Synthesis method and application of C2-substituted dihydroquinoline derivative

Abstract

The invention discloses a synthesis method and application of a C2-substituted dihydroquinoline derivative, and the method comprises the following steps: mixing a thiourea derivative (I), an olefin (II), a photosensitizer, an inorganic base catalyst, an organic phosphine small molecule and a solvent, and reacting for 16-24 hours under the conditions of room temperature and illumination to obtain the C2-substituted dihydroquinoline derivative (III). The method has the advantages that the raw materials are stable and easy to prepare; reaction conditions are mild, and experimental operation is simple; the chemical selectivity and the functional group tolerance are good, and the method is a green chemical synthesis method with a relatively good application prospect. An activity experiment result shows that the synthesized C2-substituted dihydroquinoline derivative has a very good inhibition effect on the growth of plant pathogenic fungi.

Description

Technical Field

[0001] The invention belongs to the technical field of drug synthesis and relates to a synthesis method and application of a C2-substituted dihydroquinoline derivative. Background Art

[0002] C2-substituted dihydroquinolines, as an important class of organic synthesis intermediates, show great application potential in medicinal chemistry and natural product synthesis. Their traditional synthesis methods are mainly achieved through direct reduction or nucleophilic addition reactions of quinoline, but these methods often have problems such as harsh reaction conditions, low yields or limited substrate range. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing C2-substituted dihydroquinoline derivatives. The method adopts cheap raw materials and realizes the synthesis of dihydroquinoline derivatives by a one-pot method. The method is green, economical and efficient, and provides a new idea for the design and synthesis of new drug active molecules.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for synthesizing a C2-substituted dihydroquinoline derivative comprises: using a thiourea derivative (I) and an olefin (II) as raw materials in an organic solvent, adding an organic phosphine small molecule as an additive, and a photosensitizer and an inorganic base as a catalyst, reacting for 16 to 24 hours at room temperature and under illumination conditions to obtain the C2-substituted dihydroquinoline derivative (III), wherein the structural formulas of formula I, formula II and formula III are as follows:

[0006]

[0007] Among them, R1 is at least one selected from hydrogen, halogen, alkyl, phenyl, alkoxy, carbonyl, aldehyde, carboxyl, cyano, and alkanoyloxy; R2, R3, R4, and R5 are each independently selected from one of hydrogen, alkyl, aryl, alkoxy, siloxy, cycloalkyl, ester, and heterocyclic substituents.

[0008] Preferably, the photosensitizer is (Ir[dF(CF3)ppy]2(dtbpy))PF6, [Ir(dtbbpy)(ppy)2]PF6 or [Ir(dtbbpy)(ppy)2][PF6].

[0009] Preferably, the organic phosphine small molecule is triphenylphosphine, diphenylmethylphosphine or diphenylethoxyphosphine.

[0010] Preferably, the inorganic base is dipotassium hydrogen phosphate, potassium dihydrogen phosphate or potassium tert-butoxide.

[0011] Preferably, the organic solvent is 1,2-dichloroethane, dichloromethane or toluene.

[0012] Preferably, the molar ratio of the thiourea derivative to the olefin is 1:2; the molar ratio of the thiourea derivative to the photosensitizer is 1:0.01.

[0013] Preferably, the illumination condition is blue light, and more preferably, the wavelength of the illumination condition is 450-460 nm.

[0014] Furthermore, the reaction system is subjected to separation and purification post-treatment. The reaction system is concentrated and then separated and purified by column chromatography on silica gel. The eluent is a mixture of petroleum ether and ethyl acetate. The volume ratio of the petroleum ether to the ethyl acetate is 20 to 2:1. The eluent is collected and the solvent is evaporated to obtain the C2-substituted dihydroquinoline derivative.

[0015] Another object of the present invention is to overcome the deficiencies in the prior art and provide a C2-substituted dihydroquinoline derivative for use in controlling plant fungi in agriculture or forestry, wherein the plant fungi include one or more of Sclerotinia sclerotiorum, Psoralea corylifolia, Cysticercus chrysanthemi and Rhizoctonia solani.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention utilizes photosensitizer and inorganic base as catalysts to catalyze thiourea derivatives and olefins, and uses small organic phosphine molecules as desulfurization agents to efficiently synthesize a series of dihydroquinoline derivatives with potential pharmaceutical activity through free radical reactions. Compared with the existing methods, the synthesis method of the present invention has stable raw materials and is easy to prepare, mild reaction conditions, simple experimental operation, good chemical selectivity and functional group tolerance. It is a green chemical synthesis method with good application prospects, and provides a new idea for the design and synthesis of new pharmaceutical active molecules.

[0018] (2) The present invention discloses a C2-substituted dihydroquinoline derivative for use in preventing and controlling plant fungi in agriculture or forestry, and shows good effects in preventing and controlling rapeseed sclerotinia, wheat fusarium, apple rot and sugarcane pineapple pathogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0020] Figure 1 is the general reaction formula of the compound;

[0021] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of compound IIIa prepared in Example 1;

[0022] Figure 3 Compound III prepared in Example 1 a The carbon NMR spectrum of

[0023] Figure 4 The hydrogen nuclear magnetic resonance spectrum of compound IIIb prepared in Example 2 is:

[0024] Figure 5 The carbon NMR spectrum of compound IIIb prepared in Example 2;

[0025] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of compound IIIc prepared in Example 3;

[0026] Figure 7 The carbon NMR spectrum of compound IIIc prepared in Example 3;

[0027] Figure 8 The NMR fluorine spectrum of compound IIIc prepared in Example 3;

[0028] Fig. 9 This is the hydrogen nuclear magnetic resonance spectrum of compound IIId prepared in Example 4;

[0029] Fig.10 The carbon NMR spectrum of compound IIId prepared in Example 4;

[0030] Fig.11 This is the hydrogen nuclear magnetic resonance spectrum of compound IIIe prepared in Example 5;

[0031] Fig.12 This is the carbon NMR spectrum of compound IIIe prepared in Example 5. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0035] Example 1

[0036] 1-Cyclohexyl-3-phenylthiourea Ia (0.1mmol, 1.0equiv., 23.4mg), benzyl acrylate IIa (0.2mmol, 2.0equiv., 30μL), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1mol%, 1.1mg), triphenylphosphine (0.15mmol, 1.5equiv., 39.4mg), dipotassium hydrogen phosphate (0.2mmol, 2.0equiv., 34.8mg) and 1,2-dichloroethane (2mL, 0.05M) were added to a 4mL transparent glass vial equipped with a magnetic. The vial was placed under blue light and reacted at room temperature for 16h. The reaction mixture was monitored by TLC until the thiourea raw material was consumed. After the reaction was completed, the reaction was purified by column chromatography to obtain 30.0mg of a yellow oily product IIIa, with a yield of 83% calculated based on 1-cyclohexyl-3-phenylthiourea. The structural formula of product IIIa is as follows:

[0037]

[0038] Characterization data: 1 H NMR (400MHz, Chloroform-d) δ7.37-7.32 (m, 3H), 7.29-7.27 (m, 2H), 7.21 (t, J=7. 3Hz, 2H), 7.12 (d, J = 7.9Hz, 1H), 6.94 (t, J = 7.4Hz, 1H), 5.16 (d, J = 12.5Hz, 1H), 5.1 0(d,J=12.5Hz,1H),4.46(s,1H),4.06(s,1H),3.82(t,J=5.6Hz,1H),2.61-2.51(m ,2H), 2.10-2.00(m, 2H), 1.77-1.65(m, 3H), 1.52-1.39(m,2H), 1.26-1.14(m, 3H); 13C NMR (101MHz, Chloroform-d) δ172.2, 157.4, 146.4, 135.8, 128.7, 128.5, 128.2, 128.1, 127.9 , 124.1, 122.0, 121.8, 66.7, 48.9, 41.7, 33.2, 29.4, 25.8, 24.9 (2C); HRMS (ESI, m / z)calcdfor C 23 H 27 N2O2(M+H) + :363.2067, found:363.2060; R f =0.34 (PE / EA=1:1).

[0039] Example 2

[0040] 1-(4-Chlorophenyl)-3-cyclohexylthiourea Ib (0.1mmol, 1.0equiv., 26.9mg), benzyl acrylate IIb (0.2mmol, 2.0equiv., 30μL), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1mol%, 1.1mg), triphenylphosphine (0.15mmol, 1.5equiv., 39.4mg), dipotassium hydrogen phosphate (0.2mmol, 2.0equiv., 34.8mg) and 1,2-dichloroethane (4mL, 0.025M) were added to a 4mL clear glass vial equipped with a magnetic rod. The vial was placed under blue light and reacted at room temperature for 16h. The reaction mixture was monitored by TLC until the thiourea starting material was consumed. After the reaction was completed, the reaction mixture was purified by column chromatography to obtain 16.6 mg of yellow oily product IIIb, with a yield of 42% based on 1-(4-chlorophenyl)-3-cyclohexylthiourea. The structural formula of product IIIb is as follows:

[0041]

[0042] Characterization data: 1H NMR (400MHz, Chloroform-d) δ7.39-7.33(m, 3H), 7.29-7.27(m, 2H), 7.21-7.14(m, 2H), 7. 03 (d, J = 9.1Hz, 1H), 5.16 (d, J = 12.4Hz, 1H), 5.11 (d, J = 12.4Hz, 1H), 4.48 (s, 1H), 4.03 (s, 1H), 3.76 (t, J = 5.5Hz, 1H), 2.59 (s, 1H), 2.50 (dd, J = 15.3, 6.7Hz, 1H), 2.04 (t, J = 14.4Hz, 2H), 1.74(d,J=7.9Hz, 2H), 1.66(d,J=13.0Hz, 1H), 1.45-1.38(m, 2H), 1.25-1.13(m, 3H); 13 C NMR (101MHz, Chloroform-d) δ171.5, 157.4, 145.2, 135.6, 128.6 (2C), 128.3, 127.9 (2C), 126.5, 125.2, 123.2, 67.0, 49.0, 41.5, 33.1, 29.1, 25.7, 24.9, 24.8; HRMS (ESI, m / z)calcd for C 23 H 26 ClN2O2(M+H) + :397.1678, found:397.1692; R f =0.54 (PE / EA=1:1).

[0043] Example 3

[0044] 1-(4-Trifluoromethylphenyl)-3-cyclohexylthiourea Ic (0.1mmol, 1.0equiv., 30.2mg), benzyl acrylate IIc (0.1mmol, 1.0equiv., 15μL), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1mol%, 1.1mg), triphenylphosphine (0.15mmol, 1.5equiv., 39.4mg), potassium tert-butoxide (0.15mmol, 1.5equiv., 16.8mg) and dichloromethane (2mL, 0.05M) were added to a 4mL clear glass vial equipped with a magnetic rod. The vial was placed under blue light and reacted at room temperature for 18h. The reaction mixture was monitored by TLC until the thiourea starting material was consumed. After the reaction was completed, the reaction mixture was purified by column chromatography to obtain 23.6 mg of yellow oily product IIIc, with a yield of 55% calculated based on 1-(4-trifluoromethylphenyl)-3-cyclohexylthiourea. The structural formula of product IIIc is as follows:

[0045]

[0046] Characterization data: 1 H NMR (400MHz, Chloroform-d) δ7.49-7.45(m,2H), 7.36-7.32(m,3H), 7.25(dd,J =7.3, 2.3Hz, 2H), 7.16 (d, J = 8.5Hz, 1H), 5.13 (s, 2H), 4.63 (s, 1H), 4.08 (s, 1H), 3.83 (t, J=5.7Hz, 1H), 2.65 (dd, J=15.4, 4.1Hz, 1H), 2.56 (dd, J=15.3, 6.7Hz, 1 H), 2.08-1.96 (m, 2H), 1.81-1.62 (m, 3H), 1.51-1.38 (m, 2H), 1.26-1.10 (m, 3H); 13 C NMR (101MHz, Chloroform-d) δ171.4, 158.6, 149.7, 135.4, 128.6, 128.3, 127.8, 125.8, 1 25.4, 124.0, 123.6, 123.3, 123.0, 121.9, 67.0, 49.1, 41.3, 33.0, 29.0, 25.7, 24.9, 24.8; 19 F NMR (377MHz, Chloroform-d) δ-61.4; HRMS (ESI, m / z)calcd for C 24 H 26 F3N2O2(M+H) + :431.1941, found:431.1932; R f =0.56 (PE / EA=4:1).

[0047] Example 4

[0048] 1-Cyclohexyl-3-phenylthiourea Id (0.1mmol, 1.0equiv., 23.4mg), acrylonitrile IId (0.2mmol, 2.0equiv., 13μL), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1mol%, 1.1mg), triphenylphosphine (0.15mmol, 1.5equiv., 39.4mg), dipotassium hydrogen phosphate (0.2mmol, 2.0equiv., 34.8mg) and 1,2-dichloroethane (2mL, 0.05M) were added to a 4mL transparent glass vial equipped with a magnetic rod. The vial was placed under blue light and reacted at room temperature for 24h. The reaction mixture was monitored by TLC until the thiourea raw material was consumed. After the reaction was completed, the reaction was purified by column chromatography to obtain 13.2mg of yellow oily product IIId, with a yield of 52% calculated based on 1-cyclohexyl-3-phenylthiourea. The structural formula of product IIId is as follows:

[0049]

[0050] Characterization data: 1 H NMR (400MHz, Chloroform-d) δ7.34 (d, J=7.5Hz, 1H), 7.29 (d, J=6.3Hz, 1H), 7.14 (d, J=7.9Hz, 1H), 7.02 (t, J=7.5Hz, 1H), 4.44 (s, 1H), 4.08-4.03 (m, 2H) , 2.67-2.63 (m, 1H), 2.60 (s, 1H), 2.10 (t, J = 5.4Hz, 2H), 1.77 (d, J = 13.6Hz, 2 H), 1.68 (d, J=13.2Hz, 1H), 1.46 (q, J=14.1, 13.1Hz, 2H), 1.26-1.20 (m, 3H); 13 C NMR (101MHz, Chloroform-d) δ155.2, 145.8, 129.7, 126.0, 124.5, 122.8, 119.3, 118.3, 49.2, 33.1, 30.8, 28.4, 25.7, 24.8 (2C); HRMS (ESI, m / z)calcd for C 16 H 20 N3(M+H) + :254.1652, found:254.1645; R f =0.43 (PE / EA=3:1).

[0051] Example 5

[0052] 1-(Adamantane-2-yl)-3-phenylthiourea Ie (0.1 mmol, 1.0 equiv., 28.6 mg), benzyl acrylate IIe (0.2 mmol, 2.0 equiv., 30 μL), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1 mol%, 1.1 mg), triphenylphosphine (0.15 mmol, 1.5 equiv., 39.4 mg), dipotassium hydrogen phosphate (0.2 mmol, 2.0 equiv., 34.8 mg) and 1,2-dichloroethane (2 mL, 0.05 M) were added to a 4 mL clear glass vial equipped with a magnetic rod. The vial was placed under blue light and reacted at room temperature for 20 h. The reaction mixture was monitored by TLC until the thiourea starting material was consumed. After the reaction was completed, the reaction mixture was purified by column chromatography to obtain 22.8 mg of yellow oily product IIIe, with a yield of 55% calculated based on 1-(adamantan-2-yl)-3-phenylthiourea. The structural formula of product IIIe is as follows:

[0053]

[0054] Characterization data: 1 H NMR (400MHz, Chloroform-d) δ7.39-7.34 (m, 3H), 7.32 (d, J = 8.2Hz, 2H), 7.28- 7.19 (m, 2H), 7.12 (d, J = 7.8Hz, 1H), 6.94 (t, J = 7.4Hz, 1H), 5.19 (d, J = 12.5Hz, 1H), 5.11 (d, J=12.5Hz, 1H), 3.80 (t, J=5.5Hz, 1H), 2.56 (dd, J=15.3, 4.6Hz, 1 H), 2.49 (dd, J=15.2, 6.6Hz, 1H), 2.23-2.18 (m, 6H), 2.14 (s, 3H), 1.75 (s, 6H); 13 C NMR (101MHz, Chloroform-d) δ172.3, 156.8, 146.4, 135.9, 128.6, 128.5, 128.2, 128. 0(2C), 124.4, 121.9, 121.3, 66.7, 52.7, 42.0, 41.8, 36.6, 29.7; HRMS (ESI, m / z)calcd for C 27 H 31 N2O2(M+H) + :415.2380, found:415.2372; R f =0.47 (PE / EA=6:1).

[0055] Example 6-50

[0056] Thiourea derivative I (0.1mmol, 1.0equiv.), olefin II (0.2mmol, 2.0equiv.), (Ir[dF(CF3)ppy]2(dtbpy))PF6 (1mol%, 1.1mg), triphenylphosphine (0.15mmol, 1.5equiv.), dipotassium hydrogen phosphate (0.2mmol, 2.0equiv.) and 1,2-dichloroethane (0.05M) were added to a 4mL transparent glass vial equipped with a magnetic rod. The vial was placed under blue light and reacted at room temperature for 16 to 24h. The reaction mixture was monitored by TLC until the thiourea raw material was consumed. After the reaction was completed, the reaction was purified by column chromatography to obtain the target products IIIf to IIIax.

[0057] The general reaction formula is Figure 1 The reaction products and results of different substrate selections are shown in Table 1.

[0058] Table 1 Reaction products and results of different substrate selections

[0059]

[0060] Table 1 (continued)

[0061]

[0062] Table 1 (continued)

[0063]

[0064] Embodiment 51:

[0065] The compounds IIIa-IIIe prepared in Examples 1-5 were subjected to biological activity test experiments, and the specific process is as follows: The plant fungi used in this experiment are strains stored at 4°C in the laboratory, including rapeseed sclerotinia, apple rot pathogen, golden shell cystspore and rice sheath blight pathogen. The culture medium used is potato agar glucose culture medium (PDA for short). PDA culture medium formula: 200g potatoes (peeled), 20g glucose, 15g agar, 1000mL distilled water, preparation method: wash and peel the potatoes, weigh 200g and cut into small pieces, add water and boil (boil for 20-30 minutes, can be pierced by a glass rod), filter into a beaker with eight layers of gauze, add 15-20g agar according to experimental needs, add 20g glucose, stir evenly, cool slightly after fully dissolved, add water to 1000mL, sterilize at 121°C for 15 minutes after packaging, and cool for use.

[0066] Experimental method: Growth rate method was used.

[0067] (1) First, culture the four plant fungi on a PDA plate at 25°C for about 3-6 days for later use;

[0068] (2) Heat and melt the PDA culture medium, cool it to 45-50°C, add 250 μL of 10 g / L concentration of the test compound IIIa-IIIe to prepare a culture medium containing 50 mg / L of the drug solution, and pour it into culture dishes to cool. Boscalid is used as a positive control.

[0069] (3) Using sterile techniques, use a cork puncher to punch a circular bacterial cake (0.50 cm in diameter) at the edge of the mycelium of each cultured strain (the growth conditions should be as consistent as possible), then use an inoculation needle to pick it up to the center of the drug-containing plate, and then place the culture dish upside down in an incubator (28°C) for incubation;

[0070] (4) Observe and measure the growth of mycelium at different times after treatment, measure the diameter using the cross method, process the data, and calculate the inhibition rate;

[0071] (5) Inhibition rate (%) = (control mycelium diameter - treated mycelium diameter) / (control mycelium diameter - 0.5) × 100;

[0072] (6) Each treatment was repeated 3 times.

[0073] The test results are shown in Table 2.

[0074] Table 2 Results of the inhibitory activity test of C2-substituted dihydroquinoline derivatives against four agricultural pathogenic fungi

[0075]

[0076] The results of the bactericidal activity determination of the experimental group IIIa-IIIe and the control agent boscalid are shown in Table 2. From the results in Table 2, it can be seen that at a concentration of 50 mg / L, compounds IIIa-IIIe showed different degrees of antibacterial activity against four plant fungi, among which compounds IIIa and IIIb could effectively inhibit the growth of wheat fusarium, with an inhibition rate of 64-73%; among the four pathogenic fungi tested, IIIc had an inhibition rate of 37.89% against apple rot pathogen; compound IIId had good antibacterial activity against sugarcane pineapple pathogen, with an inhibition rate of 20.06%.

[0077] The C2-substituted dihydroquinoline derivatives of the present invention have obvious structural differences and distinct chemical structural characteristics, and show good effects on preventing and treating wheat fusarium. They can be used to prevent and treat fungal diseases of agricultural or forestry plants. The preparation method of the compound is simple, the yield is high, and the product has stable properties.

[0078] The above description is only 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing a C2-substituted dihydroquinoline derivative, characterized in that: In an organic solvent, a thiourea derivative (I) and an olefin (II) are used as raw materials, an organic phosphine small molecule is added as an additive, and a photosensitizer and an inorganic base are added as a catalyst, and the reaction is carried out at room temperature and under light conditions for 16 to 24 hours to obtain the C2-substituted dihydroquinoline derivative (III). The structural formulas of the formula I, formula II, and formula III are as follows: Among them, R1 is selected from at least one of hydrogen, halogen, alkyl, phenyl, alkoxy, carbonyl, aldehyde, carboxyl, cyano, and alkanoyloxy; R2, R3, R4, and R5 are each independently selected from one of hydrogen, alkyl, aryl, alkoxy, siloxy, cycloalkyl, ester, and heterocyclic substituents.

2. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The photosensitizer is (Ir[dF(CF3)ppy]2(dtbpy))PF6, [Ir(dtbbpy)(ppy)2]PF6 or [Ir(dtbbpy)(ppy)2][PF6].

3. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The organic phosphine small molecule is triphenylphosphine, diphenylmethylphosphine or diphenylethoxyphosphine.

4. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The inorganic base is dipotassium hydrogen phosphate, potassium dihydrogen phosphate or potassium tert-butoxide.

5. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The organic solvent is 1,2-dichloroethane, dichloromethane or toluene.

6. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The molar ratio of the thiourea derivative to the olefin is 1:2; the molar ratio of the thiourea derivative to the photosensitizer is 1:0.

01.

7. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The lighting condition is blue light.

8. The method for synthesizing a C2-substituted dihydroquinoline derivative according to claim 1, characterized in that The reaction system is subjected to post-treatment of separation and purification. The reaction system is concentrated and then separated and purified by column chromatography on silica gel. The eluent is a mixture of petroleum ether and ethyl acetate. The volume ratio of the petroleum ether to the ethyl acetate is 20 to 2:

1. The eluent is collected and the solvent is evaporated to obtain the C2-substituted dihydroquinoline derivative.

9. Use of a C2-substituted dihydroquinoline derivative prepared by the preparation method according to claim 1 in preventing and controlling plant fungi in agriculture or forestry.

10. The use according to claim 9, characterized in that The plant fungi are one or more of rapeseed sclerotinia pathogen, wheat fusarium rust pathogen, apple rot pathogen and sugarcane pineapple pathogen.

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