A novel pyrazolyl derivative containing monoterpenes, its preparation method and application

Abstract

This invention discloses a novel pyrazolyl derivative containing monoterpenes, its preparation method, and its application, belonging to the field of organic synthesis technology. The novel pyrazolyl derivative containing monoterpenes, its preparation method, and its application were tested for antifungal activity using a mycelial growth rate method. In vitro antifungal testing demonstrated that this type of compound is a highly efficient broad-spectrum inhibitor of plant pathogenic fungi, with activity significantly higher than that of commonly used fungicides. Because this compound can strongly inhibit the growth of various plant pathogens at low concentrations, it has excellent application prospects in the prevention and control of plant fungi, possessing advantages such as antibacterial stability, low toxicity, high activity, strong antibacterial effect, and broad application potential.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a novel pyrazolyl derivative containing monoterpenes, its preparation method, and its application. Background Technology

[0002] While chemical fungicides are effective in controlling plant diseases, their residual toxicity, environmental pollution, and resistance to pathogenic fungi have become pressing issues, especially with increasing public concern and demands for environmental health and protection. Natural bioactive products and phytochemicals have attracted widespread attention due to their low mammalian toxicity, environmental compatibility, and biodegradability. Developing plant fungicides using natural bioactive products has been a focus of numerous studies. Terpenes are found in a large number of natural products, most of which exhibit potent biological activities, particularly pharmacological activities. Camphor and menthone are typical terpenes, possessing excellent antiviral, antibacterial, insecticidal, analgesic, and antiseptic activities; related studies have shown that derivatives synthesized using these monoterpenoid structures as lead compounds possess excellent antifungal activity.

[0003] The pyrazole ring is a common nitrogen-containing group. Due to its unique biological activity, it is often widely used in various fungicides, insecticides and herbicides. Among the 24 SDHI fungicides on the market, 12 contain the pyrazole group.

[0004] Plant fungal diseases are one of the main obstacles to the development of forestry in my country. In the past few decades, rampant plant fungal diseases have frequently led to yield reductions in various agricultural and forestry crops. For example, *Colletotrichum gloeosporioides*, the causal agent of anthracnose in camellia oleifera, typically damages the leaves, fruits, and branches, causing flower and fruit drop, and even the death of the entire plant. *Sphaeropsis sapinea*, the causal agent of pine blight, widely infects coniferous forests worldwide, causing a severe and destructive disease. Developing broad-spectrum fungicides with minimal environmental impact has become a hot topic in fungicide research. Modifying highly active natural products found in plants holds promise for synthesizing plant-derived fungicides that possess both antibacterial stability and low toxicity.

[0005] Therefore, there is a need to provide a novel pyrazolyl derivative containing monoterpenes, its preparation method, and its application, in order to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a novel pyrazolyl derivative containing monoterpenes, its preparation method, and its application, thereby resolving the problems mentioned in the background.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A novel pyrazolyl derivative containing a monoterpene has the following structure:

[0009]

[0010] Wherein, R1 is H, -CH3, -CHF2 and CF3; R2 is H, -CH3 and -CH2CH3; R3 is H, Cl and Br.

[0011] A method for preparing a novel pyrazolyl derivative containing a monoterpene includes the following steps:

[0012] Step S1: Using ethyl acetoacetate and triethyl orthoformate containing different substituents as raw materials, a condensation reaction is carried out under reflux in the presence of acetic anhydride; then, cyclization is performed in the presence of hydrazine hydrate using glacial acetic acid as solvent, and methylation is carried out using dimethyl sulfate under alkaline conditions, and finally hydrolysis is performed to obtain pyrazole-4-carboxylic acid.

[0013] Step S2: Under the action of sodium ethoxide, ketones with different substituents and diethyl oxalate undergo a condensation reaction, then cyclize them in the presence of hydrazine hydrate using glacial acetic acid as solvent, and methylate them under alkaline conditions using dimethyl sulfate. Finally, hydrolysis is performed to obtain pyrazole-5-carboxylic acid.

[0014] Step S3: Menthone or camphor undergoes an oxime reaction in a mixed aqueous ethanol solution of hydroxylamine hydrochloride and sodium acetate. After removing the solvent, the solution is recrystallized and purified to obtain menthone oxime or camphor oxime.

[0015] Step S4: Under 0°C conditions, the menthol oxime or camphor oxime obtained in step S3 is subjected to a hydrogenation reduction reaction with an ethanol alkaline solution of aluminum-nickel alloy to obtain mentholamine or camphoramine.

[0016] Step S5: Dissolve the pyrazole carboxylic acid obtained in step S1 or step S2 in dichloromethane, add oxalyl chloride dropwise under ice bath conditions, and add 1-2 drops of N,N-dimethylformamide for catalysis to obtain pyrazole acyl chloride;

[0017] Step S6: The pyrazolyl chloride obtained in step S5 is added dropwise to the dichloromethane solvent of the oxime or amine obtained in step S3 or step S4, and triethylamine is used as an acid-binding agent. Alkali washing and column chromatography are performed sequentially to finally obtain the product of the novel pyrazolyl derivative containing monoterpenes.

[0018] As a further embodiment of the present invention, in step S1, the ratio of substituted ethyl acetoacetate to triethyl orthoformate is 1 mol: 3 mol, the cyclization reaction and methylation are both carried out at 80°C, and after the reaction is completed, the mixture is separated and purified by column chromatography before hydrolysis.

[0019] As a further embodiment of the present invention, the reflux time in step S1 is 2-3 hours and the reflux temperature is 140-150°C.

[0020] As a further embodiment of the present invention, the ratio of the substituted ketone to diethyl oxalate in step S2 is 1 mol: 1 mol, and the condensation reaction is carried out overnight at -5°C.

[0021] As a further embodiment of the present invention, in step S3, the ratio of menthone or camphor, hydroxylamine hydrochloride and sodium acetate is 1 mol: 1.5 mol: 1.5 mol, and the reaction temperature is 60°C.

[0022] As a further embodiment of the present invention, in step S4, the ratio of menthol oxime or camphor oxime to aluminum-nickel alloy is 1 mol: 120 g, and the aluminum-nickel alloy is added in multiple batches at 0°C. The concentration of sodium hydroxide in the ethanol-alkali solution is 5 mol / L. After the system stabilizes, the reaction is carried out at room temperature for 10-12 h.

[0023] As a further embodiment of the present invention, the ratio of pyrazole carboxylic acid to oxalyl chloride in step S5 is 1 mol: 1.2 mol, and the entire process is waterproof.

[0024] As a further embodiment of the present invention, the ratio of oxime or amine to triethylamine in step S6 is 1 mol: 200 mL. After the reaction is completed, the product is washed sequentially with distilled water, saturated sodium carbonate and saturated brine, dried and then purified by column chromatography to obtain the novel pyrazolyl derivative product containing monoterpenes.

[0025] Application of a novel pyrazolyl derivative containing monoterpenes in the control of plant pathogens.

[0026] In summary, the embodiments of the present invention have the following beneficial effects compared with the prior art:

[0027] This invention employs the mycelial growth rate method to test the antifungal properties of novel pyrazolyl derivatives containing monoterpenes. In vitro antifungal tests demonstrate that these compounds are highly effective broad-spectrum inhibitors of plant pathogenic fungi, exhibiting significantly higher activity than commonly used fungicides. Because these compounds can strongly inhibit the growth of various plant pathogens even at low concentrations, they show great promise for novel antifungal applications in the control of plant fungi, possessing antifungal stability, low toxicity, high activity, strong antifungal efficacy, and broad application prospects.

[0028] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0031] In Example 1, the method for preparing a monoterpene-containing pyrazolyl oxime derivative includes the following steps:

[0032] Step S1: Using ethyl acetoacetate and triethyl orthoformate containing different substituents as raw materials, with the ratio of substituted ethyl acetoacetate to triethyl orthoformate being 1 mol: 3 mol, a condensation reaction is carried out under reflux in the presence of acetic anhydride for 2-3 hours at a reflux temperature of 140-150℃. Then, using glacial acetic acid as a solvent, cyclization is performed in the presence of hydrazine hydrate, followed by methylation under alkaline conditions using dimethyl sulfate. Both the cyclization reaction and methylation are carried out at 80℃. Finally, hydrolysis yields pyrazole-4-carboxylic acid.

[0033] Step S2: Ketones containing different substituents undergo a condensation reaction with diethyl oxalate in the presence of sodium ethoxide. The ratio of the substituted ketone to diethyl oxalate is 1 mol: 1 mol. The condensation reaction is carried out overnight at -5°C. Then, cyclization is performed in the presence of hydrazine hydrate using glacial acetic acid as a solvent. Methylation is carried out using dimethyl sulfate under alkaline conditions. Both the cyclization reaction and methylation are carried out at 80°C. Finally, hydrolysis yields pyrazole-5-carboxylic acid.

[0034] Step S3: Menthone or camphor undergoes an oxime reaction in a mixed aqueous ethanol solution of hydroxylamine hydrochloride and sodium acetate. After removing the solvent, the solution is recrystallized and purified to obtain menthone oxime or camphor oxime.

[0035] Step S4: Dissolve the pyrazole carboxylic acid obtained in step S3 in dichloromethane, add oxalyl chloride dropwise under ice bath conditions, and add 1-2 drops of N,N-dimethylformamide for catalysis to obtain pyrazole acyl chloride;

[0036] The steps involve adding the oxime dropwise into a dichloromethane solvent, using triethylamine as an acid-binding agent, and performing alkali washing and column chromatography separation sequentially to finally obtain the pyrazolyl oxime ester derivative containing monoterpenes.

[0037] The novel pyrazolyl derivative containing monoterpenes has the following structure:

[0038]

[0039] Wherein, R1 is H, -CH3, -CHF2 and CF3; R2 is H, -CH3 and -CH2CH3; R3 is H, Cl and Br.

[0040] Specifically, the synthetic steps for monoterpene-containing pyrazolyl oxime ester derivatives are as follows:

[0041]

[0042]

[0043] The structures of the obtained products are as follows:

[0044]

[0045]

[0046] As shown in the structure, the yield of product 1a was 84%, a white solid.

[0047] 1 HNMR(400MHz,Chloroform-d)δ7.89(d,J=9.2Hz,2H),3.92(s,3H),2.68(dt,J=18.1,4.3Hz,1H),2.19(d,J=18.1Hz,1H),1.90(dd,J=25.7, 3.7Hz,2H),1.79(dd,J=12.5,4.0Hz,1H),1.57(td,J=9.0,4.6Hz,1H),1.25(dd,J=8.0,2.3Hz,1H),1.15(s,3H),0.94(s,3H),0.84(s,3H).

[0048] 13 CNMR(126MHz,Chloroform-d)δ162.53,161.71,137.24,131.66,119.28,53.57,48.75,44.93,39.22,37.81,35.88,27.01,20.28,18.67,13.73.

[0049] HRMS(ESI,m / z): [M+H] + CalcdforC 15 H 21 N3O2: 276.1712; found: 276.1674.

[0050] As shown in the structure, the yield of product 3a was 77%, a white solid.

[0051] 1 HNMR(500MHz,Chloroform-d)δ7.91(d,J=3.5Hz,2H),3.93(s,3H),2.70(dd,J=13.4,4.7Hz,1H),2.19(dd,J=13.4,7.8Hz,2H),2.13(td,J=7.5,4.4Hz,1 H),1.94(ddt,J=17.4,8.9,4.3Hz,2H),1.85(td,J=8.4,4.1Hz,1H),1.63–1 .57(m,1H),1.26–1.19(m,1H),0.97(d,J=6.6Hz,6H),0.94(d,J=6.7Hz,3H).

[0052] 13 CNMR(126MHz,Chloroform-d)δ170.41,160.73,140.93,133.44,113.73,48.94,39.34,33.11,32.00,30.53,26.60,26.10,21.39,20.37,19.64.

[0053] HRMS(ESI,m / z): [M+H] + CalcdforC 15 H 23 N3O2: 278.1869; found: 278.1844.

[0054] In Example 2, the preparation method of the monoterpene-containing pyrazolamide derivative is basically the same as that in Example 1, except that: one of the raw materials in Example 2, menthol oxime or camphor oxime, is subjected to a hydrogenation reduction reaction with an ethanol-alkali solution of aluminum-nickel alloy at 0°C to obtain mentholamine or camphoramine. The oxime in Example 2 is replaced with an amine, and the same experimental method is used to finally obtain the monoterpene-containing pyrazolamide derivative product.

[0055] Synthetic steps of pyrazolyl oxime derivatives containing monoterpenes:

[0056]

[0057]

[0058] The structures of the obtained products are as follows:

[0059]

[0060]

[0061] As shown in the structure, the yield of product 5a was 76%, a white solid.

[0062] 1 HNMR(500MHz,Chloroform-d)δ7.90(d,J=9.2Hz,2H),3.93(s,3H),2.72–2.65(m,1H),2.20(d,J=18.0Hz,1H),1.95(t,J=4.3Hz,1H),1.87 (dt,J=12.1,3.7Hz,1H),1.82–1.69(m,2H),1.57(ddd,J=13.4,9.4,4.3Hz,1H),1.31–1.24(m,1H),1.16(s,3H),0.95(s,3H),0.85(s,3H).

[0063] 13 CNMR(126MHz,Chloroform-d)δ178.29,160.56,140.96,133.48,113.64,53.17,48.68,43.52,39.35,34.88,32.46,27.12,19.57,18.46,11.01.

[0064] HRMS(ESI,m / z): [M+H] + CalcdforC 15 H 23 N3O: 262.1919; found: 262.1929.

[0065] The yield of product 7a shown in the structure is 79%, a white solid.

[0066] 1 HNMR(500MHz,Chloroform-d)δ8.09(d,J=1.7Hz,1H),7.87(d,J=1.8Hz,1H),7 .33(d,J=7.1Hz,1H),3.95(s,3H),3.82–3.71(m,1H),1.81–1.76(m,1H),1.75– 1.69(m,1H),1.68–1.63(m,1H),1.63–1.58(m,1H),1.58–1.53(m,1H),1.53–1 .47(m,2H),1.47–1.40(m,1H),1.24–1.15(m,1H),0.89(dd,J=9.9,6.4Hz,9H).

[0067] 13CNMR(125MHz,CommonNMRSolvents)δ163.90,137.35,130.02,119.02,52.58,48.02,40.48,39.17,33.83,30.45,28.96,23.72,21.63,19.91.

[0068] HRMS(ESI,m / z): [M+H] + CalcdforC 15 H 25 N3O: 262.1919; found: 262.1929.

[0069] The mycelial growth rate method was used to test the growth inhibition effects of all target compounds at a concentration of 200 mg / L on nine plant pathogenic fungi, including *Rhizoctonia solani*, *Fusarium wilt*, *Pinus pine*, *Fusarium verticillata*, *Colletotrichum oleifera*, *Sclerotium japonicum*, *Target blight*, *Anthracnose*, and *Bacillus oryzae*. The commercially available pesticide pyraclostrobin and the SDHI fungicide pyrimethanil were selected as pesticide controls to evaluate the antifungal activity of the target compounds. The results were calculated using the following formula:

[0070]

[0071] The specific inhibitory effects are shown in the table below:

[0072]

[0073]

[0074] The antibacterial data in the table show that compounds 4g, 6h, 8f, and 8i have antibacterial activity against rice sheath blight pathogens; compounds 1d, 3d, 4g, 6d, 6h, 8c, 8f, and 8i have antibacterial activity against pine shoot blight pathogens; and compounds 5a, 6c, 6d, 6g, 6h, 8a, and 8c-8f have higher antibacterial activity against maize leaf spot pathogens than azoxystrobin. Compounds 5a and 6a-6f have higher antibacterial activity against *Fusarium verticillata* than pyraclostrobin (80.90%). Compound 6d showed a growth inhibition rate of 93.38% against *Fusarium wilt* causal agent of watermelon wilt, significantly better than azoxystrobin (91.27%) and pyraclostrobin (90.48%).

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pyrazolyl derivative containing a monoterpene, the structure of which is shown below: ； in, R1 can be H, -CH3, -CHF2, or CF3; R2 can be H, -CH3, or -CH2CH3; R3 can be H, Cl, or Br. The compound does not include: , and .

2. The method for preparing the monoterpene-containing pyrazolyl derivative according to claim 1, characterized in that, Includes the following steps: Step S1: Using ethyl acetoacetate containing different substituents Triethyl orthoformate Using acetic anhydride as a raw material, a condensation reaction is carried out under reflux to prepare the product. Then, using glacial acetic acid as a solvent, cyclization was performed under the action of hydrazine hydrate to prepare the following... And methylation was performed using dimethyl sulfate under alkaline conditions to obtain Finally, hydrolysis yields pyrazole-4-carboxylic acid. ; Step S2: Under the action of sodium ethoxide, ketones containing different substituents are... and diethyl oxalate A condensation reaction occurs to obtain Then, using glacial acetic acid as a solvent, cyclization was performed under the action of hydrazine hydrate to obtain... And methylation was performed using dimethyl sulfate under alkaline conditions to obtain Finally, hydrolysis yields pyrazole-5-carboxylic acid. Or, with The raw materials, under the action of NBS or NCS, with DMF as solvent, undergo a substitution reaction at a reaction temperature of 50°C to obtain... Then hydrolyze to obtain ; Step S3, Menthone or camphor Menthol oxime undergoes an oximation reaction with a mixed aqueous solution of hydroxylamine hydrochloride and sodium acetate in ethanol. After removing the solvent, it is purified by recrystallization to obtain menthol oxime. or camphor oxime ; Step S4: At 0°C, the menthol oxime or camphor oxime obtained in step S3 is subjected to a hydrogenation reduction reaction with an ethanol-alkali solution of aluminum-nickel alloy to obtain mentholamine. or camphoramine ; Step S5: Dissolve the pyrazole carboxylic acid obtained in step S1 or step S2 in dichloromethane, add oxalyl chloride dropwise under ice bath conditions, and add 1-2 drops of N,N-dimethylformamide for catalysis to obtain pyrazole acyl chloride; Step S6: The pyrazolyl chloride obtained in step S5 is added dropwise to the dichloromethane solvent of the oxime or amine obtained in step S3 or step S4, and triethylamine is used as an acid-binding agent. Alkali washing and column chromatography are performed sequentially to finally obtain the pyrazolyl derivative product containing monoterpenes.

3. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S1, the ratio of substituted ethyl acetoacetate to triethyl orthoformate is 1 mol: 3 mol. Both the cyclization reaction and methylation are carried out at 80°C. After the reaction is completed, the mixture is separated and purified by column chromatography and then subjected to hydrolysis.

4. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, The reflux time in step S1 is 2-3 hours, and the reflux temperature is 140-150℃.

5. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S2, the ratio of the substituted ketone to diethyl oxalate is 1 mol: 1 mol, and the condensation reaction is carried out overnight at -5°C.

6. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S3, the ratio of menthone or camphor, hydroxylamine hydrochloride, and sodium acetate is 1 mol: 1.5 mol: 1.5 mol, and the reaction temperature is 60°C.

7. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S4, the ratio of menthol oxime or camphor oxime to aluminum-nickel alloy is 1 mol: 120 g, and the aluminum-nickel alloy is added in multiple batches at 0°C. The concentration of sodium hydroxide in the ethanol-alkali solution is 5 mol / L. After the system stabilizes, the reaction is carried out at room temperature for 10-12 h.

8. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S5, the ratio of pyrazole carboxylic acid to oxalyl chloride is 1 mol: 1.2 mol, and the entire process is waterproof.

9. The monoterpene-containing pyrazolyl derivative according to claim 2, its preparation method and application, characterized in that, In step S6, the ratio of oxime or amine to triethylamine is 1 mol: 200 mL. After the reaction is complete, the product is washed sequentially with distilled water, saturated sodium carbonate, and saturated brine. After drying, the product is purified by column chromatography to obtain the pyrazolyl derivative containing monoterpenes.

10. The use of the monoterpene-containing pyrazolyl derivatives according to any one of claims 1-9 in the control of plant pathogenic fungi.

Images