The invention relates to a thermosensitive color developing agent 3, 3apos; synthesis process of-benzenesulfonyloxy diphenyl urea

Abstract

The invention discloses a synthesis process of a thermosensitive color developing agent 3, 3 '-benzenesulfonyloxy diphenyl urea, and belongs to the technical field of organic synthesis. According to the process, m-aminophenol, benzene sulfonyl chloride and triphosgene are used as raw materials, 1, 2-dichloroethane is used as a solvent, triethylamine is used as an acid-binding agent, a one-pot method is adopted to construct a two-step continuous reaction through sulfonylation and urea bonds, then acidification, liquid separation, extraction, spin-drying and methanol crystallization are performed to obtain a target product, and no intermediate needs to be separated in the whole process. According to the invention, parameters such as reaction temperature and feed ratio are optimized, the problems of tedious preparation process and low yield in the prior art are solved, the reaction condition is mild, the operation is convenient, the raw material is a conventional analytically pure reagent, the product yield is 72-76%, the purity is greater than 99.5%, the raw material utilization rate is high, the industrial application prospect is good, and the product can be widely used as a thermosensitive color developing agent.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and in particular relates to a synthesis process of a thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea. Background Technology

[0002] 3,3'-Benzenesulfonyloxydiphenylurea is a non-phenolic color developer and a core functional material in the field of thermal paper processing. Compared with traditional color developers, this compound can significantly enhance the heat sensitivity and pressure sensitivity of thermal paper, effectively optimize imaging quality and improve image clarity. It also exhibits excellent performance in key indicators such as luminescence brightness and thermal stability. Furthermore, it is environmentally friendly and non-toxic, making it a promising new generation of green color developers with broad application prospects. It can be widely used in office printing, commercial retail, logistics and medical care, cold chain monitoring, anti-counterfeiting security, and smart materials.

[0003] like Figure 1 As shown in the chemical structural formula, 3,3'-benzenesulfonyloxydiphenylurea (C 25 H 20 N2O7S 2， With a molecular weight of 524.56, this compound possesses a symmetrical structure, and the key to its synthesis lies in the construction of the urea bond. Currently, there are three main industrial methods for synthesizing the urea bond: the isocyanate method, the triphosgene method, and the chloroformate method. Considering the symmetrical structural characteristics of 3,3'-benzenesulfonyloxydiphenylurea, the triphosgene method exhibits significant advantages in atom economy and synthesis efficiency, making it a more economical and efficient choice for synthesizing this compound.

[0004] However, the existing triphosgene method for synthesizing 3,3'-benzenesulfonyloxydiphenylurea employs a stepwise synthesis approach. This involves separating, purifying, and drying the intermediate after the sulfonation reaction before proceeding with the urea bond construction reaction. This method suffers from cumbersome preparation procedures, discrete reaction steps, complex operations due to the need for intermediate separation and purification, low raw material utilization, and poor product yield, severely limiting the industrial production and large-scale application of this compound. Therefore, developing a simplified, convenient, and high-yield synthetic process for 3,3'-benzenesulfonyloxydiphenylurea has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a synthetic process for the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea, which solves the technical problems of cumbersome methods, low yield and complicated operation in the preparation of this compound in the prior art, realizes the efficient and simple synthesis of this compound, improves the utilization rate of raw materials, and provides technical support for its industrial application.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A synthetic process for a thermosensitive colorimetric reagent, 3,3'-benzenesulfonyloxydiphenylurea, is disclosed, using m-aminophenol, benzenesulfonyl chloride, and triphosgene as main raw materials, 1,2-dichloroethane (DCE) as solvent, and triethylamine as an acid-binding agent. The process employs a one-pot, continuous two-step reaction without the need for intermediate separation. The specific steps include: Step 1: Sulfonation reaction: Add m-aminophenol, 1,2-dichloroethane and triethylamine to a three-necked flask, place the reaction system in a low temperature environment of -5~10℃, and slowly add a solution of benzenesulfonyl chloride in 1,2-dichloroethane through a constant pressure dropping funnel over 1 hour. After the addition is complete, restore the reaction system to room temperature and continue stirring for 1 hour. Detect the reaction until it is complete using liquid chromatography-mass spectrometry (LCMS). The mass ratio of m-aminophenol, benzenesulfonyl chloride, and triethylamine is 100:162:138; the ratio of m-aminophenol to the initially added 1,2-dichloroethane is 100g:500mL; and the ratio of p-toluenesulfonyl chloride to the 1,2-dichloroethane in which it is dissolved is 162g:200mL.

[0007] Step 2: Urea bond construction reaction: The system from Step 1, which underwent sulfonation, was cooled to 0°C. A solution of triphosgene in 1,2-dichloroethane was slowly added dropwise through a constant-pressure dropping funnel. The ratio of triphosgene to its dissolved 1,2-dichloroethane was 80 g: 300 mL. After the addition was complete, the reaction was stirred for 1 h. The reaction was monitored by liquid chromatography-mass spectrometry (LCMS) until the end of the reaction. The amount of triphosgene added was 0.3 eq, based on m-aminophenol. In this process, the 1,2-dichloroethane solution of triphosgene is slowly added dropwise over 1 hour using a constant pressure dropping funnel, with the dropping rate being the same as in step 1. After the stirring and crystallization are completed, vacuum filtration is carried out using a 0.45μm organic filter membrane / medium-speed qualitative filter paper at room temperature of 15℃ until no obvious liquid droplets fall from the filter cake.

[0008] Step 3: Acidification and liquid-liquid extraction: Add 1 mol / L hydrochloric acid (HCl) to the reaction system of Step 2 to adjust the pH value of the system to 1~2, and then perform liquid-liquid extraction to collect the lower organic phase; extract the aqueous phase after liquid-liquid extraction twice with 1,2-dichloroethane, each time using 100 mL of 1,2-dichloroethane, collect the extract and combine it with the above organic phase to obtain the total organic phase; During separation, the reaction system is transferred to a separatory funnel and allowed to stand for 10-15 minutes until the organic and aqueous phases completely separate. The lower layer is the 1,2-dichloroethane organic phase, and the upper layer is the aqueous phase. The lower organic phase is collected. During aqueous phase extraction, the extractant is added and the separatory funnel is shaken vigorously for 5-8 minutes. After standing for 10 minutes, the layers separate and the lower organic phase is collected. The extraction is repeated twice.

[0009] Step 4: Rotary drying and crystallization: The combined total organic phase was subjected to rotary evaporation at a temperature of 40°C and a vacuum of 0.09 MPa. Rotary evaporation was stopped when no liquid dripped into the receiving flask within 5 minutes and the product in the flask was a non-flowing, dynamic solid. Methanol was added to the dried product at a ratio of 10 times the mass of the dried product (g:mL), i.e., 10 mL of methanol was added for every 1 g of dried solid product. The mixture was stirred and crystallized at 15°C for 1 hour. Then, it was filtered to obtain a white solid, which was the target product 3,3'-benzenesulfonyloxydiphenylurea. After the stirring and crystallization are completed, vacuum filtration is carried out using a 0.45μm organic filter membrane / medium-speed qualitative filter paper at room temperature of 15℃ until no obvious liquid droplets fall from the filter cake.

[0010] Furthermore, the m-aminophenol, benzenesulfonyl chloride, triphosgene, and triethylamine used in this invention are all analytical grade reagents, requiring no additional purification and reducing raw material pretreatment costs.

[0011] Furthermore, the overall yield of the two-step synthesis process of this invention can reach 72%~76%, and the purity of the target product 3,3'-benzenesulfonyloxydiphenylurea, as detected by high performance liquid chromatography (HPLC), is >99.5%, which meets the purity requirements of colorimetric agents for thermal paper processing.

[0012] This invention optimizes the process to determine the key process parameters: the temperature of the first step sulfonation reaction needs to be controlled between -5 and 10°C. If the temperature is higher than 0°C, the reaction byproducts will increase significantly, leading to a decrease in product purity and yield. The reaction effect is optimal when the total volume of solvent in the reaction system is 10 times the mass of m-aminophenol, with a byproduct content of only about 3%. The optimal feed amount of benzenesulfonyl chloride is 1 eq (based on m-aminophenol), and the optimal feed amount of triphosgene is 0.3 eq (based on m-aminophenol). Under this feed ratio, the raw material utilization rate is the highest, and the yield can reach about 75%.

[0013] The present invention has the following advantages over the prior art: (1) Simplified process and convenient operation: The present invention uses a one-pot method to synthesize 3,3'-benzenesulfonyloxydiphenylurea. After the first step of sulfonation reaction, there is no need to separate and purify the intermediate. The second step of urea bond construction reaction can be carried out directly, which effectively shortens the process flow, reduces the number of operation steps, reduces the complexity of manual operation and equipment investment costs, and is more suitable for industrial continuous production.

[0014] (2) High yield and high purity: By optimizing key process parameters such as reaction temperature, raw material feeding ratio and solvent dosage, this invention effectively suppresses the occurrence of side reactions. The total yield of the target product obtained in the two steps can reach 72%~76%, and the purity is >99.5% as detected by HPLC. This significantly improves the utilization rate of raw materials and solves the problems of low yield and poor purity in the existing technology.

[0015] (3) Mild reaction conditions and readily available raw materials: The reaction temperature of this invention is controlled within the range of low temperature to room temperature, without the need for harsh reaction conditions such as high temperature and high pressure. The reaction equipment is conventional chemical equipment (three-necked flask, constant pressure dropping funnel, rotary evaporator, etc.). The raw materials used are all commercially available analytical grade reagents, which are widely available and inexpensive, and do not require special preparation, thus reducing the total production cost.

[0016] (4) Good prospects for industrial application: The synthesis process of this invention is controllable, the process parameters are clear and the repeatability is good. The solvent can be recycled during the reaction process, which is in line with the production concept of green chemical industry. At the same time, the product yield and purity can meet the requirements of industrial production, laying a technical foundation for the large-scale production and application of 3,3'-benzenesulfonyloxydiphenylurea.

[0017] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The chemical structural formula is 3,3'-benzenesulfonyloxydiphenylurea; Figure 2 This is a process route diagram for the synthesis of a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, according to the present invention. Figure 3 This is the mass spectrum of compound 1 (intermediate) of the present invention; Figure 4This is the mass spectrum of compound 2 (3,3'-benzenesulfonyloxydiphenylurea) of the present invention; Figure 5 The image shows the 1H NMR spectrum of compound 2 (3,3'-benzenesulfonyloxydiphenylurea) of this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments, and all technical solutions based on the present invention are within the scope of protection of the present invention.

[0022] The reagents used in the embodiments of this invention are: m-aminophenol (analytical grade), benzenesulfonyl chloride (analytical grade), triphosgene (analytical grade), triethylamine (analytical grade), 1,2-dichloroethane (analytical grade), methanol (analytical grade), and 1 mol / L hydrochloric acid, all of which are commercially available conventional reagents. All analytical grade raw materials used in this invention require pretreatment: 1,2-dichloroethane is dried with anhydrous calcium chloride and then redistilled, collecting the fraction at 83-84℃; triphosgene and benzenesulfonyl chloride are dried in a vacuum drying oven at 60℃ for 2 hours before use; m-aminophenol and triethylamine are dried using 4Å molecular sieves to avoid side reactions caused by water content in the raw materials. Detection equipment: liquid chromatography-mass spectrometry (LCMS), high performance liquid chromatography (HPLC), rotary evaporator, constant pressure dropping funnel, 2L three-necked flask; the criteria for determining the completeness / completeness of the reaction using LCMS in this invention are: when the characteristic peak area ratio of the raw material is ≤1.0% and the characteristic peak area ratio of the target intermediate / product is ≥98.0%, the reaction is determined to be complete / complete.

[0023] The specific synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea is shown in the following diagram: Figure 2 As shown, it includes: Step 1: Sulfonation reaction: Add m-aminophenol, 1,2-dichloroethane and triethylamine to a three-necked flask, place the reaction system in a low temperature environment of -5~10℃, and slowly add a solution of benzenesulfonyl chloride in 1,2-dichloroethane through a constant pressure dropping funnel over 1 hour. After the addition is complete, restore the reaction system to room temperature and continue stirring for 1 hour. Detect the reaction until it is complete using liquid chromatography-mass spectrometry (LCMS). The mass ratio of m-aminophenol, benzenesulfonyl chloride, and triethylamine is 100:162:138; the ratio of m-aminophenol to the initially added 1,2-dichloroethane is 100g:500mL; and the ratio of benzenesulfonyl chloride to the 1,2-dichloroethane in which it is dissolved is 162g:200mL.

[0024] Step 2: Urea bond construction reaction: The system from Step 1, which underwent sulfonation, was cooled to 0°C. A solution of triphosgene in 1,2-dichloroethane was slowly added dropwise through a constant-pressure dropping funnel. The ratio of triphosgene to its dissolved 1,2-dichloroethane was 80 g: 300 mL. After the addition was complete, the reaction was stirred for 1 h. The reaction was monitored by liquid chromatography-mass spectrometry (LCMS) until the end of the reaction. The amount of triphosgene added was 0.3 eq, based on m-aminophenol. In this invention, eq refers to molar equivalents. The molar equivalent of m-aminophenol is 1 mol, the molar equivalent of benzenesulfonyl chloride is 1 eq (1 mol), and the molar equivalent of triphosgene is 0.3 eq (0.3 mol).

[0025] Step 3: Acidification and liquid-liquid extraction: Add 1 mol / L hydrochloric acid (HCl) to the reaction system of Step 2 to adjust the pH value of the system to 1~2, and then perform liquid-liquid extraction to collect the lower organic phase; extract the aqueous phase after liquid-liquid extraction twice with 1,2-dichloroethane, each time using 100 mL of 1,2-dichloroethane, collect the extract and combine it with the above organic phase to obtain the total organic phase; During separation, the reaction system is transferred to a separatory funnel and allowed to stand for 10-15 minutes until the organic and aqueous phases completely separate. The lower layer is the 1,2-dichloroethane organic phase, and the upper layer is the aqueous phase. The lower organic phase is collected. During aqueous phase extraction, the extractant is added and the separatory funnel is shaken vigorously for 5-8 minutes. After standing for 10 minutes, the layers separate and the lower organic phase is collected. The extraction is repeated twice.

[0026] Step 4: Rotary drying and crystallization: The combined total organic phase was subjected to rotary evaporation at a temperature of 40°C and a vacuum of 0.09 MPa. Rotary evaporation was stopped when no liquid dripped into the receiving flask within 5 minutes and the product in the flask was a non-flowing, dynamic solid. Methanol was added to the dried product at a ratio of 10 times the mass of the dried product (g:mL), i.e., 10 mL of methanol was added for every 1 g of dried solid product. The mixture was stirred and crystallized at 15°C for 1 hour, followed by filtration to obtain a white solid, which was the target product 3,3'-benzenesulfonyloxydiphenylurea. After the crystallization was completed, vacuum filtration was performed using a 0.45 μm organic filter membrane / medium-speed qualitative filter paper at 15°C until no obvious liquid dripped from the filter cake.

[0027] Example 1: A synthesis process for a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, includes the following specific steps: Step 1: Take a 2L three-necked flask, add 100g m-aminophenol, 500mL 1,2-dichloroethane, and 138g triethylamine. Place the reaction flask in a water bath at -5~10℃. Slowly add 200mL of 1,2-dichloroethane solution containing 178g benzenesulfonyl chloride through a constant pressure dropping funnel over 1 hour. After the addition is complete, move the flask to room temperature and continue stirring for 1 hour. LCMS analysis shows that the reaction is complete and the product purity is ≥95%. Step 2: Place the above reaction flask in a 0℃ water bath, and slowly add 300mL of 1,2-dichloroethane solution containing 80g of triphosgene. After the addition is complete, stir the reaction for 1h, and then detect the end of the reaction by LCMS. Step 3: Add 1 mol / L HCl to the reaction system to adjust the pH to 1-2, separate the liquid and collect the organic phase, and extract the aqueous phase twice with 100 mL of 1,2-dichloroethane. Combine the extracts with the organic phase. Step 4: The combined organic phases were evaporated to dryness at 40℃ and 0.09MPa until no solvent was distilled off. 1L of methanol was added to the evaporated product, and the mixture was stirred at 15℃ for 1h to crystallize. The product was then filtered to obtain a white solid. HPLC analysis showed that the purity of the obtained 3,3'-benzenesulfonyloxydiphenylurea was >99.5%, and the yield was 73%.

[0028] Example 2: A synthesis process for a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, includes the following specific steps: Step 1: Take a 2L three-necked flask, add 100g m-aminophenol, 500mL 1,2-dichloroethane, and 138g triethylamine. Place the reaction flask in a water bath at -5~10℃. Slowly add 200mL of 1,2-dichloroethane solution containing 162g benzenesulfonyl chloride through a constant pressure dropping funnel over 1 hour. After the addition is complete, move the flask to room temperature and continue stirring for 1 hour. LCMS is used to detect the completeness of the reaction. Step 2: Place the above reaction flask in a 0℃ water bath and slowly add 300mL of 1,2-dichloroethane solution containing 133g of triphosgene. After the addition is complete, stir the reaction for 1h. The reaction is then detected by LCMS to indicate the end of the reaction. Step 3: Add 1 mol / L HCl to the reaction system to adjust the pH to 1-2, separate the liquid and collect the organic phase, and extract the aqueous phase twice with 100 mL of 1,2-dichloroethane. Combine the extracts with the organic phase. Step 4: The combined organic phases were evaporated to dryness at 40℃ and 0.09MPa until no solvent was distilled off. 1L of methanol was added to the evaporated product, and the mixture was stirred at 15℃ for 1h to crystallize. The product was then filtered to obtain a white solid. HPLC analysis showed that the purity of the obtained 3,3'-benzenesulfonyloxydiphenylurea was >99.5%, and the yield was 72%.

[0029] Example 3: A synthesis process for a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, includes the following specific steps: Step 1: Take a 2L three-necked flask, add 100g m-aminophenol, 800mL 1,2-dichloroethane (DCE), and 138g triethylamine. Place the reaction flask in a water bath at -5~10℃. Slowly add 200mL of 1,2-dichloroethane (DCE) solution containing 162g benzenesulfonyl chloride dropwise over 1 hour using a constant pressure dropping funnel. After the addition is complete, move the flask to room temperature and continue stirring for 1 hour. Detect the reaction using liquid chromatography-mass spectrometry (LCMS) until complete. The detection criteria are: the characteristic peak area ratio of the raw material ≤1.0% and the characteristic peak area ratio of the sulfonated intermediate ≥98.0%. In this step, the total amount of 1,2-dichloroethane used is 1000mL, which is 10 times the mass of m-aminophenol. This is the optimal solvent amount, which can effectively suppress side reactions, and the content of by-products is only about 3%.

[0030] Step 2: Place the above reaction flask in a 0℃ water bath, and slowly add 300mL of 1,2-dichloroethane (DCE) solution containing 80g of triphosgene dropwise over 1 hour using a constant pressure dropping funnel. After the addition is complete, stir the reaction for 1 hour. Detect the reaction using liquid chromatography-mass spectrometry (LCMS) until the end of the reaction. The detection criteria are: the proportion of the characteristic peak area of ​​the intermediate ≤1.0% and the proportion of the characteristic peak area of ​​the target product ≥98.0%. The amount of triphosgene added is 0.3 molar equivalents, based on m-aminophenol.

[0031] Step 3: Add 1 mol / L HCl to the reaction system to adjust the pH to 1-2. Transfer the reaction system to a separatory funnel and let it stand for 10-15 min until the organic and aqueous phases completely separate. Collect the lower organic phase of 1,2-dichloroethane. Extract the aqueous phase twice with 100 mL of 1,2-dichloroethane. After each addition of the extractant, shake the separatory funnel vigorously for 5-8 min. Let it stand for 10 min to separate the phases and collect the lower organic phase. Combine the two extracts with the above organic phase to obtain the total organic phase.

[0032] Step 4: The combined total organic phase was rotary evaporated at 40℃ and 0.09MPa until no liquid dripped into the receiving flask within 5 minutes and the product in the rotary evaporation flask was a non-flowing dynamic solid. 1L of methanol (the amount of methanol added was 10 times the mass of the product after rotary evaporation, g:mL) was added to the evaporated product and stirred at 15℃ for 1 hour to induce crystallization. The product was then filtered under reduced pressure using a 0.45μm organic filter membrane at 15℃ until no obvious liquid dripped from the filter cake, yielding a white solid. HPLC analysis showed that the purity of the obtained 3,3'-benzenesulfonyloxydiphenylurea was >99.5%, and the yield was 76%.

[0033] Example 4: A synthesis process for a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, includes the following specific steps: Step 1: Take a 2L three-necked flask, add 100g m-aminophenol, 500mL 1,2-dichloroethane, and 138g triethylamine. Place the reaction flask in a 0℃ water bath and slowly add 200mL of 1,2-dichloroethane solution containing 162g benzenesulfonyl chloride dropwise over 1 hour using a constant pressure dropping funnel. After the addition is complete, move the flask to room temperature and continue stirring for 1 hour. LCMS is used to detect the completeness of the reaction. Step 2: Place the above reaction flask in a 0℃ water bath, and slowly add 300mL of 1,2-dichloroethane solution containing 80g of triphosgene. After the addition is complete, stir the reaction for 1h, and then detect the end of the reaction by LCMS. Step 3: Add 1 mol / L HCl to the reaction system to adjust the pH to 1-2, separate the liquid and collect the organic phase, and extract the aqueous phase twice with 100 mL of 1,2-dichloroethane. Combine the extracts with the organic phase. Step 4: The combined organic phases were evaporated to dryness at 40℃ and 0.09MPa until no solvent was distilled off. 1L of methanol was added to the evaporated product, and the mixture was stirred at 15℃ for 1h to crystallize. The product was then filtered to obtain a white solid. HPLC analysis showed that the purity of the obtained 3,3'-benzenesulfonyloxydiphenylurea was >99.5%, and the yield was 66%.

[0034] Experiment to investigate process parameters: (1) Effect of reaction temperature in the first step: Comparing the reaction conditions and results of Examples 1, 3 and 4, it was found that when the reaction temperature of the first step sulfonation reaction was controlled at -5~10℃, the content of by-products was low; when the temperature was controlled at only 0℃ (Example 4), the by-products increased significantly, resulting in a yield of 66%. Therefore, -5~10℃ was determined to be the optimal temperature range for the first step reaction.

[0035] (2) Effect of solvent amount: The effect of different total amounts of 1,2-dichloroethane on the reaction was investigated. The results showed that when the total amount of solvent was 10 times the volume of m-aminophenol, the reaction effect was the best, the content of by-products was only about 3%, and the raw material utilization rate was the highest.

[0036] (3) Effect of feed ratio: The effects of the feed amounts of p-toluenesulfonyl chloride and triphosgene on the reaction were investigated. The results showed that, based on m-aminophenol, the side reactions were minimized when the feed amount of p-toluenesulfonyl chloride was 1 eq and the feed amount of triphosgene was 0.3 eq, and the yield of the target product could reach about 75%, which was the optimal feed ratio.

[0037] like Figure 3 As shown, compound 1 (sulfonation reaction intermediate: toluenesulfonylpyrrole-2-acetaldehyde C) 12 H 11 The liquid chromatography-mass spectrometry (LCMS) mass spectrum of NO3S contains two characteristic peaks: peak 1 has a retention time of 4.90 min, scan number 61, and m / z range of 100-300; peak 2 has a retention time of 5.80 min, scan number 306, and m / z range of 100-800. These peaks can characterize the molecular weight of the intermediate and prove the completion of the sulfonation reaction.

[0038] Appendix Figure 4 Compound 2 (Target product: 3,3'-benzenesulfonyloxydiphenylurea-C) 25 H 20 The LCMS mass spectrum of N2O7S2 showed two characteristic peaks: peak 1 with a retention time of 5.58 min, scan number 71, and m / z range of 100–600; peak 2 with a retention time of 6.74 min, scan number 349, and m / z range of 100–900. The LCMS detection result of the target product was m / z 525.0 [m+H]+, which is consistent with the theoretical molecular mass of 3,3'-benzenesulfonyloxydiphenylurea, proving the formation of the target product.

[0039] Appendix Figure 5 The 1H NMR spectrum (¹H NMR, 400 MHz, DMSO-d6) of the target product, compound 2 (3,3'-benzenesulfonyloxydiphenylurea), shows the characteristic chemical shifts as follows: δ 9.12 (s, 2H), 7.97–7.92 (m, 4H), 7.91–7.85 (m, 2H), 7.77–7.71 (m, 4H), 7.44–7.39 (m, 2H), 7.33–7.28 (m, 4H), 6.67–6.60 (m, 2H). The characteristic peaks of this 1H spectrum correspond one-to-one with the hydrogen atom environments of the molecular structure of 3,3'-benzenesulfonyloxydiphenylurea, which can accurately characterize the chemical structure of the target product.

[0040] Industrial applications The 3,3'-benzenesulfonyloxydiphenylurea synthesized in this invention is a non-phenolic thermosensitive color developer that can be directly used as a core functional material for thermal paper. It can be applied to the production of products such as office printing thermal paper, commercial retail thermal cash register paper, logistics and medical thermal labels, cold chain monitoring thermal recording paper, anti-counterfeiting security thermal labels, and smart material thermal sensing layers. Its thermosensitivity, pressure sensitivity, thermal stability, and imaging clarity are all superior to traditional color developers. Moreover, it is environmentally friendly and non-toxic, meeting the green development requirements of modern chemical and paper processing.

[0041] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A synthesis process for a thermosensitive colorimetric agent, 3,3'-benzenesulfonyloxydiphenylurea, characterized in that, Using m-aminophenol, benzenesulfonyl chloride, and triphosgene as raw materials, 1,2-dichloroethane as solvent, and triethylamine as acid-binding agent, a one-pot synthesis was performed. The specific steps include: Step 1: Add m-aminophenol, 1,2-dichloroethane and triethylamine to a three-necked flask. Place the reaction system in a temperature environment of -5~10℃. Slowly add a solution of benzenesulfonyl chloride in 1,2-dichloroethane through a constant pressure dropping funnel over 1 hour. After the addition is complete, restore the reaction system to room temperature and continue the reaction for 1 hour until the reaction is complete. Step 2: Cool the reaction system from Step 1 to 0°C, and slowly add a solution of 1,2-dichloroethane containing triphosgene through a constant pressure dropping funnel. After the addition is complete, stir the reaction for 1 hour until the reaction is finished. Step 3: Add 1 mol / L hydrochloric acid to the reaction system of Step 2 to adjust the pH to 1-2, perform liquid-liquid separation, collect the organic phase, extract the aqueous phase with 1,2-dichloroethane, and combine the extract with the above organic phase; Step 4: The combined organic phases were evaporated to remove the solvent. Methanol was added to the evaporated product, and after stirring to crystallize, the mixture was filtered to obtain a white solid, namely 3,3'-benzenesulfonyloxydiphenylurea.

2. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to claim 1, characterized in that, In step 1, the mass ratio of intermediate aminophenol, benzenesulfonyl chloride, and triethylamine is 100:162:138; the ratio of intermediate aminophenol to the initially added 1,2-dichloroethane is 100g:500mL, and the ratio of benzenesulfonyl chloride to the 1,2-dichloroethane in which it is dissolved is 162g:200mL.

3. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to claim 1, characterized in that, In step 2, the ratio of triphosgene to 1,2-dichloroethane in which it is dissolved is 80g:300mL; based on m-aminophenol, the amount of triphosgene added is 0.3eq.

4. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to claim 1, characterized in that, The specific method for extracting the aqueous phase with 1,2-dichloroethane in step 3 is as follows: 1,2-dichloroethane mixed with the aqueous phase is used for two extractions, with 100 mL of 1,2-dichloroethane used for each extraction.

5. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to claim 1, characterized in that, The rotary evaporation process conditions in step 4 are as follows: rotary evaporation temperature 40℃, vacuum degree 0.09MPa, rotary evaporation is stopped when no liquid drops fall into the distillate receiving flask within 5 minutes and the product in the rotary evaporation flask is a non-flowing dynamic solid; the amount of methanol added is 10 times the mass of the product after rotary evaporation (g:mL), that is, 10mL of methanol is added for every 1g of solid product after rotary evaporation, the stirring temperature for crystallization is 15℃, and the stirring time is 1h.

6. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to any one of claims 1 to 5, characterized in that, The m-aminophenol, benzenesulfonyl chloride, triphosgene, and triethylamine were all analytical grade reagents; the detection method for complete reaction in steps 1 and 2 was liquid chromatography-mass spectrometry.

7. The synthesis process of the thermosensitive colorimetric agent 3,3'-benzenesulfonyloxydiphenylurea according to claim 1, characterized in that, The overall yield of the synthesis process was 72%~76%, and the purity of the obtained 3,3'-benzenesulfonyloxydiphenylurea was >99.5% as determined by high performance liquid chromatography.

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