Method for photocatalytic synthesis of tryptanthrin compound and application of tryptanthrin compound

Abstract

The invention relates to the technical field of organic synthesis and catalysis, in particular to a method for photocatalytic synthesis of tryptanthrin compounds and application of the tryptanthrin compounds. According to the specific technical scheme, the method for photocatalytic synthesis of the tryptanthrin compound comprises the steps that under the action of a photocatalyst, indole or substituted indole serves as a raw material, an oxidizing agent, alkali and an additive are added, a reaction is conducted under the illumination condition, and after the reaction is completed, a target product is obtained. The method has the advantages of cheap and easily available raw materials, no water-free and oxygen-free operation, no need of participation of complex ligand in reaction, no need of high temperature, no need of catalysis of noble metal, small use amount of the used catalyst, low cost, and conformity to the green and environment-friendly concept. By investigating the biological activity of the compounds, an important scientific basis is provided for research, development and creation of new pesticides.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis and catalysis, and in particular to a method for photocatalytic synthesis of tryptanthrin compounds and application thereof. Background Art

[0002] Natural products have the advantages of abundant sources, easy degradation, and low toxicity, and have been widely used in the fields of medicine, pesticides, materials, etc. Among them, tryptanthrin compounds (indolequinazoline-6,12-dione) are an important class of alkaloids with the unique characteristics of indolequinazoline structure. Since their first extraction from the leaves of Indigofera serrata in 1979, tryptanthrin and its analogs have attracted great interest due to their broad spectrum of biological activities in applications such as antibacterial, anti-inflammatory, antitumor, antiviral, and immunomodulatory. Therefore, it is of great significance to synthesize tryptanthrin compounds economically and efficiently under environmentally friendly and mild reaction conditions.

[0003] Currently, tryptanthrin can be obtained through self-condensation reactions using isatin as the starting material, including electrocatalytic reduction and oxidation reactions using various oxidants, such as tert-butyl hydroperoxide (TBHP) and potassium permanganate. At the same time, tryptanthrin derivatives can also be obtained through cross-condensation reactions using isatin or isatinic anhydride in the presence of metal complexes at high temperatures. In recent years, methods for synthesizing tryptanthrin compounds using transition metals such as copper and cobalt to catalyze indoles with different substituents have been reported. Although the above methods have made significant progress in this field, some problems still exist to varying degrees, including harsh reaction conditions (high temperature, toxic solvents), the use of metal oxidants, the use of chemically equivalent strong oxidants, low yields, and the need to add specific expensive metal ligands for catalysis. These factors lead to high reaction costs, high pollution, and incompatibility with the concept of green environmental protection.

[0004] Visible light is a clean, environmentally friendly, and renewable resource. Visible light catalysis, in line with the principles of green synthesis, environmental friendliness, and sustainable development, has attracted widespread attention in the field of organic synthesis. In 2016, Zhang et al. reported an aerobic photocatalytic reaction method for the synthesis of tryptanthrin from indole in the presence of a dicyanopyrazine-derived chromophore (DPZ) photocatalyst. In 2018, Hou et al. reported the cross-condensation / self-condensation of isatin or isatin with isatoic anhydride in the presence of rose Bengal under 23W fluorescent light to yield a series of tryptanthrin derivatives. While these methods have introduced greener visible light catalysis and achieved significant progress, they still utilize difficult-to-prepare substrates and expensive photocatalysts. Therefore, the development of an environmentally friendly and sustainable method for the synthesis of tryptanthrin and its derivatives under visible light using readily available raw materials and inexpensive photocatalysts is urgently needed. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for photocatalytic synthesis of tryptanthrin compounds and its application.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] The invention discloses a method for photocatalytically synthesizing tryptanthrin. Under the action of a photocatalyst, indole or substituted indole is used as a raw material, an oxidant, a base and an additive are added, and the reaction is carried out under light conditions. After the reaction is complete, the target product is obtained.

[0008] Preferably, the photocatalyst is any one of Acid Red 87, 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile, Bengal Red, tris(2,2'-bipyrazine)ruthenium di(hexafluoroborate), bis[2-(2,4-difluorophenyl)-5-trifluoromethylpyridine][2-2"-bi(4-tert-butylpyridine)]iridium(III) hexafluorophosphate, and 3,6,-di-tert-butyl-9-mesityl-10-phenylacridine-10-tetrafluoroborate.

[0009] Preferably, the oxidant is any one of oxygen, ferric chloride, copper acetate, hydrogen peroxide, tert-butyl hydroperoxide and m-chloroperbenzoic acid.

[0010] Preferably, the base is any one of cesium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium acetate, potassium carbonate, potassium phosphate, triethylamine, and 1,4-diazabicyclo[2.2.2]octane.

[0011] Preferably, the additive is any one of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, 2,2,6,6-tetramethylpiperidinium oxide and azobisisobutyronitrile.

[0012] Preferably, the molar ratio of the indole or substituted indole to the photocatalyst, the base, and the additive is 1:0.01-0.10, 1:2.0-4.0, and 1:0.6-1.6, respectively.

[0013] Preferably, the reaction is carried out in the presence of a solvent, wherein the solvent is any one of ethyl acetate, dioxane, dichloroethane, dichloromethane, toluene, n-hexane, acetonitrile, water, and a dioxane aqueous solution, a tetrahydrofuran aqueous solution, a dichloroethane aqueous solution, and an acetonitrile aqueous solution, and the concentration of the indole or substituted indole in the solvent is 0.02 to 0.10 mol / L.

[0014] Correspondingly, a tryptanthrin compound has the structural formula shown in the following formula (I):

[0015]

[0016] wherein R1 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, or optionally substituted or unsubstituted benzyl;

[0017] R2 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, and optionally substituted or unsubstituted benzyl.

[0018] Accordingly, a composition comprises a compound represented by formula (I) or a stereoisomer thereof or a salt thereof or a solvate thereof and an agriculturally usable adjuvant, fungicide, insecticide or herbicide.

[0019] Correspondingly, the use of the compound represented by formula (I) or the composition in preventing and controlling agricultural pests and diseases, wherein the agricultural diseases are plant bacterial diseases and plant fungal diseases; the bacterial diseases are any one of rice bacterial blight, citrus canker, kiwi canker, cucumber bacterial blight, konjac bacterial blight, citrus canker, tobacco bacterial wilt, grape canker, tomato canker, kiwi canker, and apple canker; and the plant fungal diseases are any one of Botrytis cinerea, Sclerotinia sclerotiorum, Verticillium dahliae of eggplant, Fusarium wilt of pepper, Gibberella oxysporum, Sheath blight of rice, Alternaria alternata of tobacco, Colletotrichum gloeosporioides, Colletotrichum tea tree and Colletotrichum sorghum.

[0020] The present invention has the following beneficial effects:

[0021] 1. The raw materials of the present invention are cheap and easy to obtain, do not involve anhydrous and oxygen-free operation, do not require complex ligands to participate in the reaction, do not require high temperature, do not require precious metal catalysis, and use a small amount of catalyst, low cost, and high yield. The operation is simple and convenient, safe and reliable, and conforms to the concept of green environmental protection.

[0022] 2. The present invention also discloses that the compound represented by formula (I) can prevent and treat agricultural diseases, which are plant bacterial diseases. Bacterial diseases mainly include rice bacterial blight, citrus canker, and kiwifruit canker. The fungal diseases mainly include Botrytis cinerea, Sclerotinia sclerotiorum, Verticillium dahliae, Fusarium wilt, Gibberella oxysporum, and Rhizoctonia solani. When using the compound represented by formula (I) or a solvate thereof, it can be directly applied to the pest or its living environment, or directly contacted with the plant, which is simple and convenient to use. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0025] The present invention discloses a method for photocatalytically synthesizing tryptanthrin compounds, wherein the reaction route of tryptanthrin is:

[0026]

[0027] The specific reaction process is as follows: indole or substituted indole is used as the raw material, an oxidant, a base, and an additive are added under the action of a photocatalyst, and the reaction is carried out under light conditions. After the reaction is complete, the target product is obtained. The light source is a blue light lamp, preferably a 9W blue light lamp, and the entire reaction is carried out at room temperature.

[0028] Furthermore, the entire reaction is carried out in the presence of a solvent, wherein the solvent is any one of ethyl acetate (EA), dioxane, dichloroethane (DCE), dichloromethane (DCM), toluene, n-hexane, acetonitrile (MeCN), water, and a dioxane aqueous solution, a tetrahydrofuran (THF) aqueous solution, a dichloroethane (DCE) aqueous solution, and an acetonitrile (MeCN) aqueous solution, and the concentration of the indole or substituted indole in the solvent is 0.02 to 0.10 mol / L. Specifically: Dioxane:H2O=10:1, v / v, THF:H2O=10:1, v / v, DCE:H2O=10:1, v / v, and MeCN:H2O=1 to 30:1, v / v.

[0029] Furthermore, the molar ratio of the indole or substituted indole to the photocatalyst, the base, and the additive is 1:0.01-0.10, 1:2.0-4.0, and 1:0.6-1.6, respectively.

[0030] Specifically, the photocatalyst is acid red 87 (Eosin Y), 2,4,5,6-tetrakis (9-carbazolyl) -isophthalonitrile (4CzIPN), Bengal red rose (Rose Bengal), tris (2,2'-bipyrazine) ruthenium di (hexafluoroborate) salt (Ru (bpz) 3 (PF6) 2), bis [2- (2,4-difluorophenyl) -5-trifluoromethylpyridine] [2-2 "-bi (4-tert-butylpyridine)] iridium (III) hexafluorophosphate (Ir [dF (CF3) ppy] 2 (dtbbpy) PF6), 3,6, -di-tert-butyl-9-mesityl-10-phenylacridine-10-tetrafluoroborate (mes-Acr + )

[0031] The oxidant is any one of oxygen (O2), ferric chloride (FeCl3), copper acetate (Cu(OAc)2), hydrogen peroxide (H2O2), tert-butyl hydroperoxide (TBHP) and meta-chloroperbenzoic acid (M-CPBA).

[0032] The base is any one of cesium carbonate (Cs2CO3), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), sodium hydroxide (NaOH), sodium acetate (NaOAc), potassium carbonate (K2CO3), potassium phosphate (K2PO4), triethylamine (Et3N), and 1,4-diazabicyclo[2.2.2]octane (DABCO).

[0033] The additive is any one of tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), tetrabutylammonium iodide (TBAI), 2,2,6,6-tetramethylpiperidinium oxide (TEMPO) and azobisisobutyronitrile (AIBN).

[0034] The present invention discloses a tryptanthrin compound synthesized by the above-mentioned synthesis method, and its structural formula is shown in the following formula (I):

[0035]

[0036] wherein R1 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, or optionally substituted or unsubstituted benzyl;

[0037] R2 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, and optionally substituted or unsubstituted benzyl.

[0038] Furthermore, R1 is one or more of hydrogen, halogen, unsubstituted alkyl, and unsubstituted ester; R2 is one or more of hydrogen, halogen, unsubstituted alkyl, and unsubstituted ester.

[0039] The present invention discloses a composition comprising a compound represented by formula (I) or a stereoisomer thereof or a salt thereof or a solvate thereof, and an agriculturally useful adjuvant, fungicide, insecticide, or herbicide. The composition is in the form of an emulsifiable concentrate, a dust, a wettable powder, a granule, an aqueous solution, a suspension, an ultra-low volume spray, a soluble powder, a microcapsule, a smoke concentrate, an aqueous emulsion, or a water-dispersible granule.

[0040] The present invention discloses the use of a compound represented by formula (I) or the composition in preventing and controlling agricultural pests and diseases, wherein the agricultural diseases are plant bacterial diseases and plant fungal diseases; the bacterial disease is any one of rice bacterial blight, citrus canker, kiwifruit canker, cucumber bacterial blight, konjac bacterial blight, citrus canker, tobacco bacterial wilt, grape canker, tomato canker, kiwifruit canker, and apple canker; and the plant fungal disease is any one of Botrytis cinerea, Sclerotinia sclerotiorum, Verticillium wilt of eggplant, Fusarium wilt of pepper, Gibberella tataricum, Sheath blight of rice, Alternaria alternata, Colletotrichum gloeosporioides, Colletotrichum teaifolia, and Colletotrichum kaoliang. When used, the compound represented by formula (I) or the composition is applied to the pest or its living environment, or the composition is directly contacted with the plant.

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] In order to further illustrate the synthesis of tryptanthrin compounds in the present invention, the present invention selectively synthesized the following substances, and described the synthesis process of each compound in conjunction with specific examples.

[0043]

[0044] Example 1

[0045] The synthetic route of tryptanthrin 3a is:

[0046]

[0047] 0.1 mmol of indole, 0.025 mmol of rose bengal, 1.25 mmol of cesium carbonate, and 0.07 mmol of TEMPO were weighed into a 6-mL colorless, transparent reaction flask. 2 mL of acetonitrile aqueous solution (20:1, MeCN:H2O, v / v) was added. The mixture was then irradiated with a 9 W blue light lamp under an oxygen atmosphere and stirred at room temperature. The reaction progress was monitored by TLC. The reaction was complete after approximately 12 h. Separation and purification by column chromatography (petroleum ether:dichloromethane = 2:5) afforded tryptanthrin 3a as a yellow solid in a 78% yield.

[0048] Its NMR data are:

[0049] indolo[2,1-b]quinazoline-6,12-dione(3a).Ayellow solid,yield 78%; 1 HNMR(400MHz,Chloroform-d)δ8.59(d,J=8.1Hz,1H),8.40(dd,J=7.9,1.6Hz,1H),8.01(d,J=8.1Hz,1H),7.9 0(d,J=7.6Hz,1H),7.84(t,J=7.6Hz,1H),7.77(t,J=7.8Hz,1H),7.66(t,J=7.6Hz,1H),7.41(t,J=7.5Hz,1H). 13 C NMR(101MHz,Chloroform-d)δ182.7,158.2,146.7,146.4,144.4,138.4,135.3,130.8,130.4,127.7,127.3,125.5,123.8,122.0,118.1.HRMS(ESI)[M+H] + calcd for C 15 H8O2N2:249.0659,found:249.0654.

[0050] Example 2

[0051] 1. The reaction conditions were the same as in Example 1, but different photocatalysts were used. The product yields are shown in Table 1. As shown in Table 1, when other reaction conditions remained unchanged and Rose Bengal was used as the photocatalyst, the product yield was the highest.

[0052] Table 1 Product yields under different photocatalysts

[0053]

[0054] The structural formula of some photocatalysts is:

[0055]

[0056] 2. The reaction conditions were the same as in Example 1, but the amount of photocatalyst Rose Bengal was changed. The product yields are shown in Table 2. As shown in Table 2, when other reaction conditions remained unchanged and the amount of photocatalyst Rose Bengal was 0.05 equivalents, the product yield was the highest.

[0057] Table 2 Product yields at different photocatalyst dosages

[0058]

[0059] Example 3

[0060] The reaction conditions were the same as in Example 1, but different oxidants were used. The product yields are shown in Table 3. As shown in Table 3, when other reaction conditions remained unchanged and the oxidant was oxygen, the product yield was the highest.

[0061] Table 3 Product yields with different oxidants

[0062] oxidants <![CDATA[O2]]> <![CDATA[FeCl3]]> <![CDATA[Cu(OAc)2]]> <![CDATA[H2O2]]> TBHP M-CPBA Yield (%) 45％ 0％ 0％ 19％ 0％ 32％

[0063] Example 4

[0064] 1. The reaction conditions were the same as in Example 1, but different base catalysts were used. The product yields are shown in Table 4. As shown in Table 4, when other reaction conditions remained unchanged and the base catalyst was cesium carbonate, the product yield was the highest.

[0065] Table 4 Product yields of products with different base catalysts

[0066] base catalyst <![CDATA[Cs2CO3]]> <![CDATA[NaHCO3]]> <![CDATA[Na2CO3]]> NaOH NaOAc <![CDATA[K2CO3]]> <![CDATA[K2PO4]]> <![CDATA[Et3N]]> DABCO Yield (%) 45％ 20％ 30％ 0％ 21％ 39％ 34％ 21％ 18％

[0067] 2. The reaction conditions were the same as in Example 1, but the amount of the base catalyst was changed. The product yields are shown in Table 5. As shown in Table 5, when other reaction conditions remained unchanged and the amount of the base catalyst was 2.5 equivalents, the product yield was the highest.

[0068] Table 5 Product yields at different alkali catalyst dosages

[0069]

[0070] Example 5

[0071] 1. The reaction conditions were the same as in Example 1, but different solvents were used. The product yields are shown in Table 6. As shown in Table 6, when other reaction conditions remained unchanged and the solvent was acetonitrile:water (10:1, v / v), the product yield was the highest.

[0072] Table 6 Product yields in different solvents

[0073]

[0074] 2. The reaction conditions were the same as in Example 1, but the ratio of the solvent acetonitrile to water was changed. The product yields are shown in Table 7. As shown in Table 7, when other reaction conditions remained unchanged and the solvent was acetonitrile:water (20:1, v / v), the product yield was the highest.

[0075] Table 7 Product yields at different solvent ratios

[0076]

[0077] Example 6

[0078] 1. The reaction conditions were the same as in Example 1, but different additives were used. The product yields are shown in Table 8. As shown in Table 8, when other reaction conditions remained unchanged and TEMPO was used as the additive, the product yield was the highest.

[0079] Table 8 Product yields with different additives

[0080] additive 1.0TBAC 1.0TBAB 1.0TBAI 1.0TEMPO 1.0AIBN Yield (%) 37％ 40％ 39％ 66％ 47％

[0081] 2. The reaction conditions were the same as in Example 1, but the amount of the additive was changed. The product yields are shown in Table 9. As shown in Table 9, when other reaction conditions remained unchanged and the amount of the additive was 1.4 equivalents, the product yield was the highest.

[0082] Table 9 Product yields at different additive dosages

[0083]

[0084] Example 7

[0085] Under the same conditions as in Example 1, different compounds were prepared by replacing the indole with different substituents, as shown in Table 10 below.

[0086] Table 10 Tryptanthrin compounds prepared from different substituted indoles

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] Example 8

[0095] Antibacterial activity of compounds (taking Xanthomonas oryzae, Xanthomonas citrifolia, and Xanthomonas kiwifruit as examples)

[0096] 1. Experimental Methods

[0097] Xanthomonas oryzae pv.oryzae, Xanthomonas axonopodis pv.citri, and Pseudomonas syringa pv.actinidiae were used as test objects, and the commercial drug thiediazole copper was used as a positive control agent. The minimum inhibitory concentration (MIC) values ​​of all target compounds against Xoo were tested using the NCCLS method. Xoo bacteria were cultured in fresh LB medium and grown to OD 595 =0.6. Then 200 μL of inoculum (OD 595 =0.6 suspension mixed with fresh LB medium at 1:100, v / v) was inoculated on a 96-well microplate. Then, the target compound was dissolved in dimethyl sulfoxide (DMSO), and an equal amount of DMSO was used as a blank control. The sample concentrations were set to 400μg / mL, 200μg / mL, 100μg / mL, 50μg / mL, 25μg / mL, 12.5μg / mL, 6.25μg / mL, 3.125μg / mL, 1.56μg / mL, 0.8μg / mL, and 0.4μg / mL, and the two-fold dilution method was used for processing to ensure that the MIC value was within the test concentration range. Finally, the prepared 96-well microplate was placed in a constant temperature incubator at 28°C for 3 to 4 days. The OD 595 After evaluation, the lowest concentration of the tested compound was the MIC, at which no significant growth was observed.

[0098] 2. Activity Data

[0099] The results are shown in Table 11. As can be seen from Table 11, target compounds 3a, 3g, 3h, 3i, and 4a exhibited good inhibitory activity against Xanthomonas oryzae in vitro. Among them, compound 3i exhibited the best inhibitory activity against Xanthomonas oryzae, with an MIC value of 0.4 μg / mL.

[0100] Table 11 Inhibitory activity (MIC) of the prepared compounds against Xanthomonas oryzae and Xanthomonas citri

[0101]

[0102]

[0103]

[0104] Example 9

[0105] Inhibitory activity of compounds against plant fungal diseases (taking Sclerotinia sclerotiorum, Botrytis cinerea, Gibberella oxysporum, Fusarium wilt, Rhizoctonia solani, and Verticillium dahliae as examples)

[0106] 1. Experimental Methods

[0107] Inhibitory activity of compounds against plant fungal diseases (50 μg / mL)

[0108] The hyphal growth rate method, also known as the toxic medium method, is a common method for determining the toxicity of fungicides. The principle is to mix the test agent with a culture medium and measure the toxicity of the agent by measuring the growth rate of the colonies on the toxic medium.

[0109] In this example, Sclerotinia sclerotiorum, Botrytis cinerea, Gibberella tataricola, Fusarium oxysporum, Rhizoctonia solani, and Verticillium dahliae were used as test objects, and DMSO was used as a blank control. The specific operation is as follows:

[0110] 1) Weigh an appropriate amount of drug according to the test concentration and dissolve it in DMSO (not to exceed 1% of the final toxic potato dextrose agar medium). Then add 0.1% Tween 20 solution to 10 mL. Pour the solution into 90 mL of melted PDA medium, mix thoroughly, and pour into 9 culture dishes for later use.

[0111] 2) Sterilize a puncher (5mm inner diameter) by burning. After cooling, punch holes in the edges of the pre-activated mycelium. Use an inoculating needle to place the mycelial surface in the center of the toxic culture medium. After treatment, incubate the culture at 25°C.

[0112] 3) After the colony diameter of the control group grows to 5.5-6.6 cm, the colony diameters of the control group and each drug treatment group are measured using the cross-cross method;

[0113] 4) The inhibition rate (%) was calculated using the following formula: inhibition rate (%) = (CT) / (C-0.5) × 100; where C is the colony diameter of the control group, T is the colony diameter of the drug-treated group, and 0.5 is the diameter of the inoculated bacterial cake.

[0114] The experimental results of the target compound prepared according to the above method are shown in Table 12.

[0115] As can be seen from the data in Table 12, in in vitro experiments, the compound showed certain inhibitory activity against plant pathogenic fungi (such as Sclerotinia rapae, Botrytis cinerea, Gibberella tataricola, Fusarium wilt, Rhizoctonia solani, and Verticillium dahliae). It showed excellent inhibitory activity against the plant pathogenic fungus Verticillium dahliae, with an EC50 value of 7.4 μg / mL, which was better than the control drug thiabendazole. It also had good inhibitory activity against Colletotrichum sorghumi, but was lower than the positive control drug thiabendazole. Therefore, it can be seen that this type of natural skeleton has extremely high research value in the discovery of new anti-plant pathogenic fungal pesticides.

[0116] Table 12 Inhibitory activity of compounds against plant pathogenic fungi (50 μg / mL)

[0117]

[0118]

[0119] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for photocatalytic synthesis of tryptanthrin compounds, characterized in that: Under the action of a photocatalyst, indole or substituted indole is used as a raw material, an oxidant, a base and an additive are added, and the reaction is carried out under light conditions. After the reaction is complete, the target product is obtained.

2. The synthesis method according to claim 1, characterized in that: The photocatalyst is any one of Acid Red 87, 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile, Bengal rose red, tris(2,2'-bipyrazine)ruthenium di(hexafluoroborate), bis[2-(2,4-difluorophenyl)-5-trifluoromethylpyridine][2-2"-bi(4-tert-butylpyridine)]iridium(III) hexafluorophosphate, and 3,6-di-tert-butyl-9-mesityl-10-phenylacridine-10-tetrafluoroborate.

3. The synthesis method according to claim 1 or 2, characterized in that: The oxidant is any one of oxygen, ferric chloride, cupric acetate, hydrogen peroxide, tert-butyl hydroperoxide and m-chloroperbenzoic acid.

4. The synthesis method according to claim 3, characterized in that: The base is any one of cesium carbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium acetate, potassium carbonate, potassium phosphate, triethylamine, and 1,4-diazabicyclo[2.2.2]octane.

5. The synthesis method according to claim 4, characterized in that: The additive is any one of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, 2,2,6,6-tetramethylpiperidinium oxide and azobisisobutyronitrile.

6. The synthesis method according to claim 1, characterized in that: The molar ratios of the indole or substituted indole to the photocatalyst, the base and the additive are 1:0.01-0.10, 1:2.0-4.0 and 1:0.6-1.6 respectively.

7. The synthesis method according to claim 1, characterized in that: The reaction is carried out in the presence of a solvent, wherein the solvent is any one of ethyl acetate, dioxane, dichloroethane, dichloromethane, toluene, n-hexane, acetonitrile, water, and a dioxane aqueous solution, a tetrahydrofuran aqueous solution, a dichloroethane aqueous solution, and an acetonitrile aqueous solution, and the concentration of the indole or substituted indole in the solvent is 0.02 to 0.10 mol / L.

8. A tryptanthrin compound synthesized by the synthesis method according to any one of claims 1 to 7, characterized in that: Its structural formula is shown in the following formula (I): Wherein, R1 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, and optionally substituted or unsubstituted benzyl; R2 is one or more of hydrogen, halogen, optionally substituted or unsubstituted alkyl, optionally substituted or unsubstituted alkoxy, optionally substituted or unsubstituted ester, optionally substituted or unsubstituted cycloalkyl, optionally substituted or unsubstituted aryl, optionally substituted or unsubstituted heteroaryl, and optionally substituted or unsubstituted benzyl.

9. A composition, characterized in that: The invention comprises the compound represented by formula (I) as claimed in claim 8 or its stereoisomer or its salt or its solvate and an agriculturally usable adjuvant, fungicide, insecticide or herbicide.

10. Use of the compound represented by formula (I) of claim 8 or the composition of claim 9 in preventing and controlling agricultural pests and diseases, characterized in that: The agricultural diseases are plant bacterial diseases and plant fungal diseases; the bacterial diseases are any one of rice bacterial blight, citrus canker, kiwi canker, cucumber bacterial blight, konjac bacterial blight, citrus canker, tobacco bacterial wilt, grape canker, tomato canker, kiwi canker, and apple canker; the plant fungal diseases are any one of Botrytis cinerea, rapeseed sclerotium, eggplant wilt, pepper wilt, wheat gibberella, rice sheath blight, tobacco alternating spot pathogen, gloeosporioides, tea tree anthracnose, and sorghum spondylosis.

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