Preparation method of halogen-free parylene material monomer

Abstract

The invention relates to the technical field of preparation methods of material monomers, and discloses a preparation method of a halogen-free parylene material monomer. The preparation method comprises the following steps: dissolving quaternary ammonium salt A1 in water, adding strong base, starting to react at 95 DEG C, continuously heating, reacting at a first temperature for a first time, reacting at a second temperature for a second time, reacting at a third temperature for a third time, reacting at a fourth temperature for a fourth time, and reacting at a fifth temperature for a fifth time to obtain A2; the mixture is the halogen-free parylene material monomer. The invention provides a novel halogen-free parylene monomer synthesis method which is environment-friendly, safe in process, simple and convenient to operate and efficient, effectively solves the problems of heavy pollution, low yield, difficulty in meeting high-purity halogen-free requirements and the like in the prior art, and is particularly suitable for industrial production with strict requirements on environmental protection and cleanliness in the production process.

Description

Technical Field

[0001] This invention relates to the field of monomer preparation methods, and in particular to a method for preparing halogen-free phenelzine monomers. Background Technology

[0002] Parylene is a high-performance polymer coating material, first developed by Union Carbide Co. in the United States. Due to its unbranched, highly crystallinity, and high molecular weight, it can form uniform, dense, pinhole-free, transparent, stress-free, and additive-free nanoscale films on various complex surfaces (including sharp edges, cracks, and internal surfaces) using vacuum room temperature chemical vapor deposition. These films not only possess excellent electrical insulation, moisture resistance, chemical corrosion resistance, and dielectric protection, but also exhibit chemical inertness and excellent biocompatibility. Having received FDA approval, they are widely used in implantable medical devices and biosensors to improve surface lubricity, biocompatibility, and long-term reliability.

[0003] The performance of phenelzine films depends on their precursor monomers, primarily dimeric p-xylene and its substituted derivatives. Based on differences in molecular structure, various types of phenelzines, such as N, C, F, and HT, have been developed to meet the needs of different applications. However, most traditional phenelzine materials contain halogens (e.g., C-type contains chlorine, F-type contains fluorine). In fields with extremely strict pollutant control, such as semiconductor manufacturing and high-end electronics, the presence of halogens can lead to ionic contamination, corrosion, or environmental hazards, limiting their application range. Therefore, developing halogen-free phenelzines has become an inevitable trend to meet the needs of high-end applications. Halogen-free phenelzines (such as N-type, DM-type, and DE-type) not only completely lack halogen atoms but also have extremely low free halide ion content in the finished product, providing excellent barrier protection. Furthermore, their production and degradation processes do not generate halogen pollutants, making them environmentally friendly and meeting the environmental protection requirements for high-end materials in markets such as Europe and the United States.

[0004] Currently, the preparation and purification technologies for halogen-free phenelzine monomers (such as N powder, DM powder, and DE powder) still have the following prominent drawbacks: 1. Severe pollution during synthesis, inconsistent with green production principles: Existing synthesis methods often use large amounts of organic solvents in the reaction system, resulting in massive amounts of waste liquid and solid waste during production. Although the final product molecular structure does not contain halogens, the entire process has a high environmental load and low resource utilization, which contradicts the direction of sustainable industrial development. 2. Low purification yield and secondary pollution: Traditional purification methods mainly rely on solvent dissolution and recrystallization to remove impurities such as polymers. This process not only consumes a large amount of solvent, generating new waste solvent pollution, but also inevitably dissolves and loses some of the target product during impurity removal, resulting in a low overall product yield and increased production costs. 3. Difficulty in meeting high halogen-free requirements: Halogen-free phenelzines have extremely strict requirements for total halogen content (including trace halide ions). In existing technical routes, some intermediates or auxiliary reagents may still contain halogens, and there is a lack of efficient and targeted post-purification methods to completely remove these halogen residues, making it difficult for the final product to consistently meet the halogen-free standards required for high-end applications such as semiconductors.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing halogen-free phenelzine material monomers, aiming to solve the pollution problem of existing methods for preparing halogen-free phenelzine material monomers.

[0007] The technical solution of the present invention is as follows: This invention provides a method for preparing halogen-free phenelzine monomers, the method comprising the following steps: Quaternary ammonium salt A1 is dissolved in water, a strong base is added, and the reaction is initiated at 95°C. The temperature is continuously increased, and the reaction proceeds at the following times: first at the first temperature for the first time, second at the second temperature for the second time, third at the third temperature for the third time, fourth at the fourth temperature for the fourth time, and fifth at the fifth temperature for the fifth time, to obtain A2, which is the monomer of the halogen-free pyreline material. The reaction route is as follows: ; The first temperature is 95-105℃, the second temperature is 105-110℃, the third temperature is 110-115℃, the fourth temperature is 115-120℃, and the fifth temperature is 120-125℃. The first time is 0.5-2h, the second time is 1-3h, the third time is 1-3h, the fourth time is 1-3h, and the fifth time is 1-4h. X is Cl, Br, or OH, and R is hydrogen, methyl, or ethyl.

[0008] Optionally, the strong base includes one or both of sodium hydroxide and potassium hydroxide.

[0009] Optionally, the mass ratio of water to quaternary ammonium salt A1 is 1:(1-5).

[0010] Preferably, the mass ratio of water to quaternary ammonium salt Al is 1:2.

[0011] Optionally, the mass ratio of the base to the quaternary ammonium salt A1 is 1:(0.3-1).

[0012] Preferably, the mass ratio of the alkali to the quaternary ammonium salt Al is 1:0.5.

[0013] Optionally, the first temperature is 100℃, the second temperature is 105℃, the third temperature is 110℃, the fourth temperature is 115℃, the fifth temperature is 120℃, the first time is 1h, the second time is 2h, the third time is 2h, the fourth time is 2h, and the fifth time is 2h.

[0014] Optionally, after reacting at the fifth temperature for the fifth time, the process further includes the step of purifying the obtained product by superheated steam distillation.

[0015] Optionally, the product is purified by superheated steam distillation, specifically as follows: The reaction system was cooled to 60-90℃, water was added and stirred, and then filtered to obtain a filter cake. The filter cake is subjected to distillation to obtain the halogen-free phenelzine material monomer.

[0016] Optionally, the distillation process takes 4-8 hours, and the amount of water added is 1-10 times the amount of filter cake.

[0017] Optionally, an auxiliary agent, including paraffin oil, may be added during the distillation process.

[0018] The present invention has the following beneficial effects: This invention provides a method for preparing halogen-free phenelzine monomers, which has the following advantages compared with existing methods: 1. Achieving a green, environmentally friendly, and low-pollution synthesis process: The method described in this invention abandons the traditional approach of using large amounts of organic solvents in the synthesis route, and innovatively adopts a solvent-free reaction system with water as the medium for monomer preparation. The entire synthesis process and subsequent purification steps do not use any organic solvents, thus avoiding the generation of large amounts of toxic and harmful waste liquids and waste solvents from the source, significantly reducing the environmental burden and the cost of waste treatment, in line with the concepts of green chemistry and sustainable development. 2. Improving reaction efficiency and conversion rate, and ensuring production safety: This invention designs and adopts a stepped heating method to slowly evaporate water during the reaction process. This strategy can precisely maintain the alkali concentration in the reaction system at a relatively constant level, providing a stable and efficient kinetic environment for the decomposition and cyclization reaction of quaternary ammonium salts. This method effectively overcomes the mass and heat transfer challenges that may exist in solvent-free systems, promoting the full and stable conversion of reactants. This ensures smooth reaction and high conversion rates under high solids content or solvent-free conditions, while avoiding safety hazards caused by localized overheating or runaway reactions. 3. It simplifies the process and helps improve product purity: Because the reaction system is pure and contains no organic solvents or other complex additives, it not only simplifies post-reaction processing steps but also reduces the possibility of impurities introduced by solvents. Combined with specific temperature control, it facilitates the formation of structurally regular target products, laying a solid foundation for obtaining high-purity halogen-free pyreline monomers.

[0019] In summary, this invention provides a novel, environmentally friendly, safe, easy-to-operate, and efficient method for synthesizing halogen-free phenelzine monomers. It effectively solves the problems of heavy pollution, low yield, and difficulty in meeting the requirements for high purity halogen-free phenelzine in existing technologies. It is particularly suitable for industrial production with stringent requirements for environmental protection and cleanliness of the production process. Detailed Implementation

[0020] This invention provides a method for preparing halogen-free phenelzine monomers. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0021] Currently, the industrial preparation of halogen-free phenelzine monomers (such as N-type, DM-type, and DE-type) mainly relies on several traditional synthetic routes. While these routes can achieve the construction of the target molecules, they have significant drawbacks in terms of environmental friendliness, economic efficiency, and product purity control. The following details the main existing preparation methods and their existing problems: 1. The Hoffmann elimination process has the following reaction pathway: ; This method is currently the most common route for synthesizing phenelzine monomer materials. The general process is as follows: First, benzyl halogen-substituted p-xylene or its derivatives are reacted with trimethylamine to generate the corresponding quaternary ammonium salt; subsequently, this quaternary ammonium salt undergoes a Hoffmann elimination reaction under the action of a strong base (such as sodium hydroxide or potassium hydroxide), and through cyclization and dimerization, finally generates the target phenelzine monomer.

[0022] However, this method has the following prominent problems: 1. Poor environmental and operational friendliness: The trimethylamine used in the reaction has a strong odor, which is extremely unfriendly to the production environment and operators, and subsequent treatment is difficult. At the same time, the large amount of waste alkaline liquid generated by the reaction causes serious environmental pressure. 2. Severe equipment corrosion: The strong alkaline environment is highly corrosive to the reaction equipment, increasing equipment maintenance costs and safety hazards. 3. Narrow product spectrum: This method is mainly suitable for synthesizing the simplest phenelzine N (unsubstituted) and phenelzine C (monochlorosubstituted). For phenelzine monomers with other complex substituents (such as DM type, DE type, etc.), its reaction efficiency is significantly reduced or difficult to carry out, limiting product diversity.

[0023] 2. The zinc powder reduction dimerization method has the following reaction pathway: ; This method represents another feasible synthetic route. Typically, dihalogenated p-xylene derivatives are used as raw materials, undergoing a coupling reaction under the reducing action of zinc powder to directly dimerize and generate phenelzine monomers. The advantage of this method is its ability to synthesize various phenelzine monomers with different substituents. However, its disadvantages are equally prominent: 1. Poor atom economy and high cost: The reaction requires stoichiometric, or even excessive, zinc powder as a reducing agent, resulting in low atom utilization and difficulty in controlling production costs.

[0024] 2. Low yield: Due to numerous side reactions, the separation yield of the target product is generally low, which further affects the economic feasibility of the process.

[0025] Based on this, embodiments of the present invention provide a method for preparing halogen-free phenelzine material monomers, the preparation method comprising the following steps: Quaternary ammonium salt A1 is dissolved in water, a strong base is added, and the reaction is initiated at 95°C. The temperature is continuously increased, and the reaction proceeds at the following times: first at the first temperature for the first time, second at the second temperature for the second time, third at the third temperature for the third time, fourth at the fourth temperature for the fourth time, and fifth at the fifth temperature for the fifth time, to obtain A2, which is the monomer of the halogen-free pyreline material. The reaction route is as follows: ; The first temperature is 95-105℃, the second temperature is 105-110℃, the third temperature is 110-115℃, the fourth temperature is 115-120℃, and the fifth temperature is 120-125℃. The first time is 0.5-2h, the second time is 1-3h, the third time is 1-3h, the fourth time is 1-3h, and the fifth time is 1-4h. X is Cl, Br, or OH, and R is hydrogen, methyl, or ethyl.

[0026] This invention provides a green preparation method for halogen-free phenelzine monomers. The core of this method lies in controlling the reaction process through a specific stepwise temperature increase program in a reaction system that completely avoids the use of organic solvents, thereby obtaining the target product with high conversion and high selectivity.

[0027] 1. Overview of the reaction principle This method is based on the Hoffmann elimination reaction. The starting material is a quaternary ammonium salt A1 with a specific structure. Upon heating in a strongly alkaline aqueous solution, this quaternary ammonium salt first undergoes Hoffmann elimination, generating a highly reactive p-xylene diradical intermediate. This intermediate then undergoes intermolecular dimerization and cyclization to form the target product—the halogen-free phenelzine monomer A2.

[0028] It is particularly important to note that while the Hoffmann elimination reaction is a conventional reaction in the field, carrying out this reaction in a homogeneous or high-concentration heterogeneous system with no organic solvents and only water as the medium and dispersant presents unique technical challenges. In systems conventionally diluted with organic solvents, a strong base is usually required to be continuously or batch-wise added to maintain reaction efficiency. However, in the solvent-free (or near-anhydrous) aqueous system of this invention, without the specific control methods of this invention, the reaction conversion rate will be significantly reduced, or even impossible to carry out.

[0029] 2. Key technical solutions of the present invention To solve the reaction problems in the solvent-free system mentioned above, the present invention adopts the following synergistic technical means: (1) Using water as the only reaction medium to construct an organic solvent-free system: all reactants (quaternary ammonium salt A1 and strong base) are directly dissolved or dispersed in water. This step completely eliminates the use of organic solvents in the traditional process, and eliminates the pollution, safety risks and subsequent complex solvent recovery problems caused by solvents from the source.

[0030] (2) Implement a precise stepped heating program: After the reaction starts, instead of using a constant temperature or free heating method, a strictly controlled stepped heating program is implemented. In a preferred embodiment, the heating program is as follows: the reaction starts at about 95°C, and then is maintained at a first temperature (e.g., 100°C) for a first time (e.g., 1h), at a second temperature (e.g., 105°C) for a second time (e.g., 2h), at a third temperature (e.g., 110°C) for a third time (e.g., 2h), at a fourth temperature (e.g., 115°C) for a fourth time (e.g., 2h), and at a fifth temperature (e.g., 120°C) for a fifth time (e.g., 2h). This heating program is a necessary condition for the successful implementation of this method. If a staged, slow heating method is not used, the reaction will not be able to proceed continuously and effectively, and the conversion rate will stagnate at a low level. (3) Dynamically maintain the concentration of key reactants through water evaporation: During the above-mentioned stepped heating process, water is gradually and slowly evaporated. This process is of paramount importance: it allows the concentration of strong base and the local concentration of reactants in the reaction system to be dynamically maintained within a suitable and efficient reaction range. Heating promotes the reaction rate, while the reduction of water compensates for the possible decrease in base concentration due to reaction consumption and dilution effect, forming a positive driving force. This is the key to the reaction continuing to completion under solvent-free conditions. If the base concentration cannot be maintained, the reaction will terminate prematurely. (4) Suppression of side reactions: The method of the present invention effectively suppresses the main side reaction—that is, the uncontrolled self-polymerization of the active intermediate, generating random polymers. By controlling the reaction of reactants at appropriate concentrations (controlled by the initial feeding and evaporation process) and staged temperatures, the ordered and selective intermolecular dimerization cyclization pathway of the diradical intermediate is promoted, thereby improving the selectivity of generating the target dimer (A2).

[0031] In summary, the embodiments of the present invention ingeniously combine a solvent-free aqueous phase system with a precise step-by-step temperature-evaporation control strategy, thus cleverly solving the problems of low conversion rate and incomplete reaction of conventional Hoffmann elimination method under green process conditions, and successfully realizing the efficient and environmentally friendly preparation of halogen-free phenelzine monomers.

[0032] In some embodiments, the strong base includes one or both of sodium hydroxide and potassium hydroxide.

[0033] In some embodiments, the mass ratio of water to quaternary ammonium salt A1 is 1:(1-5).

[0034] In some preferred embodiments, the mass ratio of water to quaternary ammonium salt A1 is 1:2.

[0035] In some embodiments, the mass ratio of the base to the quaternary ammonium salt A1 is 1:(0.3-1).

[0036] In some preferred embodiments, the mass ratio of the alkali to the quaternary ammonium salt A1 is 1:0.5.

[0037] In some embodiments, the first temperature is 100°C, the second temperature is 105°C, the third temperature is 110°C, the fourth temperature is 115°C, the fifth temperature is 120°C, the first time is 1 hour, the second time is 2 hours, the third time is 2 hours, the fourth time is 2 hours, and the fifth time is 2 hours.

[0038] In some embodiments, after reacting at a fifth temperature for a fifth time, the step of purifying the obtained product by superheated steam distillation is further included.

[0039] The purification of halogen-free pyreline using superheated steam distillation can stably and efficiently reduce the halogen impurity content in crude pyreline monomer to extremely low levels. After this purification step, the total halogen residue of the obtained halogen-free pyreline monomer product can be stably below 50 ppm, or even lower (such as below 10 ppm), fully meeting the quality standards of high-end electronic and semiconductor packaging materials.

[0040] In some embodiments, the step of purifying the obtained product by superheated steam distillation specifically includes: The reaction system was cooled to 60-90℃, water was added and stirred, and then filtered to obtain a filter cake. The filter cake is subjected to distillation to obtain the halogen-free phenelzine material monomer.

[0041] In some embodiments, the distillation process takes 4-8 hours and the amount of water added is 1-10 times the amount of filter cake.

[0042] In some embodiments, an auxiliary agent, including paraffin oil, is also added during the distillation process.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0044] The following detailed description uses specific examples.

[0045] Example 1 The preparation of halogen-free phenelzine monomers includes the following steps: Add 50g of quaternary ammonium salt 1 to the reaction flask, add 100mL of purified water and stir until well mixed. Add 25g of sodium hydroxide solid in batches, stirring until the alkali is completely dissolved. Install the distillation apparatus on the reaction flask and turn on the cooling water. Pass the tail gas into a hydrochloric acid aqueous solution for absorption.

[0046] Turn on the heater and react at 95℃ for 1 hour, when bubbles slowly emerge. Increase the temperature to 100℃ and react for 2 hours, then to 105℃ and react for 2 hours, when water slowly evaporates. Continue heating to 110℃ and react for 2 hours, then 115℃ and 120℃ for 2 hours, until almost no distillate drips from the condenser. Continue reacting for another 2 hours. Cool down to below 90℃, add 100mL of water, and maintain the temperature at 90℃ with stirring for 1 hour. Filter while hot, and wash the filter cake with 20mL of purified water.

[0047] Add the filter cake to a distillation flask, add 100 mL of purified water, and heat to reflux. Extend the steam generator tubing to the bottom of the distillation flask. Set up the collection apparatus, add 50 mL of ice water to the collection flask, and submerge the collection tube below the liquid surface. Start the distillation; a white solid precipitates in the collection flask. Distill for 4 hours, then sample the solid from the distillation flask and add dichloromethane. TLC analysis shows almost no product. Stop the distillation.

[0048] Collect the suspension in the flask, cool to 0℃, filter, and dry the filter cake at 50℃. 17.2 g of diphenylmethyl ether N (dimeric p-xylene). Yield 66%, purity 99%. Halogen content less than 50 ppm, non-volatile residues ≤0.2%. 1 HNMR (CDCl3) δ: 6.54~6.69 (m, 8H), 3.03~3.10 (s, 8H).

[0049] The reaction pathway described above is as follows: .

[0050] Example 2 The preparation of halogen-free phenelzine monomers includes the following steps: Add 50g of quaternary ammonium salt 2 to the reaction flask, add 100mL of purified water and stir well. Add 30g of potassium hydroxide solid in batches, stirring until the alkali is completely dissolved. Install the distillation apparatus on the reaction flask and turn on the cooling water. Pass the tail gas into a hydrochloric acid aqueous solution for absorption.

[0051] Turn on the heater and react at 95℃ for 1 hour, when bubbles slowly emerge. Increase the temperature to 100℃ and react for 2 hours, then to 105℃ and react for 2 hours, when water slowly evaporates. Continue heating to 110℃ and react for 2 hours, then 115℃ and 120℃ for 2 hours, until almost no distillate drips from the condenser. Continue reacting for another 2 hours. Cool down to below 90℃, add 150mL of water, and maintain the temperature at 90℃ with stirring for 1 hour. Filter while hot, and wash the filter cake with 20mL of purified water.

[0052] Add the filter cake to a distillation flask, add 200 mL of purified water, and heat to reflux. Extend the steam generator tubing to the bottom of the distillation flask. Set up the collection apparatus, add 50 mL of ice water to the collection flask, and insert the collection tube below the liquid surface. Start the distillation; a white solid precipitates in the collection flask. Distill for 6 hours, then sample the solid from the distillation flask and add dichloromethane. TLC analysis shows almost no product. Stop the distillation.

[0053] Collect the suspension in the bottle, cool to 0℃, filter, and dry the filter cake at 50℃. DM 12.8g. Yield 56%, purity 98%. Halogen content less than 30ppm, non-volatile residues ≤0.1%. 1 HNMR(CDCl3)δ: 6.77~6.79(m, 2H), 6.36~6.38(d, 2H), 6.18(s, 2H), 3.34~3.40(m, 2H), 3.06~3.08(m, 4H), 2.82~2.88(m, 2H), 2.22(s, 6H).

[0054] The reaction pathway described above is as follows: .

[0055] Example 3 The preparation of halogen-free phenelzine monomers includes the following steps: Add 50g of quaternary ammonium salt 3 to the reaction flask, add 100mL of purified water and stir until well mixed. Add 22g of sodium hydroxide solid in batches, stirring until the alkali is completely dissolved. Install the distillation apparatus on the reaction flask and turn on the cooling water. Pass the tail gas into a hydrochloric acid aqueous solution for absorption.

[0056] Turn on the heater and react at 95℃ for 1 hour, when bubbles slowly emerge. Increase the temperature to 100℃ and react for 2 hours, then to 105℃ and react for 2 hours, when water slowly evaporates. Continue heating to 110℃ and react for 2 hours, then 115℃ and 120℃ for 2 hours, until almost no distillate drips from the condenser. Continue reacting for another 2 hours. Cool down to below 90℃, add 100mL of water, and maintain the temperature at 90℃ with stirring for 1 hour. Filter while hot, and wash the filter cake with 20mL of purified water.

[0057] Add the filter cake to a distillation flask, add 100 mL of purified water, and heat to reflux. Extend the steam generator tubing to the bottom of the distillation flask. Set up the collection apparatus, add 50 mL of ice water to the collection flask, and submerge the collection tube below the liquid surface. Start the distillation; a white solid precipitates in the collection flask. Distill for 6 hours, then sample the solid from the distillation flask and add dichloromethane. TLC analysis shows almost no product. Stop the distillation.

[0058] Collect the suspension in the bottle, cool to 0°C, filter, and dry the filter cake at 50°C. 15.1 g of Depyrelin (DE). Yield 52%, purity 99%. Halogen content less than 50 ppm, non-volatile residues ≤0.1%. 1 HNMR(CDCl3)δ: 6.58~6.61(m, 2H), 6.30~6.32(d, 2H), 6.12(s, 2H), 3.29~3.38(m, 2H), 2.56~3.07(m, 4H), 2.23~2.33(m, 2H), 1.24~2.49(m,4H), 0.88~0.92(m,6H).

[0059] The reaction pathway described above is as follows: .

[0060] Comparative Example The preparation of halogen-free phenelzine monomers includes the following steps: Add 50g of quaternary ammonium salt 1 to the reaction flask, add 100mL of purified water and stir until well mixed. Add 25g of sodium hydroxide solid in batches, stirring until the alkali is completely dissolved. Install the distillation apparatus on the reaction flask and turn on the cooling water. Pass the tail gas into a hydrochloric acid aqueous solution for absorption.

[0061] Turn on the heater and react at 95℃ for 1 hour, when bubbles slowly emerge. Increase the temperature to 100℃ and react for 2 hours, then to 105℃ and react for 2 hours, when water slowly evaporates. Continue heating to 110℃ and react for 2 hours, then 115℃ and 120℃ for 2 hours, until almost no distillate drips from the condenser. Continue reacting for another 2 hours. Cool down to below 90℃, add 100mL of water, and maintain the temperature at 90℃ with stirring for 1 hour. Filter while hot, and wash the filter cake with 20mL of purified water.

[0062] The filter cake was added to 300 mL of dichloromethane and heated under reflux for 1 h. After filtration, the filtrate was collected and concentrated to dryness under reduced pressure. 200 mL of ethanol was added, and the mixture was heated under reflux for 30 min. The mixture was then cooled to 0-10 °C and stirred to crystallize for 1 h. After filtration and drying, 13.6 g of phenelzine N was obtained, with a yield of 52% and a purity of 93%. Halogen residue > 3000 ppm.

[0063] The reaction pathway described above is as follows: .

[0064] This invention discloses a method for preparing halogen-free phenelzine monomers, which has the following significant advantages: First, in the synthesis stage, this invention creatively employs a solvent-free aqueous phase system coupled with a specific stepwise heating program. By gradually increasing the temperature and slowly evaporating water, the alkali concentration in the reaction system is dynamically and precisely maintained, thereby efficiently driving the Hoffmann elimination and cyclization dimerization reaction of the quaternary ammonium salt without the need for any organic solvents, ensuring high conversion rates and the green and environmentally friendly nature of the process. Second, in the post-treatment stage, the purity of the reaction system greatly simplifies the product separation steps. After the reaction, there is no need for extraction with organic solvents; unreacted raw materials, excess alkali, and generated inorganic salts can be effectively removed simply by direct water washing, simplifying the operation and avoiding solvent contamination and recovery issues. Finally, in the purification stage, this invention cleverly utilizes the essential difference in volatility between the target product (para-xylene dimer) and its byproducts (polymers with larger molecular weights). By employing steam distillation technology, selective sublimation and separation of the dimer monomers are achieved. This process not only efficiently removes polymer impurities that are difficult to remove by conventional methods, but also effectively separates trace amounts of residual halide ions in the product, thereby stably obtaining high-standard halogen-free pyreline monomers with extremely low total halogen content (less than 50 ppm), fully meeting the stringent requirements for material purity in high-end semiconductor and other fields.

[0065] In summary, this invention forms a complete process route that is solvent-free, green, efficient, and capable of producing ultra-high purity products, from synthesis and post-processing to purification.

[0066] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a halogen-free phenelzine monomer, characterized in that, The preparation method includes the following steps: Quaternary ammonium salt A1 is dissolved in water, a strong base is added, and the reaction is initiated at 95°C. The temperature is continuously increased, and the reaction proceeds at the following times: first at the first temperature for the first time, second at the second temperature for the second time, third at the third temperature for the third time, fourth at the fourth temperature for the fourth time, and fifth at the fifth temperature for the fifth time, to obtain A2, which is the monomer of the halogen-free pyreline material. The reaction route is as follows: ； The first temperature is 95-105℃, the second temperature is 105-110℃, the third temperature is 110-115℃, the fourth temperature is 115-120℃, and the fifth temperature is 120-125℃. The first time is 0.5-2h, the second time is 1-3h, the third time is 1-3h, the fourth time is 1-3h, and the fifth time is 1-4h. X is Cl, Br, or OH, and R is hydrogen, methyl, or ethyl.

2. The method for preparing halogen-free phenelzine monomers according to claim 1, characterized in that, The strong base includes one or both of sodium hydroxide and potassium hydroxide.

3. The method for preparing halogen-free phenelzine monomers according to claim 1, characterized in that, The mass ratio of water to quaternary ammonium salt A1 is 1:(1-5).

4. The method for preparing halogen-free phenelzine material monomers according to claim 3, characterized in that, The mass ratio of water to quaternary ammonium salt A1 is 1:

2.

5. The method for preparing halogen-free phenelzine monomers according to claim 1, characterized in that, The mass ratio of the alkali to the quaternary ammonium salt A1 is 1:(0.3-1).

6. The method for preparing halogen-free phenelzine material monomers according to claim 5, characterized in that, The mass ratio of the alkali to the quaternary ammonium salt A1 is 1:0.

5.

7. The method for preparing halogen-free phenelzine material monomers according to claim 1, characterized in that, The first temperature is 100℃, the second temperature is 105℃, the third temperature is 110℃, the fourth temperature is 115℃, the fifth temperature is 120℃, the first time is 1h, the second time is 2h, the third time is 2h, the fourth time is 2h, and the fifth time is 2h.

8. The method for preparing halogen-free phenelzine material monomers according to claim 1, characterized in that, After reacting at the fifth temperature for the fifth time, the process also includes purifying the product by superheated steam distillation.

9. The method for preparing halogen-free phenelzine material monomers according to claim 8, characterized in that, The purification steps for the obtained product by superheated steam distillation are as follows: The reaction system was cooled to 60-90℃, water was added and stirred, and then filtered to obtain a filter cake. The filter cake is subjected to distillation to obtain the halogen-free phenelzine material monomer.

10. The method for preparing halogen-free phenelzine material monomers according to claim 9, characterized in that, The distillation process takes 4-8 hours, and the amount of water added is 1-10 times the volume of the filter cake.

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