A method for synthesizing high purity δ-lactones

Abstract

The present application relates to the technical field of delta-lactone synthesis, in particular to a high-purity delta-lactone synthesis method, comprising the following steps: using potassium carbonate to catalyze Michael addition reaction of the active methylene functional group of dimethyl malonate and the alpha, beta-alkenyl functional group of 1-octene-3-ketone to generate intermediate product I; intermediate product I generates decarboxylation reaction under the catalysis of boric acid to generate intermediate product II; chiral ligand supported nickel catalyst catalyzes asymmetric hydrogenation reaction of the delta-carbonyl functional group of intermediate product II to generate chiral delta-hydroxyl functional group, and ester exchange reaction of the chiral delta-hydroxyl functional group and the ester functional group of intermediate product II to generate chiral delta-decalactone. The present application designs and synthesizes four chiral ligand supported nickel catalysts on one hand, and designs a new route capable of synthesizing chiral delta-decalactone with high optical purity on the other hand.

Description

Technical Field

[0001] This invention relates to the field of δ-lactone synthesis technology, specifically a method for synthesizing high-purity δ-lactone. Background Technology

[0002] Lactones are compounds formed by the intramolecular esterification of hydroxy fatty acid molecules. When naming lactones, the parent compound, a hydroxy acid, is obtained by breaking down the lactone. The first carbon atom next to the carbonyl group is positioned at the α-position, the second at the β-position, the third at the γ-position, the fourth at the δ-position, and so on, corresponding to the α, β, β, and β positions, respectively. δ-decyl lactone is also known as δ-n-pentyl-δ-pentyl lactone or δ-decyl lactone (chemical structural formula as shown in Figure 1). Figure 6-3 As shown, R-δ-decanolide is as follows Figure 6-4 As shown, S-δ-decanolide, as Figure 6-5 As shown in the figure, it is a lactone with ten carbon atoms in the carbon chain and a branch chain containing five carbon atoms at the T position.

[0003] Eudelactone is found in coconut and raspberry. It is a colorless and transparent oily liquid that, when diluted, has a coconut and milky aroma and a strong and lasting creamy flavor. It is an important raw material for flavoring milk and cream, and is also widely used in blending coconut, strawberry, peach and other flavorings. It is also widely used in margarine, ice cream, soft drinks, candy, baked goods and seasonings.

[0004] Clinical medical evidence shows that excessive consumption of butter can easily lead to cardiovascular diseases. This is because butter contains a large amount of fat, which, after being absorbed by the body, can easily cause hyperlipidemia and other diseases, leading to blood vessel blockage and cardiovascular diseases. Therefore, some countries use vegetable oil butter flavorings as a milk flavoring additive in artificial low-fat butter in the food industry, achieving quite good results, with a flavor almost identical to natural butter. Thus, a new high-quality butter flavoring comparable to natural butter can be formulated using δ-decanolide. Using this new flavoring can improve food quality while reducing the butter content in food. The synthesis of δ-decanolide is of great significance in protecting human health.

[0005] In fact, δ-decanolide was already used as a butter flavoring as early as 1955. Subsequently, there were documents on the chemical synthesis of δ-decanolide, but the general chemical synthesis methods generally produce racemic compounds, and most commercially available δ-decanolides are of this type. Organic synthesis in ordinary environments can only produce racemic mixtures, and products synthesized by chemical methods are less safe. Furthermore, due to optical purity limitations, the quality and threshold of their aroma are inferior to those of natural products. Moreover, synthetic products are often mixtures of isomers, which can easily alter the aroma. Therefore, the synthesis of chiral δ-decanolide is of particular importance.

[0006] Most lactones are chiral, and their physiological activity often depends on the absolute configuration of the lactone molecule. Among natural butyldecyl lactones, R-butyldecyl lactone is dominant, and its aroma is stronger than that of its S-butyldecyl enantiomer. For example, the R:S configuration ratio in butter is 82:18, and in cheese, the R-enantiomer accounts for 75%. Therefore, synthesizing chiral R-butyldecyl lactones can more closely approximate the formulation of naturally occurring flavorings, ensuring greater safety and achieving an aroma quality that better meets people's pursuit of natural purity. Summary of the Invention

[0007] The purpose of this invention is to provide a method for synthesizing chiral δ-decanolide with high optical purity, the specific implementation of which is as follows:

[0008] A method for synthesizing high-purity δ-lactone includes the following steps: a Michael addition reaction is catalyzed by potassium carbonate to react the active methylene functional group of dimethyl malonate with the α,β-alkenyl functional group of 1-octen-3-one to generate intermediate I; intermediate I undergoes decarboxylation under boric acid catalysis to generate intermediate II; an asymmetric hydrogenation reaction is catalyzed by a nickel catalyst supported on a chiral ligand to generate a chiral δ-hydroxyl functional group from the δ-carbonyl functional group of intermediate II; the chiral δ-hydroxyl functional group undergoes transesterification with the ester functional group of intermediate II to generate chiral δ-decyl lactone.

[0009] The chiral ligand-supported nickel catalyst is selected from one of the following: R-configuration ligand I supported nickel catalyst I-R, S-configuration ligand I supported nickel catalyst I-S, branched R-configuration ligand II supported nickel catalyst II-R, and branched S-configuration ligand II supported nickel catalyst II-S.

[0010] Preferably, the preparation method of the nickel catalyst I-R supported by the R-configuration ligand I is as follows:

[0011] Step S1-1: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional groups of two equivalents of R(+)-alpha-methylbenzylamine to generate R-configuration ligand I.

[0012] In steps S1-2, the nitrogen functional group of R-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate nickel catalyst I-R supported on R-configuration ligand I.

[0013] Preferably, the preparation method of the S-configuration ligand I supported nickel catalyst I-S is as follows:

[0014] Step S2-1: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional groups of two equivalents of S-1-phenylethylamine to generate S-configuration ligand I.

[0015] In step S2-2, the nitrogen functional group of S-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate S-configuration ligand I supported nickel catalyst I-S.

[0016] Preferably, the preparation method of the branched R-configuration ligand II supported nickel catalyst II-R is as follows:

[0017] Step S3-1: Using the Schiff base condensation reaction, a dehydration condensation reaction is carried out between the carbonyl functional group of one equivalent branched terminal acetyl monomer M-acetyl and the amino functional groups of two equivalent R(+)-alpha-methylbenzylamine to generate branched R configuration ligand II.

[0018] Step S3-2: The nitrogen functional group of the branched R configuration ligand II undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate the branched R configuration ligand II supported nickel catalyst II-R.

[0019] Preferably, the preparation method of the branched S-configuration ligand II supported nickel catalyst II-S is as follows:

[0020] Step S4-1: Using the Schiff base condensation reaction, the carbonyl functional group of one equivalent branched terminal acetyl monomer M-acetyl undergoes a dehydration condensation reaction with the amino functional groups of two equivalent S-1-phenylethylamine to generate branched S-configuration ligand II.

[0021] Step S4-2 involves a chemical coordination reaction between the nitrogen functional group of branched S-configuration ligand II and nickel ions of nickel chloride dimethoxyethane to generate branched S-configuration ligand II supported nickel catalyst II-S.

[0022] Preferably, the branched terminal acetyl monomer M-acetyl is prepared as follows:

[0023] Step S5-1: Using the Aza-Michael reaction, an azira-Michael addition reaction is carried out between the amino functional group of one equivalent of dodecylamine and the α,β-alkenyl functional groups of two equivalents of acrylamide to generate the branched terminal amide monomer M-acylamino.

[0024] Step S5-2: Using the Schiff base condensation reaction, the amino functional group of one equivalent branched terminal amide monomer M-acylamino undergoes a dehydration condensation reaction with the carbonyl functional groups of two equivalent 2,3-butanedione to generate the branched terminal acetyl monomer M-acetyl.

[0025] The chiral δ-decanolide prepared according to the above-described high-purity δ-lactone synthesis method has an optical purity of op > 60%.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] This invention: On one hand, four chiral ligand-supported nickel catalysts were designed and synthesized, namely: nickel catalyst I-R supported by R-configuration ligand I, nickel catalyst I-S supported by S-configuration ligand I, nickel catalyst II-R supported by branched R-configuration ligand II, and nickel catalyst II-S supported by branched S-configuration ligand II.

[0028] Furthermore, asymmetric hydrogenation reactions catalyzed by chiral ligand-supported nickel catalysts were used to obtain chiral alcohols;

[0029] On the other hand, a new route for synthesizing chiral δ-decanolide was designed, specifically including: using potassium carbonate to catalyze a Michael addition reaction between the active methylene functional group of dimethyl malonate and the α,β-alkenyl functional group of 1-octen-3-one to generate intermediate I; intermediate I undergoes a decarboxylation reaction under boric acid catalysis to generate intermediate II; a chiral ligand-supported nickel catalyst catalyzes an asymmetric hydrogenation reaction of the δ-carbonyl functional group of intermediate II to generate a chiral δ-hydroxy functional group; the chiral δ-hydroxy functional group undergoes an alcoholysis reaction (i.e., transesterification) with the ester functional group of intermediate II to generate chiral δ-decanolide;

[0030] Experimental results showed that: when using R-configuration ligands to support nickel for asymmetric hydrogenation catalysis, the product configuration is predominantly R; when using S-configuration ligands to support nickel for asymmetric hydrogenation catalysis, the product configuration is predominantly S; and when using branched ligands to support nickel for asymmetric hydrogenation catalysis, the product optical purity is even better. Attached Figure Description

[0031] Figure 1-1 The chemical structural formula of R-configuration ligand I;

[0032] Figure 1-2 The chemical structural formula of nickel catalyst I-R supported by R-configuration ligand I;

[0033] Figure 2-1 The chemical structural formula of S-configuration ligand I;

[0034] Figure 2-2The chemical structural formula of nickel catalyst I-S supported by S-configuration ligand I;

[0035] Figure 3-1 The chemical structural formula of the branched terminal amide monomer M-acylamino;

[0036] Figure 3-2 The chemical structural formula of the branched terminal acetyl monomer M-acetyl;

[0037] Figure 4-1 The chemical structural formula of branched R-configuration ligand II;

[0038] Figure 4-2 The chemical structural formula of nickel catalyst II-R supported by branched R-configuration ligand II;

[0039] Figure 5-1 The chemical structural formula of branched S-configuration ligand II;

[0040] Figure 5-2 The chemical structural formula of nickel catalyst II-S supported by branched S-configuration ligand II;

[0041] Figure 6-1 The chemical structural formula of intermediate product I is shown below.

[0042] Figure 6-2 The chemical structural formula of intermediate product II;

[0043] Figure 6-3 The chemical structural formula of δ-decanolide is given.

[0044] Figure 6-4 The chemical structural formula of R-δ-decanolide is given.

[0045] Figure 6-5 The chemical structural formula of S-δ-decanolide is given. Detailed Implementation

[0046] Experimental Example 1:

[0047] Preparation of R-configuration ligand I: R-configuration ligand I was generated via a Schiff base condensation reaction, through a dehydration condensation reaction between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional groups of two equivalents of R(+)-alpha-methylbenzylamine. Its chemical structural formula is shown below. Figure 1-1 ;

[0048] The specific synthesis steps of R-configuration ligand I are as follows: 2.2 mL of 2,3-butanedione, 6.4 mL of LR(+)-alp ha-methylbenzylamine, and 80 mL of anhydrous ethanol were added to a reactor equipped with a mechanical stirrer, a temperature control device, a feeding device, and a nitrogen protection device. Nitrogen protection and mechanical stirring were turned on, and 1.25 mL of acetic acid catalyst was added through the feeding device. The temperature was raised to 70 °C and stirred for 3 h. After cooling to room temperature, the mixture was washed successively with distilled water and anhydrous ethanol, and dried under vacuum at 40 °C to constant weight to obtain R-configuration ligand I.

[0049] 1 H NMR (400MHz, CDCl3, δ): 1.47-1.49 (d, 6H), 2.09 (s, 6H), 5.0-5.06 (m, 2H), 7.28-7.40 (m, 10H);

[0050] Preparation of R-configuration ligand I supported nickel catalyst I-R: The R-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate R-configuration ligand I supported nickel catalyst I-R, whose chemical structural formula is shown below. Figure 1-2 ;

[0051] The specific synthesis steps of R-configuration ligand I supported nickel catalyst I-R are as follows: 5.8 g of R-configuration ligand I, 4.4 g of nickel chloride dimethoxyethane, and 80 mL of dichloromethane were added to a reactor equipped with a mechanical stirrer, a temperature control device, and a nitrogen protection device. The nitrogen protection and mechanical stirring were turned on, and the reaction was carried out at 25 °C for 4 h. The product was precipitated using a mixture of anhydrous ethanol and N,N-dimethylformamide (equal volumes mixed), filtered under negative pressure, and dried under vacuum at 40 °C to constant weight to obtain R-configuration ligand I supported nickel catalyst I-R.

[0052] Experimental Example 2:

[0053] Preparation of S-configuration ligand I: S-configuration ligand I was generated via a Schiff base condensation reaction, through a dehydration condensation reaction between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional groups of two equivalents of S-1-phenylethylamine. Its chemical structural formula is shown below. Figure 2-1 ;

[0054] The synthesis steps for S-configuration ligand I are the same as those for R-configuration ligand I, the only difference being that S-configuration ligand I uses 6.4 mS-1-phenylethylamine as the starting material.

[0055] 1 H NMR (400MHz, CDCl3, δ): 1.47-1.49 (d, 6H), 2.07 (s, 6H), 5.0-5.07 (m, 2H), 7.32-7.39 (m, 10H);

[0056] Preparation of S-configuration ligand I supported nickel catalyst I-S: The S-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate the S-configuration ligand I supported nickel catalyst I-S, whose chemical structural formula is shown below. Figure 2-2 ;

[0057] The synthesis steps of S-configuration ligand I supported nickel catalyst I-S are the same as those of R-configuration ligand I supported nickel catalyst I-R, the only difference being that 5.8 g of S-configuration ligand I is used as the synthesis starting material for S-configuration ligand I supported nickel catalyst I-S.

[0058] Experimental Example 3:

[0059] Preparation of the branched terminal amide monomer M-acylamino: The branched terminal amide monomer M-acylamino is generated via an Aza-Michael addition reaction, where the amino functional group of one equivalent of dodecylamine reacts with the α,β-alkenyl functional groups of two equivalents of acrylamide. Its chemical structure is shown below. Figure 3-1 ;

[0060] The specific synthesis steps of the branched terminal amide monomer M-acylamino are as follows: 7.4 g of dodecylamine and 60 mL of anhydrous methanol were added to a reactor equipped with a mechanical stirrer, a temperature control device and a separatory funnel. After the mechanical stirrer was turned on until the solid was completely dissolved, 40 mL of methanol solution containing 5.7 g of acrylamide was added dropwise to the reactor at a rate of 1 drop / second using a separatory funnel. After the addition was completed, the reaction was stirred at 30 °C for 8 h. The methanol solvent was removed by vacuum distillation using a rotary evaporator to obtain the branched terminal amide monomer M-acylamino.

[0061] Preparation of the branched terminal acetyl monomer M-acetyl: The branched terminal acetyl monomer M-acetyl is generated by dehydration condensation reaction of the amino functional group of one equivalent of the branched terminal amide monomer M-acylamino with the carbonyl functional groups of two equivalents of 2,3-butanedione, using the Schiff base polycondensation reaction. Its chemical structure is shown below. Figure 3-2 ;

[0062] The specific synthesis steps of the branched terminal acetyl monomer M-acetyl are as follows: 10.5 g of branched terminal acetyl monomer M-acetyl, 5.6 mL of 2,3-butanedione, 5 mL of acetic acid catalyst, and 150 mL of anhydrous ethanol were added to a reactor equipped with a mechanical stirrer, a temperature control device, and a nitrogen protection device. The nitrogen protection and mechanical stirring were turned on, and the temperature was raised to 80 °C and stirred for 6 h. The mixture was washed with distilled water and anhydrous ethanol, and dried under vacuum at 40 °C to constant weight to obtain the branched terminal acetyl monomer M-acetyl.

[0063] Experiment Example 4:

[0064] Preparation of branched R-configuration ligand II: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of one equivalent of the branched terminal acetyl monomer M-acetyl and the amino functional groups of two equivalents of R(+)-alpha-methylbenzylamine to generate branched R-configuration ligand II, the chemical structure of which is shown below. Figure 4-1 ;

[0065] The synthesis steps for branched R-configuration ligand II are the same as those for R-configuration ligand I, with the only difference being that branched R-configuration ligand II uses 11.6 g of branched terminal acetyl monomer M-acetyl as the starting material.

[0066] 1 H NMR (400MHz, CDCl3, δ): 0.89 (t, 3H), 1.26-1.37 (m, 18H), 1.45-1.46 (d, 6H), 1.47-1.54 (m, 2H), 2.2 1-2.23(d, 12H), 2.5(t, 2H), 2.76(t, 4H), 2.78-2.94(m, 4H), 4.94-4.99(m, 2H), 7.26-7.34(m, 10H);

[0067] Preparation of branched R-configuration ligand II supported nickel catalyst II-R: The branched R-configuration ligand II undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate branched R-configuration ligand II supported nickel catalyst II-R, whose chemical structural formula is shown below. Figure 4-2 ;

[0068] The synthesis steps of the branched R-configuration ligand II supported nickel catalyst II-R are the same as those of the R-configuration ligand I supported nickel catalyst I-R, the only difference being that the branched R-configuration ligand II supported nickel catalyst II-R uses 13.4 g of the branched R-configuration ligand II supported nickel catalyst II-R as the synthesis raw material.

[0069] Experimental Example 5:

[0070] Preparation of branched S-configuration ligand II: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of a branched terminal acetyl monomer M-acetyl and the amino functional groups of two equivalents of S-1-phenylethylamine to generate branched S-configuration ligand II, whose chemical structural formula is shown below. Figure 5-1 ;

[0071] The synthesis steps for branched S-configuration ligand II are the same as those for R-configuration ligand I, with the only difference being that branched S-configuration ligand II uses 11.6 g of branched terminal acetyl monomer M-acetyl and 6.4 mL S-1-phenylethylamine as the starting materials.

[0072] 1 H NMR (400MHz, CDCl3, δ): 0.9 (t, 3H), 1.24-1.37 (m, 18H), 1.45-1.46 (d, 6H), 1.45-1.54 (m, 2H), 2.15 -2.23(d, 12H), 2.5(t, 2H), 2.78(t, 4H), 2.83-2.98(m, 4H), 4.94-5.01(m, 2H), 7.21-7.36(m, 10H);

[0073] Preparation of branched S-configuration ligand II supported nickel catalyst II-S: The branched S-configuration ligand II undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate branched S-configuration ligand II supported nickel catalyst II-S, whose chemical structural formula is shown below. Figure 5-2 ;

[0074] The synthesis steps of the branched S-configuration ligand II supported nickel catalyst II-S are the same as those of the R-configuration ligand I supported nickel catalyst I-R, the only difference being that 13.4 g of the branched S-configuration ligand II supported nickel catalyst II-S is used as the synthesis raw material.

[0075] Example 1:

[0076] Preparation of chiral δ-decyl lactone I-R: A Michael addition reaction is catalyzed by potassium carbonate to react the active methylene functional group of dimethyl malonate with the α,β-alkenyl functional group of 1-octen-3-one, generating intermediate I (its chemical structure is shown below). Figure 6-1 (As shown); Intermediate product I undergoes a decarboxylation reaction under boric acid catalysis to generate intermediate product II (its chemical structural formula is shown). Figure 6-2 (As shown); The nickel catalyst I-R supports the R-configuration ligand I and catalyzes the asymmetric hydrogenation of the δ-carbonyl functional group of intermediate II to generate a chiral δ-hydroxy functional group. The chiral δ-hydroxy functional group then undergoes an alcoholysis reaction with the ester functional group of intermediate II (here, the alcoholysis reaction is also known as the transesterification reaction) to generate chiral δ-decanolide I-R.

[0077] The synthesis steps of chiral δ-decanolide I-R are as follows: 11.4 mL of dimethyl malonate and 1.38 g of potassium carbonate were added to a reactor equipped with a mechanical stirrer, temperature control device, feeding device, and distillation device. Stirring was started, and the temperature was controlled at 60 °C. 15.1 mL of 1-octen-3-one was gradually added using the feeding device over a period of 1 hour. After the addition was completed, the reaction was stirred at 60 °C for 2 hours. 6.2 g of boric acid was added using the feeding device, and the distillation device was started at 165 °C. The reaction was stirred for 4 hours, cooled, filtered, and the boric acid was removed by vacuum distillation to obtain intermediate product II. 15 g of intermediate product II, 30 mL of methanol, and 6.3 g of nickel catalyst I-R supported on R configuration ligand I were added to a high-pressure reactor. Stirring was started, and 3 MPa of hydrogen gas was introduced. The temperature was gradually increased to 150 °C. When the pressure inside the reactor remained constant, the reaction was stirred at 150 °C for 4 hours. After the reaction was completed, the temperature was lowered to room temperature, filtered, and the fraction at 126–128 °C / 2 mmHg was collected by vacuum distillation to obtain chiral δ-decanolide I-R.

[0078] The R-configuration δ-decanolide was dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL; the S-configuration δ-decanolide was also dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL; the specific rotation of the R-configuration δ-decanolide was determined to be 55.6° dextrorotatory (denoted as [α]) using a polarimeter (Autopal IV, sodium light source, wavelength 589 nm) at 25 °C. 25 D = +55.6°), the specific rotation of the S-configuration δ-decanolide is levorotatory 55.6° (denoted as [α]). 25 D = -55.6°);

[0079] Chiral δ-decanolide I-R was dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL. Its specific rotation was measured at 25 °C using a polarimeter (Autopal IV, sodium light source, wavelength 589 nm) and found to be 37.3° dextrorotatory, indicating that the configuration of chiral δ-decanolide I-R is R. The optical purity of chiral δ-decanolide I-R was calculated to be 67.1%.

[0080] Example 2:

[0081] For the preparation of chiral δ-decanolide I-S, the preparation method and steps are the same as those for chiral δ-decanolide I-R, with the only difference being:

[0082] Chiral δ-decyl lactone I-R was selected using nickel catalyst I-R supported by ligand I with configuration R as the chiral ligand supported nickel catalyst;

[0083] Chiral δ-decyl lactone I-S was selected using S-configuration ligand I supported nickel catalyst I-S as the chiral ligand supported nickel catalyst;

[0084] Chiral δ-decanolide I-S was dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL. Its specific rotation was measured at 25 °C using a polarimeter (Autopal IV, sodium light source, wavelength 589 nm) and found to be -33.7° levorotatory, indicating that the configuration of chiral δ-decanolide I-S is S. The optical purity of chiral δ-decanolide I-S was calculated to be 60.6%.

[0085] Example 3:

[0086] The preparation method and steps for chiral δ-decanolide II-R are the same as those for chiral δ-decanolide I-R, with the only difference being:

[0087] Chiral δ-decyl lactone I-R was selected using nickel catalyst I-R supported by ligand I with configuration R as the chiral ligand supported nickel catalyst;

[0088] Chiral δ-decyl lactone II-R was selected using branched R-configuration ligand II supported nickel catalyst II-R as the chiral ligand supported nickel catalyst.

[0089] Chiral δ-decanolide II-R was dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL. Its specific rotation was measured at 25 °C using a polarimeter (Autopal IV, sodium light source, wavelength 589 nm) and found to be 46.2° dextrorotatory, indicating that the configuration of chiral δ-decanolide II-R is R. The optical purity of chiral δ-decanolide II-R was calculated to be 83.1%.

[0090] Example 4:

[0091] For the preparation of chiral δ-decanolide II-S, the preparation method and steps are the same as those for chiral δ-decanolide I-R, with the only difference being:

[0092] Chiral δ-decyl lactone I-R was selected using nickel catalyst I-R supported by ligand I with configuration R as the chiral ligand supported nickel catalyst;

[0093] Chiral δ-decyl lactone II-S was prepared by using branched S-configuration ligand II supported nickel catalyst II-S as the chiral ligand supported nickel catalyst.

[0094] Chiral δ-decanolide II-S was dissolved in methanol to prepare a solution with a concentration of 1 g / 100 mL. Its specific rotation was measured at 25 °C using a polarimeter (Autopal IV, sodium light source, wavelength 589 nm) and found to be -43.9° levorotatory, indicating that the configuration of chiral δ-decanolide II-S is S. The optical purity of chiral δ-decanolide II-S was calculated to be 79.0%.

[0095] Example 5:

[0096] The following conclusions can be drawn from the experimental results of Examples 1-4:

[0097] First: The asymmetric hydrogenation reaction was catalyzed using nickel catalyst I-R supported by R-configuration ligand I and nickel catalyst II-R supported by branched R-configuration ligand II, with the product having the R configuration as the main component.

[0098] Conversely, when using S-configuration ligand I supported nickel catalyst I-S and branched S-configuration ligand II supported nickel catalyst II-S to catalyze asymmetric hydrogenation reactions, the product configuration is mainly S.

[0099] Second: The optical purity of the products from the asymmetric hydrogenation reaction catalyzed by branched R-configuration ligand II supported nickel catalyst II-R and branched S-configuration ligand II supported nickel catalyst II-S is superior to that of R-configuration ligand I supported nickel catalyst I-R and S-configuration ligand I supported nickel catalyst I-S.

Claims

1. A method for synthesizing high-purity δ-lactone, characterized in that, Includes the following steps: A Michael addition reaction was catalyzed by potassium carbonate to react the active methylene functional group of dimethyl malonate with the α,β-alkenyl functional group of 1-octen-3-one to generate intermediate product I. Intermediate product I undergoes a decarboxylation reaction under boric acid catalysis to generate intermediate product II; A chiral ligand-supported nickel catalyst catalyzes an asymmetric hydrogenation reaction of the δ-carbonyl functional group of intermediate II to generate a chiral δ-hydroxy functional group. The chiral δ-hydroxy functional group then undergoes transesterification with the ester functional group of intermediate II to generate chiral δ-decanolide. The chiral ligand-supported nickel catalyst is selected from one of the following: R-configuration ligand I supported nickel catalyst I-R, S-configuration ligand I supported nickel catalyst I-S, branched R-configuration ligand II supported nickel catalyst II-R, and branched S-configuration ligand II supported nickel catalyst II-S. The chemical structural formula of nickel catalyst I-R supported by ligand I with configuration R is: ； The chemical structural formula of nickel catalyst I-S supported by S-configuration ligand I is: ； The chemical structural formula of the nickel catalyst II-R supported by the branched R-configuration ligand II is as follows: ； The chemical structural formula of the nickel catalyst II-S supported by the branched S-configuration ligand II is as follows: 。 2. The method for synthesizing high-purity δ-lactone according to claim 1, characterized in that, The preparation method of the nickel catalyst I-R supported by the R-configuration ligand I is as follows: Step S1-1: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional groups of two equivalents of R(+)-alpha-methylbenzylamine to generate R-configuration ligand I. In steps S1-2, the nitrogen functional group of R-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate R-configuration ligand I supported nickel catalyst I-R.

3. The method for synthesizing high-purity δ-lactone according to claim 1, characterized in that, The preparation method of the nickel catalyst I-S supported by the S-configuration ligand I is as follows: Step S2-1: Using the Schiff base condensation reaction, a dehydration condensation reaction occurs between the carbonyl functional group of one equivalent of 2,3-butanedione and the amino functional group of two equivalents of S-1-phenylethylamine to generate S-configuration ligand I. In step S2-2, the nitrogen functional group of S-configuration ligand I undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate S-configuration ligand I supported nickel catalyst I-S.

4. The method for synthesizing high-purity δ-lactone according to claim 1, characterized in that, The preparation method of the nickel catalyst II-R supported by the branched R-configuration ligand II is as follows: Step S3-1: Using the Schiff base condensation reaction, a dehydration condensation reaction is carried out between the carbonyl functional group of one equivalent branched terminal acetyl monomer M-acetyl and the amino functional groups of two equivalent R(+)-alpha-methylbenzylamine to generate branched R configuration ligand II. Step S3-2: The nitrogen functional group of the branched R configuration ligand II undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate the branched R configuration ligand II supported nickel catalyst II-R.

5. The method for synthesizing high-purity δ-lactone according to claim 1, characterized in that, The preparation method of the nickel catalyst II-S supported by the branched S-configuration ligand II is as follows: Step S4-1: Using the Schiff base condensation reaction, the carbonyl functional group of one equivalent branched terminal acetyl monomer M-acetyl undergoes a dehydration condensation reaction with the amino functional groups of two equivalent S-1-phenylethylamine to generate branched S-configuration ligand II. Step S4-2: The nitrogen functional group of the branched S-configuration ligand II undergoes a chemical coordination reaction with the nickel ions of nickel chloride dimethoxyethane to generate the branched S-configuration ligand II supported nickel catalyst II-S.

6. The method for synthesizing high-purity δ-lactone according to claim 4 or 5, characterized in that, The preparation method of the branched terminal acetyl monomer M-acetyl is as follows: Step S5-1: Using the Aza-Michael reaction, an azira-Michael addition reaction is carried out between the amino functional group of one equivalent of dodecylamine and the α,β-alkenyl functional groups of two equivalents of acrylamide to generate the branched terminal amide monomer M-acylamino. In step S5-2, the branched terminal acetyl monomer M-acetyl is generated by dehydration condensation reaction of the amino functional group of one equivalent branched terminal amide monomer M-acylamino with the carbonyl functional groups of two equivalent 2,3-butanedione.

7. The chiral δ-decyl lactone prepared by the high-purity δ-lactone synthesis method according to any one of claims 1-5 has an optical purity of op > 60%.

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