Preparation method of 4-methoxyphenylhydrazine hydrochloride

Abstract

The invention relates to the technical field of chemical synthesis, and particularly provides a preparation method of 4-methoxyphenylhydrazine hydrochloride, which comprises the following steps: S1, carrying out reduction reaction on diazonium 4-methoxybenzene and triphenylphosphine to generate (4-methoxyphenylhydrazine) triphenylphosphine chloride; and step S2, enabling the (4-methoxyphenylhydrazine) triphenylphosphonium chloride to react with hydrochloric acid, so as to generate the 4-methoxyphenylhydrazine hydrochloride. According to the preparation method provided by the embodiment of the invention, the whole process is simple to operate, the post-treatment process is also simple and feasible, and the used raw materials are high in safety and low in cost, so that the preparation method is very suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and more specifically, relates to a disodium 4-nitrophenyl phosphate and a preparation method thereof. Background Art

[0002] 4-Methoxyphenylhydrazine hydrochloride is a very important intermediate, widely used in pharmaceutical intermediates and dyes.

[0003] At present, the main synthesis method of 4-methoxyphenylhydrazine hydrochloride is to use diazo 4-methoxybenzene as raw material for diazonium salt reduction. There are two main routes for diazonium salt reduction: one is to use sulfite and sodium pyrosulfite as reducing agents to first form phenylhydrazine disulfonate, and then hydrolyze with hydrochloric acid to obtain 4-methoxyphenylhydrazine hydrochloride; the other is to use concentrated hydrochloric acid solution of stannous chloride at 5-10°C.

[0004] However, the above processes all have certain disadvantages, such as the use of a large amount of reducing agent in the reaction, the highly toxic stannous chloride, the generation of a large amount of saline wastewater, which causes serious pollution, low yield and high cost. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing 4-methoxyphenylhydrazine hydrochloride which is simple to operate, has little three wastes, is highly safe, has a high yield and is suitable for industrial production.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The preparation method of 4-methoxyphenylhydrazine hydrochloride according to an embodiment of the present invention comprises: Step S1, reducing 4-methoxybenzene diazo and triphenylphosphine to generate (4-methoxyphenylhydrazine)triphenylphosphine chloride; Step S2, reacting the (4-methoxyphenylhydrazine)triphenylphosphine chloride with hydrochloric acid to generate 4-methoxyphenylhydrazine hydrochloride.

[0007] In some embodiments of the present invention, the preparation method further comprises: Step S01, diazotizing 4-methoxyaniline to generate the diazo 4-methoxybenzene.

[0008] Furthermore, the step S01 includes: The 4-methoxyaniline is dissolved with hydrochloric acid and an aqueous solution, and a sodium nitrite aqueous solution is added dropwise thereto to cause the diazotization reaction to generate the diazo 4-methoxybenzene.

[0009] Furthermore, the temperature of the diazotization reaction is 0-10° C., the mass fraction of the sodium nitrite aqueous solution is 10%-30%, the molar ratio of 4-methoxyaniline: hydrochloric acid: sodium nitrite is 1:(2.3-3.2):(1-1.2), and the reaction time is 1-3 hours.

[0010] In some embodiments of the present invention, step S1 comprises: After the reaction in step S01 is completed, tetrahydrofuran is added to the reaction system until it is completely dissolved, and the triphenylphosphine is added in batches to cause the reduction reaction to generate the (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0011] Furthermore, the molar ratio of the diazo 4-methoxybenzene to triphenylphosphine is 1:(1-3).

[0012] Furthermore, the step S1 further includes: After the reduction reaction is completed, the mixture is concentrated, and the concentrated residue is dissolved with dichloromethane, and then crystallized at 0-5° C. to obtain the (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0013] In some embodiments of the present invention, step S2 includes: Step S21, subjecting the (4-methoxyphenylhydrazine)triphenylphosphine chloride to an acidification reaction in a concentrated hydrochloric acid solution, and alkalizing the solution with a sodium hydroxide solution to generate 4-methoxyphenylhydrazine; Step S22, causing the 4-methoxyphenylhydrazine to react with hydrochloric acid gas to generate 4-methoxyphenylhydrazine hydrochloride.

[0014] Furthermore, the step S21 includes: The (4-methoxyphenylhydrazine)triphenylphosphine chloride is heated to reflux in the presence of acetonitrile and hydrochloric acid to cause the acidification reaction, and is alkalized using a sodium hydroxide solution to generate the 4-methoxyphenylhydrazine, wherein the molar ratio of the (4-methoxyphenylhydrazine)triphenylphosphine chloride:hydrochloric acid is 1:(3-6).

[0015] Furthermore, in the step S21, after the acidification reaction is completed, the mixture is filtered, the pH of the filtrate is adjusted to 10-12, and the upper organic phase is separated to obtain the acetonitrile solution of 4-methoxyphenylhydrazine for use in step S22.

[0016] Furthermore, the step S22 includes: The acetonitrile solution of 4-methoxyphenylhydrazine is dried over anhydrous sodium sulfate, filtered, and hydrochloric acid gas is passed through the filtrate at 20-30° C. to precipitate a solid; The solid was filtered, rinsed with acetonitrile and dried to obtain the 4-methoxyphenylhydrazine hydrochloride.

[0017] The above technical solution of the present invention has at least one of the following beneficial effects: Compared with the prior art, the preparation method according to the embodiment of the present invention does not need to use excessive, toxic reducing agents, the reaction conditions are relatively mild and easy to control, and the post-treatment is simple, the pollution is small, the yield is high, and it is suitable for industrial production; Furthermore, (4-methoxyphenylhydrazine)triphenylphosphine chloride is reacted with hydrochloric acid in two steps to generate 4-methoxyphenylhydrazine hydrochloride. In the first step, a hydrochloric acid solution is used for acidification reaction and sodium hydroxide is reacted to generate 4-methoxyphenylhydrazine. In the second step, 4-methoxyphenylhydrazine is reacted with hydrochloric acid gas to generate a salification reaction, thereby achieving higher purity and higher yield. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0019] The following first describes in detail the preparation method of 4-methoxyphenylhydrazine hydrochloride according to an embodiment of the present invention.

[0020] The preparation method of 4-methoxyphenylhydrazine hydrochloride according to an embodiment of the present invention comprises: Step S1, reducing 4-methoxybenzene diazo and triphenylphosphine to generate (4-methoxyphenylhydrazine)triphenylphosphine chloride; Step S2, reacting the (4-methoxyphenylhydrazine)triphenylphosphine chloride with hydrochloric acid to generate 4-methoxyphenylhydrazine hydrochloride.

[0021] That is to say, according to the preparation method of the present invention, triphenylphosphine is used as a reducing agent for the reaction. Compared with stannous chloride, triphenylphosphine is less toxic and more environmentally friendly. Compared with sodium sulfite, it does not require the use of excessive reducing agents, and produces less wastewater and is more environmentally friendly.

[0022] In some embodiments of the present invention, the preparation method further comprises: Step S01, diazotizing 4-methoxyaniline to generate the diazo 4-methoxybenzene.

[0023] That is, as diazo 4-methoxybenzene, a commercially available product may be used, or it may be prepared by subjecting 4-methoxyaniline as a starting material to a diazotization reaction.

[0024] Below, taking 4-methoxyaniline as the starting raw material as an example, each step is described in detail.

[0025] (i) S01, diazotizing 4-methoxyaniline to generate the diazo 4-methoxybenzene.

[0026] That is to say, the preparation method of the present application uses the more readily available and stable 4-methoxyaniline as the starting raw material, which is first diazotized to obtain diazo 4-methoxybenzene.

[0027] In some embodiments of the present invention, step S01 includes: The 4-methoxyaniline is dissolved with hydrochloric acid and an aqueous solution, and a sodium nitrite aqueous solution is added dropwise thereto to cause the diazotization reaction to generate the diazo 4-methoxybenzene.

[0028] Specifically, the reaction formula of the diazotization reaction is shown in the following formula (1): (1) Wherein, the mass fraction of the sodium nitrite aqueous solution is 10% to 30%.

[0029] The temperature of the diazotization reaction is 0-10°C, and the reaction time is 1-3h.

[0030] The molar ratio of 4-methoxyaniline: hydrochloric acid: sodium nitrite is 1: (2.3-3.2): (1-1.2).

[0031] (ii) S1, 4-methoxybenzene diazo and triphenylphosphine undergo reduction reaction to generate (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0032] That is, after obtaining the diazonium salt, it is first subjected to a reduction reaction to obtain an intermediate.

[0033] In view of the problems existing in the existing reduction routes (either too much reducing agent is used, a lot of wastewater is produced, or the reducing agent is highly toxic and not suitable for industrial production), the inventors of the present invention proposed, based on repeated studies, for the first time, using triphenylphosphine as a reducing agent to reduce it to (4-methoxyphenylhydrazine)triphenylphosphine chloride, and then obtaining the target product 4-methoxyphenylhydrazine through an acidification reaction.

[0034] Specifically, the reaction equation of the reduction reaction is shown in the following equation (2): (2) According to some embodiments of the present invention, step S1 comprises: After the reaction in step S01 is completed, tetrahydrofuran is added to the reaction system until it is completely dissolved, and the triphenylphosphine is added in batches to cause the reduction reaction to generate the (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0035] That is, after the diazotization reaction, there is no need to perform special treatment on the system. By using a one-pot method, tetrahydrofuran is directly added to the system until it is completely dissolved, and then triphenylphosphine is added in batches to cause a reduction reaction.

[0036] In some embodiments of the present invention, the molar ratio of diazo 4-methoxybenzene to triphenylphosphine is 1:(1-3).

[0037] In some embodiments of the present invention, the step S1 further includes: After the reduction reaction is completed, the mixture is concentrated, and the concentrated residue is dissolved with dichloromethane, and then crystallized at 0-5° C. to obtain the (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0038] That is to say, after the reduction reaction, only simple concentration and crystallization treatment are required, and the obtained (4-methoxyphenylhydrazine)triphenylphosphine chloride can be directly used in subsequent reactions, which is simple to operate, reduces three wastes, and is low in cost.

[0039] (iii) S2, reacting the (4-methoxyphenylhydrazine)triphenylphosphine chloride with hydrochloric acid to generate 4-methoxyphenylhydrazine hydrochloride.

[0040] That is, after the intermediate (4-methoxyphenylhydrazinyl)triphenylphosphine chloride is obtained by reduction reaction, it is first reacted with hydrochloric acid to produce 4-methoxyphenylhydrazine hydrochloride.

[0041] The inventors of the present invention have found through repeated studies that the reaction between (4-methoxyphenylhydrazinyl)triphenylphosphine chloride and hydrochloric acid is divided into two steps, namely: S21, subjecting (4-methoxyphenylhydrazine)triphenylphosphine chloride to an acidification reaction in a concentrated hydrochloric acid solution, and alkalizing with a sodium hydroxide solution to generate 4-methoxyphenylhydrazine; S22, causing 4-methoxyphenylhydrazine to react with hydrochloric acid gas to generate 4-methoxyphenylhydrazine hydrochloride.

[0042] This can not only improve the purity of the product, but also effectively improve the overall yield.

[0043] In some embodiments of the present invention, step S21 includes: The (4-methoxyphenylhydrazine)triphenylphosphine chloride is heated under reflux in the presence of acetonitrile and hydrochloric acid to cause the acidification reaction, and then alkalized with a sodium hydroxide solution to generate the 4-methoxyphenylhydrazine.

[0044] That is, the acidification reaction produces 4-methoxyphenylhydrazine hydrochloride, which is then alkalized with a sodium hydroxide aqueous solution to produce 4-methoxyphenylhydrazine.

[0045] Specifically, the reaction equation of the acidification reaction is shown in the following equation (3): (3) Wherein, the molar ratio of (4-methoxyphenylhydrazine)triphenylphosphine chloride:hydrochloric acid is 1:(3~6).

[0046] In some embodiments of the present invention, in step S21, after the acidification reaction is completed, the reaction is filtered, and the pH of the filtrate is adjusted to 10-12 using, for example, NaOH, and the upper organic phase is separated to obtain the acetonitrile solution of 4-methoxyphenylhydrazine for use in step S22.

[0047] In other words, the post-treatment of the acidification reaction is also simple and easy to operate, does not produce excessive wastewater, and has low cost.

[0048] In some embodiments of the present invention, step S22 includes: reacting the 4-methoxyphenylhydrazine with hydrochloric acid gas to generate 4-methoxyphenylhydrazine hydrochloride.

[0049] That is, after obtaining 4-methoxyphenylhydrazine, 4-methoxyphenylhydrazine is further reacted with hydrochloric acid gas to generate the target product 4-methoxyphenylhydrazine hydrochloride.

[0050] Specifically, the reaction equation of the salification reaction is shown in the following equation (4): (4) In some embodiments of the present invention, step S22 includes: The acetonitrile solution of 4-methoxyphenylhydrazine was dried over anhydrous sodium sulfate, filtered, and hydrochloric acid gas was passed through the filtrate at 20-30°C to precipitate a solid; The solid was filtered, rinsed with acetonitrile and dried to obtain the 4-methoxyphenylhydrazine hydrochloride.

[0051] When hydrochloric acid is introduced, yellow solid begins to precipitate from the system until it turns pink, indicating that the reaction is complete, and the hydrochloric acid gas is stopped. After the gas is completed, the solid is filtered out, rinsed with acetonitrile, and dried to obtain the 4-methoxyphenylhydrazine hydrochloride.

[0052] It can be seen from the above records that according to the preparation method of the present application, the whole process is simple to operate, and the post-treatment process is also simple and easy, the raw materials used are highly safe and low in cost, and are very suitable for industrial-scale production.

[0053] Below, the preparation method of 4-methoxyphenylhydrazine hydrochloride of the present invention is further described in detail by specific examples. Example 1

[0054] 1): Take a 5000ml three-necked flask, add water (483ml, 2V) and concentrated hydrochloric acid (595g, 5.88mol, 3.0eq), add 4-methoxyaniline (241.5g, 1.96mol, 1.0eq) in batches, and cool to 0-10℃. Add 25% sodium nitrite aqueous solution (552g, 2.0mol, 1.02eq) dropwise, control the dropping temperature to 0-10℃, and the dropping time is about 2-3 hours; after the dropping is completed, keep warm and stir at 0-10℃ for 1-2 hours to obtain diazo 4-methoxybenzene solution.

[0055] 2): Add tetrahydrofuran (725ml, 3V) to the diazo 4-methoxybenzene solution until it is completely dissolved, add triphenylphosphine (565.5g, 2.16mol, 1.1eq) in batches at 0-5℃, raise the temperature to 30℃ after completion, and react for 3.5 hours. Control the temperature at 55-65℃, concentrate to dryness under reduced pressure, add dichloromethane (725ml, 3V) to the concentrated residue to dissolve, slowly cool to 0-5℃ to crystallize, filter, and dry to obtain (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0056] 3): Take a 5000ml three-necked flask, add (4-methoxyphenylhydrazine)triphenylphosphine chloride (674g, 1.67mol, 1.0eq), acetonitrile (2022ml, 3V) and concentrated hydrochloric acid (677g, 6.68mol, 4.0eq), heat to 80℃ and react for 2-3 hours. After the reaction is completed, cool to 20-25℃, filter to remove insoluble solids, adjust the filtrate to pH = 10-12 with sodium hydroxide aqueous solution to obtain 4-methoxyphenylhydrazine acetonitrile solution.

[0057] 4): Add 67g of anhydrous sodium sulfate to the acetonitrile solution of 4-methoxyphenylhydrazine, stir for 5-10 minutes, filter, pass hydrochloric acid gas into the filtrate at 20-30°C, and a yellow solid begins to precipitate from the reaction system until it turns pink. Stop passing hydrochloric acid gas, filter, rinse with acetonitrile, and dry to obtain 241.7g of 4-methoxyphenylhydrazine hydrochloride, with a liquid content of 99.7%, a melting point of 168.2°C, and a final molar total yield of 70.6% (calculated based on the amount of p-methoxyaniline fed).

[0058] The structure of the obtained product was confirmed by nuclear magnetic resonance experiment, and the data are as follows: 1The detection results of H NMR (400 MHz,DMSO-d6) δ 3.69 (s, 3H), 6.89 (d,2H,J=8.8Hz), 7.02(d, 2H,J=8.8Hz), 10.12(brs,3H,D2O exch.) were consistent with the structure of 4-methoxyphenylhydrazine hydrochloride. Example 2

[0059] 1): Take a 5000ml three-necked flask, add water (483ml, 2V) and concentrated hydrochloric acid (595g, 5.88mol, 3.0eq), add 4-methoxyaniline (241.5g, 1.96mol, 1.0eq) in batches, and cool to 0-10℃. Add 25% sodium nitrite aqueous solution (552g, 2.0mol, 1.02eq) dropwise, control the dropping temperature to 0-10℃, and the dropping time is about 2-3 hours; after the dropping is completed, keep warm and stir at 0-10℃ for 1-2 hours to obtain diazo 4-methoxybenzene solution.

[0060] 2): Add tetrahydrofuran (725ml, 3V) to the diazo 4-methoxybenzene solution until it is completely dissolved, add triphenylphosphine (1286.8g, 2.5eq) in batches at 0-5℃, raise the temperature to 30℃ after completion, and react for 3.5 hours. Control the temperature at 55-65℃, concentrate to dryness under reduced pressure, add dichloromethane (725ml, 3V) to the concentrated residue to dissolve, slowly cool to 0-5℃ to crystallize, filter, and dry to obtain (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0061] 3): Take a 5000ml three-necked flask, add (4-methoxyphenylhydrazine)triphenylphosphine chloride (680g, 1.68mol, 1.0eq), acetonitrile (2040ml, 3V) and concentrated hydrochloric acid (681g, 6.72mol, 4.0eq), heat to 80℃ and react for 2-3 hours. After the reaction is completed, cool to 20-25℃, filter to remove insoluble solids, adjust the filtrate to pH = 10-12 with sodium hydroxide aqueous solution to obtain 4-methoxyphenylhydrazine acetonitrile solution.

[0062] 4): Add 68g of anhydrous sodium sulfate to the acetonitrile solution of 4-methoxyphenylhydrazine, stir for 5-10 minutes, filter, pass hydrochloric acid gas into the filtrate at 20-30°C, and a yellow solid begins to precipitate from the reaction system until it turns pink. Stop passing hydrochloric acid gas, filter, rinse with acetonitrile, and dry to obtain 247.8g of 4-methoxyphenylhydrazine hydrochloride, with a liquid content of 99.9%, a melting point of 168.2°C, and a final molar total yield of 72.3% (calculated based on the amount of p-methoxyaniline fed).

[0063] The NMR data results are the same as those in Example 1, and their detailed description is omitted here.

[0064] Example 3 1): Take a 5000ml three-necked flask, add water (483ml, 2V) and concentrated hydrochloric acid (497g, 4.9mol, 2.5eq), add p-methoxyaniline (241.5g, 1.96mol, 1.0eq) in batches, and cool to 0-10℃. Add 25% sodium nitrite aqueous solution (595g, 2.16mol, 1.1eq) dropwise, control the dropping temperature to 0-10℃, and the dropping time is about 2-3 hours; after the dropping is completed, keep warm and stir at 0-10℃ for 1-2 hours to obtain diazo 4-methoxybenzene solution.

[0065] 2): Add tetrahydrofuran (725ml, 3V) to the diazo 4-methoxybenzene solution until it is completely dissolved, add triphenylphosphine (1542.5g, 5.88mol, 3.0eq) in batches at 0-5℃, raise the temperature to 30℃ after completion, and react for 3.5 hours. Control the temperature at 55-65℃, concentrate to dryness under reduced pressure, add dichloromethane (725ml, 3V) to the concentrated residue to dissolve, slowly cool to 0-5℃ to crystallize, filter, and dry to obtain (4-methoxyphenylhydrazine)triphenylphosphine chloride.

[0066] 3): Take a 5000ml three-necked flask, add (4-methoxyphenylhydrazine)triphenylphosphine chloride (691g, 1.71mol, 1.0eq), acetonitrile (2073ml, 3V) and concentrated hydrochloric acid (866.9g, 8.55mol, 5.0eq), heat to 80℃ and react for 2-3 hours. After the reaction is completed, cool to 20-25℃, filter to remove insoluble solids, adjust the filtrate to pH = 10-12 with sodium hydroxide aqueous solution to obtain 4-methoxyphenylhydrazine acetonitrile solution.

[0067] 4): Add 69g of anhydrous sodium sulfate to the acetonitrile solution of 4-methoxyphenylhydrazine, stir for 5-10 minutes, filter, pass hydrochloric acid gas into the filtrate at 20-30°C, and a yellow solid begins to precipitate from the reaction system until it turns pink. Stop passing hydrochloric acid gas, filter, rinse with acetonitrile, and dry to obtain 254.1g of 4-methoxyphenylhydrazine hydrochloride, with a liquid content of 99.9%, a melting point of 168.2°C, and a final molar total yield of 74.24% (calculated based on the amount of p-methoxyaniline fed).

[0068] In summary, the preparation method of 4-methoxyphenylhydrazine hydrochloride of the present invention has the advantages of less three wastes, low toxicity, short synthesis route, simple operation, low cost and high yield.

[0069] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing 4-methoxyphenylhydrazine hydrochloride, characterized in that, include: Step S1, reducing 4-methoxybenzene diazo and triphenylphosphine to generate (4-methoxyphenylhydrazine)triphenylphosphine chloride; Step S2, reacting the (4-methoxyphenylhydrazine)triphenylphosphine chloride with hydrochloric acid to generate 4-methoxyphenylhydrazine hydrochloride.

2. The preparation method according to claim 1, characterized in that: Also includes: Step S01, diazotizing 4-methoxyaniline to generate the diazo 4-methoxybenzene.

3. The preparation method according to claim 2, characterized in that: The step S01 comprises: The 4-methoxyaniline is dissolved with hydrochloric acid and an aqueous solution, and a sodium nitrite aqueous solution is added dropwise thereto to cause the diazotization reaction to generate the diazo 4-methoxybenzene.

4. The preparation method according to claim 3, characterized in that: The temperature of the diazotization reaction is 0-10° C., the mass fraction of the sodium nitrite aqueous solution is 10%-30%, the molar ratio of 4-methoxyaniline: hydrochloric acid: sodium nitrite is 1: (2.3-3.2): (1-1.2), and the reaction time is 1-3 hours.

5. The preparation method according to claim 3, characterized in that: The step S1 comprises: After the reaction in step S01 is completed, tetrahydrofuran is added to the reaction system until it is completely dissolved, and the triphenylphosphine is added in batches to cause the reduction reaction to generate the (4-methoxyphenylhydrazine)triphenylphosphine chloride. Wherein, the molar ratio of diazo 4-methoxybenzene to triphenylphosphine is 1:(1-3).

6. The preparation method according to claim 5, characterized in that: The step S1 further comprises: After the reduction reaction is completed, the mixture is concentrated, and the concentrated residue is dissolved with dichloromethane, and then crystallized at 0-5° C. to obtain the (4-methoxyphenylhydrazine)triphenylphosphine chloride.

7. The preparation method according to claim 1, characterized in that: The step S2 comprises: Step S21, subjecting the (4-methoxyphenylhydrazine)triphenylphosphine chloride to an acidification reaction in a concentrated hydrochloric acid solution, and alkalizing the solution with a sodium hydroxide solution to generate 4-methoxyphenylhydrazine; Step S22, causing the 4-methoxyphenylhydrazine to react with hydrochloric acid gas to generate 4-methoxyphenylhydrazine hydrochloride.

8. The preparation method according to claim 7, characterized in that: The step S21 comprises: The (4-methoxyphenylhydrazine)triphenylphosphine chloride is heated to reflux in the presence of acetonitrile and hydrochloric acid to cause the acidification reaction, and is alkalized using a sodium hydroxide solution to generate the 4-methoxyphenylhydrazine, wherein the molar ratio of the (4-methoxyphenylhydrazine)triphenylphosphine chloride:hydrochloric acid is 1:(3-6).

9. The preparation method according to claim 8, characterized in that: In the step S21, after the acidification reaction is completed, the reaction is filtered, the pH of the filtrate is adjusted to 10-12, and the upper organic phase is separated to obtain the acetonitrile solution of 4-methoxyphenylhydrazine for use in the step S22.

10. The preparation method according to claim 9, characterized in that: The step S22 comprises: The acetonitrile solution of 4-methoxyphenylhydrazine is dried over anhydrous sodium sulfate, filtered, and hydrochloric acid gas is passed through the filtrate at 20-30° C. to precipitate a solid; The solid was filtered, rinsed with acetonitrile and dried to obtain the 4-methoxyphenylhydrazine hydrochloride.