A method for synthesizing a cyclic lactone

Abstract

The present invention provides a method for synthesizing a cyclic lactone. An alkylene oxide shown by formula I reacts with carbon monoxide under the action of a catalytic system of a tetradentate metal complex and a metal carbonyl compound to carry out a ring expansion reaction to obtain a cyclic lactone compound shown by formula II. The catalytic system of the tetradentate metal complex and the metal carbonyl compound can achieve the ring expansion carbonylation reaction of the alkylene oxide to generate a cyclic lactone under mild reaction conditions. The conversion rate of the reaction substrate is as high as over 99%, and the regioselectivity of the product is as high as over 99%. The catalyst is simple to synthesize, has good activity and high yield, and the synthesis of the catalyst avoids the synthesis of cobalt salts sensitive to air and light. The obtained catalyst is easier to store and the catalytic reaction operation is more convenient.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing cyclic lactones, and particularly to a catalytic system composed of a tetradentate coordinated metal complex and a metal carbonyl compound for catalyzing the ring expansion of different structural epoxyalkanes with carbon monoxide to prepare cyclic lactones. Background Art

[0002] The ring expansion synthesis of cyclic lactones from epoxyalkanes and carbon monoxide has broad application prospects due to its atom economy and environmental friendliness. As the basis of one-carbon chemistry, carbon monoxide is widely used in the production of methanol, phosgene and many organic raw materials, and epoxyalkanes can be efficiently prepared from bulk basic chemicals - olefins through one-step epoxidation. The rich raw material sources provide a cost advantage for the preparation of cyclic lactones, which can further reduce the price of cyclic lactones and is conducive to the large-scale preparation of cyclic lactones.

[0003] The carbonylation ring expansion reaction of epoxides and carbon monoxide can be traced back to the 1970s. Aumann et al. used [Rh(cod)Cl]2 as a catalyst to realize the carbonylation of 2-vinyl-2-methyloxirane with carbon monoxide to obtain β,γ-unsaturated lactone (Angew. Chem. Int. Ed. 1977, 16(1), 50). Drent adopted the octacarbonylcobalt Co2(CO)8 / 3-hydroxypyridine catalytic system to achieve the efficient synthesis of β-propiolactone (EP577206, 1994). Alper et al. used a catalytic system of phosphazene and carbonylcobalt to achieve the stereoselective carbonylation of epoxyalkanes under the synergistic action of BF3·Et2O (J. Org. Chem. 2001, 66, 5424-5426). The [Lewis acid] + [Co(CO)4] - catalyst developed by Coates of Cornell University in the United States for the carbonylation reaction of epoxyalkanes with carbon monoxide to expand the ring and prepare cyclic lactones all showed relatively excellent catalytic activities (J. Am. Chem. Soc. 2002, 124, 7, 1174–1175; J. Am. Chem. Soc. 2005, 127, 32, 11426–11435).

[0004] Although the above-developed catalytic systems can achieve the ring expansion of epoxyalkanes and carbon monoxide to generate cyclic lactones, the long synthesis steps of the catalysts, low yields, harsh catalytic reaction conditions and high catalyst usage limit their large-scale preparation of cyclic lactones. Therefore, developing a catalytic system with good stability, high reaction activity and mild reaction conditions has become an urgent problem to be solved. Summary of the Invention

[0005] The object of the present invention is to provide a catalytic system with simple synthesis and high reaction activity for the efficient preparation of cyclic lactones under mild conditions, aiming at the problems existing in the current catalytic system for the ring expansion of alkylene oxides with carbon monoxide to prepare lactones, such as harsh reaction conditions, complex catalyst synthesis, high catalyst usage, and being unfavorable for industrial production.

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

[0007] A method for synthesizing a cyclic lactone, the method being: an alkylene oxide shown in Formula I and carbon monoxide are subjected to a ring expansion reaction under the action of a catalytic system of a tetradentate metal complex and a metal carbonyl compound to obtain a cyclic lactone compound shown in Formula II:

[0008]

[0009] In the above Formula I and II, R a and R b are each independently H, an alkyl group with 1 to 10 carbon atoms, an alkoxy group with 1 to 10 carbon atoms, or an aryl group with 6 to 10 carbon atoms;

[0010] The H on the alkyl group with 1 to 10 carbon atoms and the alkoxy group with 1 to 10 carbon atoms is not substituted or is substituted by one or more substituents A, and the substituent A is an aryl group with 6 to 10 carbon atoms, an alkyl group with 1 to 5 carbon atoms, an alkoxy group with 1 to 5 carbon atoms, or a halogen;

[0011] The H on the aryl group with 6 to 10 carbon atoms is not substituted or is substituted by one or more substituents B, and the substituent B is an alkyl group with 1 to 5 carbon atoms, an alkoxy group with 1 to 5 carbon atoms, or a halogen;

[0012] The R a and R b can also be connected together and, together with the two carbons on the epoxy group, form a cycloalkyl group with 4 to 8 carbon atoms or a heterocyclic group containing one or more of oxygen, nitrogen, and sulfur atoms in the carbon chain; the H on the cycloalkyl group or heterocyclic group is not substituted or is substituted by one or more substituents C, and the substituent C is an alkyl group with 1 to 5 carbon atoms, an alkoxy group with 1 to 5 carbon atoms, or a halogen;

[0013] Furthermore, preferably, R a is H, and R b is H or an alkyl group with 1 to 5 carbon atoms. More preferably, R b is H, methyl, or ethyl;

[0014] Or R a and R b are connected together and, together with the two carbons on the epoxy group, form a cyclohexyl group.

[0015] The structural formula of the tetradentate metal complex is as shown in Formula III:

[0016]

[0017] In formula III, M is Al 3+ , Cr 3+ , Co 3+ , Fe 3+ , Mn 3+ , In 3+ or Ni 3+ ; preferably Al 3+ , Cr 3+ or Co 3+ .

[0018] R1 is H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen, or a nitro group; preferably H, CH3, C(CH3)3, OCH3, F, Cl, Br, or NO2; more preferably tert-butyl or methyl.

[0019] R2 is H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen, or a nitro group; preferably H, CH3, C(CH3)3, OCH3, F, Cl, Br, or NO2; more preferably tert-butyl or methyl.

[0020] R3 is an alkylene group having 2 to 6 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 10 carbon atoms; preferably one of the following

[0021]

[0022] In R3 represents a single bond;

[0023] In formula III, the connecting Y and Z to the benzene ring represents a single bond or a double bond;

[0024] Y and Z are each independently a nitrogen atom or a sulfur atom;

[0025] When Y or Z is a nitrogen atom, the bond connecting the nitrogen atom and the methyl group on the benzene ring is a double bond;

[0026] When Y or Z is a sulfur atom, the bond connecting the sulfur atom and the methyl group on the benzene ring is a single bond.

[0027] X is one of the following:

[0028] Cl - , Br - , I - , CH3COO - , NO3 - , Co(CO)4 - , ClO4 - , BF4 -, preferably Cl - or CH3COO - .

[0029] More preferably, the tetradentate metal complex is one of the following formulas III-A1, III-A3, III-B17, III-C30:

[0030]

[0031]

[0032] Furthermore, the metal carbonyl compound is dicobalt octacarbonyl, dimanganese decacarbonyl, chromium hexacarbonyl, titanium heptacarbonyl, divanadium dodecacarbonyl, molybdenum hexacarbonyl, iron pentacarbonyl, nickel tetracarbonyl, dirhenium decacarbonyl or ruthenium pentacarbonyl, preferably dicobalt octacarbonyl.

[0033] The molar ratio of the tetradentate coordination metal complex to the alkylene oxide shown in formula I is 1:100 to 10000.

[0034] The molar ratio of the tetradentate coordination metal complex to the metal carbonyl compound is 1:1 to 4, preferably 1:1 to 1.5.

[0035] The ring expansion reaction is carried out without solvent or in an organic solvent, and the organic solvent is any one of tetrahydrofuran, ethylene glycol dimethyl ether, benzene, and dichloromethane, preferably without solvent or tetrahydrofuran.

[0036] The reaction temperature of the ring expansion reaction is 20 to 180 °C, preferably 30 to 100 °C. The reaction time is 0.1 - 72 hours, preferably 2 - 24 hours.

[0037] The pressure of carbon monoxide is 0.1 to 10 MPa, preferably 2 to 10 MPa.

[0038] Furthermore, the synthesis method of the cyclic lactone is preferably carried out according to the following steps: The alkylene oxide shown in formula I and carbon monoxide are subjected to a ring expansion reaction in tetrahydrofuran or without solvent under the action of a catalytic system of a tetradentate metal complex and a metal carbonyl compound. The molar ratio of the tetradentate coordination metal complex to the alkylene oxide shown in formula I is 1:100 to 10000; the molar ratio of the tetradentate coordination metal complex to the metal carbonyl compound is 1:1 to 4, the reaction temperature is 20 to 180 °C, the pressure of carbon monoxide is 0.1 to 10 MPa, and the reaction is carried out for 0.1 - 72 hours to obtain the cyclic lactone compound shown in formula II.

[0039] After the reaction of the present invention is completed, the reaction solution is post-treated to obtain the cyclic lactone compound shown in Formula II. The method for post-treating the reaction solution is as follows: after the reaction is completed, it is placed in a -10°C cold bath for 30 minutes, carbon monoxide is slowly released, and then the reaction solution is filtered to remove the precipitate. The obtained filtrate is distilled under normal pressure or reduced pressure to obtain the cyclic lactone compound shown in Formula II.

[0040] In the present invention, the tetradentate metal complex is prepared by the following method:

[0041] (1) Preparation of ligands

[0042] (a) When Y = N and Z = N, prepare the ligand shown in Formula c

[0043] Under the protection of a nitrogen atmosphere, the salicylaldehyde compound shown in Formula a and the diamine compound shown in Formula b are dissolved in absolute ethanol in a molar ratio of 2:1, and heated under reflux for 4 hours. The obtained reaction solution a is post-treated to obtain the ligand shown in Formula c. The reaction formula is shown in Formula (1). The general method for post-treating the reaction solution a is: the reaction solution a is cooled and filtered to remove the solvent, and the filter cake is recrystallized with cyclohexane to obtain the ligand shown in Formula c;

[0044]

[0045] (b) When Y = N and Z = S, prepare the ligand shown in Formula f:

[0046] Under the protection of a nitrogen atmosphere, the mercaptoamino compound or its salt shown in Formula d is dissolved in anhydrous tetrahydrofuran, and then 1.25 equivalents of triethylamine are added. After stirring evenly, a tetrahydrofuran solution of the salicylaldehyde compound shown in Formula a is added. The mixture is heated under reflux for 2 hours, and the solid is filtered off under nitrogen protection. Again, 1.25 equivalents of triethylamine are added to the filtrate, and then a tetrahydrofuran solution of the 6-bromomethylphenol compound shown in Formula e is added dropwise. The mixture is stirred at room temperature for 2 hours. The obtained reaction solution b is post-treated to obtain the ligand shown in Formula f; the reaction formula is shown in Formula (2).

[0047] The molar ratio of the mercaptoamino compound or its salt shown in Formula d, the salicylaldehyde compound shown in Formula a, and the 6-bromomethylphenol compound shown in Formula e is 1:1.25:1

[0048] The method for post-treating the reaction solution b is: the reaction solution b is filtered to remove the precipitate, the filtrate is concentrated to obtain the crude product, and the crude product is separated and purified by column chromatography to obtain the ligand shown in Formula f.

[0049]

[0050] (c) When Y = S and Z = S, prepare the ligand shown in Formula h:

[0051] Under the protection of a nitrogen atmosphere, dissolve the dithiol compound shown by formula g in anhydrous tetrahydrofuran, then add triethylamine. After stirring evenly, dropwise add a tetrahydrofuran solution of the 6-bromomethylphenol compound shown by formula e. Stir and react at room temperature for 4 hours. After post-treatment of the obtained reaction solution c, a ligand shown by formula h is prepared; the reaction formula is as shown in formula (3).

[0052] The molar ratio of the dithiol compound shown by formula g, triethylamine, and the 6-bromomethylphenol compound shown by formula e is 1:2.5:2;

[0053] The method for post-treatment of the reaction solution c is: filter the reaction solution c to remove the precipitate, concentrate the filtrate to obtain a crude product, and purify the crude product by column chromatography to prepare the ligand shown by formula h;

[0054]

[0055] (2) Preparation of tetradentate metal complex

[0056] Under the protection of a nitrogen atmosphere, dissolve the ligand shown by formula c, formula f or formula h in a tetrahydrofuran solvent, and then react with the metal organic compound MX m (R c ) n Stir and react at room temperature, or react with the metal salt MX p Stir and react at room temperature, and then oxidize by introducing oxygen. After post-treatment of the obtained reaction solution d, the corresponding tetradentate metal complex is prepared, as shown in formula III-A, III-B, and III-C respectively.

[0057]

[0058] In MX m (R c ) n , the definitions of M and X are as described above, R c is an alkyl group with 1 to 5 carbon atoms, m is an integer from 1 to 4, preferably 1 or 2, and n is an integer from 1 to 4, preferably 1 or 2.

[0059] In MX p , the definitions of M and X are as described above, and p is an integer from 1 to 4, preferably 2 or 3;

[0060] The molar ratio of the ligand shown by formula c, formula f or formula h and the metal organic compound or metal salt is 1:1 to 1.1.

[0061] The method for post-treatment of the reaction solution d is: remove the solvent from the reaction solution d, wash the solid with n-hexane, and dry it under vacuum to obtain the tetradentate metal complex.

[0062] Preferably, the diamine compound is ethylenediamine, 1,2-propanediamine, 1,2-butanediamine, 1,2-cyclohexanediamine, o-phenylenediamine, diphenyl ethylenediamine, etc.

[0063] Preferably, the mercaptoamino compound or its salt compound represented by formula d is mercaptoethylamine salt, 3-mercapto-1-propylamine (hydrochloride), 3-amino-2,2-dimethyl-1-propanethiol (hydrochloride), 2-aminobenzenethiol, etc.

[0064] Preferably, the dithiol compound is ethanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 2,3-propanedithiol, 1,2-butanedithiol, 2,3-butanedithiol, 3,4-hexanedithiol, 1,2-cyclohexanedithiol, 1,2-benzenedithiol, toluene-3,4-dithiophenol, etc.

[0065] The beneficial effects of the present invention are as follows:

[0066] The catalytic system of the tetradentate metal complex and the metal carbonyl compound adopted in the present invention can realize the ring-expansion carbonylation reaction of epoxyalkanes to generate lactones under mild reaction conditions. The conversion rate of the reaction substrate is up to more than 99%, and the regioselectivity of the product is up to more than 99%. The catalyst is simple to synthesize and has a high yield. Moreover, the synthesis of the catalyst avoids the synthesis of air-sensitive and light-sensitive cobalt salts, and the obtained catalyst is easier to store and the catalytic reaction operation is more convenient. More importantly, the catalyst prepared by the present invention exhibits very excellent catalytic activity. Description of the Drawings

[0067] Figure 1 1H NMR spectrum of the ligand used in Example 1.

[0068] Figure 2 1H NMR spectrum of the metal complex used in Example 11.

[0069] Figure 3 1H NMR spectrum of the catalytic product in Example 1. Detailed Embodiments

[0070] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the specific embodiments (Table 1). It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention.

[0071] Example 1:

[0072] In a glove box under a nitrogen atmosphere, 0.1 g of a metal complex, an equimolar amount of the metal carbonyl compound Co2(CO)8 (62.0 mg), and 1.05 g of propylene oxide were successively added to a 50 mL stainless steel high-pressure reactor at room temperature. Without solvent, 6 MPa of carbon monoxide was then introduced, and the temperature was rapidly raised to the set temperature of 50 °C. The reaction was carried out for 22 hours, the stirring was stopped, and it was placed in a -10 °C cold bath for 30 minutes. The carbon monoxide was slowly released, and the reaction solution was taken for characterization by 1H NMR. The conversion rate of propylene oxide was greater than 99%, and the selectivity of the lactone product was 91%. Subsequently, the reaction solution was filtered, and the filtrate was distilled to obtain a pure β-butyrolactone product. The 1H NMR spectrum of the product is as shown in Figure 3 shown.

[0073] By changing the general formula, substituents, metal ions, and anions in the metal complex, the epoxy monomer raw materials, reaction temperature, time, etc., as shown in Table 1, the substrate conversion rate and product selectivity results are shown in Table 1.

[0074] Table 1 Reaction conditions and results for the preparation of lactones by ring expansion of epoxyalkanes with carbon monoxide catalyzed by a metal complex and a metal carbonyl compound

[0075]

[0076]

[0077]

[0078] In Table 1, the carbonyl source S1 represents Co2(CO)8.

[0079] The general formula of the metal complex in Experiments 1-10 is as shown in Formula III-A. The metal complex of Experiment 1 was prepared as follows:

[0080]

[0081] (1) Under nitrogen protection, ethylenediamine (1.028 g, 17.08 mmol) and 3,5-di-tert-butylsalicylaldehyde (8 g, 34.16 mmol) were dissolved in 60 mL of absolute ethanol and heated under reflux for 4 hours. After the reaction was completed, the solvent was removed by filtration and recrystallized with cyclohexane to obtain a yellow solid (8.2 g, 100%). The 1H NMR spectrum of the ligand is as shown in Figure 1 shown. 1 H NMR (400 MHz, Chloroform-d) δ 13.64 (s, 2H), 8.38 (s, 2H), 7.36 (d, J = 2.5 Hz, 2H), 7.06 (d, J = 2.5 Hz, 2H), 3.92 (s, 4H), 1.43 (s, 18H), 1.28 (s, 18H).

[0082] (2) Under nitrogen protection, dissolve 1 g (2 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, and then dropwise add 2 mL of a hexane solution of diethylaluminum chloride (1 M) to the reaction solution. Stir the reaction at room temperature for 24 hours. Then remove the solvent and wash the crude product with n-hexane to obtain yellow solid III-A1 (1.06 g, 95%).

[0083]

[0084] When preparing the metal complex III-A2 of Preparation Experiment 2, the above step (2) is correspondingly changed to: Under nitrogen protection, dissolve 1 g (2 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, and then add 0.274 g (2.2 mmol) of anhydrous chromium dichloride to the reaction solution. Stir the reaction at room temperature for 24 hours, then pass sufficient oxygen into the reaction system and stir for 3 h. Then remove the solvent and wash the crude product with n-hexane to obtain the metal complex III-A2.

[0085]

[0086] When preparing the metal complex III-A3 of Preparation Experiment 3, the above step (2) is correspondingly changed to: Under nitrogen protection, dissolve 1 g (2 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, and then add 0.523 g (2.2 mmol) of cobalt chloride to the reaction solution. Stir the reaction at room temperature for 24 hours, then add 40 mL of 1 mol / L hydrochloric acid methanol solution to the reaction system and pass sufficient oxygen, and stir for 24 h. Then remove the solvent and wash the crude product with n-hexane to obtain the metal complex III-A3.

[0087]

[0088] Other metal complexes can be prepared by changing the raw materials.

[0089] In Table 1, when R1 and R2 are methyl, the raw material used changes the 3,5-di-tert-butylsalicylaldehyde in step (1) to 3,5-dimethylsalicylaldehyde.

[0090] When R3 is change ethylenediamine in step (1) to o-phenylenediamine.

[0091] The metal organic compounds or metal salts that M and X can select are diethylaluminum chloride, anhydrous chromium dichloride (Cr-Cl), cobalt dichloride (Co-Cl), and cobalt acetate (Co-acetate).

[0092] The general formula of the metal complexes in Experiments 11 to 20 is as shown in Formula III-B. The metal complex of Experiment 11 is prepared according to the following method:

[0093]

[0094] (1) Under the protection of nitrogen atmosphere, dissolve 2.3 g (20 mmol) of mercaptoethylamine hydrochloride in 20 mL of anhydrous tetrahydrofuran, then add 2.5 g (25 mmol) of triethylamine. After stirring evenly, add a tetrahydrofuran solution (20 mL, 1.25 M) of 5.6 g (25 mmol) of 3,5 - di - tert - butylsalicylaldehyde compound, and reflux the reaction for 2 hours. Filter to remove the solid under nitrogen protection. Again, add 2.5 g (25 mmol) of triethylamine to the filtrate, and then dropwise add a tetrahydrofuran solution (10 mL, 2 M) of 5.9 g (20 mmol) of 2,4 - di - tert - butyl - 6 - bromomethylphenol, and stir at room temperature for 2 hours. Filter to remove the precipitate, concentrate the filtrate to obtain the crude product, and purify the crude product by column chromatography to obtain the ligand.

[0095] (2) Under nitrogen protection, dissolve 1 g (1.95 mmol) of the ligand prepared above in 40 mL of anhydrous tetrahydrofuran, and then dropwise add 1.95 mL of a hexane solution (1 M) of diethylaluminum chloride to the reaction solution. Stir the reaction at room temperature for 24 hours, then remove the solvent, and wash the crude product with n - hexane to obtain III - B11. The proton nuclear magnetic resonance spectrum of the metal complex is as Figure 2 shown.

[0096]

[0097] When preparing the metal complex III - B15 of Preparation Experiment 15, step (2) above is correspondingly changed to: Under nitrogen protection, dissolve 1 g (1.95 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, then add 0.267 g (2.145 mmol) of anhydrous chromium dichloride to the reaction solution. After stirring the reaction at room temperature for 24 hours, introduce sufficient oxygen into the reaction system and stir for 3 h. Then remove the solvent, and wash the crude product with n - hexane to obtain III - B15.

[0098]

[0099] When preparing the metal complex III - B17 of Preparation Experiment 17, step (2) above is correspondingly changed to: Under nitrogen protection, dissolve 1 g (1.95 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, then add 0.38 g (2.145 mmol) of cobalt acetate to the reaction solution. After stirring the reaction at room temperature for 24 hours, add 2.5 mL of acetic acid solution to the reaction system and introduce sufficient oxygen, and stir for 24 h. Then remove the solvent, and wash the crude product with n - hexane to obtain III - B17.

[0100]

[0101] Other metal complexes can be prepared by changing the raw materials.

[0102] In Table 1, when R1 and R2 are methyl groups, the raw material used changes the 2,4-di-tert-butyl-6-bromomethylphenol in step (1) to 2,4-dimethyl-6-bromomethylphenol.

[0103] When R3 is the mercaptoethylamine hydrochloride in step (1) is changed to 2-aminobenzenethiol.

[0104] The metal organic compounds or metal salts that M and X can select are diethylaluminum chloride, anhydrous chromium dichloride (Cr-Cl), cobalt dichloride (Co-Cl), and cobalt acetate (Co-acetate).

[0105] The general formula of the metal complexes in Experiments 21 to 20 is shown as Formula III-C. The metal complex of Experiment 21 is prepared according to the following method:

[0106]

[0107] (1) Under the protection of a nitrogen atmosphere, 1.88 g (20 mmol) of ethanedithiol is dissolved in 20 mL of anhydrous tetrahydrofuran, and then 5.0 g (50 mmol) of triethylamine is added. After stirring evenly, 8.96 g (40 mmol) of a tetrahydrofuran solution (40 mL, 1 M) of 3,5-di-tert-butylsalicylaldehyde compound is added dropwise. The mixture is stirred at room temperature for 4 hours, the precipitate is filtered off, the filtrate is concentrated to obtain a crude product, and the crude product is separated and purified by column chromatography.

[0108] (2) Under nitrogen protection, 1 g (2 mmol) of the above ligand is dissolved in 40 mL of anhydrous tetrahydrofuran, and then 2 mL of a hexane solution (1 M) of diethylaluminum chloride is added dropwise to the reaction solution. The mixture is stirred at room temperature for 24 hours, then the solvent is removed, and the crude product is washed with n-hexane to obtain III-C21.

[0109]

[0110] When preparing the metal complex III-C25 of Experiment 25, the above step (2) is correspondingly changed to: Under nitrogen protection, 1 g (2 mmol) of the above ligand is dissolved in 40 mL of anhydrous tetrahydrofuran, and then 0.274 g (2.2 mmol) of anhydrous chromium dichloride is added to the reaction solution. After stirring at room temperature for 24 hours, sufficient oxygen is introduced into the reaction system and stirred for 3 h. Then the solvent is removed, and the crude product is washed with n-hexane to obtain III-C25.

[0111]

[0112] When preparing the metal complex III-C26 of Experiment 26, step (2) above was correspondingly changed to: Under nitrogen protection, dissolve 1 g (2 mmol) of the above ligand in 40 mL of anhydrous tetrahydrofuran, and then add 0.39 g (2.2 mmol) of cobalt acetate to the reaction solution. After stirring at room temperature for 24 hours, add 2.5 mL of acetic acid solution to the reaction system and introduce sufficient oxygen, and stir for 24 h. Subsequently, remove the solvent, and wash the crude product with n-hexane to obtain III-C25.

[0113]

[0114] Other metal complexes can be prepared by changing the raw materials.

[0115] In Table 1, when R1 and R2 are methyl, the raw material used changes the 2,4-di-tert-butyl-6-bromomethylphenol in step (1) to 2,4-dimethyl-6-bromomethylphenol.

[0116] R3 is When, change the ethanedithiol in step (1) to o-phenylenedithiol.

[0117] The metal organic compounds or metal salts that M and X can select are diethylaluminum chloride, anhydrous chromium dichloride (Cr-Cl), cobalt dichloride (Co-Cl), and cobalt acetate (Co-acetate).

Claims

1. A method for synthesizing a cyclic lactone, the method comprising: subjecting an alkylene oxide shown in Formula I and carbon monoxide to a ring-expansion reaction under the action of a catalytic system of a tetradentate metal complex and a metal carbonyl compound to obtain a cyclic lactone compound shown in Formula II: In the formulas I and II, R a , R b are each independently H, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms; The H on the C1-C10 alkyl group is unsubstituted or substituted by one or more substituents A, and the substituent A is an aryl group having 6-10 carbon atoms, an alkyl group having 1-5 carbon atoms, an alkoxy group having 1-5 carbon atoms, or a halogen; The H on the aryl group having 6-10 carbon atoms is unsubstituted or substituted by one or more substituents B, and the substituent B is an alkyl group having 1-5 carbon atoms, an alkoxy group having 1-5 carbon atoms, or a halogen; or said R a , R b are connected, and together with two carbons on the epoxy, form a C4-C8 cycloalkyl group or a heterocyclic group containing one or more of oxygen, nitrogen, and sulfur atoms in the carbon chain; the H on the cycloalkyl group or heterocyclic group is unsubstituted or substituted by one or more substituents C, and the substituent C is a C1-C5 alkyl group, a C1-C5 alkoxy group, or a halogen; The structural formula of the tetradentate metal complex is shown in Formula III-B or Formula III-C: In Formula III-B or Formula III-C, M is Al 3+ , Cr 3+ , Co 3+ ; represents a single bond or a double bond; R1 is H, CH3, C(CH3)3, OCH3, F, Cl, Br or NO2; R2 is H, CH3, C(CH3)3, OCH3, F, Cl, Br or NO2; R3 is one of the following: In R3 represents a single bond.

2. The method according to claim 1, characterized in that The tetradentate metal complex is one of the following Formula III-A1, III-A3, III-B17 or III-C30:

3. The method according to claim 1, characterized in that The metal carbonyl compound is dicobalt octacarbonyl, dimanganese decacarbonyl, chromium hexacarbonyl, titanium heptacarbonyl, divanadium dodecacarbonyl, molybdenum hexacarbonyl, iron pentacarbonyl, nickel tetracarbonyl, dirhenium decacarbonyl or ruthenium pentacarbonyl.

4. The method according to claim 1, characterized in that The molar ratio of the tetradentate coordination metal complex to the alkylene oxide shown in Formula I is 1:100-10000; The molar ratio of the tetradentate coordination metal complex to the metal carbonyl compound is 1:1-4.

5. The method according to claim 1, characterized in that The ring-expansion reaction is carried out without a solvent or in an organic solvent, and the organic solvent is any one of tetrahydrofuran, ethylene glycol dimethyl ether, benzene, and dichloromethane.

6. The method according to claim 1, wherein The reaction temperature of the ring-expansion reaction is 20-180 °C, the reaction time is 0.1-72 hours; the pressure of carbon monoxide is 0.1-10 MPa.

7. The method according to claim 1, wherein The tetradentate metal complex is prepared by the following method: (1) Preparation of a ligand (b) Y = N, Z = S, preparation of a ligand shown in Formula f: Under the protection of a nitrogen atmosphere, dissolve the mercaptoamino compound or its salt shown in Formula d in anhydrous tetrahydrofuran, then add 1.25 equivalents of triethylamine, stir evenly and then add a tetrahydrofuran solution of the salicylaldehyde compound shown in Formula a, heat and reflux for 2 hours, filter to remove solids under nitrogen protection, add 1.25 equivalents of triethylamine to the filtrate again, and then dropwise add a tetrahydrofuran solution of the 6-bromomethylphenol compound shown in Formula e, stir at room temperature for 2 hours, and subject the obtained reaction solution b to post-treatment to obtain the ligand shown in Formula f; the reaction formula is shown in Formula (2); The molar ratio of the mercaptoamino compound or its salt shown in Formula d, the salicylaldehyde compound shown in Formula a, and the 6-bromomethylphenol compound shown in Formula e is 1:1.25:1; (c) Y = S, Z = S, preparation of a ligand shown in Formula h: Under the protection of a nitrogen atmosphere, the dithiol compound shown by formula g was dissolved in anhydrous tetrahydrofuran, and then triethylamine was added. After stirring evenly, a tetrahydrofuran solution of the 6-bromomethylphenol compound shown by formula e was added dropwise. The reaction was stirred at room temperature for 4 hours, and the obtained reaction solution c was post-treated to obtain the ligand shown by formula h; the reaction formula is shown by formula (3); The molar ratio of the dithiol compound shown by formula g, triethylamine, and the 6-bromomethylphenol compound shown by formula e is 1:2.5:2; (2) Preparation of the tetradentate metal complex Under nitrogen atmosphere protection, dissolve the ligand shown in formula f or formula h in a tetrahydrofuran solvent, and then react it with the organometallic compound MX m (R c ) n Stir and react at room temperature, or react with the metal salt MX p After stirring and reacting at room temperature, oxidize by introducing oxygen. After post-treatment of the obtained reaction solution d, the corresponding tetradentate metal complexes are prepared, as shown in formula III-B and III-C respectively; The MX m (R c ) n wherein, M and X are defined as described in claim 2, and R c is an alkyl group having 1 to 5 carbon atoms, m is an integer of 1 to 4, and n is an integer of 1 to 4; The MX p wherein, M and X are defined as described in claim 1, and p is an integer from 1 to 4; The molar ratio of the ligand shown by formula f or formula h and the organometallic compound or metal salt is 1:1 to 1.

1.

8. The method according to claim 1, characterized in that After the ring expansion reaction is completed, the reaction solution is post-treated to obtain the cyclic lactone compound shown by formula II. The method for post-treating the reaction solution is as follows: after the reaction is completed, it is placed in a -10°C cold bath for 30 minutes, carbon monoxide is slowly released, and then the reaction solution is filtered to remove the precipitate. The obtained filtrate is distilled under normal pressure or reduced pressure to obtain the cyclic lactone compound shown by formula II.

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