Five-membered cycloalkenyl borate compound and preparation method thereof

Abstract

The invention relates to the field of chemical synthesis, and discloses a five-membered cycloalkenyl boric acid ester compound and a preparation method thereof, the five-membered cycloalkenyl boric acid ester compound comprises racemic five-membered cycloalkenyl boric acid ester, chiral five-membered cycloalkenyl boric acid ester and derivative structures of the racemic five-membered cycloalkenyl boric acid ester and the chiral five-membered cycloalkenyl boric acid ester. The preparation method comprises the following steps: carrying out epoxy ring opening on a tertiary racemic or chiral cyclohexane epoxy compound and 1, 1-gem-diboron lithium, and heating and editing into five-membered cycloalkenyl borate under the action of Lewis acid (zinc salt). The synthesis method is safe and simple to operate, reagents used in the reaction are cheap and easy to obtain, the reaction conditions are mild, the substrate applicability is wide, and a rapid strategy is provided for synthesis of the molecular skeleton.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and specifically discloses a five-membered cycloalkenyl borate compound and a preparation method thereof. Background Art

[0002] Racemic or asymmetric alkenyl borate fragments are very important and useful structural units in organic chemistry. Their structures exist in many clinical drug molecules, bioactive molecules and natural products, which can not only improve metabolic stability but also show excellent biological activity. In addition, the drug molecule design of alkenyl borate fragments has been around for many years and is widely used in a variety of commercial products that benefit the people, such as anticancer, antibacterial, antiviral, insecticide, and herbicide. Therefore, the introduction of alkenyl borate fragments into compounds is one of the current focuses of synthetic chemistry.

[0003] In addition, alkenyl borate esters can also undergo a variety of transformations to obtain a series of useful functionalized high-value-added molecules, which play an important role in the modification of drug molecule libraries. For example, the transformation of small molecules is used in WO2004017911 A2 to eventually synthesize protease inhibitors, or as a substrate for the preparation of small molecule inhibitors in WO2024078370A1, such as:

[0004]

[0005] Despite this, there are almost no reports on the direct one-step synthesis of complex five-membered ring alkenyl borate compounds without any directing group induction, and the synthesis technology of this type of molecular skeleton is relatively backward. We need to redesign the substrates and experiments and develop new catalytic systems to achieve the editing of simple to complex five-membered ring alkenyl borate compounds, and provide reference value for the synthesis of this type of skeleton drugs in the future. Summary of the invention

[0006] In view of the prior art, the first aspect of the present invention provides a five-membered cycloalkenyl borate compound, as shown in formula (I):

[0007]

[0008] The R1 is selected from hydrogen, C1-C3 alkyl, C3-C5 alkenyl;

[0009] Said R2 and R3 are each independently selected from hydrogen and C1-C3 alkyl;

[0010] The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

[0011] In some specific embodiments of the first aspect of the present invention, R1 and R3 together with the atoms to which they are connected form a ring Ar, such as formula (II):

[0012]

[0013] The ring Ar is selected from a monocyclic heterocyclic group, a condensed heterocyclic group, a monocyclic aromatic group, a condensed aromatic group, and a carbocyclic group;

[0014] The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

[0015] In some specific embodiments of the first aspect of the present invention, the ring Ar is selected from a C3-C6 carbocyclic group, and any H on the C3-C6 carbocyclic group is replaced by an alkoxy group, and / or the ring Ar is fused with a first ring, and the first ring is fused with a second ring, and the first ring and the second ring are each independently selected from a C3-C6 carbocyclic group, and the hydrogen on the first ring and the second ring is optionally replaced by an alkyl or alkoxy group.

[0016] In some specific embodiments of the first aspect of the present invention, the H on the first ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in R configuration.

[0017] In some specific embodiments of the first aspect of the present invention, the H on the second ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in S configuration.

[0018] In some specific embodiments of the first aspect of the present invention, any H on the first ring or the second ring is substituted by an alkyl group, and the carbon to which the alkyl group is connected is in S configuration.

[0019] In some specific embodiments of the first aspect of the present invention, the R2 is selected from ethyl, and any H on R2 is replaced by R a Substitution, the R a Selected from amino groups.

[0020] In some specific embodiments of the first aspect of the present invention, the R1 is selected from methyl, propenyl, and any H on R1 is replaced by R b Substitution, the R b Selected from alkoxy.

[0021] In some specific embodiments of the first aspect of the present invention, the R a Any H in the above is substituted by p-toluenesulfonyl or alkyl.

[0022] In some specific embodiments of the first aspect of the present invention, the R b Selected from methoxy.

[0023] The second aspect of the present invention provides a specific form of the five-membered cycloalkenyl borate compound described in the first aspect:

[0024]

[0025] The third aspect of the present invention provides a compound represented by formula (III), such as:

[0026]

[0027] The R1 is selected from hydrogen, C1-C3 alkyl, C3-C5 alkenyl;

[0028] Said R2 and R3 are each independently selected from hydrogen and C1-C3 alkyl;

[0029] The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

[0030] In some specific embodiments of the third aspect of the present invention, R1 and R3 together with the atoms to which they are connected form a ring Ar, such as formula (IV),

[0031]

[0032] The ring Ar is selected from a C3-C6 carbocyclic group, any H on the C3-C6 carbocyclic group is replaced by an alkoxy group, and / or the ring Ar is fused with a first ring, the first ring is fused with a second ring, the first ring and the second ring are each independently selected from a C3-C6 carbocyclic group, and hydrogen on the first ring and the second ring is optionally replaced by an alkyl or alkoxy group.

[0033] The fourth aspect of the present invention provides a method for synthesizing the five-membered cycloalkenyl borate of formula (I) described in the first aspect, comprising:

[0034] Compound of formula (III) Mix with 1,1-geminal diboron lithium in an organic solvent, then add Lewis acid and heat to obtain a five-membered cycloalkenyl borate ester represented by formula (I):

[0035] wherein R1, R2, and R3 are as defined in the first aspect.

[0036] The fifth aspect of the present invention provides a method for synthesizing the five-membered cycloalkenyl borate of formula (V) described in the first aspect, comprising:

[0037] Compound of formula (IV) Mix with 1,1-geminal diboron lithium in an organic solvent, then add Lewis acid and heat to obtain a five-membered cycloalkenyl borate ester represented by formula (V):

[0038] Wherein R1, R2, and R3 are as defined in the first aspect;

[0039] The sixth aspect of the present invention provides an application of the five-membered cycloalkenyl borate ester described in the first aspect in the synthesis of cyclopentanal derivatives, such as:

[0040]

[0041] Said R1, R2, and R3 are as defined in the first aspect;

[0042] The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

[0043] The term "Bipn" group structure is as follows:

[0044] The term "carbocyclic ring (base)" refers to a saturated or partially unsaturated monocyclic or polycyclic cyclic hydrocarbon group, and the carbocyclic ring can include 3 to 20 carbon atoms, preferably includes 3 to 12 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12) carbon atoms, more preferably includes 3 to 6 carbon atoms. Wherein the partially unsaturated monocyclic or polycyclic cyclic hydrocarbon group is a saturated cycloalkyl or can optionally include one, two or more double bonds and / or triple bonds on its ring, thus forming a so-called cycloalkenyl or cycloalkynyl group. Preferably, the carbocyclic group is a cycloalkyl, i.e., a saturated monocyclic or polycyclic cyclic hydrocarbon group, more preferably a saturated monocyclic hydrocarbon group. For example, the non-limiting examples of monocyclic carbocyclic rings include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cycloheptatrienyl, cyclooctyl, cyclooctatetraenyl, etc.

[0045] The term "heterocyclyl" refers to a non-aromatic fully saturated or partially unsaturated cyclic group (e.g., a 3 to 7-membered monocyclic ring) having at least one heteroatom in a ring containing at least one carbon atom. Preferably, the heterocyclyl is a 5-membered or 6-membered heterocyclyl. Each ring of the heterocyclic group containing a heteroatom may have 1, 2, 3 or 4 heteroatoms selected from nitrogen atoms, oxygen atoms and / or sulfur atoms, wherein the nitrogen and sulfur heteroatoms may be optionally oxidized and the nitrogen heteroatom may be optionally quaternized. Non-limiting exemplary heterocyclic groups include thienyl, furanyl, pyrrolyl, pyrazole, imidazole, oxazole, isoxazole, thiazole, isothiazole, pyridazinyl, pyrimidinyl, pyrazinyl, piperidinyl, piperazinyl, azetidinyl, azocanyl, diazepanyl, diazaoctanyl, morpholin-4-yl, oxazepanyl, pyrrolidinyl, thiomorpholin-4-yl, tetrahydrofuranyl, tetrahydropyranyl, oxiranyl, thiiranyl, 2-imidazolinyl, isoxazolinyl, oxazolidinyl, isoxazolidinyl, thiazolidinyl, isothiazolidinyl, succinimidyl, 2H-pyrrolyl, 1-pyrrolidinyl, 2-pyrrolidinyl, 3-pyrrolidinyl, 2 2-Oxopiperazinyl, homopiperazinyl, 2-pyrazolinyl, tetrahydro-2H-pyranyl, 2H-pyranyl, 4H-pyranyl, 3,4-dihydro-2H-pyranyl, oxetanyl, thietanyl, 3-dioxolanyl, 1,4-dioxanyl, 2,5-dioximidazolidinyl, 2-oxopiperidinyl, 2-oxopyrrolodinyl, tetrahydrothienyl, 1,3-dioxolanyl, 1,4-oxathianyl, 1,4-dithianyl, 1,3,5-trioxanyl, tetrahydro-1,1-dioxathienyl, N-formylpiperazinyl.

[0046] "Room temperature" refers to the indoor ambient temperature, which can be 12°C to 37°C, 20°C to 30°C, or 25°C to 30°C, or about 25°C.

[0047] Advantages of the present invention:

[0048] 1. The present invention discloses a five-membered cycloalkenyl borate compound and a preparation method thereof. The five-membered cycloalkenyl borate compound includes a racemic five-membered cycloalkenyl borate, a chiral five-membered cycloalkenyl borate and their derivative structures. The five-membered cycloalkenyl borate can be converted into intermediates such as 1-methylcyclopentanal. The method of the present invention is specifically that a tertiary racemic or chiral cyclohexane epoxy compound and 1,1-geminal diboron lithium are subjected to epoxide ring opening, and then heated and edited into a five-membered cycloalkenyl borate under the action of a Lewis acid (zinc salt). The synthetic method is safe and simple to operate, the reagents used in the reaction are cheap and easy to obtain, the reaction conditions are mild, and the substrate has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the H NMR spectrum of the sample prepared in Example 1 of the present invention;

[0050] Figure 2 The NMR carbon spectrum of the sample prepared in Example 1 of the present invention;

[0051] Figure 3 This is the H NMR spectrum of the sample prepared in Example 2 of the present invention;

[0052] Figure 4 The NMR carbon spectrum of the sample prepared in Example 2 of the present invention;

[0053] Figure 5 This is the H NMR spectrum of the sample prepared in Example 3 of the present invention;

[0054] Figure 6 The NMR carbon spectrum of the sample prepared in Example 3 of the present invention;

[0055] Figure 7 This is the H NMR spectrum of the sample prepared in Example 4 of the present invention;

[0056] Figure 8 This is the NMR carbon spectrum of the sample prepared in Example 4 of the present invention;

[0057] Fig. 9 This is the H NMR spectrum of the sample prepared in Example 5 of the present invention;

[0058] Fig.10 This is the NMR carbon spectrum of the sample prepared in Example 5 of the present invention; DETAILED DESCRIPTION

[0059] The present invention is further described below in conjunction with specific embodiments. It is worth noting that these embodiments are only used to illustrate the present invention and are not intended to limit the present invention in any way. Improvements and adjustments made by technicians according to the present invention in practical applications still fall within the scope of protection of the present invention.

[0060] Example 1

[0061]

[0062] In a glove box, 0.2 mmol of chiral epoxy compound a1 was added to a cyclopentyl methyl ether (1.5 mL) solution containing 1,1-geminal diboron lithium (1.4 equiv), and the reaction was stirred at 45° C. for 24 hours. Zinc trifluoromethanesulfonate (2.0 equiv) and tetrabutylammonium bromide (50 mol%) were then added, and the reaction was heated to 100° C. for 24 hours. The reaction was then cooled to room temperature and citric acid solution was added to quench the reaction. Ethyl acetate was added for extraction, and the organic phase was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the target five-membered cycloalkenyl borate product b1 with an EZ ratio of >20:1 was obtained by column chromatography separation and purification. The yield was 75%, and the dr value was >20:1.

[0063] The hydrogen spectrum and carbon spectrum data are as follows:

[0064] 1 H NMR (400MHz, CDCl3) δ6.71(d,J=18.3Hz,1H),5.37(d,J=18.3Hz,1H),4.69(s,1H),4.64(s,1H),2.7 3–2.64(m,1H),1.89–1.82(m,1H),1.78–1.70(m,4H),1.58–1.40(m,4H),1.26(s,12H),1.10(s,3H).

[0065] 13 C NMR (101MHz, CDCl3) δ163.84,148.51,108.32,83.02,46.08,45.89,44.31,38.87,30.26,25.65,24.80,20.90.

[0066] Example 2

[0067]

[0068] In a glove box, 0.2 mmol of the epoxy compound a2 was added to a cyclopentyl methyl ether (1.5 mL) solution containing 1,1-geminal diboron lithium (1.4 equiv), and the reaction was stirred at 45° C. for 24 hours. Zinc bromide (2.0 equiv) was then added, and the reaction was heated to 100° C. for 24 hours. The reaction was then cooled to room temperature and citric acid solution was added to quench the reaction. Ethyl acetate was added for extraction, and the organic phase was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the target five-membered cycloalkenyl borate product b2 with an EZ ratio of 13:1 was obtained by column chromatography separation and purification in a yield of 88%.

[0069] We oxidized b2: 0.2 mmol of b2 was dissolved in tetrahydrofuran (1.0 mL), and 3 M sodium hydroxide solution (0.5 mL) and 30% hydrogen peroxide (0.5 mL) were added successively at room temperature. After stirring for 1 hour, water was added to quench the reaction, and ethyl acetate was added for extraction. After the organic phase was dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and c2 was obtained by column chromatography separation and purification with a yield of 92%.

[0070] The hydrogen spectrum and carbon spectrum data of b2 are as follows:

[0071] 1 H NMR (600MHz, CDCl3) δ6.67(d,J=18.3Hz,1H),5.36(d,J=18.3Hz,1H),1.66–1.61(m,6H),1.38–1.36(m,2H),1.26(s,12H),1.05(s,3H).

[0072] 13 C NMR (151MHz, CDCl3) δ163.50,82.96,46.56,39.00,25.21,24.80,24.37.

[0073] Example 3

[0074] Synthesis of a3: At room temperature, place the substrate (8 mmol, 1.0 equiv) and sodium bicarbonate (12 mmol, 1.5 equiv) in 30 mL of dichloromethane and cool to 0°C. Slowly add m-chloroperbenzoic acid (9.6 mmol, 1.2 equiv) and stir overnight. After the reaction is completed, add saturated sodium thiosulfate solution, continue stirring for 2 hours, extract with dichloromethane (2×30 mL), and dry the collected organic phase with anhydrous sodium sulfate. Remove the solvent by rotary evaporation and pass through a column to obtain a3.

[0075]

[0076] The hydrogen spectrum and carbon spectrum data are as follows:

[0077] 1 H NMR(500MHz, CDCl3)δ7.65(d,J=8.3Hz,2H),7.30(d,J=8.0Hz,2H),3.22–3.16(m,1H),3.03–2.97(m,2H) ,2.68(s,3H),2.41(s,3H),1.91–1.82(m,3H),1.79–1.73(m,3H),1.43–1.35(m,2H),1.32–1.20(m,2H).

[0078] 13C NMR (126MHz, CDCl3) δ143.39,134.37,129.72,127.40,58.49,58.33,46.41,35.84,34.85,27.77,24.66,21.53,19.98,19.38.

[0079]

[0080] In a glove box, 0.2 mmol of the epoxy compound a3 was added to a cyclopentyl methyl ether (1.5 mL) solution containing 1,1-gem-diboron lithium (1.4 equiv), and the reaction was stirred at 45° C. for 24 hours. Zinc trifluoromethanesulfonate (3.0 equiv) and tetrabutylammonium bromide (75 mol%) were then added. The reaction was then heated to 100° C. for 24 hours. The reaction was then cooled to room temperature and citric acid solution was added to quench the reaction. Ethyl acetate was added for extraction. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The target product b3 of the five-membered cycloalkenyl borate ester with an EZ ratio of 8:1 was obtained by column chromatography separation and purification. The yield was 83%.

[0081] The hydrogen spectrum and carbon spectrum data are as follows:

[0082] 1 H NMR (600MHz, CDCl3) δ7.64(d,J=6.3Hz,2H),7.30(d,J=4.6Hz,2H),6.49(d,J=18.4Hz,1H),5.33(d,J=18.3Hz,1H ),2.92–2.90(m,2H),2.71(s,3H),2.42(s,3H),1.68–1.66(m,4H),1.58(s,4H),1.41–1.39(m,2H),1.27(s,12H).

[0083] 13 C NMR (151MHz, CDCl3) δ159.98,143.07,135.07,129.60,127.37,83.12,49.21,47.41,37.71,36.58,34.85,24.78,23.69,21.47.

[0084] Example 4

[0085]

[0086] In a glove box, 0.2 mmol of the chiral epoxy compound a4 was added to a cyclopentyl methyl ether (1.5 mL) solution containing 1,1-geminal diboron lithium (1.4 equiv), and the reaction was stirred at 45° C. for 24 hours. Zinc trifluoromethanesulfonate (2.0 equiv) and tetrabutylammonium bromide (50 mol%) were then added. The reaction was then heated to 100° C. for 24 hours. The reaction was then cooled to room temperature and a citric acid solution was added to quench the reaction. Ethyl acetate was added for extraction. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The target product of five-membered cycloalkenyl borate with an EZ ratio of>20:1 was obtained by column chromatography separation and purification. The yield was 68%, and the dr value was>20:1.

[0087] The hydrogen spectrum and carbon spectrum data are as follows:

[0088] 1 H NMR (600MHz, CDCl3) δ6.68(d,J=18.2Hz,1H),5.34(d,J=18.3Hz,1H),3.40(dd,J=9.1,5.1Hz,1H),3.31(s,3H),3.22–3.19(m,1H),1.95(dd,J= 12.9,7.9Hz,1H),1.85–1.81(m,1H),1.70–1.67(m,2H),1.54(dd,J=13.1,9.6Hz,1H),1.26(s,12H),1.14–1.11(m,4H),1.00(d,J=6.5Hz,3H).

[0089] 13 C NMR (151MHz, CDCl3) δ164.21,83.00,76.84,58.89,48.41,46.93,44.81,43.80,37.31,27.72,24.80,19.80.

[0090] Example 5

[0091]

[0092] In a glove box, 0.2 mmol of chiral epoxy compound a5 was added to a cyclopentyl methyl ether (1.5 mL) solution containing 1,1-geminal diboron lithium (1.4 equiv), and the reaction was stirred at 45° C. for 24 hours. Zinc trifluoromethanesulfonate (2.0 equiv) and tetrabutylammonium bromide (10 mol%) were then added, and the reaction was heated to 100° C. for 24 hours. The reaction was then cooled to room temperature and citric acid solution was added to quench the reaction. Ethyl acetate was added for extraction, and the organic phase was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the target five-membered cycloalkenyl borate product b6 with an EZ ratio of >20:1 was obtained by column chromatography separation and purification. The yield was 60%, and the dr value was >20:1.

[0093] The hydrogen spectrum and carbon spectrum data are as follows:

[0094] 1 H NMR(600MHz, CDCl3)δ6.72(d,J=18.2Hz,1H),5.30(d,J=18.2Hz,1H),3.34(s,3H), 3.23(t,J=8.3Hz,1H),2.02–1.96(m,1H),1.85–1.82(m,2H),1.79–1.76(m,1H),1. 65–1.63(m,3H),1.58–1.51(m,3H),1.46–1.41(m,1H),1.28–1.19(m,15H),1.14–1 .09(m,4H),1.04–0.98(m,4H),0.88–0.80(m,1H),0.75(s,3H),0.72–0.68(m,1H).

[0095] 13 C NMR (151MHz, CDCl3) δ165.32,91.01,82.98,57.89,50.18,50.01,49.16,46.52,46.42,43 .96,43.87,43.49,41.22,38.01,31.04,30.81,28.49,27.66,27.01,24.81,23.40,11.72.

[0096] The method of the present invention has been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein within the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention.

Claims

1. A five-membered cycloalkenyl borate compound, as shown in formula (I): The R1 is selected from hydrogen, C1-C3 alkyl, C3-C5 alkenyl; Said R2 and R3 are each independently selected from hydrogen and C1-C3 alkyl; or, The R1 and R3 are not hydrogen, and the R1 and R3 together with the atoms to which they are connected form a ring Ar, such as formula (II): The ring Ar is selected from a monocyclic heterocyclic group, a condensed heterocyclic group, a monocyclic aromatic group, a condensed aromatic group, and a carbocyclic group; The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

2. The five-membered cycloalkenyl borate compound according to claim 2, characterized in that: The ring Ar is fused with a first ring, the first ring is fused with a second ring, the first ring and the second ring are each independently selected from a C3-C6 carbocyclic group, and the hydrogen atoms on the first ring and the second ring are optionally replaced by an alkyl group or an alkoxy group.

3. The five-membered cycloalkenyl borate compound according to claim 3, characterized in that: The H on the first ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in R configuration, and / or, the H on the second ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in S configuration, and / or, any H on the first ring or the second ring is substituted by an alkyl group, and the carbon to which the alkyl group is connected is in S configuration.

4. The five-membered cycloalkenyl borate compound according to claim 1, characterized in that: The R2 is selected from ethyl, and any H on the R2 is replaced by R a Substitute, the R a is selected from amino, and / or, said R1 is selected from methyl, propenyl, and any H on said R1 is replaced by R b Substitute, the R b Selected from alkoxy.

5. The five-membered cycloalkenyl borate compound according to claim 4, characterized in that: The R a Any H is substituted by p-toluenesulfonyl or alkyl, and / or the R b Selected from methoxy.

6. A five-membered cycloalkenyl borate compound, specifically:

7. A compound represented by formula (III), such as: The R1 is selected from hydrogen, C1-C3 alkyl, C3-C5 alkenyl; Said R2 and R3 are each independently selected from hydrogen and C1-C3 alkyl; Or, said R1 and R3 are not hydrogen, and said R1 and R3 together with the atoms to which they are connected form a ring Ar, such as formula (IV), The ring Ar is selected from a C3-C6 carbocyclic group, any H on the C3-C6 carbocyclic group is replaced by an alkoxy group, and / or the ring Ar is fused with a first ring, the first ring is fused with a second ring, the first ring and the second ring are each independently selected from a C3-C6 carbocyclic group, and hydrogen on the first ring and the second ring is optionally replaced by an alkyl or alkoxy group. The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

8. A method for synthesizing a five-membered cycloalkenyl borate, comprising: Compound of formula (III) Mix with 1,1-geminal diboron lithium in an organic solvent, then add Lewis acid and heat to obtain a five-membered cycloalkenyl borate ester represented by formula (I): The R1 is selected from hydrogen, C1-C3 alkyl, C3-C5 alkenyl; Said R2 and R3 are each independently selected from hydrogen and C1-C3 alkyl; And / or, said R1 and R3 are not hydrogen, and said R1 and R3 together with the atoms to which they are connected form a ring Ar, such as formula (II): The ring Ar is fused with a first ring, the first ring is fused with a second ring, the first ring and the second ring are each independently selected from a C3-C6 carbocyclic group, and the hydrogen atoms on the first ring and the second ring are optionally replaced by an alkyl group or an alkoxy group; The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

9. The method for synthesizing a five-membered cycloalkenyl borate according to claim 8, characterized in that: The H on the first ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in R configuration, and / or, the H on the second ring is substituted by an alkoxy group, and the carbon to which the alkoxy group is connected is in S configuration, and / or, any H on the first ring or the second ring is substituted by an alkyl group, and the carbon to which the alkyl group is connected is in S configuration.

10. Use of the five-membered cycloalkenyl borate according to any one of claims 1 to 6 in the synthesis of cyclopentanal derivatives, such as: The R1, R2, and R3 are the same as defined above; The carbon chiral centers marked with * are independently R-configuration, S-configuration, or achiral carbon atoms.

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