Episulfide for optical material as well as preparation method and application of episulfide

Abstract

The invention provides an episulfide for an optical material and a preparation method and application thereof, and the preparation method of the episulfide comprises the following steps: in the presence of an inorganic salt catalyst and a phase transfer catalyst, reacting an alkene sulfur-containing monomer with hydrogen peroxide to obtain an epoxy sulfur-containing compound; and reacting the epoxy sulfur-containing compound with thiourea to obtain the episulfide. According to the preparation method, the alkene sulfur-containing monomer is subjected to the epoxidation reaction to form the epoxy sulfur-containing compound in one step, and then the epoxy sulfur-containing compound is vulcanized to form the episulfide, so that the preparation process is simplified. According to the present invention, the hydrogen peroxide oxidation system is adopted to synthesize the epoxy sulfur-containing compound, such that the reaction time is shortened, the generation of the by-product is reduced, and the purity and the yield of the product are improved, the preparation method is simple and controllable, is easy for large-scale production, and is suitable for industrial application; and high refractive index (low lens thickness), high light transmittance, low dispersion and the like of the lens can be ensured.

Description

Technical Field

[0001] This application belongs to the field of optical monomer preparation technology, and relates to a cyclic sulfide for optical materials, its preparation method and application. Background Technology

[0002] As a key material in modern optics, optical resins are gradually surpassing and even replacing traditional optical glass in various applications due to their excellent comprehensive performance. Compared with optical glass, the most significant advantages of optical resins are their light weight, ease of dyeing and processing, and excellent impact resistance (less prone to breakage). Among them, optical resin lenses with high refractive index (usually referring to refractive index n≥1.6) are particularly outstanding. Under the premise of the same lens design parameters (such as center thickness, edge thickness, power / refractive power), the higher the refractive index of the lens, the thinner it can be made, and the lighter the overall weight. This is crucial for pursuing aesthetics (thin lens edges) and wearing comfort. In the field of optical materials chemistry, cyclic sulfide compounds (monomers containing thiohexacyclic propane structures) are one of the key precursors for synthesizing high-performance (especially high refractive index) optical resins. The current main synthesis route mainly adopts the classic route with epichlorohydrin as the epoxy group source, combined with a specific vulcanizing agent. This process often involves demanding intermediate separation and purification operations, inevitably causing material loss. Complex operations increase the difficulty of process control and the risk of introducing new sources of pollution.

[0003] Therefore, it is particularly important to develop new synthetic routes for cyclic sulfides that can bypass complex intermediate purification, reduce or eliminate the use of solvents, and achieve one-step high-selectivity synthesis. This is the key to overcoming current process limitations and obtaining ultra-high-quality cyclic sulfide monomers suitable for high-end optical resin applications (such as top-grade eyeglass lenses and high-precision optical components). Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a cyclic sulfide for optical materials, its preparation method and application.

[0005] To achieve this objective, the following technical solution is adopted in this application:

[0006] In a first aspect, this application provides a method for preparing cyclic sulfides for optical materials, the method comprising the following steps:

[0007] (1) In the presence of an inorganic salt catalyst and a phase transfer catalyst, the alkene sulfur-containing monomers shown in Formula II react with hydrogen peroxide to obtain the epoxy sulfur-containing compound shown in Formula III.

[0008] (2) The epoxy sulfur-containing compound shown in Formula III reacts with a sulfurizing agent to obtain the cyclic sulfur compound shown in Formula I.

[0009]

[0010] R is a sulfur-containing group.

[0011] In this application, the organic hydrogen peroxide method used to synthesize epoxide-containing sulfur compounds is an important and efficient olefin epoxidation strategy in modern organic synthesis. Organic hydrogen peroxide (ROOH) provides an active source of "O" atoms. A transition metal catalyst coordinates with ROOH or undergoes oxidative addition, lowering the energy barrier for O / O bond breaking, generating highly active metal-oxygen (M=O) or metal-peroxygen (M-OOR) species, which act as actual oxidants attacking olefins to generate epoxide-containing sulfur compounds. The reaction conditions are mild. The main byproducts are alcohols (ROH) and water, which are easy to handle and more environmentally friendly. Furthermore, it exhibits good tolerance to various functional groups. The epoxide-containing sulfur compounds are then sulfided with thiourea to obtain cyclic sulfides.

[0012] In this application, R is any one of the following groups:

[0013]

[0014] In this application, the inorganic salt catalyst in step (1) is selected from transition metal salt catalysts; the transition metal salt catalyst is selected from sodium dodecyl tungstate dihydrate (Na2W). 12 O 40 (·2H2O), sodium molybdate, manganese sulfate or copper nitrate, or any one or a combination of at least two of them.

[0015] In this application, sodium dodecyl tungstate dihydrate is a polyoxometalate (POM) used as an oxidative catalytic precursor.

[0016] In this application, the phase transfer catalyst in step (1) is selected from any one or a combination of at least two of trioctylmethylammonium chloride, quaternary ammonium phosphotungstic acid, hexadecyltrimethylammonium bromide or methylrhenium trioxide.

[0017] In this application, the role of the phase transfer catalyst is to significantly improve the reaction contact efficiency between the water-soluble oxidation catalyst and the oil-soluble substrate monomer by transferring anions (such as active tungstate anions) at the interface in this heterogeneous (water / organic) system, thereby accelerating the reaction rate and potentially improving selectivity.

[0018] In this application, the molar ratio of the alkene sulfur-containing monomer shown in Formula II in step (1) to hydrogen peroxide is 1:2-1:4, for example 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, 1:3.3, 1:3.6, 1:3.8 or 1:4.

[0019] In this application, the hydrogen peroxide is added dropwise to a reaction system containing an inorganic salt catalyst, followed by the addition of an alkene sulfur-containing monomer and a phase transfer catalyst as shown in Formula II.

[0020] In this application, the hydrogen peroxide in step (1) is added to the reaction system in the form of an aqueous solution of hydrogen peroxide.

[0021] In this application, the mass percentage concentration of the hydrogen peroxide aqueous solution is 30%-50%, for example 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, or 50%.

[0022] In this application, the total amount of H2O2 added is strictly determined based on the molar amount of the target monomer substrate and its estimated consumption. Slow dropwise addition is used to control the exothermic rate (H2O2 decomposition and oxidation reactions are often exothermic processes), avoid drastic temperature fluctuations or rapid, ineffective decomposition of H2O2 due to localized overheating, ensure the effective conduct of the oxidation reaction, and improve the utilization rate of the oxidant.

[0023] In this application, the molar ratio of the inorganic salt catalyst in step (1) to the sulfur-containing alkene monomer of formula II is 3:1-6:1, for example 3:1, 3.3:1, 3.5:1, 3.8:1, 4:1, 4.5:1, 4.8:1, 5:1, 5.5:1, 5.8:1 or 6:1.

[0024] In this application, the molar ratio of the phase transfer catalyst in step (1) to the sulfur-containing alkene monomer of formula II is 1:1-2:1, for example 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1.

[0025] In this application, the reaction described in step (1) further includes a step of adjusting the pH of the system to acidic.

[0026] In this application, the pH adjustment of the system is accomplished using phosphoric acid.

[0027] In this application, phosphoric acid plays a crucial role in two ways: first, by providing the necessary acidic environment to activate the tungstate catalyst (potentially forming a more active phosphotungstic heteropolyacid structure); and second, by adjusting the pH of the reaction system to the range most suitable for catalytic oxidation.

[0028] In this application, the temperature of the reaction in step (1) is 50-60°C, for example 50°C, 55°C, 58°C, 60°C, and the reaction time is 2-8 hours, for example 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0029] In this application, the reaction in step (1) is controlled by a constant temperature oil bath to ensure the temperature uniformity and stability of the entire reaction process.

[0030] In this application, the sulfiding agent in step (2) is selected from any one or a combination of at least two of thiourea, phosphorus pentasulfide or Lawson reagent.

[0031] In this application, the molar ratio of the epoxy sulfur-containing compound shown in Formula III in step (2) to thiourea is 1:1 to 1:3, for example 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.5, 1:2.8 or 1:3.

[0032] In this application, the epoxy sulfur-containing compound of Formula III is added dropwise to a reaction system containing thiourea under an ice bath at 0-5°C and with stirring.

[0033] In this application, the reaction in step (2) is carried out in a solvent selected from any one or a combination of at least two of ethanol, acetonitrile, toluene, and ethyl acetate.

[0034] In this application, the reaction in step (2) is carried out at room temperature (i.e., 15-35°C, for example 15°C, 18°C, 20°C, 25°C, 30°C or 35°C) for a duration of 3-8 hours, for example 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0035] This application uses hydrogen peroxide (H2O2) as the oxidant, which has significant advantages over traditional epoxidation methods. Especially in the context of pursuing green, safe, and sustainable chemistry, this application mainly demonstrates the following advantages:

[0036] (1) The main byproduct is water: In the epoxidation reaction, oxygen atoms are transferred to olefins to form epoxy groups, and the oxygen atoms themselves are reduced to water (H2O). Apart from water, almost no other salts or harmful organic byproducts are produced. This greatly simplifies wastewater treatment and environmental protection.

[0037] (2) High safety: It eliminates the risk of explosion and fire caused by the use of high concentrations of easily decomposable epichlorohydrin.

[0038] (3) Cost-effectiveness: Hydrogen peroxide is a basic chemical product with huge global production and mature production technology (mainly the anthraquinone process). Compared with conventional epoxidation methods, it is much cheaper. Since the byproduct is mainly water, there is no need for complicated desalination or neutralization steps, which simplifies the post-reaction processing and reduces the cost and energy consumption of separation and purification.

[0039] (4) Good selectivity: Using a mild H2O2 / catalyst system, it generally has good tolerance to acid-sensitive groups (such as acetals, tetrahydropyran ethers, ester groups), base-sensitive groups, and other groups that are easily destroyed by strong oxidants in the substrate molecule. In contrast, traditional epoxidation methods sometimes oxidize other groups or lead to ring-opening side reactions.

[0040] Secondly, this application provides cyclic sulfides prepared by the preparation method described above.

[0041] In this application, the cyclic sulfide has the structure shown in Formula I:

[0042]

[0043] Formula I

[0044] R is a sulfur-containing group.

[0045] In this application, R is selected from any one of the following groups:

[0046]

[0047] Thirdly, this application provides the use of the cyclic sulfides described above in lenses.

[0048] In this application, a cyclic sulfide is polymerized with a polyisocyanate (e.g., xylene diisocyanate (XDI)) to form a prepolymer, which is then cured under a specific mold to form a lens.

[0049] The polyisocyanate component provides isocyanate groups (-NCO) that react with thiol groups (-SH) or epoxy groups of the cyclic sulfide to form a polysulfuric ester / polysulfide crosslinking network.

[0050] Cyclosulfide and polyisocyanate were mixed at a functional group molar ratio (NCO / SH molar ratio controlled at 1:1), and impurities and bubbles were removed by degassing under reduced pressure or filtration (pore size ≤1μm). A glass or metal casting mold was used, with the inner surface of the mold pre-coated with a release agent. The injection temperature was controlled at 15–25℃ to avoid premature reaction. The temperature was then increased to 80–90℃ at a rate of 1–2℃ / h, and reacted at 80–90℃ for 10–15 hours to promote deep polymerization. Demolding was then performed to obtain the final lens.

[0051] Compared with the prior art, this application has the following advantages:

[0052] Compared to traditional synthesis methods, this application simplifies the preparation process by epoxidizing olefinic sulfur-containing monomers to form epoxide sulfur-containing compounds in one step, followed by sulfidation to form cyclic sulfides. This application uses a peroxide-hydrogen peroxide system to synthesize epoxide sulfur-containing compounds, shortening the reaction time, reducing byproduct generation, and improving product purity and yield. The preparation method is simple and controllable, easy to scale up, and suitable for industrial applications. Using the prepared cyclic sulfides in eyeglass lenses can ensure high refractive index (low lens thickness), high light transmittance, and low dispersion.

[0053] The preparation method described in this application represents a revolutionary advancement over traditional epichlorohydrin epoxidation methods (such as Comparative Example 1), where hydrogen peroxide is used as the oxidant. This advancement not only improves environmental friendliness but also encompasses upgrades in safety, economic efficiency, and molecular compatibility. The main improvements are as follows:

[0054] (1) Environmental compatibility: Eliminating pollution at the source, the essence of H2O2 participating in epoxidation is the oxygen atom transfer process ("oxene" transfer mechanism), and its reduction product is only water molecules, which conforms to the highest principle of green chemistry. In contrast, for every 1 mol of epoxide generated by the epichlorohydrin route, 1 mol of sodium chloride byproduct and chlorine-containing wastewater are inevitably produced.

[0055] (2) Intrinsic safety: Eliminating the risks of handling high-risk chemicals

[0056] Epichlorohydrin is classified as a Group 1B carcinogen (determined carcinogenicity) by the International Agency for Research on Cancer (IARC). Its vapor explosion limits (1.5%-21.3%) and flash point (31℃) place it in my country's "List of Hazardous Chemicals" as a Class 3.2 flammable liquid and a Class 8 corrosive substance. In contrast, H₂O₂ possesses safe characteristics (30-50% aqueous solution), is non-flammable and non-explosive (self-decomposition temperature > 110℃), and has a low LD₂. 50 (Oral in rats) >2,000 mg / kg (low acute toxicity), meets NFPA 704 safety rating: health hazard level 1 (mild), flammability level 0.

[0057] (3) Yield advantage: a dual improvement from side reaction inhibition to separation efficiency enhancement

[0058] The high yield of the hydrogen peroxide epoxidation process is essentially due to the atomic precision of the reaction pathway and the simplicity of product separation, while the traditional epichlorohydrin route suffers significant yield loss due to multiple side reactions and salt residue problems.

[0059] The H2O2 route of this application: Under the action of inorganic salt catalyst, H2O2 achieves stereospecific epoxidation of olefins by forming metal peroxide active species (such as [WO(O2)2]2- or Ti-OOH, etc.). This process only involves homolytic cleavage of OO bonds and oxygen atom transfer, without carbon skeleton rearrangement or ionic intermediates, and the yield is stable at ≥85%.

[0060] The epichlorohydrin route: When epichlorohydrin (ECH) reacts with a nucleophile (such as alkoxide RO-), in addition to generating the target chlorohydrin intermediate, at least the following three side reactions occur: Epoxy group hydrolysis: The ECH epoxy ring is attacked by water / OH- to generate 3-chloro-1,2-propanediol (yield loss 5-10%); Dichloro byproduct: The unclosed chlorohydrin intermediate combines with Cl- to generate 1,3-dichloro-2-propanol (yield loss 8-15%); Etherification side reaction: The epoxy group of the newly generated epoxide is ring-opened again by RO-, forming polyether impurities (yield loss 3-8%). Detailed Implementation

[0061] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0062] Example 1

[0063] This embodiment provides a method for preparing cyclic sulfides for optical materials, and the reaction process is as follows:

[0064]

[0065] The preparation method specifically includes the following steps:

[0066] Sodium dodecyl tungstate dihydrate (Na2W) was added to a dry, clean reactor containing 20 ml of toluene solvent. 12 O 40 • 2H₂O (2.53 g, 8.75 mmol). The temperature was set to 50 °C. Subsequently, 40% (w / w) phosphoric acid (0.44 g, 4.18 mmol) was added. Simultaneously, 30% (w / w) hydrogen peroxide solution (0.14 g, 4.18 mmol) was slowly and dropwise added with stirring. Finally, 3-[(2-propen-1-ylthio)methyl]thio-1-propenyl (0.34 g, 2.14 mmol, CAS: 18068-26-3) was added all at once. A phase transfer catalyst was also added simultaneously. 336 (trioctylmethylammonium chloride 1.41 g, 3.5 mmol). The reaction was carried out at a set oil bath temperature of 50 °C with vigorous magnetic stirring for 2 hours to obtain the final crude product, an epoxy sulfur-containing compound. After the reaction was complete, the aqueous and organic phases were separated. The combined organic phase was washed with brine, dried with sodium sulfate, filtered, concentrated, and purified by column chromatography (n-hexane:diethyl ether volume ratio = 1:1) to give white crystals EP-1 (yield 92%).

[0067] In a dry three-necked flask containing 10 mL of ethanol, a measured amount of thiourea (0.36 g, 4.8 mmol) was added. Then, under ice bath cooling at 0–5 °C and with good stirring, a 10 mL ethanol solution of EP-1 (0.376 g, 2 mmol) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the system was slowly heated to room temperature and stirred at this temperature for 4 hours. After the reaction was complete, distilled water was added to dilute the reaction mixture, followed by multiple extractions with dichloromethane (e.g., 3 × 50 mL). The organic extracts were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was rapidly purified by short column chromatography (e.g., silica gel column, eluted with petroleum ether / diethyl ether). The product was a colorless oily liquid (TH-1, yield 82%). Characterization data are as follows:

[0068] 1 H NMR (DMSO 400MHz): δ 3.59 (d, 2H,), 2.54 (s, 2H), 2.33 (m, 2H), 2.085 (m, 2H), 2.88 (t, 2H), 2.625 (m, 2H).

[0069] Example 2

[0070] This embodiment provides a method for preparing cyclic sulfides for optical materials, and the reaction process is as follows:

[0071]

[0072] The preparation method specifically includes the following steps:

[0073] Sodium dodecyl tungstate dihydrate (Na2W) was added to a dry, clean reactor containing 20 ml of toluene solvent. 12 O 40 • 2H₂O (2.53 g, 8.75 mmol). The temperature was set to 50 °C. Subsequently, 40% (w / w) phosphoric acid (0.44 g, 4.18 mmol) was added. Simultaneously, 30% (w / w) hydrogen peroxide solution (0.14 g, 4.18 mmol) was slowly and dropwise added with stirring. Finally, diallyl disulfide (0.31 g, 2.14 mmol, CAS: 2179-57-9) was added all at once. A phase transfer catalyst was also added simultaneously. 336 (trioctylmethylammonium chloride 1.41 g, 3.5 mmol). The reaction was carried out at a set oil bath temperature of 50 °C with vigorous magnetic stirring for 2 hours to obtain the final crude product, an epoxy sulfur-containing compound. After the reaction was complete, the aqueous and organic phases were separated. The combined organic phases were washed with brine, dried with sodium sulfate, filtered, concentrated, and purified by column chromatography (n-hexane:diethyl ether volume ratio = 1:1) to give white crystals EP-2 (yield 89%).

[0074] In a dry three-necked flask containing 10 mL of ethanol, a measured amount of thiourea (0.36 g, 4.8 mmol) was added. Then, under ice bath cooling at 0–5 °C and with good stirring, a 10 mL ethanol solution of EP-2 (0.356 g, 2 mmol) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the system was slowly heated to room temperature and stirred at this temperature for 4 hours. After the reaction was complete, the reaction mixture was diluted with distilled water and then extracted multiple times with dichloromethane (e.g., 3 x 50 mL). The organic extracts were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was rapidly purified by short column chromatography (e.g., silica gel column, eluted with petroleum ether / diethyl ether). The product is usually a colorless oily liquid (TH-2, yield 83%). Characterization data are as follows:

[0075] 1 H NMR (DMSO 400MHz): δ 2.54 (d, 2H), 2.33 (m, 2H), 2.08 (m, 2H), 3.00 (s, 2H), 2.73 (d, 2H).

[0076] Example 3

[0077] This embodiment provides a method for preparing cyclic sulfides for optical materials, and the reaction process is as follows:

[0078]

[0079] The preparation method specifically includes the following steps:

[0080] Sodium dodecyl tungstate dihydrate (Na2W) was added to a dry, clean reactor containing 20 ml of toluene solvent. 12 O 40 • 2H₂O (2.53 g, 8.75 mmol). The temperature was set to 50 °C. Subsequently, 40% (w / w) phosphoric acid (0.44 g, 4.18 mmol) was added. Simultaneously, 30% (w / w) hydrogen peroxide solution (0.14 g, 4.18 mmol) was slowly and dropwise added with stirring. Finally, diallyl trisulfide (0.37 g, 2.14 mmol, CAS: 2050-87-5) was added all at once. A phase transfer catalyst was also added simultaneously. 336 (trioctylmethylammonium chloride 1.41 g, 3.5 mmol). The reaction was carried out at a set oil bath temperature of 50 °C with vigorous magnetic stirring for 2 hours to obtain the final crude product, an epoxy sulfur-containing compound. After the reaction was complete, the aqueous and organic phases were separated. The combined organic phase was washed with brine, dried with sodium sulfate, filtered, concentrated, and purified by column chromatography (n-hexane:diethyl ether volume ratio = 1:1) to give pale yellow crystals EP-3 (yield 94%).

[0081] In a dry three-necked flask containing 10 mL of ethanol, a measured amount of thiourea (0.36 g, 4.8 mmol) was added. Then, under ice bath cooling at 0–5 °C and with good stirring, a 10 mL ethanol solution of EP-3 (0.420 g, 2 mmol) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the system was slowly heated to room temperature and stirred at this temperature for 4 hours. After the reaction was complete, the reaction mixture was diluted with distilled water and then extracted multiple times with dichloromethane (e.g., 3 × 50 mL). The organic extracts were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was rapidly purified by short column chromatography (e.g., silica gel column, eluted with petroleum ether / diethyl ether). The product is usually a pale yellow oily liquid (TH-3, 80% yield). Characterization data are as follows:

[0082] 1 H NMR (DMSO 400MHz): δ 2.67 (s, 2H), 2.14 (d, 2H), 2.12 (d, 2H), 3.10 (m, 2H), 2.43 (t, 2H).

[0083] Example 4

[0084] This embodiment provides a method for preparing cyclic sulfides for optical materials, and the reaction process is as follows:

[0085]

[0086] The preparation method specifically includes the following steps:

[0087] Sodium dodecyl tungstate dihydrate (Na2W) was added to a dry, clean reactor containing 20 ml of toluene solvent. 12 O 40 • 2H₂O (2.53 g, 8.75 mmol). The temperature was set to 50 °C, and then 40% (w / w) phosphoric acid (0.44 g, 4.18 mmol) was added. Simultaneously, 30% (w / w) hydrogen peroxide solution (0.14 g, 4.18 mmol) was slowly and dropwise added with stirring. Finally, diallyl tetrasulfide (0.45 g, 2.14 mmol, CAS: 2444-49-7) was added all at once. A phase transfer catalyst was also added simultaneously. 336 (trioctylmethylammonium chloride 1.41 g, 3.5 mmol). The reaction was carried out at a set oil bath temperature of 50 °C with vigorous magnetic stirring for 2 hours to obtain the final crude product, an epoxy sulfur-containing compound. After the reaction was complete, the aqueous and organic phases were separated. The combined organic phase was washed with brine, dried with sodium sulfate, filtered, concentrated, and purified by column chromatography (n-hexane:diethyl ether volume ratio = 1:1) to give pale yellow crystals EP-4 (yield 90%).

[0088] In a dry three-necked flask containing 10 mL of ethanol, a measured amount of thiourea (0.36 g, 4.8 mmol) was added. Then, under ice bath cooling at 0–5 °C and with good stirring, a 10 mL ethanol solution of EP-4 (0.468 g, 2 mmol) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the system was slowly heated to room temperature and stirred at this temperature for 4 hours. After the reaction was complete, distilled water was added to dilute the reaction mixture, followed by multiple extractions with dichloromethane (e.g., 3 × 50 mL). The organic extracts were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was rapidly purified by short column chromatography (e.g., silica gel column, eluted with petroleum ether / diethyl ether). The product is usually a pale yellow oily liquid (TH-4, yield 91%). Characterization data are as follows:

[0089] 1 H NMR (DMSO 400MHz): δ 2.62 (m, 2H), 2.32 (t, 2H), 2.21 (s, 2H), 3.16 (m, 2H), 2.41 (d, 2H).

[0090] Example 5

[0091] This embodiment provides a method for preparing cyclic sulfides for optical materials, and the reaction process is as follows:

[0092]

[0093] The preparation method specifically includes the following steps:

[0094] Sodium dodecyl tungstate dihydrate (Na2W) was added to a dry, clean reactor containing 20 ml of toluene solvent. 12 O 40 • 2H₂O (2.53 g, 8.75 mmol). The temperature was set to 50 °C. Then, 40% (w / w) phosphoric acid (0.44 g, 4.18 mmol) was added. Simultaneously, 30% (w / w) hydrogen peroxide solution (0.14 g, 4.18 mmol) was slowly and dropwise added with stirring. Finally, diallyl sulfide (0.24 g, 2.14 mmol, CAS: 592-88-1) was added all at once. A phase transfer catalyst was also added simultaneously. 336 (trioctylmethylammonium chloride 1.41 g, 3.5 mmol). The reaction was carried out at a set oil bath temperature of 50 °C with vigorous magnetic stirring for 2 hours to obtain the final crude product, an epoxy sulfur-containing compound. After the reaction was complete, the aqueous and organic phases were separated. The combined organic phase was washed with brine, dried with sodium sulfate, filtered, concentrated, and purified by column chromatography (n-hexane:diethyl ether volume ratio = 1:1) to give pale yellow crystals EP-5 (yield 85%).

[0095] In a dry three-necked flask containing 10 mL of ethanol, a measured amount of thiourea (0.36 g, 4.8 mmol) was added. Then, under ice bath cooling at 0–5 °C and with good stirring, a 10 mL ethanol solution of EP-5 (0.484 g, 2 mmol) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the system was slowly heated to room temperature and stirred at this temperature for 4 hours. After the reaction was complete, the reaction mixture was diluted with distilled water and then extracted multiple times with dichloromethane (e.g., 3 × 50 mL). The organic extracts were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation. The crude product was rapidly purified by short column chromatography (e.g., silica gel column, eluted with petroleum ether / diethyl ether). The product is usually a pale yellow oily liquid (TH-5, yield 78%). Characterization data are as follows:

[0096] 1 H NMR (DMSO 400MHz): δ2.52(d,2H), 2.09(s,2H), 2.02(t,2H), 2.98(m,2H), 2.43(m,2H).

[0097] Comparative Example 1

[0098] In this comparative example, a method for preparing cyclic sulfides is provided, and the reaction process is as follows:

[0099]

[0100] A solution of 0.4 g (5 mmol) of 70% sodium hydrosulfide dissolved in 10 ml of methanol was added dropwise to 2.32 g (25 mmol) of epichlorohydrin while stirring at 5–10 °C, followed by stirring for 1 hour. Next, a solution of 0.7 g (17.5 mmol) of sodium hydroxide dissolved in 2 ml of water was added dropwise while stirring at 5–10 °C, followed by stirring for 1 hour. After the reaction was complete, the solution was extracted with 50 ml of toluene, followed by washing with 50 ml of water until the pH of the wash water was below 9. The solvent was removed by distillation to give 0.5 g of di(epoxypropyl) sulfide (60% yield).

[0101] 1H NMR (DMSO 400MHz): δ2.54 (s, 2H), 2.33 (t, 2H), 2.08 (d, 2H), 2.88 (t, 2H), 2.62 (m, 2H).

[0102] The products P1 to P5 obtained in Examples 1 to 5 above were tested as follows.

[0103] 1. Refractive Index Test. Cyclosulfide and XDI were mixed at a functional group molar ratio (NCO / SH molar ratio controlled at 1:1), and impurities and bubbles were removed by degassing under reduced pressure or filtration (pore size ≤ 1 μm). A 1 mm thick glass or metal casting mold was used, with the inner surface of the mold pre-coated with a release agent. The injection temperature was controlled at 15–25 °C to avoid premature reaction. The temperature was then increased to 80–90 °C at a rate of 1–2 °C / h, and reacted at this temperature for 10–15 hours to promote deep polymerization. Demolding was then performed to obtain the final lens. Its refractive index was measured using an ellipsometer. The refractive indices of lenses P1 to P5 obtained in Examples 1 to 5 are shown in Table 1.

[0104] 2. Abbe number test. The Abbe number is calculated using the refractive index at wavelengths of 486.0 nm, 587.6 nm, and 656.3 nm. The calculation formula is as follows:

[0105] Vd = (nD-1) / (nF-nC), where Vd is the Abbe number, nD is the refractive index at 587.6 nm, nF is the refractive index at 486.0 nm, and nC is the refractive index at 656.3 nm.

[0106] The Abbe numbers of lenses P1 to P5 prepared in Examples 1 to 5 are shown in Table 1.

[0107] 3. Light transmittance test. A haze meter was used for testing. The light transmittance of lenses P1 to P5 prepared in Examples 1 to 5 is shown in Table 1.

[0108] 4. Ultraviolet aging test: Ultraviolet aging test chamber (light source power 650mw, irradiation for 4 hours, stop for 4 hours as one cycle, total 24 cycles).

[0109] Table 1 Performance tests of lenses P1 to P5 in Examples 1-5

[0110]

[0111] This application successfully developed a highly efficient and controllable process for preparing cyclic sulfides. Through a two-step tandem reaction pathway of "hydrogen peroxide epoxide-thiourea sulfidation," the key preparation of novel optical materials was achieved. Compared with the traditional epichlorohydrin process (Comparative Example 1), this method exhibits significant advantages in yield and simplified post-processing.

[0112] This method was used for the first time to synthesize cyclic sulfides TH-1 / TH-3 / TH-4. After curing, lenses P3 and P4 of TH-3 / TH-4 showed refractive indices of 1.765 and 1.77 respectively, Abbe numbers exceeding 40, and light transmittance exceeding 92%. While maintaining minimal changes in yellowness after UV aging, their overall performance significantly surpasses that of existing compounds EP2 / EP5. Furthermore, this process simultaneously meets the triple optical requirements of high refractive index reduction, low dispersion aberration correction, and ultra-transmittance visual optimization, providing a high-quality raw material solution for the manufacture of ultra-thin optical lenses. This process has significant industrialization potential and broad application prospects in high-refractive-index optical resins and smart lenses.

[0113] The applicant declares that this application illustrates the cyclic sulfide for optical materials, its preparation method, and its application through the above embodiments. However, this application is not limited to the above embodiments, meaning that this application does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this application, equivalent substitutions of raw materials for the products of this application, additions of auxiliary components, and selection of specific methods, all fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing cyclic sulfides for optical materials, characterized in that, The preparation method includes the following steps: (1) In the presence of an inorganic salt catalyst and a phase transfer catalyst, the alkene sulfur-containing monomers shown in Formula II react with hydrogen peroxide to obtain the epoxy sulfur-containing compound shown in Formula III. (2) The epoxy sulfur-containing compound shown in Formula III reacts with a sulfurizing agent to obtain the cyclic sulfur compound shown in Formula I. R is a sulfur-containing group.

2. The preparation method according to claim 1, characterized in that, R can be any one of the following groups:

3. The preparation method according to claim 1, characterized in that, The inorganic salt catalyst in step (1) is selected from transition metal salt catalysts; the transition metal salt catalyst is selected from any one or a combination of at least two of sodium dodecyl tungstate dihydrate, sodium molybdate, manganese sulfate or copper nitrate; The phase transfer catalyst in step (1) is selected from any one or a combination of at least two of the following: trioctylmethylammonium chloride, quaternary ammonium phosphotungstic acid, hexadecyltrimethylammonium bromide, or methylrhenium trioxide.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the alkene sulfur-containing monomer shown in Formula II in step (1) to hydrogen peroxide is 1:2-1:

4.

5. The preparation method according to claim 1, characterized in that, The hydrogen peroxide is added dropwise to the reaction system containing the inorganic salt catalyst, followed by the addition of the alkene sulfur-containing monomer and phase transfer catalyst shown in Formula II; In step (1), the hydrogen peroxide is added to the reaction system in the form of an aqueous solution of hydrogen peroxide, and the mass percentage concentration of the aqueous solution of hydrogen peroxide is 30%-50%.

6. The preparation method according to claim 1, characterized in that, The molar ratio of the inorganic salt catalyst to the sulfur-containing alkene monomer shown in formula II in step (1) is 3:1-6:

1. The molar ratio of the phase transfer catalyst in step (1) to the sulfur-containing alkene monomer shown in Formula II is 1:1-2:

1.

7. The preparation method according to claim 1, characterized in that, Step (1) includes a step of adjusting the pH of the system to acidic before the reaction, which is accomplished using phosphoric acid. The reaction temperature in step (1) is 50℃-60℃, and the reaction time is 2-8 hours.

8. The preparation method according to claim 1, characterized in that, The sulfiding agent in step (2) is selected from any one or a combination of at least two of thiourea, phosphorus pentasulfide, or Lawson reagent; In step (2), the molar ratio of the epoxy sulfur-containing compound shown in Formula III to thiourea is 1:1-1:3; In step (2), the epoxy sulfur-containing compound shown in Formula III is added dropwise to the reaction system containing thiourea under an ice bath at 0-5°C and with stirring. The reaction in step (2) is carried out in a solvent selected from any one or a combination of at least two of ethanol, acetonitrile, toluene, and ethyl acetate; The reaction in step (2) is carried out at room temperature for 3-8 hours.

9. The cyclic sulfide prepared by any one of claims 1-8.

10. The use of the cyclic sulfide according to claim 9 in spectacle lenses.

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