate conversion rate can reach over 99%, and the product regioselectivity can reach over 99%. It is expected to improve the industrial production efficiency of alkylene oxide carbonylation reactions while reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is the H NMR spectrum of β-butyrolactone;

[0061] Figure 2 This is the H NMR spectrum of β-propiolactone. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention.

[0063] Component A and its number in the catalyst system used in the examples are as follows:

[0064]

[0065] Component B and its number in the catalyst system used in the examples are as follows:

[0066] The epoxy substrates used in the examples and their numbers are as follows:

[0067]

[0068] The solvents used in the examples and their abbreviations are as follows:

[0069]

[0070] Examples 1-44

[0071] In a glove box, in a 50mL stainless steel high-pressure reactor, catalytic component A (complex A), catalyst component B (complex B), epoxy substrate and solvent (if any) were added in sequence at room temperature, and then a certain pressure of carbon monoxide was introduced, and the temperature was rapidly raised to the set temperature. After the reaction time, stirring was stopped, and the mixture was placed in a -10°C cold bath for 30 minutes to slowly release carbon monoxide. The reaction solution was characterized by nuclear magnetic resonance hydrogen spectrum, and then the reaction solution was distilled to obtain a pure β-lactone product. The experimental results are shown in Table 1. The obtained β-propiolactone and β-butyrolactone nuclear magnetic spectra are shown in Table 1. Figure 1 and Figure 2 shown.

[0072] Table 1 Epoxide carbonylation reaction conditions and results

[0073]

[0074]

[0075]

[0076] In the table:

[0077] Synthesis method of A-1:

[0078] Under nitrogen, 2,3-butanedithiol (0.33 g, 2.0 equiv.) was dissolved in anhydrous tetrahydrofuran, followed by the addition of triethylamine (0.27 g, 2.5 equiv.). After stirring, a solution of o-hydroxybenzyl bromide (1.0 g, 1.0 equiv.) in tetrahydrofuran was added dropwise. The mixture was stirred at room temperature for 4 hours. The resulting reaction solution was post-treated to obtain the ligand. Under nitrogen, the aforementioned ligand (0.5 g, 1.0 equiv.) was dissolved in 20 mL of anhydrous tetrahydrofuran, followed by the addition of anhydrous chromium dichloride (0.22 g, 1.1 equiv.). After stirring at room temperature for 24 hours, sufficient oxygen was introduced into the reaction system and stirred for 3 hours. The solvent was then removed, and the crude product was washed with n-hexane to obtain the metal complex A-1.

[0079]

[0080] Synthesis method of A-2:

[0081] Under nitrogen atmosphere, a thiolamino compound (0.63 g, 1.0 equiv.) was dissolved in anhydrous tetrahydrofuran, followed by the addition of triethylamine (1.03 g, 1.25 equiv.). After stirring, a tetrahydrofuran solution of salicylaldehyde (1.00 g, 1.0 equiv.) was added, and the mixture was heated under reflux for 2 hours. The solid was removed by filtration under nitrogen, and triethylamine (1.03 g, 1.25 equiv.) was added to the filtrate again. Then, a tetrahydrofuran solution of o-hydroxybenzyl bromide (1.53 g, 1.0 equiv.) was added dropwise, and the mixture was stirred at room temperature for 2 hours. The resulting reaction solution was post-treated to obtain a ligand. The ligand was chromated in the same manner as the above-mentioned preparation method of A-1.

[0082]

[0083] Synthesis methods of A-3, A-4, A-7 and A-8:

[0084] Under nitrogen, a salicylaldehyde compound (2.1 equiv.) and a diamine compound (1.0 equiv.) were dissolved in anhydrous methanol and heated under reflux for 4 hours. The resulting reaction solution was filtered to obtain the ligand. The method for introducing Co and Mn into the ligands was the same as the method for introducing Cr described above, and A-3 and A-7 were prepared accordingly. The method for introducing Al into the ligands was as follows: Under nitrogen, the ligand (1.0 equiv.) was dissolved in anhydrous dichloromethane, followed by the addition of diethylaluminum chloride (1.1 equiv.) to the reaction solution. The reaction was stirred at room temperature for 24 hours, after which the solvent was removed and the crude product was washed with n-hexane to obtain the metal complex A-4. A-8 was synthesized by dissolving the ligand (1.0 equiv.) in anhydrous tetrahydrofuran under nitrogen, followed by the addition of manganese acetate (1.1 equiv.) to the reaction solution. The reaction was stirred at room temperature for 24 hours, after which the solvent was removed and the crude product was washed with n-hexane to obtain the metal complex A-8.

[0085] Synthesis method of A-5, A-6 and A-9:

[0086] Pyrrole (1.0 equiv.) and aldehyde (1.0 equiv.) were added to a flask, followed by propionic acid (6.0 equiv.). The reaction mixture was refluxed for 45 minutes. After the reaction, the mixture was filtered and washed with methanol to obtain the ligand. The method for introducing Cr, Al, and Co into the ligand was the same as described above to prepare A-5, A-6, and A-9.

[0087]

[0088] Synthesis method of B-1 to B-8:

[0089] Taking B-3 as an example, NaCo(CO)4 (1.0 equiv.) and the ligand (1.0 equiv.) were dissolved in diethyl ether under a nitrogen atmosphere. Stirred under ice water for 10 minutes and purged with CO gas for a few minutes. Under a CO environment, a diethyl ether solution of iodomethane (1.0 equiv.) was added dropwise to the flask. The reaction was continued under ice water for 1 hour and then at room temperature for 4 hours. After the reaction was completed, the solution was vacuum filtered. The filtrate was concentrated under vacuum, and pentane was slowly added with stirring. The mixture was placed in a refrigerator at -20°C and cooled overnight. After filtering, it was washed with pentane to obtain B-3. The remaining metal complexes only need to use the corresponding sodium salts and ligands.

Claims

1. Use of a two-component metal complex in catalyzing the carbonylation of epoxides to prepare β-lactones, characterized in that: The two-component metal complex comprises complex A and complex B, and the structure of complex A is shown in formula (I) or formula (II): ； The structure of complex B is shown in formula (III) or formula (IV): ； Wherein, M1 and M2 are metal centers, M1 is selected from Cr, Co, Al or Co, and M2 is selected from Mn, Fe, Co, Ni or In; represents a single bond or a double bond; X1 and X2 are each independently selected from N or S atoms; X3, X4, and X5 are each independently selected from N or P atoms; Y is selected from Cl, Br, I, CH3COO; The R1 is selected from the following structures: ； in, is a single bond; R2~R4 are selected from the following structures: ； R5 is selected from C2~C6 alkylene; R 10 is a substituted or unsubstituted C1-C6 alkyl group with or without branches, wherein the branches and the main chain are substituted by one or more atoms of O, S, or N; R6~R9, R 11 ~R 13 Selected from the following structures: 。 2. The use according to claim 1, characterized in that The structure of the complex A is selected from the following structures: 。 3. The use according to claim 1, characterized in that The structure of the complex B is selected from the following structures: 。 4. A method for preparing β-lactone by carbonylation of epoxide catalyzed by a two-component metal complex, characterized in that: The method comprises: performing a ring expansion reaction on an alkylene oxide represented by formula (V) and carbon monoxide (CO) under the catalytic action of a two-component metal complex according to any one of claims 1 to 3 to prepare a four-membered ring β-lactone compound represented by formula (VI), which is represented by: ； Among them, in formula (V) and (VI), R a 、R b Each independently represents H, a C1-C10 alkyl group, a C1-C10 alkoxy group, or a C6-C10 aromatic group; or the R a 、R b It forms a bond to form a ring, and together with the two carbon atoms on the epoxy group, it forms a C4~C8 cycloalkyl group; the H on the cycloalkyl group is not substituted or is substituted with one or more substituents C, and the substituent C is a C1~C5 alkyl group or a halogen; The H on the C1~C10 alkyl group or C1~C10 alkoxy group is not substituted or is substituted with one or more substituents D, and the substituent D is a C6~C10 aromatic group, a C1~C5 alkyl group, a C1~C5 alkoxy group or a halogen; The H on the C6-C10 aromatic group is not substituted or is substituted with one or more substituents E, and the substituents E are C1-C5 alkyl, C1-C5 alkoxy or halogen.

5. The method for preparing β-lactone by carbonylation of epoxide catalyzed by a two-component metal complex according to claim 4, characterized in that: The molar ratio of the two-component metal complex to the alkylene oxide is 1:100-100000; in the two-component metal complex, the molar ratio of the complex A to the complex B is 1:1-4.

6. The method for preparing β-lactone by carbonylation of epoxide catalyzed by a two-component metal complex according to claim 4, characterized in that: The ring amplification reaction is carried out without solvent or in an organic solvent; when carried out in an organic solvent, the organic solvent is any one of tetrahydrofuran, ethylene glycol dimethyl ether, toluene, benzene, and dichloromethane.

7. The method for preparing β-lactone by carbonylation of epoxide catalyzed by a two-component metal complex according to claim 4, characterized in that: The reaction temperature of the ring amplification reaction is 60-180° C., the reaction time is 0.1-170 hours, and the carbon monoxide pressure is 0.1-10 MPa.

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