Preparation method of quinmerac compound

Abstract

The invention relates to the technical field of organic synthesis, in particular to a preparation method and application of a quinoline compound. The preparation method of the quinmerac compound comprises the following steps: carrying out oxidation reaction on a halogenated quinoline compound and a first catalyst in an oxygen-containing atmosphere at the temperature of 80-190 DEG C under the pressure of 0.2-4 Mpa to obtain # imgabs0 # X which represents chlorine or bromine; r1, R2 and R3 are independently identical or different selected from hydrogen, alkyl or alkoxy; the first catalyst is a mixture of a metal salt catalyst and a non-metal catalyst, and the metal salt catalyst comprises one or more of platinum salt, palladium salt, silver salt, cobalt salt, manganese salt, copper salt and vanadium salt; the non-metal catalyst comprises one or more of hydrobromic acid, nitric acid and N-hydroxyphthalimide. By optimizing the reaction system, the production of three wastes can be greatly reduced, meanwhile, the reaction yield and the process safety are further improved, and industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a preparation method and application of quinoline compounds. Background Art

[0002] Quinclorac is a quinoline carboxylic acid hormone-type selective herbicide, which is suitable for use in cereal crops, rapeseed and sugar beet fields before and after emergence to control cleavers, veronica and other weeds. Umbelliferae crops are very sensitive to it. The product was developed by BASF AG of Germany and patented in Germany in 1984. In existing literature reports, it is mainly prepared from 7-chloro-2,8-dimethylquinoline. For example, US4957608A, US4715889A, and US4845226A disclose that: 7-chloro-3,8-dimethylquinoline is first brominated with bromine and n-bromosuccinimide to obtain 8-(bromomethyl)-7-chloro-3-methylquinoline, and then oxidized with nitric acid / sulfuric acid to obtain quinclorac; CN115745883A discloses: 3,8-dimethyl-7-chloroquinoline is dissolved in sulfuric acid to prepare a mixed solution; vanadium pentoxide and cobalt acetate solution are prepared in nitric acid to prepare a mixed solution; the two prepared solutions are passed into a tubular reactor to pass oxygen / air for reaction, and quinclorac is obtained after post-treatment; in the above synthesis methods, the oxidation reaction is reacted under strong acid and high temperature, the conditions are violent, the equipment is highly corrosive, and a large amount of acid is generated in the process, and a large amount of wastewater is generated during post-treatment; if nitric acid is added during the oxidation process, a large amount of nitrogen oxide waste gas will be generated, and the tail gas equipment conditions in industrial production are relatively high. CN 112390752 A discloses clomeclorac and a preparation method thereof, but it uses a mixed gas of ozone and air or pure ozone as an oxidant, which has a high risk of explosion during the reaction and low safety, and is actually not suitable for industrial production.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for preparing a quinmerac acid compound, which can greatly reduce the amount of reaction wastewater and waste gas while improving the yield.

[0005] In a first aspect, the present invention first provides a method for preparing a quinclorac compound, comprising: subjecting a halogenated quinoline compound and a first catalyst to an oxidation reaction in an oxygen-containing atmosphere at 80 to 190° C. and 0.2 to 4 MPa to obtain Wherein, the halogenated quinoline compound includes and / or X represents chlorine or bromine; R 1 , R 2 , R 3are each independently the same or different and are selected from hydrogen, alkyl or alkoxy;

[0006] The first catalyst is a mixture of a metal salt catalyst and a non-metal catalyst, wherein the metal salt catalyst includes one or more of platinum salt, palladium salt, silver salt, cobalt salt, manganese salt, copper salt and vanadium salt; the non-metal catalyst includes one or more of hydrobromic acid, nitric acid and N-hydroxyphthalimide.

[0007] The present invention finds that when a mixture of a metal salt catalyst and a non-metal catalyst is used as the catalyst for the oxidation reaction, the yield can be ensured while avoiding the use of concentrated acid, thereby greatly reducing the difficulty of post-treatment and the amount of wastewater.

[0008] In the present invention, the oxygen-containing atmosphere is air.

[0009] Preferably, the metal salt catalyst includes one or more of platinum nitrate, palladium nitrate, palladium acetate, silver nitrate, silver nitrate, cobalt acetate, cobalt nitrate, manganese acetate, manganese nitrate, copper acetate, copper nitrate, vanadium nitrate and the like.

[0010] Preferably, in the first catalyst, the mass ratio of the metal salt catalyst to the non-metal catalyst is 1-3:1-3.

[0011] More preferably, in the first catalyst, when the mass ratio of the metal salt catalyst to the non-metal catalyst is (1-2):1, the product yield can be further improved.

[0012] Preferably, based on the total mass of the oxidation reaction liquid, the amount of the first catalyst is 0.5-10 wt %.

[0013] Preferably, the molar ratio of the halogenated quinoline compound to oxygen is (1-1.5):1.

[0014] Preferably, the post-treatment of the oxidation reaction comprises: cooling to 20-30° C. after the reaction is completed, and then filtering, salting, decolorizing, acidifying and drying in sequence.

[0015] As a preferred embodiment of the present invention, the post-treatment of the oxidation reaction comprises:

[0016] 1) After the reaction is completed, the temperature is lowered to 20-30° C., and then filtered to separate the solid;

[0017] 2) adding liquid alkali to the solid to adjust the pH to alkaline, and forming a salt to obtain quinaclotide; preferably, the pH is adjusted to 12-13;

[0018] 3) adding the quinclorac salt to activated carbon for decolorization;

[0019] 4) adding acid to the decolorized quinmersalate to adjust the pH to acidic, separating and drying to obtain quinmersalic acid; preferably, the pH is adjusted to 1-2.

[0020] Preferably, the reaction conditions of the oxidation reaction include: a reaction temperature of 120 to 160° C. and a reaction pressure of 0.8 to 1.8 MPa.

[0021] Preferably, the quinclorac compound is The halogenated quinoline compound is and / or

[0022] Preferably, the preparation method of the quinmerac acid compound comprises the following reaction route:

[0023]

[0024] Specifically, the method comprises: subjecting 3-chloro-2-methylaniline and α, β unsaturated aldehydes and ketones to a cyclization reaction to generate a quinoline compound; and then subjecting the quinoline compound to a halogenation reaction and an oxidation reaction in sequence to obtain a quinclorac compound.

[0025] Preferably, the cyclization reaction comprises: mixing 3-chloro-2-methylaniline, α, β unsaturated aldehydes and ketones, a solvent and a second catalyst, and carrying out a cyclization reaction in an oxygen-containing atmosphere at 120 to 250° C. and 0.8 to 1.5 MPa; the solvent is selected from one or more of formic acid, acetic acid, propionic acid, butyric acid, oxalic acid and sulfuric acid; and the first catalyst is a superacid.

[0026] Preferably, the superacid includes Bronsted superacid, Lewis superacid, solid superacid; more preferably, it is a solid superacid.

[0027] Preferably, based on the total mass of the cyclization reaction solution, the amount of the superacid used is 3 to 15 wt %.

[0028] Preferably, the molar ratio of 3-chloro-2-methylaniline to 2-methylacrolein is 1:1 to 5, more preferably 1:1 to 1.5.

[0029] In the present invention, the post-treatment operation of the cyclization reaction in the reaction system is simple and efficient, and only the catalyst needs to be filtered out, and the filtrate of the reaction solution can be directly subjected to a halogenation reaction with a halogen source.

[0030] Preferably, the halogenation reaction comprises: mixing 3,8-dimethyl-7-chloroquinoline, a halogen source and an initiator, and reacting at 20 to 45° C.;

[0031] The initiator is a light source, an azo initiator or an organic peroxide initiator; the azo initiator includes azobisisobutyronitrile and / or azobisisoheptylnitrile; the organic peroxide initiator includes one or more of cumene hydroperoxide, tert-butyl hydroperoxide and benzoyl peroxide; the halogen source includes a bromine source or a chlorine source, and the bromine source includes one or more of bromine, sodium bromide, potassium bromide, sodium bromate, potassium bromate, hydrogen bromide and N-bromosuccinimide; the chlorine source includes chlorine gas.

[0032] In the present invention, the halogenation reaction is performed to obtain and / or Both of them can obtain quinmerac acid compounds through the oxidation reaction.

[0033] As a preferred embodiment of the present invention, the quinmerac acid compound is quinmerac acid, and its preparation method comprises the following reaction route:

[0034]

[0035] Specifically, the method comprises: reacting 3-chloro-2-methylaniline with 2-methylacrolein to generate 3,8-dimethyl-7-chloroquinoline; and then reacting the 3,8-dimethyl-7-chloroquinoline with a halogen source to obtain a halogenated product. and / or The halogenated product is then oxidized to obtain quinmerac acid.

[0036] In the present invention, those skilled in the art can select the reactor for the cyclization reaction, halogenation reaction and oxidation reaction as a tower reactor, a tubular reactor, a microchannel reactor and a supergravity reactor, etc. according to actual needs, and no limitation is made here.

[0037] Based on the above technical solution, the beneficial effects of the present invention are:

[0038] The present invention can greatly reduce the generation of three wastes by optimizing the reaction system, and at the same time further improve the reaction yield and process safety, which is conducive to industrial production. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Unless otherwise specified, all raw materials used in the examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0041] Example 1

[0042] This embodiment provides a method for preparing quinmeracil, which specifically comprises the following steps:

[0043] S1. Synthesis of 3,8-dimethyl-7-chloroquinoline:

[0044] 1) 98 wt % of 3-chloro-2-methylaniline and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 3-chloro-2-methylaniline, and 95 wt % of 2-methylacrolein and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 2-methylacrolein, and the prepared solutions are used for standby;

[0045] 2) controlling the temperature at 170° C. and the pressure at 1 MPa; passing the two mixed solutions into a tubular continuous reactor loaded with a solid superacid through a high-pressure plunger metering pump, with a flow rate of 3.83 g / min for the 3-chloro-2-methylaniline acetic acid mixed solution and a flow rate of 2.93 g / min for the 2-methylacrolein acetic acid mixed solution, and a residence time of 3 min; the equivalent ratio of 3-chloro-2-methylaniline to 2-methylacrolein is 1:1.55; and the content of the solid superacid in the reaction system is 10 wt %;

[0046] 3) Post-treatment: The solid acid in the reaction solution is filtered and removed, the reaction solution filtrate directly enters the next step reaction, and the super acid returns to the cyclization reaction;

[0047] S2. Synthesis of 8-(chloromethyl)-7-chloro-3-methylquinoline:

[0048] 1) Control the temperature of the continuous microreactor to 35° C. and turn on the light source; pass a high-pressure plunger metering pump into the reaction liquid filtrate obtained in S1 at a flow rate of 6.76 g / min, and chlorine is metered into the reactor through a flow meter. The molar ratio of 3,8-dimethyl-7-chloroquinoline and chlorine in the reaction liquid filtrate is 1:1.5, and the residence time is 3 min to obtain a chlorination reaction liquid;

[0049] 2) Post-treatment: passing nitrogen gas into the chlorination reaction liquid to drive out excess chlorine and hydrogen chloride gas and then proceed to the next step of reaction;

[0050] S3, Synthetic Quinclorac:

[0051] 1) preparing a catalyst solution: based on the mass of the chlorination reaction solution, 2.5 wt% of silver acetate, 2.5 wt% of cobalt acetate, 2.5 wt% of nitric acid and acetic acid are mixed to obtain a catalyst solution;

[0052] 2) controlling the continuous oxidation reactor at 150° C. and a pressure of 1.2 MPa; introducing the chlorination reaction solution and the catalyst solution into the oxidation reactor simultaneously through a high-pressure plunger metering pump, with flow rates of 6.76 g / min and 0.676 g / min, respectively; and metering air into the reactor through a flow meter, with a molar ratio of oxygen in the air to 8-(chloromethyl)-7-chloro-3-methylquinoline in the chlorination reaction solution of 6:1, and a residence time of 30 min;

[0053] 3) Post-treatment: The reaction solution was cooled to 25° C., the solid was separated by filtration, water was added and liquid alkali was added dropwise to adjust the pH value to 13, and then activated carbon was added for decolorization, and hydrochloric acid was further used to acidify the pH value to 1, and finally separated and dried to obtain 98% quinmerac acid, with a total yield of 75%.

[0054] Example 2

[0055] This embodiment provides a method for preparing quinmeracil, which specifically comprises the following steps:

[0056] S1. Synthesis of 3,8-dimethyl-7-chloroquinoline:

[0057] 1) 98 wt % of 3-chloro-2-methylaniline and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 3-chloro-2-methylaniline, and 95 wt % of 2-methylacrolein and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 2-methylacrolein, and the prepared solutions are used for standby;

[0058] 2) controlling the temperature at 150° C. and the pressure at 1 MPa; passing the two mixed solutions into a tubular continuous reactor loaded with a solid superacid through a high-pressure plunger metering pump, with a flow rate of 2.30 g / min for the 3-chloro-2-methylaniline acetic acid mixed solution and a flow rate of 2.28 g / min for the 2-methylacrolein acetic acid mixed solution, and a residence time of 5 min; the equivalent ratio of 3-chloro-2-methylaniline to 2-methylacrolein is 1:2; and the solid superacid content in the reaction system is 10 wt%;

[0059] 3) Post-treatment: The solid acid in the reaction solution is filtered out and the reaction solution filtrate is directly used for the next step reaction; the super acid is returned to the cyclization reaction;

[0060] S2. Synthesis of 8-(bromomethyl)-7-chloro-3-methylquinoline:

[0061] 1) Control the temperature of the continuous microreactor to 40° C. and turn on the light source; feed the reaction solution filtrate obtained in S1 through a high-pressure plunger metering pump at a flow rate of 4.58 g / min; meter bromine into the reactor through a flow meter; the molar ratio of 3,8-dimethyl-7-chloroquinoline to bromine in the reaction solution filtrate is 1:1.1; the residence time is 2 min to obtain a bromination reaction solution;

[0062] 2) Post-treatment: distill 30% of the acetic acid from the bromination reaction liquid to remove hydrogen bromide and excess bromine; add 30% fresh acetic acid to the distillate to enter the next step of reaction;

[0063] S3, Synthetic Quinclorac:

[0064] 1) preparing a catalyst solution: based on the mass of the bromination reaction solution, 2.5 wt% of cobalt acetate, 2.5 wt% of manganese acetate, 2.5 wt% of NHPI (N-hydroxyphthalimide) and acetic acid are mixed to obtain a catalyst solution;

[0065] 2) controlling the continuous oxidation reactor at 130° C. and a pressure of 1.0 MPa; simultaneously introducing the bromination reaction solution and the catalyst solution into the oxidation reactor through a high-pressure plunger metering pump, with flow rates of 4.58 g / min and 0.458 g / min, respectively; and metering air into the reactor through a flow meter, with the molar ratio of oxygen in the air to 8-(bromomethyl)-7-chloro-3-methylquinoline in the chlorination reaction solution being 8:1, and the residence time being 30 min;

[0066] 3) Post-treatment: The reaction solution was cooled to 25° C., the solid was separated by filtration, and water was added and then liquid alkali was added dropwise to adjust the pH value to 13, and then activated carbon was added for decolorization, and hydrochloric acid was further used to acidify the pH value to 1, and finally separated and dried to obtain 98% content and 78% yield of quinmerac acid.

[0067] Example 3

[0068] This embodiment provides a method for preparing quinmerac acid, which differs from embodiment 2 only in that the solid superacid is replaced by an equal amount of Lewis superacid. The final yield of quinmerac acid is 74.9% and the purity is 98%.

[0069] Example 4

[0070] This embodiment provides a method for preparing quinmerac acid, which differs from Embodiment 2 only in that:

[0071] The metal salt catalyst is palladium nitrate and copper acetate, and the non-metal catalyst is hydrobromic acid, and the mass ratio of the two is 1: 1. The final yield of quinmerac acid is 75.8%, and the purity is 98%.

[0072] Example 5

[0073] This embodiment provides a method for preparing a quinmerac acid compound, which specifically comprises the following steps:

[0074] S1. Synthesis of 7-chloro-8-methyl-2-phenylquinoline by cyclization reaction:

[0075] 1) 98wt% of 3-chloro-2-methylaniline and 99wt% of acetic acid are formulated into an acetic acid solution of 20wt% 3-chloro-2-methylaniline, and 95wt% of cinnamaldehyde and 99wt% of acetic acid are formulated into an acetic acid solution of 20wt% cinnamaldehyde, and the prepared solutions are used for standby;

[0076] 2) controlling the temperature at 180° C. and the pressure at 1.2 MPa; passing the two mixed solutions into a tubular continuous reactor loaded with a solid superacid through a high-pressure plunger metering pump, with a flow rate of 3.83 g / min for the 3-chloro-2-methylaniline acetic acid mixed solution and a flow rate of 6.42 g / min for the cinnamaldehyde acetic acid mixed solution, and a residence time of 4 min; the molar equivalent ratio of 3-chloro-2-methylaniline to cinnamaldehyde is 1:1.8; and the content of the solid superacid in the reaction system is 10 wt%;

[0077] 3) Post-treatment: The solid acid in the reaction solution is filtered and removed, the reaction solution filtrate directly enters the next step reaction, and the super acid returns to the cyclization reaction;

[0078] S2. Synthesis of 7-chloro-8-(chloromethyl)-2-phenylquinoline by chlorination reaction:

[0079] 1) Control the temperature of the continuous microreactor to 35° C. and turn on the light source; feed the reaction solution filtrate obtained in S1 through a high-pressure plunger metering pump at a flow rate of 10.25 g / min; meter chlorine gas into the reactor through a flow meter; the molar ratio of 7-chloro-8-methyl-2-phenylquinoline to chlorine gas in the reaction solution filtrate is 1:1.5; the residence time is 4 min, and a chlorination reaction solution is obtained;

[0080] 2) Post-treatment: passing nitrogen gas into the chlorination reaction liquid to drive out excess chlorine and hydrogen chloride gas and then proceed to the next step of reaction;

[0081] S3. Synthesis of 7-chloro-2-phenylquinoline-8-carboxylic acid:

[0082] 1) preparing a catalyst solution: based on the mass of the chlorination reaction solution, 2.5 wt% of silver acetate, 2.5 wt% of cobalt acetate, 2.5 wt% of nitric acid and acetic acid are mixed to obtain a catalyst solution;

[0083] 2) controlling the continuous oxidation reactor at 160° C. and a pressure of 1.3 MPa; introducing the chlorination reaction solution and the catalyst solution into the oxidation reactor simultaneously through a high-pressure plunger metering pump, with flow rates of 10.25 g / min and 1.025 g / min, respectively; and metering air into the reactor through a flow meter, with the molar ratio of oxygen in the air to 7-chloro-8-(chloromethyl)-2-phenylquinoline in the chlorination reaction solution being 6:1, and the residence time being 30 min;

[0084] 3) Post-treatment: The reaction solution was cooled to 25° C., the solid was separated by filtration, and water was added and then liquid alkali was added dropwise to adjust the pH value to 13, and then activated carbon was added for decolorization, and hydrochloric acid was further used to acidify the pH value to 1, and finally 7-chloro-2-phenylquinoline-8-carboxylic acid was separated and dried to obtain 98% purity and 66% total yield.

[0085] Example 6

[0086] This embodiment provides a method for preparing a quinazoline compound, which specifically comprises the following steps:

[0087] S1. Synthesis of 7-chloro-3-ethyl-8-methylquinoline by cyclization reaction:

[0088] 1) 98 wt % of 3-chloro-2-methylaniline and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 3-chloro-2-methylaniline, and 95 wt % of 2-ethylacrolein and 99 wt % of acetic acid are formulated into an acetic acid solution containing 20 wt % of 2-2-ethylacrolein, and the mixture is prepared for standby use;

[0089] 2) controlling the temperature at 170° C. and the pressure at 1 MPa; passing the two mixed solutions into a tubular continuous reactor loaded with a solid superacid through a high-pressure plunger metering pump, with a flow rate of 3.83 g / min for the 3-chloro-2-methylaniline acetic acid mixed solution and a flow rate of 5.00 g / min for the 2-ethylacrolein acetic acid mixed solution, and a residence time of 5 min; the molar equivalent ratio of 3-chloro-2-methylaniline to 2-ethylacrolein is 1:2.2; and the content of the solid superacid in the reaction system is 10 wt%;

[0090] 3) Post-treatment: The solid acid in the reaction solution is filtered and removed, the reaction solution filtrate directly enters the next step reaction, and the super acid returns to the cyclization reaction;

[0091] S2. Synthesis of 7-chloro-8-(chloromethyl)-3-ethylquinoline by chlorination reaction:

[0092] 1) Control the temperature of the continuous microreactor to 35° C. and turn on the light source; feed the reaction solution filtrate obtained in S1 through a high-pressure plunger metering pump at a flow rate of 8.83 g / min; meter chlorine gas into the reactor through a flow meter; the molar ratio of 7-chloro-3-ethyl-8-methylquinoline to chlorine gas in the reaction solution filtrate is 1:1.5; the residence time is 6 min, and a chlorination reaction solution is obtained;

[0093] 2) Post-treatment: passing nitrogen gas into the chlorination reaction liquid to drive out excess chlorine and hydrogen chloride gas and then proceed to the next step of reaction;

[0094] S3. Synthesis of 7-chloro-3-ethylquinoline-8-carboxylic acid:

[0095] 1) preparing a catalyst solution: based on the mass of the chlorination reaction solution, 2.5 wt% of silver acetate, 2.5 wt% of cobalt acetate, 2.5 wt% of nitric acid and acetic acid are mixed to obtain a catalyst solution;

[0096] 2) controlling the continuous oxidation reactor at 150° C. and a pressure of 1.5 MPa; introducing the chlorination reaction solution and the catalyst solution into the oxidation reactor simultaneously through a high-pressure plunger metering pump, with flow rates of 8.83 g / min and 0.883 g / min, respectively; and metering air into the reactor through a flow meter, with the molar ratio of oxygen in the air to 7-chloro-8-(chloromethyl)-3-ethylquinoline in the chlorination reaction solution being 6:1, and the residence time being 30 min;

[0097] 3) Post-treatment: The reaction solution was cooled to 25° C., the solid was separated by filtration, water was added and liquid alkali was added dropwise to adjust the pH value to 13, and then activated carbon was added for decolorization, and hydrochloric acid was further used to acidify the pH value to 1, and finally 7-chloro-3-ethylquinoline-8-carboxylic acid was separated and dried to obtain 98% purity and 61% total yield.

[0098] Example 7

[0099] This embodiment provides a method for preparing quinmerac, which differs from embodiment 2 only in that the mass ratio of the metal salt catalyst (cobalt acetate and manganese acetate) to the non-metal catalyst (NHPI) is 1:3. The final yield of quinmerac is 71.5% and the purity is 98%.

[0100] Example 8

[0101] This embodiment provides a method for preparing quinmerac acid, which differs from embodiment 2 only in that the solid superacid content is 20 wt %. The final yield of quinmerac acid is 71.8% and the purity is 98%.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing quinmerac acid, which differs from Example 2 only in that the catalyst solution in Example 2 is replaced by an equal amount of concentrated sulfuric acid. The final yield of quinmerac acid is 68.3% and the purity is 98%.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a quinclorac compound, characterized in that: include: The halogenated quinoline compound and the first catalyst are subjected to an oxidation reaction in an oxygen-containing atmosphere at 80 to 190° C. and 0.2 to 4 MPa to obtain Wherein, the halogenated quinoline compound includes and / or X represents chlorine or bromine; R1, R2, R3 are independently selected from hydrogen, alkyl or alkoxy; The first catalyst is a mixture of a metal salt catalyst and a non-metal catalyst, wherein the metal salt catalyst includes one or more of platinum salt, palladium salt, silver salt, cobalt salt, manganese salt, copper salt and vanadium salt; the non-metal catalyst includes one or more of hydrobromic acid, nitric acid and N-hydroxyphthalimide.

2. The method for preparing the quinclorac compound according to claim 1, characterized in that: In the first catalyst, the mass ratio of the metal salt catalyst to the non-metal catalyst is 1-3:1-3.

3. The method for preparing a quinmerac acid compound according to claim 1 or 2, characterized in that: Based on the total mass of the oxidation reaction liquid, the amount of the first catalyst used is 0.5 to 5 wt %.

4. The method for preparing a quinmerac acid compound according to any one of claims 1 to 3, characterized in that: The molar ratio of the halogenated quinoline compound to oxygen is (1-1.5):

1.

5. The method for preparing a quinmerac acid compound according to any one of claims 1 to 4, characterized in that: The post-treatment of the oxidation reaction includes: cooling to 20-30° C. after the reaction is completed, and then filtering, salifying, decolorizing, acidifying and drying in sequence.

6. The method for preparing quinmerac acid compounds according to any one of claims 1 to 5, characterized in that: The quinclorac compound is The halogenated quinoline compound is and / or 7. The method for preparing quinmerac acid compounds according to any one of claims 1 to 6, characterized in that: The following reaction routes are included: Specifically, the method comprises: subjecting 3-chloro-2-methylaniline and α, β unsaturated aldehydes and ketones to a cyclization reaction to generate a quinoline compound; and then subjecting the quinoline compound to a halogenation reaction and an oxidation reaction in sequence to obtain a quinclorac compound.

8. The method for preparing the quinmerac acid compound according to claim 7, characterized in that: The cyclization reaction comprises: 3-chloro-2-methylaniline, α, β unsaturated aldehydes and ketones, a solvent and a second catalyst are mixed, and a cyclization reaction is carried out in an oxygen-containing atmosphere at 120-250° C. and 0.8-1.5 MPa; the solvent is selected from one or more of formic acid, acetic acid, propionic acid, butyric acid, oxalic acid and sulfuric acid; and the first catalyst is a superacid.

9. The method for preparing a quinoline compound according to claim 8, wherein Based on the total mass of the reaction solution of the cyclization reaction, the amount of the super acid used is 3 to 15 wt %.

10. The method for preparing quinmerac acid according to any one of claims 7 to 9, characterized in that: The halogenation reaction comprises: mixing 3,8-dimethyl-7-chloroquinoline, a halogen source and an initiator, and reacting at 20 to 45° C.; The initiator is a light source, an azo initiator or an organic peroxide initiator; the azo initiator includes azobisisobutyronitrile and / or azobisisoheptylnitrile; the organic peroxide initiator includes one or more of cumene hydroperoxide, tert-butyl hydroperoxide and benzoyl peroxide; the halogen source includes a bromine source or a chlorine source, and the bromine source includes one or more of bromine, sodium bromide, potassium bromide, sodium bromate, potassium bromate, hydrogen bromide and N-bromosuccinimide; the chlorine source includes chlorine gas.

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