阅读说明：本技术 一种由2,4,6-三氨基甲苯制备间苯三酚的方法 (Method for preparing phloroglucinol from 2,4, 6-triaminotoluene ) 是由 黄木华 张志豪 邓汉林 罗贤升 彭山青 于 2021-08-13 设计创作，主要内容包括：本发明提供了一种由2,4,6-三氨基甲苯制备间苯三酚的方法。该方法包括：以2,4,6-三氨基甲苯及其盐酸盐为原料,经过三烯胺的水解-异构化反应得到2,4,6-三羟基甲苯；再经过2,4,6-三羟基甲苯的氧化脱甲基反应,得到目标产物间苯三酚。该方法中,2,4,6-三氨基甲苯及其盐酸盐到2,4,6-三羟基甲苯的转化以便宜易得的酸为试剂,以77-90％实现三烯胺的水解-异构化,以71-97％产率实现2,4,6-三羟基甲苯的脱甲基反应得到目标产物间苯三酚。总之,该方法以简单、高效、安全和温和的路径创新了间苯三酚的合成路线,为实现其低成本和规模化制备奠定了坚实的基础。(The invention provides a method for preparing phloroglucinol from 2,4, 6-triaminotoluene. The method comprises the following steps: 2,4, 6-triaminotoluene and hydrochloride thereof are taken as raw materials, and hydrolysis-isomerization reaction of trienylamine is carried out to obtain 2,4, 6-trihydroxytoluene; and performing oxidative demethylation reaction on the 2,4, 6-trihydroxytoluene to obtain the target product phloroglucinol. In the method, cheap and easily-obtained acid is used as a reagent for converting the 2,4, 6-triaminotoluene and the hydrochloride thereof into the 2,4, 6-trihydroxytoluene, the hydrolysis-isomerization of trienylamine is realized by 77-90%, and the demethylation reaction of the 2,4, 6-trihydroxytoluene is realized by 71-97% of yield to obtain the target product phloroglucinol. In a word, the method innovates a synthetic route of phloroglucinol by a simple, efficient, safe and mild path, and lays a solid foundation for realizing low-cost and large-scale preparation of phloroglucinol.)

1. A process for preparing phloroglucinol from 2,4, 6-triaminotoluene, which comprises:

step 1: taking 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof as raw materials, and carrying out hydrolysis-isomerization reaction on enamine in an acid system to obtain 2,4, 6-trihydroxytoluene shown in a structural formula II;

step 2: taking 2,4, 6-trihydroxytoluene shown in a structural formula II as a raw material, and carrying out oxidation demethylation reaction to obtain a target product phloroglucinol shown in a structural formula I;

2. the method according to claim 1, wherein in step 1, the acid selected in the acidic system comprises at least one of sulfuric acid, phosphoric acid, methanesulfonic acid and p-toluenesulfonic acid.

3. The method according to claim 2, wherein when the acid system is an acid system consisting of sulfuric acid and an ammonium chloride solution, the sulfuric acid is diluted to 5-60% by mass fraction, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 90-120 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2-12 h;

when the acid system is composed of phosphoric acid solution, the phosphoric acid solution is diluted to 5-60% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and hydrochloride thereof is 20: 1-4: 1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 24-72 hours;

when the acid system is an acid system consisting of methanesulfonic acid and an ammonium chloride solution, the methanesulfonic acid is diluted to 5-60% by mass, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 4-14 hours;

when the acid system is an acid system consisting of p-toluenesulfonic acid and an ammonium chloride solution, the p-toluenesulfonic acid is diluted to 5-60% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2-12 hours.

4. The method of claim 1, wherein in step 2, the oxidative demethylation reaction comprises:

under the action of an oxidant, performing CH oxidation reaction to obtain an oxidation reaction system containing 2,4, 6-trihydroxybenzoic acid shown in a structural formula IV;

and heating the oxidation reaction system to 60-180 ℃ for in-situ decarboxylation reaction for 2-6 h to obtain the target product phloroglucinol shown in the structural formula I.

5. The method according to claim 4, wherein in the step 2, the oxidizing agent is any one of potassium permanganate, potassium dichromate and lead dioxide.

6. The method according to claim 5, wherein when the oxidizing agent is potassium permanganate, an oxidation system of the CH oxidation reaction is a potassium permanganate and magnesium sulfate aqueous solution oxidation system;

wherein the mass ratio of the potassium permanganate to the 2,4, 6-trihydroxytoluene is 2: 1-10: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene is 1: 2-2: 1; the reaction temperature of the oxidation reaction is 60-100 ℃, the reaction time of the oxidation reaction is 1-4 h, and the reaction solvent of the oxidation reaction is water.

7. The method of claim 5, wherein when the oxidizing agent is lead dioxide, the oxidation system of the CH oxidation reaction is a lead dioxide and potassium hydroxide aqueous system;

wherein the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene is 4: 1-8: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene is 4: 1-6: 1; the reaction temperature of the oxidation reaction is 90-150 ℃, the reaction pressure of the oxidation reaction is 0.4-1.2 MPa, the reaction time of the oxidation reaction is 0.5-3 h, and the reaction solvent of the oxidation reaction is water.

8. The method according to claim 5, wherein when the oxidizing agent is potassium dichromate, an in-situ oxidation reaction is performed in a reaction system obtained after completion of the hydrolysis-isomerization reaction by an electrochemical electrode reaction, and an oxidation system of the CH oxidation reaction is an oxidizing agent system composed of potassium dichromate and a dilute sulfuric acid solution;

wherein the mass ratio of the potassium dichromate to the 2,4, 6-trihydroxytoluene is 3: 1-1: 10; the dilute sulfuric acid solution is a sulfuric acid solution diluted to 5-60% in mass fraction, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 20: 1-5: 1; the reaction temperature of the oxidation reaction is 30-110 ℃, the reaction time of the oxidation reaction is 1-8 h, and the reaction solvent of the oxidation reaction is water.

9. The method of claim 5, wherein after the in situ decarboxylation reaction, the method further comprises: performing second post-treatment on a decarboxylation reaction system obtained after the in-situ decarboxylation reaction to obtain a target product phloroglucinol shown in a structural formula I;

wherein, when the oxidant is potassium permanganate, the second post-treatment is as follows: adjusting the decarboxylation reaction system to be alkaline, filtering, acidifying the filtrate, concentrating the acidified filtrate, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of the frozen crystal is-1-4 ℃;

when the oxidizing agent is lead dioxide, the second post-treatment is: carrying out reduced pressure filtration on the decarboxylation reaction system, then carrying out lead removal filtration, acidifying the filtrate after lead removal, concentrating the filtrate after acidification, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of the frozen crystal is-1-4 ℃;

when the oxidizing agent is potassium dipotassium, the second post-treatment is as follows: and carrying out reduced pressure filtration on the reaction stock solution after the oxidation reaction, washing filter residues with deionized water, collecting filtrate, concentrating, and recrystallizing the concentrated solution.

10. The method of claim 9, wherein the recrystallizing the concentrate is: freezing and crystallizing the concentrated solution; or extracting the concentrated solution with ethyl acetate, concentrating the extractive solution, and recrystallizing.

Technical Field

The invention relates to the field of chemical engineering and materials, and mainly relates to a method for preparing phloroglucinol from 2,4, 6-triaminotoluene.

Background

Phloroglucinol (Phloroglucinol, trade name: Spaent) is an important spasmolytic and is widely used for treating diseases caused by smooth muscle spasm. Meanwhile, the compound is used as a chemical raw material and a synthetic intermediate, and plays an important role in the fields of medicines, organic porous materials, insensitive explosives and the like. In particular to the field of medicine, phloroglucinol and derivatives (such as flavonoid compounds) prepared by the phloroglucinol have the potential of being used for developing various medical products, such as anti-AIDS drugs, anti-tumor drugs and the like. Due to the characteristic of C3 symmetrical trihydroxy functionality of phloroglucinol, a large amount of compounds and advanced materials with application values can be derived and prepared. However, although phloroglucinol is widely distributed in nature and found in plants, microorganisms, and the like, and derivatives thereof, it is not easy to isolate phloroglucinol directly from these natural sources. Therefore, the method has important value for the artificial synthesis of phloroglucinol and the application research of advanced materials.

At present, phloroglucinol is mainly prepared by methods such as oxidation of 1,3, 5-triisopropylbenzene, hydrolysis of 1,3, 5-trihalobenzene, and biosynthesis. However, these synthetic routes all have certain problems, so that the production cost of phloroglucinol is high, and the development of a low-cost synthetic method is urgently needed. Therefore, there is a need in the art for a simple, efficient, safe, mild, and low-cost synthetic method for phloroglucinol.

Disclosure of Invention

In order to solve the problems, the invention provides a method for preparing phloroglucinol from 2,4, 6-triaminotoluene, so as to realize the purpose of synthesizing phloroglucinol simply, efficiently, safely and at low cost. The specific contents are as follows:

step 1: taking 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof as raw materials, and carrying out hydrolysis-isomerization reaction on enamine in an acid system to obtain 2,4, 6-trihydroxytoluene shown in a structural formula II;

step 2: taking 2,4, 6-trihydroxytoluene shown in a structural formula II as a raw material, and performing oxidation demethylation reaction to prepare a target product phloroglucinol shown in a structural formula I;

optionally, in step 1, the acid selected in the acidic system includes at least one of sulfuric acid, phosphoric acid, methanesulfonic acid, and p-toluenesulfonic acid.

Optionally, when the acid system is an acid system consisting of sulfuric acid and an ammonium chloride solution, the sulfuric acid is diluted to 5-60% by mass fraction, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 90-120 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2-12 hours;

when the acid system is composed of phosphoric acid solution, the phosphoric acid solution is diluted to 5-60% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and hydrochloride thereof is 20: 1-4: 1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 24-72 hours;

when the acid system is an acid system consisting of methanesulfonic acid and an ammonium chloride solution, the methanesulfonic acid is diluted to 5-60% by mass, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 4-14 hours;

when the acid system is an acid system consisting of p-toluenesulfonic acid and an ammonium chloride solution, the p-toluenesulfonic acid is diluted to 5-60% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2-12 hours.

Optionally, in step 2, the oxidative demethylation reaction comprises:

under the action of an oxidant, performing CH oxidation reaction to obtain an oxidation reaction system containing 2,4, 6-trihydroxybenzoic acid shown in a structural formula IV;

and heating the oxidation reaction system to 60-180 ℃ for in-situ decarboxylation reaction for 2-6 h to obtain the target product phloroglucinol shown in the structural formula I.

Optionally, in the step 2, the oxidizing agent is any one of potassium permanganate, lead dioxide and potassium dichromate. Optionally, when the oxidizing agent is potassium permanganate, the oxidizing system of the CH oxidizing reaction is a potassium permanganate and magnesium sulfate aqueous solution oxidizing system;

wherein the mass ratio of the potassium permanganate to the 2,4, 6-trihydroxytoluene is 2: 1-10: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene is 1: 2-2: 1; the reaction temperature of the oxidation reaction is 60-100 ℃, the reaction time of the oxidation reaction is 1-4 h, and the reaction solvent of the oxidation reaction is water.

Optionally, when the oxidizing agent is lead dioxide, the oxidation system of the CH oxidation reaction is a lead dioxide and potassium hydroxide aqueous solution system;

wherein the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene is 4: 1-8: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene is 4: 1-6: 1; the reaction temperature of the oxidation reaction is 90-150 ℃, the reaction pressure of the oxidation reaction is 0.4-1.2 MPa, the reaction time of the oxidation reaction is 0.5-3 h, and the reaction solvent of the oxidation reaction is water.

Optionally, when the oxidizing agent is potassium dichromate, performing an in-situ oxidation reaction in a reaction system obtained after the hydrolysis-isomerization reaction is completed through an electrochemical electrode reaction, and an oxidation system of the CH oxidation reaction is an oxidizing agent system consisting of potassium dichromate and a dilute sulfuric acid solution;

wherein the mass ratio of the potassium dichromate to the 2,4, 6-trihydroxytoluene is 3: 1-10: 1; the dilute sulfuric acid solution is a sulfuric acid solution diluted to 5-60% in mass fraction, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 20: 1-5: 1; the reaction temperature of the oxidation reaction is 30-100 ℃, the reaction time of the oxidation reaction is 1-8 h, and the reaction solvent of the oxidation reaction is water.

Optionally, after the in situ decarboxylation reaction, the method further comprises: performing second post-treatment on a decarboxylation reaction system obtained after the in-situ decarboxylation reaction to obtain a target product phloroglucinol shown in a structural formula I;

wherein, when the oxidant is potassium permanganate, the second post-treatment is as follows: adjusting the decarboxylation reaction system to be alkaline, filtering, acidifying the filtrate, concentrating the acidified filtrate, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of the frozen crystal is-1-4 ℃;

when the oxidizing agent is lead dioxide, the second post-treatment method is as follows: carrying out reduced pressure filtration on the decarboxylation reaction system, then carrying out lead removal filtration, acidifying the filtrate after lead removal, concentrating the filtrate after acidification, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of the frozen crystal is-1-4 ℃;

when the oxidizing agent is potassium dipotassium, the second post-treatment method comprises the following steps: and carrying out reduced pressure filtration on the reaction stock solution after the oxidation reaction, washing filter residues with deionized water, collecting filtrate, concentrating, and recrystallizing the concentrated solution.

Optionally, the recrystallizing the concentrated solution is: freezing and crystallizing the concentrated solution; or extracting the concentrated solution with ethyl acetate, concentrating the extractive solution, and recrystallizing.

The invention provides a method for preparing phloroglucinol from 2,4, 6-triaminotoluene. The method comprises the following steps: 2,4, 6-triaminotoluene and hydrochloride thereof are taken as raw materials, and hydrolysis-isomerization reaction of enamine is carried out to obtain 2,4, 6-trihydroxytoluene; the method comprises the steps of taking 2,4, 6-trihydroxytoluene as a raw material, carrying out oxidation demethylation reaction under the action of an oxidant to obtain a target product phloroglucinol (namely, an intermediate 2,4, 6-trihydroxybenzoic acid is obtained through oxidation of CH of benzyl, and then in-situ decarboxylation is directly carried out on the intermediate 2,4, 6-trihydroxybenzoic acid to obtain the target product phloroglucinol). Compared with the prior art, the invention at least comprises the following advantages:

1. the synthetic route provided by the invention takes 2,4, 6-triaminotoluene and hydrochloride thereof as raw materials, and introduces hydroxyl functional groups through hydrolysis-isomerization reaction of triene amine, so that on one hand, the hydroxyl functional groups can accurately substitute target sites, the generation of byproducts of the hydroxyl functional groups under high-temperature conditions is reduced, on the other hand, the oxidation resistance of the raw materials can be enhanced, and the stability of a product intermediate in the production process is easier to improve.

2. The invention adopts the oxidation demethylation reaction to successfully prepare phloroglucinol, firstly, the selective oxidation reagent is used for carrying out CH oxidation on benzyl, and the in-situ decarboxylation is carried out on the obtained oxidation product, thus directly obtaining the target product. The synthesis process of the oxidative demethylation reaction has the advantages of simple operation and low cost, and is beneficial to promoting large-scale preparation.

3. All routes of the method are safe and controllable, and the intermediates are non-explosive compounds, so that the safety of the synthesis process is improved.

4. The synthesis method provided by the invention has the advantages that the by-products generated in the reaction process are few, the solvent catalyst and the like can be recycled, and the environmental pollution and the resource waste are reduced.

In conclusion, the method provided by the invention uses 2,4, 6-triaminotoluene and hydrochloride thereof as starting materials to prepare the 2,4, 6-trihydroxytoluene, and then prepares the target product phloroglucinol by the demethylation reaction of the 2,4, 6-trihydroxytoluene, so that a simple, efficient, safe and mild synthetic route is realized, and a solid foundation is laid for the large-scale preparation of phloroglucinol.

Drawings

FIG. 1 shows a process flow diagram of a method for synthesizing phloroglucinol in accordance with an embodiment of the present invention;

FIG. 2 is the NMR spectrum of 2,4, 6-trihydroxytoluene obtained in example 1 of the present invention;

FIG. 3 is the NMR spectrum of 2,4, 6-trihydroxytoluene obtained in example 1 of the present invention;

FIG. 4 is an infrared spectrum of 2,4, 6-trihydroxytoluene obtained in example 1 of the present invention;

FIG. 5 is a high resolution mass spectrum of 2,4, 6-trihydroxytoluene obtained in example 1 of the present invention;

FIG. 6 is a nuclear magnetic resonance hydrogen spectrum of 2,4, 6-trihydroxybenzoic acid obtained in example 1 of the present invention;

FIG. 7 is a nuclear magnetic resonance carbon spectrum of 2,4, 6-trihydroxybenzoic acid obtained in example 1 of the present invention;

FIG. 8 is an infrared spectrum of 2,4, 6-trihydroxybenzoic acid obtained in example 1 of the present invention;

FIG. 9 is a high-resolution mass spectrum of 2,4, 6-trihydroxybenzoic acid obtained in example 1 of the present invention;

FIG. 10 is a NMR chart of phloroglucinol obtained in example 1 of the present invention;

FIG. 11 is a NMR chart of phloroglucinol obtained in example 1 of the present invention;

FIG. 12 is an infrared spectrum of phloroglucinol obtained in example 1 of the present invention;

FIG. 13 is a high resolution mass spectrum of phloroglucinol obtained in example 1 of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The specific experimental procedures or conditions not specified in the examples can be performed according to the procedures or conditions of the conventional experimental procedures described in the prior art in this field. The reagents and other instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

The embodiment of the invention provides a safe synthesis method of phloroglucinol shown in a structural formula I, and referring to figure 1, the synthesis method comprises the following steps:

step 1 (S1): taking 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof as raw materials, and carrying out hydrolysis-isomerization reaction on enamine in an acid system to obtain 2,4, 6-trihydroxytoluene shown in a structural formula II.

In the specific implementation, 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof are used as raw materials, heating reflux is carried out under an acidic condition, enamine hydrolysis-isomerization reaction is carried out, separation and purification treatment (namely first post-treatment) is carried out after the reaction is finished, and 2,4, 6-trihydroxytoluene shown in a structural formula II is obtained.

2,4, 6-triaminotoluene and hydrochloride thereof are used as raw materials, and hydroxyl functional groups are introduced through hydrolysis-isomerization reaction of enamine, so that on one hand, the enamine can accurately substitute a target site, the generation of byproducts of the enamine under a high-temperature condition is reduced, on the other hand, the oxidation resistance of the raw materials can be enhanced, and the stability of a product intermediate in a production process is easier to improve.

Step 2 (S2): taking 2,4, 6-trihydroxy toluene shown in a structural formula II as a raw material, and carrying out oxidation demethylation reaction to obtain a target product phloroglucinol shown in a structural formula I. The method comprises the steps of firstly carrying out CH oxidation reaction under the action of an oxidant to obtain an oxidation reaction system containing 2,4, 6-trihydroxybenzoic acid shown in a structural formula IV, and then heating the oxidation reaction system to 60-180 ℃ to carry out in-situ decarboxylation reaction for 2-6 hours to prepare the target product phloroglucinol shown in the structural formula I.

In specific implementation, 2,4, 6-trihydroxy toluene shown in a structural formula II is used as a raw material to perform CH oxidation reaction, so that 2,4, 6-trihydroxy benzoic acid shown in a structural formula IV is obtained. In the implementation step, the benzyl is selectively oxidized by the selective oxidation reagent, other side reactions are basically avoided, and the obtained oxidation products are carboxylic acid intermediates shown in a structural formula IV. And (3) carrying out in-situ decarboxylation reaction on the 2,4, 6-trihydroxybenzoic acid shown in the structural formula IV at the temperature of 60-180 ℃ for 2-6 h to obtain the target product phloroglucinol shown in the structural formula I.

All routes in the embodiment of the invention are safe and controllable, and the intermediates are non-explosive compounds, which is beneficial to improving the safety of the synthesis process. In addition, the synthesis method provided by the embodiment has the advantages that by-products generated in the reaction process are few, the solvent, the catalyst and the like can be recycled, and the environmental pollution and the resource waste are reduced.

In this embodiment, optionally, in step 1, the acid used in the acidic system includes at least one of sulfuric acid, phosphoric acid, methanesulfonic acid and p-toluenesulfonic acid. That is, in specific implementation, the acid may be one of sulfuric acid, phosphoric acid, methanesulfonic acid and p-toluenesulfonic acid, or a mixture of several of them, which is not limited in this embodiment.

In the specific implementation of this embodiment, optionally, when the acidic system is an acidic system composed of sulfuric acid and an ammonium chloride solution, the sulfuric acid is diluted to 5% to 60% by mass, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene shown in the structural formula III and the hydrochloride thereof is 20:1 to 4:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene shown in the structural formula III and the hydrochloride thereof is 1:5 to 1:10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 90 to 120 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2 to 12 hours;

when the acid system is composed of phosphoric acid solution, the phosphoric acid solution is 5-60% by mass, the mass ratio of the phosphoric acid solution to 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof is 20: 1-4: 1, the reaction temperature of the hydrolysis-isomerization reaction of enamine is 180-250 ℃, the reaction solvent of the hydrolysis-isomerization reaction of enamine is water, and the reaction time of the hydrolysis-isomerization reaction of enamine is 24-72 hours;

when the acid system is composed of methanesulfonic acid and ammonium chloride solution, the methanesulfonic acid is diluted to 5% -60% by mass, the mass ratio of the methanesulfonic acid to 2,4, 6-triaminotoluene shown in a structural formula III and hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to 2,4, 6-triaminotoluene shown in the structural formula III and hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of enamine is water, and the reaction time of the hydrolysis-isomerization reaction of enamine is 4-14 h;

when the acid system is an acid system consisting of p-toluenesulfonic acid and an ammonium chloride solution, the p-toluenesulfonic acid is diluted to 5-60% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene shown in the structural formula III and the hydrochloride thereof is 20: 1-4: 1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene shown in the structural formula III and the hydrochloride thereof is 1: 5-1: 10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60-180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, and the reaction time of the hydrolysis-isomerization reaction of the enamine is 2-12 hours.

In this embodiment, optionally, in step 2, the oxidizing agent is any one of potassium permanganate, lead dioxide, and potassium dichromate.

In the specific implementation of this embodiment, optionally, when the oxidizing agent is potassium permanganate or lead dioxide, in step 1, the 2,4, 6-trihydroxytoluene shown in structural formula II needs to be subjected to product extraction. Thus, after the hydrolysis-isomerization reaction of the enamine is complete, the process provided in this example further comprises: obtaining the 2,4, 6-trihydroxytoluene shown in the structural formula II through first post-treatment.

Wherein the first post-processing comprises: adding inorganic base to adjust to a solution with pH of 2-5, filtering again, washing the filter residue for multiple times, collecting filtrate, concentrating and crystallizing; the inorganic base is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

In specific implementation, the first post-treatment may be: after the hydrolysis-isomerization reaction of enamine is finished, adjusting the pH value of the filtrate of the system after the hydrolysis-isomerization reaction of enamine to pH 2-5 by using inorganic base, filtering the adjusted filtrate, washing filter residues for multiple times after filtering, collecting the filtrate, concentrating and crystallizing the filtrate, and obtaining the crystal which is 2,4, 6-trihydroxytoluene shown in the structural formula II.

In a specific implementation of this embodiment, optionally, when the oxidizing agent is potassium permanganate, the oxidation system of the CH oxidation reaction is an oxidation system of potassium permanganate and magnesium sulfate aqueous solution;

wherein the mass ratio of the potassium permanganate to the 2,4, 6-trihydroxytoluene shown in the structural formula II is 2: 1-10: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene shown in the structural formula II is 1: 2-2: 1; the reaction temperature of the oxidation reaction is 60-100 ℃, the reaction time of the oxidation reaction is 1-4 h, and the reaction solvent of the oxidation reaction is water.

In the specific implementation of this embodiment, optionally, when the oxidizing agent is lead dioxide, the oxidation system of the CH oxidation reaction is a system of lead dioxide and an aqueous solution of potassium hydroxide;

wherein the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene shown in the structural formula II is 4: 1-8: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene shown in the structural formula II is 4: 1-6: 1; the reaction temperature of the oxidation reaction is 100-200 ℃, the reaction time of the oxidation reaction is 0.5-3 h, and the reaction solvent of the oxidation reaction is water.

In specific implementation of this embodiment, optionally, when the oxidizing agent is potassium dichromate, without separating 2,4, 6-trihydroxytoluene shown in structural formula II, an in-situ oxidation reaction is performed in a reaction system obtained after the hydrolysis-isomerization reaction is completed through an electrochemical electrode reaction, and an oxidation system of the CH oxidation reaction is an oxidizing agent system composed of potassium dichromate and a dilute sulfuric acid solution;

wherein the mass ratio of potassium dichromate to 2,4, 6-trihydroxytoluene is 3: 1-1: 10; the dilute sulfuric acid solution is a sulfuric acid solution diluted to 5-60% in mass fraction, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 20: 1-5: 1; the reaction temperature of the oxidation reaction is 30-100 ℃, the reaction time of the oxidation reaction is 1-8 h, and the reaction solvent of the oxidation reaction is water.

In this embodiment, optionally, after the in situ decarboxylation reaction, the method further includes: and carrying out second post-treatment on the decarboxylation reaction system obtained after the in-situ decarboxylation reaction to obtain the target product phloroglucinol shown in the structural formula I.

In this embodiment, optionally, when the oxidizing agent is potassium permanganate, the second post-treatment method is: adjusting the decarboxylation reaction system to be alkaline, filtering, acidifying the filtrate, concentrating the acidified filtrate, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of freezing crystallization is-1-4 ℃.

In a specific implementation of this embodiment, optionally, when the oxidizing agent is lead dioxide, the second post-treatment method is: filtering the decarboxylation reaction system under reduced pressure, removing lead, filtering, acidifying the filtrate after removing lead, concentrating the filtrate after acidification, and recrystallizing the concentrated solution; wherein the acid used for acidification is concentrated hydrochloric acid, the volume ratio of the concentrated hydrochloric acid to the filtrate is 1: 20-1: 5, and the temperature of freezing crystallization is-1-4 ℃.

In this embodiment, optionally, when the oxidizing agent is potassium dipotassium, the second post-treatment method is as follows: and (3) carrying out reduced pressure filtration on the reaction stock solution after the oxidation reaction, washing filter residues with deionized water, collecting and concentrating filtrate, and then recrystallizing the concentrated solution.

In specific implementation, the "recrystallizing the concentrated solution" may be performed by: freezing and crystallizing the concentrated solution; or extracting the concentrated solution with ethyl acetate, concentrating the extractive solution, and recrystallizing.

It should be noted that the value ranges of the above substances and the value ranges of the above parameters are only preferred embodiments of the present invention, and the present invention is not limited to the values, and all the value ranges applicable to the present invention are feasible.

In order to make the present invention better understood by those skilled in the art, the following examples are provided to illustrate the present invention by way of example only.

Example 1

Step 1: preparation of 2,4, 6-trihydroxytoluene.

2,4, 6-Triaminotoluene hydrochloride (100mmol, 24.65g) was dissolved in 130g of 5% by weight dilute sulfuric acid (6.5g sulfuric acid, 123.5g deionized water), and NH was added₄Cl (45mmol, 2.4g) and heated to 105 ℃ under reflux for 4 h. After the reaction is finished, cooling to room temperature, gradually adding sodium hydroxide solid into the solution to adjust the pH value of the solution to be weakly acidic pH value of 5, and filtering under reduced pressure. The residue was washed three times with deionized water (3X 200mL), all filtrates were collected, concentrated and crystallized by rotary evaporation at 50 ℃ under 100mbar, and the solid product, 2,4, 6-trihydroxytoluene II (12.6g, 90% yield), was collected by filtration.

Referring to fig. 2, 3, 4 and 5, there are shown a nuclear magnetic resonance hydrogen spectrum, a nuclear magnetic resonance carbon spectrum, an infrared spectrum and a high resolution mass spectrum of the product 2,4, 6-trihydroxytoluene II obtained in step 1 of example 1 of the present invention. It should be noted that, in order to detect the first intermediate 2,4, 6-trihydroxytoluene II generated in step 1 of this embodiment, the reaction may be temporarily interrupted according to the reaction progress, the reaction system is processed to obtain a pure first intermediate 2,4, 6-trihydroxytoluene II, and the pure first intermediate 2,4, 6-trihydroxytoluene II is detected, so as to determine the generation of the first intermediate 2,4, 6-trihydroxytoluene II according to various detected spectrograms.

Nuclear magnetic resonance hydrogen spectrum¹H-NMR(400MHz,DMSO-D6)δ(ppm):8.81(s,2H),8.68(s,1H),5.77(s,2H),1.80(s,3H).

Nuclear magnetic resonance carbon spectrum¹³C-NMR(101MHz,DMSO-D6)δ(ppm):156.92,155.98,101.17,94.46,8.50.

Infrared spectrum FT-IR (ATR, cm)^-1):3240cm^-1,1599cm^-1，1518cm^-1，1469cm^-1，1278cm^-1，1139cm^-1，1074cm^-1，1003cm^-1，814cm^-1。

High resolution mass spectrum HR-MS (ESI) 139.040084[ M-H [ ]]^-(C₇H₇O₃,required139.040068)。

Step 2 preparation of phloroglucinol

Dissolving 2,4, 6-trihydroxytoluene (14g, 100mmol) and magnesium sulfate (20g) in water (300ml), heating to 60 ℃ and stirring, gradually adding potassium permanganate solid powder (30g, 200mmol) into the mixed solution, continuously stirring until purple color in the solution disappears, monitoring the raw material conversion process through a TLC chromatographic column, reacting for 4 hours, raising the temperature to 150 ℃, and refluxing for 4 hours to achieve the purpose of oxidative demethylation.

NaOH (10g, 0.25mmol) was added as a solid to the solution to adjust the solution to alkaline, and MnO in the reaction solution was filtered off₂The filtrate was collected, the solution pH was adjusted to acidic by adding concentrated hydrochloric acid, placed in a freezer for 6 hours and filtered to give phloroglucinol (11.6g, 97%).

Referring to fig. 6, 7, 8 and 9, there are shown a nuclear magnetic resonance hydrogen spectrum, a nuclear magnetic resonance carbon spectrum, an infrared spectrum and a high resolution mass spectrum of the oxidation intermediate product 2,4, 6-trihydroxybenzoic acid of step 2 of example 1 of the present invention. Since this intermediate product is not stable over a long period of time, its relevant characterization spectrum was isolated and characterized only in example 1.

Nuclear magnetic resonance hydrogen spectrum:¹H-NMR(400MHz,DMSO-D6)δ(ppm):10.21,6.54,5.81.。

nuclear magnetic resonance carbon spectrum:¹³C-NMR(101MHz,DMSO-D6)δ(ppm):172.66,164.28,162.98,95.17,94.04。

infrared spectrum FT-IR (ATR, cm)^-1):3576cm^-1,3470cm^-1，3120cm^-1，2617cm^-1，1614cm^-1，1465cm^-1，1378cm^-1，1255cm^-1，1164cm^-1,1066cm^-1，1014cm^-1，834cm^-1，822cm^-1，723cm^-1，694cm^-1。

High resolution mass spectrum HR-MS (ESI) 169.014206[ M-H [ ]]^-(C₇H₅O₃,required169.014247)。

Referring to fig. 10, 11, 12 and 13, there are shown a nuclear magnetic resonance hydrogen spectrum, a nuclear magnetic resonance carbon spectrum, an infrared spectrum and a high-resolution mass spectrum of phloroglucinol I, which is a product of step 2 of example 1 of the present invention.

Nuclear magnetic resonance hydrogen spectrum:¹H-NMR(400MHz,DMSO-D6)δ(ppm):8.95,5.67.

nuclear magnetic resonance carbon spectrum:¹³C-NMR(101MHz,DMSO-D6)δ(ppm):159.38,94.55.

infrared spectrogram: 3208cm^-1,1621cm^-1，1504cm^-1，1415cm^-1，1331cm^-1，1298cm^-1，1153cm^-1，1006cm^-1，997cm^-1,813cm^-1，799cm^-1，666cm^-1，579cm^-1，518cm^-1。

High resolution mass spectrum: HR-MS (ESI) 125.024444[ M-H ]]-(C₆H₅O₃,required125.024418)。

Example 2

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 1, except that: the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:5, the reaction temperature is 90 ℃, the reaction time is 2 hours, the used inorganic base is sodium carbonate, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 86%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 1, except that: the mass ratio of potassium permanganate to 2,4, 6-trihydroxytoluene is 2: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene is 1: 2; the reaction temperature of the oxidation reaction is 60 ℃, the reaction time of the oxidation reaction is 1h, and the yield of the phloroglucinol finally obtained is 91%.

Example 3

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 1, except that: the sulfuric acid is diluted to 20% by mass, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 10:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:7, the reaction temperature is 100 ℃, the reaction time is 6h, the used inorganic base is sodium bicarbonate, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 88%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 1, except that: the mass ratio of potassium permanganate to 2,4, 6-trihydroxytoluene is 6: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene is 1: 1.5; the reaction temperature of the oxidation reaction is 80 ℃, the reaction time of the oxidation reaction is 2 hours, and the yield of the phloroglucinol finally obtained is 94%.

Example 4

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 1, except that: the sulfuric acid is diluted to 40% by mass, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 15:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:9, the reaction temperature is 110 ℃, the reaction time is 10 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 91%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 1, except that: the mass ratio of potassium permanganate to 2,4, 6-trihydroxytoluene is 10: 1; the mass ratio of the magnesium sulfate to the 2,4, 6-trihydroxytoluene is 2: 1; the reaction temperature of the oxidation reaction is 100 ℃, the reaction time of the oxidation reaction is 4 hours, and the yield of the phloroglucinol finally obtained is 95%.

Example 5

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 1, except that: the sulfuric acid is diluted to 60% by mass, the mass ratio of the sulfuric acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 4:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:10, the reaction temperature is 120 ℃, the reaction time is 12 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 94%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 1, and is not described in detail in this embodiment.

In the above examples 2 to 5, the obtained nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high resolution mass spectrum of 2,4, 6-trihydroxytoluene II are respectively the same as those in fig. 2, 3, 4 and 5, and are not repeated in examples 2 to 5; the nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrogram and high-resolution mass spectrogram of the obtained phloroglucinol are respectively the same as those in the figures 10, 11, 12 and 13, and are not repeated in the examples 2 to 5.

Example 6

Step 1: preparation of 2,4, 6-trihydroxytoluene.

2,4, 6-Triaminotoluene hydrochloride (100mmol, 24.65g) was dissolved in 150g of a 10% phosphoric acid solution (17.6g, 85 wt% phosphoric acid solution, 132.4g deionized water) and heated to 130 ℃ under reflux for 24 h. After the reaction is finished, cooling to room temperature, gradually adding sodium hydroxide solid into the solution to adjust the pH value of the solution to be weakly acidic pH value of 4, and filtering under reduced pressure. The residue was washed three times with deionized water (3X 200mL), all filtrates were collected, concentrated and crystallized by rotary evaporation at 50 ℃ under 100mbar, and the solid product, 2,4, 6-trihydroxytoluene II (12.6g, 90% yield), was collected by filtration.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of the 2,4, 6-trihydroxytoluene II obtained in the present embodiment are the same as those in fig. 2, 3, 4 and 5, respectively, and are not repeated in the present embodiment.

Step 2 preparation of phloroglucinol

Dissolving 2,4, 6-trihydroxytoluene (14g, 100mmol) and lead dioxide (56g, 234mmol) in 200mL deionized water, adding potassium hydroxide solid (70g, 1.25mol), heating to 135 deg.C, refluxing for 3 hr, monitoring the raw material conversion process by TLC chromatographic column, raising temperature to 150 deg.C after the raw material conversion is complete, and refluxing for 6 hr to achieve the purpose of oxidative demethylation.

NaOH (10g, 0.25mmol) was added to the solution as a solid to adjust the solution to alkaline, insoluble solids were filtered, the filtrate was collected, concentrated HCl was added to adjust the pH of the solution to acidic, and the solution was placed in a freezer for 6 hours to give phloroglucinol (11.3g, 90% yield) after filtration.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of phloroglucinol I obtained in the present embodiment are respectively the same as those in fig. 10, fig. 11, fig. 12 and fig. 13, and are not repeated in this embodiment.

Example 7

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 6, except that: the phosphoric acid solution is diluted to 5% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20:1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 24 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 89%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 6, except that: the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene is 4: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene is 4: 1; the reaction temperature of the oxidation reaction is 90 ℃, the reaction pressure of the oxidation reaction is 0.4MPa, the reaction time of the oxidation reaction is 0.5h, and the yield of the phloroglucinol finally obtained is 91%.

Example 8

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 6, except that: the phosphoric acid solution is diluted to 20% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 15:1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 100 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 36h, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 91%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 6, except that: the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene is 6: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene is 5: 1; the reaction temperature of the oxidation reaction is 120 ℃, the reaction pressure of the oxidation reaction is 0.8MPa, the reaction time of the oxidation reaction is 1.5h, and the yield of the phloroglucinol obtained finally is 93%.

Example 9

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 6, except that: the phosphoric acid solution is diluted to 40% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 10:1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 140 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 48h, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 92%.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 6, except that: the mass ratio of the lead dioxide to the 2,4, 6-trihydroxytoluene is 8: 1; the mass ratio of the potassium hydroxide to the 2,4, 6-trihydroxytoluene is 6: 1; the reaction temperature of the oxidation reaction is 150 ℃, the reaction pressure of the oxidation reaction is 1.2MPa, the reaction time of the oxidation reaction is 3h, and the yield of the phloroglucinol obtained finally is 93%.

Example 10

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 6, except that: the phosphoric acid solution is diluted to 60% by mass, the mass ratio of the phosphoric acid solution to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 4:1, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 180 ℃, the reaction solvent of the hydrolysis-isomerization reaction of the enamine is water, the reaction time of the hydrolysis-isomerization reaction of the enamine is 72 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 92%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

In examples 7 to 10, the obtained nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high resolution mass spectrum of 2,4, 6-trihydroxytoluene II are respectively the same as those in fig. 2, 3, 4 and 5, and are not repeated in examples 7 to 10; the obtained hydrogen nuclear magnetic resonance spectrum, carbon nuclear magnetic resonance spectrum, infrared spectrogram and high-resolution mass spectrogram of phloroglucinol are respectively the same as those in figures 10, 11, 12 and 13, and are not repeated in examples 7 to 10.

Example 11

Step 1: preparation of 2,4, 6-trihydroxytoluene.

2,4, 6-Triaminotoluene hydrochloride (100mmol, 24.65g) was dissolved in 200g of a 5% by weight solution of methanesulfonic acid (10g of methanesulfonic acid, 190g of deionized water), and NH was added₄Cl (50mmol, 2.6g), heated to 90 ℃ under reflux for 10 h. After the reaction is finished, cooling to room temperature, gradually adding sodium hydroxide solid into the solution to adjust the pH value of the solution to be weakly acidic pH value of 4, and filtering under reduced pressure. The residue was washed three times with deionized water (3X 200mL), all filtrates were collected, concentrated and crystallized by rotary evaporation at 50 ℃ under 100mbar, and the solid product, 2,4, 6-trihydroxytoluene II (12.3g, 88% yield), was collected by filtration.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of the 2,4, 6-trihydroxytoluene II obtained in the present embodiment are the same as those in fig. 2, 3, 4 and 5, respectively, and are not repeated in the present embodiment.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment. The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of phloroglucinol I obtained in the present embodiment are respectively the same as those in fig. 10, fig. 11, fig. 12 and fig. 13, and are not repeated in this embodiment.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of phloroglucinol I obtained in the present embodiment are respectively the same as those in fig. 10, fig. 11, fig. 12 and fig. 13, and are not repeated in this embodiment.

Example 12

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 11, except that: the methanesulfonic acid is diluted to 5 mass percent, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:5, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 4 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 87%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 13

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 11, except that: the methanesulfonic acid is diluted to 20 mass percent, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 15:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:7, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 100 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 8 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 88 percent.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 14

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 11, except that: the methanesulfonic acid is diluted to 40% by mass, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 10:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:9, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 140 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 10 hours, the reaction solvent of the oxidation reaction is chloroform, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 90%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 15

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 11, except that: the methanesulfonic acid is diluted to 60 mass percent, the mass ratio of the methanesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 4:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 180 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 14h, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 91%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment. In examples 12 to 15, the obtained nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high resolution mass spectrum of 2,4, 6-trihydroxytoluene II are respectively the same as those in fig. 2, 3, 4 and 5, and are not repeated in examples 12 to 15; the obtained hydrogen nuclear magnetic resonance spectrum, carbon nuclear magnetic resonance spectrum, infrared spectrogram and high-resolution mass spectrogram of phloroglucinol are respectively the same as those in figures 10, 11, 12 and 13, and are not repeated in examples 12 to 15.

Example 16

Step 1: preparation of 2,4, 6-trihydroxytoluene.

2,4, 6-Triaminotoluene hydrochloride (100mmol, 24.65g) was dissolved in 150g of a 10% by mass p-toluenesulfonic acid solution (15g of methanesulfonic acid, 145g of deionized water) and heated to 70 ℃ under reflux for 4 h. After the reaction is finished, cooling to room temperature, gradually adding sodium hydroxide solid into the solution to adjust the pH value of the solution to be weakly acidic pH value of 5, and filtering under reduced pressure. The residue was washed three times with deionized water (3X 200mL), all filtrates were collected, concentrated and crystallized by rotary evaporation at 50 ℃ under 100mbar, and the solid product, 2,4, 6-trihydroxytoluene II (11.9g, 85% yield), was collected by filtration.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of the 2,4, 6-trihydroxytoluene II obtained in the present embodiment are the same as those in fig. 2, 3, 4 and 5, respectively, and are not repeated in the present embodiment.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment. The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of phloroglucinol I obtained in the present embodiment are respectively the same as those in fig. 10, fig. 11, fig. 12 and fig. 13, and are not repeated in this embodiment.

Example 17

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 16, except that: the p-toluenesulfonic acid is diluted to 5% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 20:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:5, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 60 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 2 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 84%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 18

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 16, except that: the p-toluenesulfonic acid is diluted to 20% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 15:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:7, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 100 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 4 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 88%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 19

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 16, except that: the p-toluenesulfonic acid is diluted to 40% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 10:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:9, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 140 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 8 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 90%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment.

Example 20

The implementation of step 1 in this embodiment is similar to that of step 1 in embodiment 16, except that: the p-toluenesulfonic acid is diluted to 60% by mass, the mass ratio of the p-toluenesulfonic acid to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 4:1, the mass ratio of the ammonium chloride to the 2,4, 6-triaminotoluene and the hydrochloride thereof is 1:10, the reaction temperature of the hydrolysis-isomerization reaction of the enamine is 180 ℃, the reaction time of the hydrolysis-isomerization reaction of the enamine is 12 hours, and the yield of the finally obtained 2,4, 6-trihydroxytoluene II is 91%.

The implementation content of step 2 in this embodiment is the same as the implementation content of step 2 in embodiment 6, and is not described in detail in this embodiment. In the above examples 17 to 20, the obtained nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high resolution mass spectrum of 2,4, 6-trihydroxytoluene II are respectively the same as those in fig. 2, 3, 4 and 5, and are not repeated in examples 17 to 20; the obtained hydrogen nuclear magnetic resonance spectrum, carbon nuclear magnetic resonance spectrum, infrared spectrogram and high-resolution mass spectrogram of phloroglucinol are respectively the same as those in figures 10, 11, 12 and 13, and are not repeated in examples 17 to 20.

Example 21

Step 1: preparation of 2,4, 6-trihydroxytoluene.

2,4, 6-Triaminotoluene hydrochloride (100mmol, 24.65g) was dissolved in 130g of 5% by weight dilute sulfuric acid (6.5g sulfuric acid, 123.5g deionized water), and NH was added₄Cl (45mmol, 2.4g) and heated to 105 ℃ under reflux for 4 h. After the reaction was completed, it was cooled to room temperature. The mixture is directly transferred into an electrolytic bath without further separation.

Step 2 preparation of phloroglucinol

Potassium dichromate (29g,100mmol) and 24g of dilute sulfuric acid solution diluted to 40% mass fraction are sequentially added to the reaction solution, a carbon electrode is inserted at the cathode, and an anode is insertedAdding Cr electrode, heating to 50 deg.C, regulating voltage to 3.3V, and regulating current to 550 A.m^-2. The reaction was continued for about 4 hours with continued stirring until the solution changed from orange to grayish green, the conversion of starting material was monitored by TLC, and the electrodes were removed. The temperature is increased to 150 ℃ again, and the reflux is carried out for 4 hours, thereby achieving the purpose of oxidative demethylation.

NaOH (10g, 0.25mmol) was added to the solution to adjust the solution to alkaline, insoluble solids in the reaction solution were filtered off, the filtrate was collected, concentrated hydrochloric acid was added to adjust the pH of the solution to acidic, and the solution was placed in a refrigerator for 6 hours to obtain phloroglucinol (11.6g, 97%) after filtration.

The nuclear magnetic resonance hydrogen spectrum, nuclear magnetic resonance carbon spectrum, infrared spectrum and high-resolution mass spectrum of phloroglucinol I obtained in the present embodiment are respectively the same as those in fig. 10, fig. 11, fig. 12 and fig. 13, and are not repeated in this embodiment.

Example 22

The implementation content of step 1 in this embodiment is the same as the implementation content of step 1 in embodiment 16, and is not described herein again.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 23, except that: the mass ratio of the potassium dichromate to the 2,4, 6-trihydroxytoluene is 3: 1; the dilute sulfuric acid solution is diluted to 15% by mass, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 20: 1; the reaction temperature of the oxidation reaction is 30 ℃, the reaction time of the oxidation reaction is 1h, the anode material is carbon, the cathode material is carbon, the voltage is 2.5V, and the current density is 400 A.m^-2。

Example 23

The implementation content of step 1 in this embodiment is the same as the implementation content of step 1 in embodiment 16, and is not described herein again.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 23, except that: the mass ratio of the potassium dichromate to the 2,4, 6-trihydroxytoluene is 1: 2; the dilute sulfuric acid solution is a sulfuric acid solution diluted to 30% by mass, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 15: 1; reaction of oxidation reactionThe reaction temperature is 60 ℃, the reaction time of the oxidation reaction is 4h, the anode material is Pt, the cathode material is Pt, the voltage is 3V, and the current density is 500 A.m^-2。

Example 24

The implementation content of step 1 in this embodiment is the same as the implementation content of step 1 in embodiment 16, and is not described herein again.

The implementation of step 2 in this embodiment is similar to that of step 2 in embodiment 23, except that: the mass ratio of the potassium dichromate to the 2,4, 6-trihydroxytoluene is 1: 10; the dilute sulfuric acid solution is diluted to 60% by mass, and the mass ratio of the dilute sulfuric acid solution to the 2,4, 6-trihydroxytoluene is 5: 1; the reaction temperature of the oxidation reaction is 110 ℃, the reaction time of the oxidation reaction is 8h, the anode material is Cr, the cathode material is Cr, the voltage is 3.5V, and the current density is 600 A.m^-2。

In examples 22 to 24, the nuclear magnetic resonance hydrogen spectrum, the nuclear magnetic resonance carbon spectrum, the infrared spectrum, and the high-resolution mass spectrum of the phloroglucinol obtained were the same as those in fig. 10, 11, 12, and 13, respectively, and were not repeated in examples 22 to 24.

It should be noted that the steps and methods in the embodiments of the present application are not limited to the corresponding embodiments, and the details of the operations and the cautions of the embodiments are all corresponding to each other.

For simplicity of explanation, the method embodiments are described as a series of acts or combinations, but those skilled in the art will appreciate that the present invention is not limited by the order of acts, as some steps may occur in other orders or concurrently in accordance with the invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are preferred embodiments and that the acts and elements referred to are not necessarily required to practice the invention.

The method for preparing phloroglucinol from 2,4, 6-triaminotoluene provided by the invention is described in detail above, and the principle and the implementation mode of the invention are explained in the text by applying specific examples, and the description of the examples is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.