A novel cyan dye compound, a preparation method and application thereof

Abstract

This invention relates to the field of fine chemical technology, specifically to a novel cyan dye compound, its preparation method, and its applications. The method involves first activating the compound with dichloro, then introducing different electron-donating groups stepwise using steric hindrance and electronic effect differences to selectively modify both ends of the spirocyclic skeleton sphene ring. A highly selective unilateral nucleophilic aromatic substitution reaction is achieved through Lewis acid catalysis to introduce indoline groups. Finally, a zinc-base synergistic catalytic system is used to complete the aromatic amination of the remaining chlorination sites. The reaction conditions are mild and controllable, with high yield and purity, showing promising industrial application potential. The resulting compound has a novel structure and significantly improved color density, effectively solving the problems of insufficient depth and low contrast in existing cyan dye-printed images. This results in a deeper and richer cyan color in printed images, significantly enhancing detail and effectively filling the technological gap in high-performance cyan dyes.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, and more specifically, to a novel cyan dye compound, its preparation method, and its application. Background Technology

[0002] In the field of thermal transfer printing, one of the core evaluation indicators of image quality is optical density (OD value). OD value reflects the ability of the ink layer in a printed material to absorb light, directly determining the image's contrast, depth, and color saturation. As printing technology develops towards higher definition and higher fidelity, the market is placing increasingly stringent demands on printing dyes: not only do they need to possess suitable chromaticity and vibrancy, but they also need to exhibit sufficiently high optical density on the printing medium to achieve deep blacks and rich colors, meeting the needs of high-end printed products (such as anti-counterfeiting documents, high-quality photo printing, and industrial labels).

[0003] Spirocyclic dyes, especially compounds containing a spiro[benzofuran-xanthone]one skeleton, exhibit great application potential in the field of functional dyes, particularly as cyan dyes, due to their excellent molar extinction coefficient, good photothermal stability, and tunable absorption wavelength. However, the performance of these dyes is closely related to the type and position of substituents and the electron-pull effects in their molecular structure. How to create a novel cyan dye with excellent optical density in thermal transfer applications through ingenious molecular design is a crucial technological direction that urgently needs breakthroughs in this field.

[0004] In thermal transfer ribbon (TTR) printing applications, commercially available cyan dyes and similar spirocyclic dyes disclosed in existing technologies generally have low maximum optical density (OD value) under normal printing conditions (e.g., using a Zebra printer for density and speed standardization testing), typically failing to exceed 0.5. This low OD value results in insufficient cyan depth in the printed images, manifesting as pale tones, low image contrast, and significant loss of detail, failing to meet the high-definition and high-color-density requirements of applications such as ID card printing and high-end labels.

[0005] In addition, existing methods for synthesizing such complex spirocyclic dyes often suffer from problems such as unreasonable route design, difficulty in obtaining key intermediates, or lack of selectivity in the introduction of substituents. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a novel cyan dye compound, its preparation method and its application.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a novel method for preparing a cyan dye compound, using meta-substituted diphenolic compounds and tetrafluorophthalic anhydride as raw materials, and obtaining an intermediate containing a spiro[benzofuran-xanthones]one skeleton and two phenolic hydroxyl groups through acid-catalyzed condensation, and then performing dichloroation on the two phenolic hydroxyl groups to obtain a dichloro intermediate; The dichloro intermediate is reacted with 3,3,5-trimethylindoline via a Lewis acid catalysis to undergo a one-sided nucleophilic aromatic substitution reaction, in which one chlorine substituent is replaced by an aromatic amine group. Then, an aromatic amination reaction is promoted with an aromatic primary amine compound through a zinc salt-solid base synergistic catalysis system, in which the other chlorine substituent is replaced by an aromatic amine group, to obtain the novel cyan dye compound.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the temperature of the aromatic amination reaction is 140-180℃, the reaction time is 8-20 hours, and the solvent for the reaction is a high-boiling-point polar aprotic solvent; the zinc salt-solid base synergistic catalytic system includes zinc chloride and zinc oxide.

[0010] Furthermore, the aromatic primary amine compound is one of aniline, 2-methylaniline, 3,4-dimethylaniline, 2,5-dimethylaniline, 2-methoxy-4-methylaniline, 4-methoxy-2-methylaniline, 4-ethoxyaniline, 2,4-dimethylaniline, 2,4-diethylaniline, and 2,4-diisopropylaniline.

[0011] Furthermore, the acid-catalyzed condensation reaction temperature is 100-160℃, and the reaction time is 1-5 hours; the acid used in the acid-catalyzed condensation is methanesulfonic acid. The meta-substituted diphenolic compounds include one of resorcinol, 3-methoxyphenol, 3-ethoxyphenol, and 3,5-dihydroxybenzoate.

[0012] Furthermore, the dichlorination is carried out using a chlorinating agent under the catalysis of a catalyst at a reaction temperature of 120-150℃ for a reaction time of 12-20 hours. The chlorination reagent is phosphorus oxychloride, a combination of phosphorus trichloride and chlorine, phosphorus pentachloride, oxalyl chloride, or thionyl chloride.

[0013] Furthermore, the one-sided nucleophilic aromatic substitution reaction is carried out in a reaction system containing aluminum trichloride and a catalytic amount of organic base, at a temperature of 100-140°C and a time of 15-25 hours. The Lewis acid is one of aluminum trichloride, boron trifluoride ether, titanium tetrachloride, tin tetrachloride, zinc chloride, and scandium trifluoromethanesulfonate; the catalytic organic base is one of 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, N,N-diisopropylethylamine, triethylamine, N-methylmorpholine, pyridine, potassium carbonate, and cesium carbonate.

[0014] Furthermore, the method also includes a post-treatment step for the novel cyan dye compound; the post-treatment involves cooling, filtering and drying the reaction product after the reaction is completed to obtain a crude product, dissolving, washing and evaporating the crude product, and purifying the organic phase residue by silica gel column chromatography.

[0015] The present invention also provides a novel cyan dye compound, which is prepared by the method described above.

[0016] Furthermore, the chemical name of the compound is 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one, and its molecular formula is C2. 39 H 30 N2O3F4, chemical formula as shown in formula (1): Equation (1).

[0017] The present invention also provides the application of the novel cyan dye compound as described above in the preparation of heat transfer cyan dye.

[0018] The beneficial effects of this invention are as follows: (1) The method for preparing the novel cyan dye compound of the present invention involves stepwise and selective double modification of both ends of the spirocyclic skeleton succinyl ring, realizing the synthesis strategy of "first activating with dichloroation, and then introducing different electron-donating groups stepwise by utilizing the differences in steric hindrance and electronic effects", which has good effect; (2) The method for preparing the novel cyan dye compound of the present invention achieves a highly selective single-sided nucleophilic aromatic substitution (SNAr) reaction by Lewis acid catalysis and introduces an indoline group, while the chlorine atom on the other side is retained for subsequent modification, thus overcoming the technical problem that the two active sites have similar reactivity and are prone to double substitution. (3) The method for preparing the novel cyan dye compound of the present invention, in the fourth step of the present invention, uses a zinc chloride / zinc oxide synergistic catalytic system to complete the aromatic amination of the remaining chlorination sites, which breaks through the technical bottleneck and realizes the efficient aromatic amination of this special substrate; (4) The preparation method of the novel cyan dye compound of the present invention has mild and controllable reaction conditions, high yield and purity, and has industrialization prospects. (5) The novel cyan dye compound of the present invention constructs an efficient push-pull electron conjugation system, which significantly improves the color density of the compound and effectively solves the problems of insufficient depth and low contrast of existing cyan dye printed images, making the cyan of the printed matter more profound and full, and significantly enhancing the detail expression. (6) The novel cyan dye compound of the present invention has a novel structure and effectively fills the technical gap in high-performance cyan dyes. Attached Figure Description

[0019] Figure 1 The infrared spectrum of intermediate product 1 in Example 1 of the present invention; Figure 2 In Embodiment 1 of the present invention, intermediate product 1 1 H NMR spectrum; Figure 3 In Embodiment 1 of the present invention, intermediate product 1 13 C10 NMR spectrum; Figure 4 In Embodiment 1 of the present invention, intermediate product 1 19 F NMR spectrum; Figure 5 This is the UV-Vis absorption spectrum of intermediate product 1 in Example 1 of the present invention; Figure 6 This is the HPLC spectrum of intermediate product 1 in Example 1 of the present invention; Figure 7 The infrared spectrum of intermediate product 2 in Example 1 of the present invention; Figure 8 In Example 1 of the present invention, intermediate product 2 1 H NMR spectrum; Figure 9 In Example 1 of the present invention, intermediate product 2 13 C10 NMR spectrum; Figure 10 In Example 1 of the present invention, intermediate product 2 19 F NMR spectrum; Figure 11 The UV-Vis absorption spectrum of intermediate product 2 in Example 1 of the present invention is shown. Figure 12 This is the HPLC spectrum of intermediate product 2 in Example 1 of the present invention; Figure 13 The infrared spectrum of intermediate product 3 in Example 1 of the present invention; Figure 14 In Example 1 of the present invention, intermediate product 3 1 H NMR spectrum; Figure 15 In Example 1 of the present invention, intermediate product 3 13 C10 NMR spectrum; Figure 16 In Example 1 of the present invention, intermediate product 3 19 F NMR spectrum; Figure 17 The UV-Vis absorption spectrum of intermediate product 3 in Example 1 of the present invention is shown. Figure 18 This is the HPLC spectrum of intermediate product 3 in Example 1 of the present invention; Figure 19 The infrared spectrum of the target product in Embodiment 1 of the present invention; Figure 20 In Embodiment 1 of the present invention, the target product is 1 H NMR spectrum; Figure 21 In Embodiment 1 of the present invention, the target product is 13 C10 NMR spectrum; Figure 22 In Embodiment 1 of the present invention, the target product is 19 F NMR spectrum; Figure 23 The UV-Vis absorption spectrum of the target product in Example 1 of the present invention; Figure 24 This is the HPLC spectrum of the target product in Example 1 of the present invention. Detailed Implementation

[0020] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] The present invention discloses a method for preparing a novel cyan dye compound, using meta-substituted diphenolic compounds and tetrafluorophthalic anhydride as raw materials. An intermediate containing a spiro[benzofuran-xanthones]one skeleton and two phenolic hydroxyl groups is obtained through acid-catalyzed condensation. The two phenolic hydroxyl groups are then dichlorosubstituted to obtain a dichloro intermediate. The dichloro intermediate is then reacted with 3,3,5-trimethylindoline via a Lewis acid-catalyzed unilateral nucleophilic aromatic substitution reaction, replacing one chlorine substituent with an aromatic amine group. This is further followed by a reaction with an aromatic primary amine compound via a zinc salt-solid base synergistic catalytic system to promote amination, replacing the other chlorine substituent with an aromatic amine group, thus yielding the novel cyan dye compound.

[0022] The method for preparing the novel cyan dye compound of this invention adopts a synthetic strategy of "first activating with dichloroation, and then introducing different electron-donating groups stepwise by utilizing steric hindrance and differences in electronic effects". In the third step, an indoline group is introduced through a highly selective single-sided SNAr reaction catalyzed by Lewis acid, while the chlorine atom on the other side is retained for subsequent modification, overcoming the technical difficulty of similar reactivity of the two active sites and easy double substitution.

[0023] Specifically, the two chlorination sites on the zeaton ring have similar activities, making it difficult to achieve efficient unilateral selective substitution using existing technologies. In the third step of this invention, by controlling the amount of Lewis acid and reaction conditions, and utilizing the steric hindrance and electronic effects of 3,3,5-trimethylindoline, a highly selective unilateral SNAr reaction is achieved. The chlorine on the other side is retained for further derivatization in the fourth step. This stepwise dual-modification strategy and the selection of conditions are not inspired by existing technologies.

[0024] The preparation method of this invention constructs a highly efficient push-pull electron conjugated system, which optimizes the absorption spectrum and molar extinction coefficient of the compound, thereby effectively improving the color density.

[0025] The specific steps of the preparation method of the novel cyan dye compound of the present invention are as follows: (1) Acid-catalyzed condensation to construct spirocyclic rings: Under the action of strong acid (methanesulfonic acid), resorcinol, tetrafluorophthalic anhydride and meta-substituted diphenols are used as raw materials to construct a core skeleton of spiro[benzofuran-xanthones]one containing dihydroxyl groups.

[0026] Among them, meta-substituted diphenols include one of resorcinol, 3-methoxyphenol, 3-ethoxyphenol, and 3,5-dihydroxybenzoate; these phenols can all undergo Friedel-Crafts acylation reactions and participate in the construction of spirocyclic skeletons.

[0027] In this step, methanesulfonic acid is preferably used as both a solvent and a catalyst. Strong acidic media such as polyphosphoric acid (PPA), trifluoromethanesulfonic acid, concentrated sulfuric acid, methanesulfonic acid / acetic acid mixed solvent, and ionic liquids can be used to catalyze this type of Friedel-Crafts condensation reaction to construct spirocyclic rings.

[0028] Based on the above reaction mechanism, the molar ratio of meta-substituted diphenolic compounds to tetrafluorophthalic anhydride is 2:1, and an appropriate excess can be used in practice. Since the strong acid acts as both a solvent and a catalyst, its amount can be much greater than that of the reactants; the specific amount can be selected according to the actual situation.

[0029] Preferably, in order to ensure the effectiveness of subsequent steps, the product obtained in this step is first treated by conventional methods such as cooling, static crystallization, and purification. The specific conditions for these treatments are all conventionally selected.

[0030] (2) Phenolic hydroxyl dichlorination: Under the action of chlorination reagent and catalytic amount of organic base (such as triethylamine), the two phenolic hydroxyl groups of the first step product are completely converted into chlorine atoms to obtain the dichlorinated intermediate.

[0031] The chlorinating agents are phosphorus oxychloride (POCl3), phosphorus trichloride / chlorine combination (PCl3 / Cl2), phosphorus pentachloride (PCl5), oxalyl chloride, and thionyl chloride (SOCl2). All of these chlorinating agents can convert phenolic hydroxyl groups into chlorine atoms. Among them, phosphorus oxychloride, phosphorus trichloride / chlorine combination, and phosphorus pentachloride use triethylamine as a catalyst, while oxalyl chloride and thionyl chloride use DMF as a catalyst.

[0032] The chlorination reagent also serves as a reaction solvent in this step, and its amount can be much greater than that of the reaction raw materials. The specific amount can be selected according to the actual situation.

[0033] Preferably, in order to ensure the effectiveness of subsequent steps, the product obtained in this step is first treated by conventional methods such as cooling, removing chlorination reagents, ultrasonic dispersion, and crystallization. The specific conditions for these treatments are all conventionally selected.

[0034] (3) Lewis acid-catalyzed single-sided SNAr introduction of indoline: In the presence of Lewis acid and organic base, 3,3,5-trimethylindoline group is selectively introduced into one chlorine site of the dichlorinated intermediate zanthion ring to achieve single-sided substitution.

[0035] Based on the above reaction mechanism, the molar ratio of the 3,3,5-trimethylindoline group to the dichloro intermediate is 1:1, and an appropriate excess can be used in practice. The amounts of Lewis acid and organic base should be determined to meet the requirements of catalytic activity and suppression of side reactions. Typically, the Lewis acid is 1-3 equivalents relative to the dichloro intermediate, and the organic base is 0.2-1 equivalents.

[0036] Lewis acids are one of aluminum trichloride (AlCl3), boron trifluoride diethyl ether (BF3·Et2O), titanium tetrachloride (TiCl4), tin tetrachloride (SnCl4), zinc chloride (ZnCl2), and scandium trifluoromethanesulfonate (Sc(OTf)3). These Lewis acids can also coordinate with carbonyl oxygen and chlorine atoms, enhancing the electrophilicity of the zeolite ring and weakening the C-Cl bond, thus promoting nucleophilic substitution.

[0037] The organic base is one of 2,4,6-trimethylpyridine (Keladin), N,N-diisopropylethylamine (DIPEA), triethylamine (TEA), N-methylmorpholine (NMM), pyridine, potassium carbonate, and cesium carbonate. Among them, the steric hindrance effect of 2,6-dimethylpyridine and its analogues is the preferred choice to balance basicity and low nucleophilicity, but other organic or inorganic bases can also meet the requirements and achieve the target reaction under appropriate conditions.

[0038] Preferably, in order to ensure the effectiveness of subsequent steps, the product obtained in this step is first treated by conventional methods such as cooling, extraction and purification, and the specific conditions of these treatments are all conventionally selected.

[0039] (4) Zinc salt promotes the amination of aromatic compounds to complete the double modification: using a zinc chloride / zinc oxide synergistic catalytic system, the remaining chlorination sites in the third step product are reacted with aromatic primary amine compounds to complete the introduction of the second electron-donating group and obtain the final product.

[0040] Based on the above reaction mechanism, the molar ratio of aromatic primary amine compounds to the product of the third step is 1:1, and an appropriate excess can be used in practice. The amounts of zinc chloride and zinc oxide should be determined to achieve synergistic catalysis and effective activation of chlorination sites. Typically, zinc chloride is 2-4 equivalents relative to the product of the third step, and zinc oxide is 1-2 equivalents.

[0041] This step employs a zinc chloride (ZnCl2) / zinc oxide (ZnO) synergistic catalytic system to achieve the aromatic amination reaction at the remaining chlorination sites. Zinc chloride, acting as a Lewis acid, coordinates with the carbonyl oxygen and chlorine atom of the substrate, weakening the C-Cl bond; zinc oxide, acting as a solid base, assists in the deprotonation of the NH group of 2,4-dimethylaniline, enhancing the nucleophilicity of nitrogen. The synergistic effect of these two components enables highly efficient aromatic amination under mild conditions, a process difficult to achieve using traditional methods.

[0042] Preferably, the molar ratio of zinc chloride to zinc oxide is 1:0.2 to 1:1, and synergistic catalytic effects can be achieved within this range.

[0043] Traditional aromatic amination methods (such as Ullmann condensation and Buchwald-Hartwig coupling) are extremely inefficient or completely ineffective on sterically hindered spirocyclic substrates with polyfluorinated substitutions. Using zinc chloride alone also yields poor results. This invention employs a zinc chloride / zinc oxide two-component synergistic system, which creatively solves the aromatic amination problem of this specific substrate through the synergistic activation effect of a Lewis acid and a solid base.

[0044] The zinc salt-solid base synergistic catalytic system is essentially composed of zinc salt and base. Based on the above-mentioned mechanism, the zinc salt can also be one of zinc bromide (ZnBr2), zinc iodide (ZnI2), zinc acetate (Zn(OAc)2), or zinc trifluoromethanesulfonate (Zn(OTf)2), and the solid base can also be one of zinc carbonate (ZnCO3), zinc hydroxide (Zn(OH)2), magnesium oxide (MgO), sodium carbonate (Na2CO3), or potassium carbonate (K2CO3).

[0045] The amination reaction in this step is carried out at a temperature of 140-180℃ for 8-20 hours. The solvent used in the reaction is a high-boiling-point polar aprotic solvent, which can be one of the following: sulfolane, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolinone (DMI), or hexamethylphosphoric triamine (HMPA). These solvents all have good solubility for zinc salts and aromatic amines and can withstand reaction temperatures of 150-180℃, and can replace sulfolane as the reaction medium.

[0046] Aromatic primary amine compounds are one of aniline, 2-methylaniline, 3,4-dimethylaniline, 2,5-dimethylaniline, 2-methoxy-4-methylaniline, 4-methoxy-2-methylaniline, 4-ethoxyaniline, 2,4-diethylaniline, and 2,4-diisopropylaniline.

[0047] Preferably, the reaction temperature in this step is 160-175℃, and the reaction time is 10 hours.

[0048] Furthermore, there are several options for the order in which the substrate, zinc chloride, zinc oxide, and aromatic primary amine compounds are added in this step. The product from the previous step, zinc chloride, zinc oxide, and aromatic primary amine compounds can be added to the solvent, or the zinc chloride and zinc oxide can be activated in the solvent by heating first, followed by the addition of the product from the previous step and the aromatic primary amine compounds.

[0049] All four steps of the present invention are carried out under the protection of an inert gas to avoid oxidation of sensitive intermediates (such as catechol structural analogs or dopamine moieties) in the reaction system, which is a conventional operation replacement.

[0050] After completing the above four reaction steps, the preparation method of the present invention further includes post-processing, which includes cooling, filtering and drying the reaction products to obtain a crude product, dissolving, washing and evaporating the crude product, and separating and purifying the organic phase residue by silica gel column chromatography.

[0051] The novel cyan dye compound of the present invention, prepared by the above method, has good color density and can be used to prepare thermal transfer cyan dye.

[0052] In one embodiment of the present invention, the reactants used in the first step of acid-catalyzed condensation to construct the spiro[benzofuran-xanthone]one skeleton are resorcinol and 3,4,5,6-tetrafluorophthalic anhydride; the chlorinating agent used in the second step is phosphorus oxychloride, and the catalyst is triethylamine; the organic base used in the third step is 2,6-dimethylpyridine, and the Lewis acid is aluminum trichloride; the aromatic amine used in the fourth step is 2,4-dimethylaniline.

[0053] The chemical name of the compound prepared in the above examples is 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one. Taking this as an example, its specific synthetic route, mechanism and effects are described below: The molecular formula of this compound is C2. 39 H 30 N2O3F4, chemical formula as shown in formula (1): Equation (1).

[0054] Its synthetic route is as follows: (1) Acid-catalyzed condensation to construct the spiro[benzofuran-xanthone]one skeleton: Under an inert atmosphere (such as nitrogen), resorcinol and 3,4,5,6-tetrafluorophthalic anhydride are added to methanesulfonic acid, stirred evenly, and then heated to 100-160°C and kept at that temperature for 1-5 hours, preferably at 130°C for 2 hours.

[0055] In the strong acid environment of methanesulfonic acid, one carbonyl group of tetrafluorophthalic anhydride is protonated and activated, enhancing its electrophilicity. One molecule of resorcinol attacks this carbonyl group via Friedel-Crafts acylation, ring-opening to generate a benzophenone intermediate (containing a carboxyl group and a phenolic hydroxyl group). A second molecule of resorcinol continues to attack the other carbonyl carbon, forming a triarylmethanol central structure. Subsequently, the carboxyl group is protonated again, and the oxygen atom adjacent to the phenolic hydroxyl group performs an intramolecular nucleophilic attack on the carbonyl carbon, resulting in dehydration and ring closure to form a five-membered lactone, yielding a spiro[benzofuran-xanthones]one skeleton with dihydroxyl groups at the 3',6' positions.

[0056] After the reaction in this step is completed, the reaction system is cooled to room temperature. The reaction solution is then slowly poured into ice water, stirred, and allowed to stand to crystallize. The solid is obtained by filtration. The resulting filter cake is added to ethyl acetate, stirred and dissolved at room temperature, and then filtered again to obtain the crude product.

[0057] The crude product was purified by silica gel column chromatography to obtain an orange-yellow powder, namely intermediate 1: 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0058] Preferably, the eluent used in this step of silica gel column chromatography purification is ethyl acetate and petroleum ether, and 1% glacial acetic acid is also added during elution.

[0059] (2) Dichloroation of the phenolic hydroxyl group yields a dichloro intermediate: Under an inert atmosphere, intermediate product 1 is added to phosphorus oxychloride, and a catalytic amount of triethylamine (about one drop) is added dropwise. After stirring evenly, the mixture is heated to 120-150°C and kept at that temperature for 12-20 hours. Preferably, the temperature is 135°C and the holding time is 16 hours.

[0060] In this step, under the action of excess phosphorus oxychloride and a catalytic amount of triethylamine, the phenolic hydroxyl group of the hydroxyl intermediate first reacts with POCl3 to generate a phosphate leaving group (Ar–O–P(O)Cl2). Under high temperature (135℃) and strong acid conditions, this group dissociates from the electron-rich zeolite ring to form a resonance-stable aryl carbocation, which is then captured by chloride ions in the system, converting both phenolic hydroxyl groups into chlorine atoms, yielding the 3',6'-dichloro intermediate.

[0061] After the reaction was completed, the mixture was cooled to room temperature, and excess phosphorus oxychloride was evaporated under reduced pressure at 60°C. After the system cooled, deionized water was added, and the mixture was ultrasonically dispersed and allowed to stand to crystallize. The crystals were then filtered to obtain a light green powder, which was the intermediate product 2: 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0062] (3) Lewis acid-catalyzed single-sided SNAr introduction of indoline group: Under an inert atmosphere, intermediates 2, 2,6-dimethylpyridine, aluminum trichloride, and 3,3,5-trimethylindoline are added to sulfolane, stirred until homogeneous, and then heated to 100-140°C and held for 15-25 hours. Preferably, the mixture is heated to 120°C and held for 20 hours.

[0063] In the presence of AlCl3, the dichloro intermediate coordinates with the Lewis acid and carbonyl oxygen and chlorine atoms, significantly enhancing the electron-deficient nature of the xanthonium ring and polarizing the C–Cl bond. The nitrogen atom of 3,3,5-trimethylindoline acts as a nucleophile, attacking the activated chloroaromatic carbon. Through the Meisenheimer complex intermediate, 2,6-dimethylpyridine loses its proton on the nitrogen atom, and the chloride ion departs, restoring the aromaticity. Due to differences in steric hindrance and electronic effects, only unilateral substitution occurs, introducing an indoline group.

[0064] After the reaction was completed, the mixture was cooled to 40°C, and the reaction solution was poured into a mixture of dichloromethane and water. The mixture was stirred and extracted, and the organic phase was collected after phase separation. The organic phase was dried over anhydrous sodium sulfate and the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography to obtain an orange-yellow liquid, which was the intermediate 3:6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0065] Preferably, the specific process of silica gel column chromatography purification in this step is as follows: first, the column is moistened with petroleum ether and dichloromethane, then unreacted raw materials are eluted with petroleum ether and dichloromethane, and finally the target product is eluted with pure dichloromethane.

[0066] (4) ZnCl2 / ZnO synergistic catalytic amination yields the target dye: Under an inert atmosphere, intermediate product 3, zinc chloride, zinc oxide and 2,4-dimethylaniline were added to sulfolane, stirred until homogeneous and heated to 160-175℃ for 10 h.

[0067] In this step, the remaining chlorination sites are further activated in the three-component zinc system (ZnCl2 / ZnO): ZnCl2 acts as a Lewis acid to coordinate with the carbonyl group and chlorine, weakening the C-Cl bond; ZnO acts as a solid base to assist in the deprotonation of the NH group of 2,4-dimethylaniline, enhancing the nucleophilicity of nitrogen. Subsequently, the aromatic amine nitrogen attacks the polarized chlorinated aromatic carbon via SNAr, and after addition-elimination, the chloride ion is removed, completing the introduction of the second aromatic amine group and obtaining the final spirocyclic dye product.

[0068] After the reaction was complete, the reaction mixture was poured into an ice / water / hydrochloric acid mixture, stirred, filtered, and dried to obtain the crude product. The crude product was dissolved in dichloromethane, washed with a saturated sodium bicarbonate aqueous solution, and evaporated to dryness. The organic phase residue was purified by silica gel column chromatography to obtain a dark blue solid, which is the target compound.

[0069] Preferably, in this step, the eluent used for silica gel column chromatography separation and purification is dichloromethane and ethyl acetate.

[0070] In the above preparation process, 4,5,6,7-tetrafluoro substituents (strong electron-withdrawing groups), 3,3,5-trimethylindololino and 2,4-dimethylaniline groups (two electron-donating groups of different strengths) are simultaneously introduced into the spiro[benzofuran-xanthone]one skeleton to construct a highly efficient push-pull electron conjugated system, which optimizes its absorption spectrum and molar extinction coefficient. This structural innovation enables the maximum OD value of the cyan dye of this invention to reach 0.5. Compared with the typical commercially available cyan dyes with an OD value of only 0.3-0.4 under the same conditions, the color rendering density of this invention is significantly improved, effectively solving the problems of insufficient depth and low contrast in printed images caused by existing cyan dyes, making the cyan of the printed products deeper and fuller, and significantly enhancing the detail expression.

[0071] The four-step synthesis method of this invention operates within a relatively mild temperature range (120-175°C), eliminating the need for demanding equipment such as ultra-low temperatures or high pressures. The products from each step can be obtained in high purity (HPLC purity exceeding 98%) through recrystallization or simple column chromatography. The fourth step, zinc salt-catalyzed aromatic amination reaction, replaces traditional aromatic amination methods that require precious metal catalysts or stringent conditions, resulting in lower costs and simpler operation, thus laying a solid technological foundation for large-scale production.

[0072] The effects of the present invention will be specifically illustrated below through specific embodiments and comparative examples.

[0073] Example 1 In this embodiment, the target intermediate 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one was prepared, and the products obtained in each step were tested and identified.

[0074] The four-step synthesis route in this embodiment is as follows: (1) Acid-catalyzed condensation to construct the spiro[benzofuran-xanthones]one skeleton Under an inert atmosphere (such as nitrogen), resorcinol (200 mg) and 3,4,5,6-tetrafluorophthalic anhydride (199.87 mg) were added to methanesulfonic acid (10 mL), stirred until homogeneous, and then heated to 130 °C and maintained at that temperature for 2 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was slowly poured into 40 mL of ice water. The mixture was stirred and allowed to stand for 12 h to crystallize. The solid was then obtained by filtration.

[0075] The obtained filter cake was added to ethyl acetate, with a mass ratio of filter cake to ethyl acetate of 1:4. After stirring and dissolving at room temperature for 1 hour, the mixture was filtered again to obtain the crude product. The crude product was purified by silica gel column chromatography with ethyl acetate and petroleum ether in a volume ratio of 2:1 and 1% glacial acetic acid (Rf = 0.6~0.7) added to obtain an orange-yellow powder.

[0076] The orange-yellow powder is intermediate product 1 of the first step, and its chemical name is 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0077] (2) The dichloro intermediate is obtained by dichloroation of the phenolic hydroxyl group. Under an inert atmosphere, intermediate 1 (50 mg) was added to phosphorus oxychloride (5 mL), and approximately one drop of triethylamine was added dropwise. After stirring until homogeneous, the mixture was heated to 135 °C and held at that temperature for 16 h. After the reaction was complete, the mixture was cooled to room temperature, and excess phosphorus oxychloride was evaporated under reduced pressure at 60 °C. After the system cooled, deionized water (10 mL) was added, and the mixture was ultrasonically dispersed and allowed to stand for crystallization for 12 h. The resulting light green powder was obtained by filtration.

[0078] The light green powder is intermediate product 2 from the second step, and its chemical name is 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0079] (3) Lewis acid-catalyzed single-sided SNAr introduction of indoline group Under an inert atmosphere, intermediate 2 (147 mg), 2,6-dimethylpyridine (71 mg), aluminum trichloride (178 mg), and 3,3,5-trimethylindoline (54 mg) were added to sulfolane (10 mL), stirred until homogeneous, and heated to 120 °C for 20 h. After the reaction was complete, the mixture was cooled to 40 °C, and the reaction solution was poured into a mixture of dichloromethane and water. The mixture was stirred and extracted for 15 min. After phase separation, the organic phase was collected, dried over anhydrous sodium sulfate, and the solvent was removed by vacuum distillation. The residue was purified by silica gel column chromatography. Specifically, the column was first moistened with petroleum ether and dichloromethane in a volume ratio of 4:1, then unreacted reactants were eluted with petroleum ether and dichloromethane in a volume ratio of 3:1, and finally the target product was eluted with pure dichloromethane to obtain an orange-yellow liquid.

[0080] The orange-yellow liquid is intermediate product 3 of the third step, and its chemical name is 6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0081] (4) ZnCl2 / ZnO co-catalyzed aromatic amination to obtain the target dye Under an inert atmosphere, intermediate 3 (0.10 g, 0.17 mmol), zinc chloride (0.08 g, 0.59 mmol), zinc oxide (0.016 g, 0.20 mmol), and 2,4-dimethylaniline (0.048 g, 0.40 mmol) were added to sulfolane (2 mL), stirred until homogeneous, and then heated to 160 °C for 10 h. After the reaction was complete, the reaction mixture was poured into an ice / water / hydrochloric acid mixture, stirred for 0.5 h, filtered, and dried to obtain the crude product.

[0082] The crude product was dissolved in dichloromethane, washed with a saturated sodium bicarbonate aqueous solution, and evaporated to dryness. The organic phase residue was purified by silica gel column chromatography, either by dry loading after evaporation or by wet loading after dissolution. The eluent used for silica gel column chromatography was dichloromethane and ethyl acetate in a 3:1 volume ratio. After separation and purification, a dark blue solid was obtained.

[0083] The dark blue solid is the target intermediate 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one.

[0084] In the above preparation process, the products of each step and the target product were tested and identified respectively. The specific process and results are as follows: (1) Testing and identification of intermediate product 1: 1. Infrared spectroscopy analysis: FT-IR spectroscopy is used to identify functional groups in molecules. The FT-IR spectrum of intermediate 1 in this example is as follows: Figure 1 As shown in Table 1, the main absorption peaks in the spectrum and their assignments are as follows: Table 1. Assignment of major absorption peaks and functional groups in the infrared spectrum of intermediate product 1. As can be seen, the above infrared spectrum shows a clear strong absorption at the lactone carbonyl group (~1709–1725 cm⁻¹). -1 ), Aromatic ring skeletal vibration (~1600–1635 cm) -1 The absorption of ether bonds and C–F related structures is highly consistent with the structural features of the target compound 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0085] The spectrum did not show any sharp O–H absorption of the free phenolic hydroxyl group, which may be due to intramolecular hydrogen bonding of the hydroxyl group or the influence of fluorine substitution, which is common in practical infrared detection. The overall spectrum supports the correctness of the provided structure.

[0086] 2. 1 H NMR spectral analysis: 1 1H NMR spectroscopy provides detailed information on the chemical environment, number, and coupling relationships of hydrogen atoms in the molecule. Intermediate product 1 in this embodiment... 1 H NMR spectrum as Figure 2 As shown in Table 2, the proton peak assignment table is shown in Table 2.

[0087] Table 2. Intermediate Product 1 1Table of proton peak assignments in 1H NMR spectra It can be seen that, 1 The 1H NMR spectrum clearly shows all proton signals: the aromatic region (δ7.35–6.19, 3H) belongs to the aromatic ring system, and δ10.47 (1H OH) corresponds to the phenolic hydroxyl group. It is a perfect match with the target structure.

[0088] 3. 13 C NMR spectral analysis: 13 C10 NMR spectroscopy is used to determine the carbon skeleton in a molecule. The intermediate product 1 in this example... 13 C NMR spectra as follows Figure 3 As shown in Table 3, the carbon peak assignment table is as follows: Table 3. Intermediate Product 1 13 C NMR Spectrum Carbon Peak Assignment Table

[0089] Key conclusions and spectral verification: The number of signals is consistent with the structure: molecular formula C 20 H8O5F4 contains 20 carbons, and the spectrum shows 17 distinguishable signals, which is in line with expectations (some aromatic quaternary carbons may overlap due to shifts that are close to each other caused by fluorine substitution).

[0090] All characteristic signals are present: lactone carbonyl (δ164.97), spirocentric carbon (δ109.84), C2 carbon (OCO) (δ104.86), four aromatic fluorocarbons (δ147.87–145.25), and four aromatic proton carbons (δ134.75–114.34). The shift patterns are reasonable: all signals appear in the expected chemical shift range, especially the fluorinated aromatic carbons, which are all above δ145 ppm, consistent with the strong electron-withdrawing substitution effect; the phenolic hydroxyl substituted carbons are located at ~154 ppm, consistent with the oxygen-donating conjugation effect.

[0091] Structural confirmation: 13 The C10 NMR spectrum closely matches the predicted values ​​of the target molecule 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one, providing solid spectroscopic evidence for its structure.

[0092] In conclusion, 13The C10 NMR spectrum shows a typical lactone carbonyl signal at 164.97 ppm, with dense aromatic quaternary carbon signals appearing in the 145–163 ppm region. These correspond to the C–F carbons of the tetrafluoro-substituted benzene ring, the C–O–C ether carbons of the xanthonium ring, and the aromatic carbons substituted by the phenolic hydroxyl group. Signals in the 104–135 ppm range are attributed to the CH carbons on the aromatic ring, the spirocentric carbon, and the quaternary carbons connected to dioxane in the benzofuran ring. The overall spectral characteristics are completely consistent with the highly substituted spirocyclic lactone structure of 4,5,6,7-tetrafluoro-3′,6′-dihydroxy-3H-spiro[2-benzofuran-1,9′-xanthonium]-3-one, further verifying the structure of this compound.

[0093] 4. 19 F NMR spectral analysis: 19 F NMR spectroscopy is used to determine the F substitution status in compounds, specifically intermediate 1. 19 F NMR spectrum as Figure 4 As shown in Table 4, the peak analysis of the fluorine spectrum is shown in Table 5, and the peak shape coupling characteristics are shown in Table 5.

[0094] Table 4. Intermediate Product 1 19 F NMR Spectral Peak Analysis Table Table 5. Intermediate Product 1 19 F NMR Spectral Peak Shape Coupling Characteristic Analysis Table It can be seen that, 19 The F NMR spectrum showed four well-separated singlet signals in the range of -139.78 to -155.76 ppm, labeled A, B, C, and D. The number of signals corresponds to the number of four fluorine atoms in the molecule, and the chemical shifts are all within the typical aromatic fluorine (Ar–F) range, confirming that the fluorine atoms are all attached to the aromatic ring. The four signals have different chemical shifts, indicating that the four fluorine atoms are in completely different chemical environments, which is perfectly consistent with the structural characteristics of the benzofuranone ring in the target molecule, where the 4, 5, 6, and 7-positions are tetrafluoro-substituted with an asymmetric substitution pattern.

[0095] No obvious F–F coupling splits were observed in the spectrum (possibly due to spectral resolution or sample conditions), but the independence of the signals and the shift order further support the structure of this highly substituted spirocyclic lactone.

[0096] In summary, this 19 The F NMR spectrum provided conclusive experimental evidence for the structural fragment “4,5,6,7-tetrafluoro”, verifying the molecular structure of the target compound.

[0097] 5. Ultraviolet-Vis absorption spectroscopy analysis: Ultraviolet-visible absorption spectroscopy reflects the ability of electrons in a compound to transition from the ground state to an excited state after absorbing ultraviolet or visible light of a specific wavelength. The position, intensity, and shape of the absorption peaks mainly depend on the electronic structure of the molecule, especially the properties of the conjugated system, chromophore, and substituents.

[0098] The UV-Vis absorption spectrum of intermediate product 1 in this embodiment is as follows: Figure 5 As shown, its maximum absorption wavelength is 275 nm, which is consistent with the expected characteristics of the target product.

[0099] 6. HPLC chromatographic analysis HPLC chromatograms can reflect the purity and polarity of a product. The HPLC test parameters for intermediate 1 in this example are shown in Table 6, and the chromatogram is shown below. Figure 6 As shown in Table 7, the chromatographic peak information in the chromatogram is as follows.

[0100] Table 6 HPLC test parameters for intermediate product 1 Table 7 Information on each chromatographic peak in the HPLC chromatogram The purity of 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one was calculated using the area normalization method and found to be 99.95%.

[0101] Integrating FT-IR, 1 H NMR, 13 C NMR, 19 Data from F NMR, UV and HPLC are highly consistent with the structure of 4,5,6,7-tetrafluoro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one, confirming the structure of intermediate 1.

[0102] (2) Testing and identification of intermediate product 2: 1. Infrared spectroscopy analysis: The FT-IR spectrum of intermediate product 2 in this embodiment is as follows: Figure 7 As shown in Table 8, the main absorption peaks in the spectrum and their assignments are as follows: Table 8. Assignment of major absorption peaks and functional groups in the infrared spectrum of intermediate product 2. It can be seen that the infrared spectrum is at 1780.65 cm⁻¹ -1The characteristic high wavenumber absorption at the carbonyl group of the lactone clearly supports the spirocyclic lactone structure; the absorption at 1115–1083 cm⁻¹... -1 Strong C-F absorption and below 900 cm -1 The C–Cl related absorptions confirmed the presence of tetrafluorine and dichloro substitution, respectively; aromatic skeleton vibrations (~1565–1599 cm⁻¹) were also observed. -1 ) and ether bond absorption (~1230–1310 cm⁻¹) -1 The structures of the samples were highly consistent with those of the target intermediate 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one. The absence of O–H absorption in the spectra further confirmed the absence of hydroxyl groups in the molecule, consistent with the structural formula.

[0103] 2. 1 H NMR spectral analysis: intermediate product 2 1 H NMR spectrum as shown Figure 8 As shown in Table 9, the proton peak assignment table is as follows: Table 9. Intermediate Product 2 1 Table of proton peak assignments in 1H NMR spectra It can be seen that, 1 The 1H NMR spectrum showed a clean signal, entirely located in the aromatic hydrogen region, with the integral sum consistent with the number of hydrogen atoms in the molecular formula. No aliphatic or hydroxyl signals were observed, consistent with the structural characteristics of a fully aromatic, polyhalogenated spirocyclic lactone. A large coupling constant (J = 216.0 Hz) further confirmed the presence of fluorine substitution on the aromatic ring. The overall spectrum showed a high degree of agreement with the structure of 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0104] 3. 13 C NMR spectral analysis: intermediate product 2 13 C NMR spectra as follows Figure 9 As shown in Table 10, the carbon peak attribution table is as follows.

[0105] Table 10 Intermediate Product 2 13 C NMR Spectrum Carbon Peak Assignment Table Spectrum Analysis and Explanation: Carbonyl carbon signal: The signal appearing at 163.01 ppm is a typical resonance peak for the carbonyl carbon (C=O) of lactones. This signal is located at a low field, consistent with the characteristics of spirocyclic lactone carbonyls. Due to the influence of multiple strong electron-withdrawing groups (F, Cl) in the structure, the chemical shift may be slightly shifted to a higher or lower field compared to ordinary ester carbonyls, but it is still within the typical carbonyl region (δ160–180 ppm).

[0106] Aromatic quaternary carbon region (δ145–162 ppm): This region has dense signals (152.33–161.15 ppm and 145.91–140.53 ppm), mainly corresponding to quaternary carbons (COC) on aromatic rings bonded to oxygen and aromatic quaternary carbons directly bonded to fluorine / chlorine. Fluorine-substituted carbons (CF) usually appear in δ140–165 ppm (coupling splits are often invisible or broad peaks), and chlorine-substituted carbons (C-Cl) also fall in a similar range. Therefore, the multiple signals in this region are highly consistent with the highly substituted aromatic structure of tetrafluorodichloro.

[0107] Aromatic CH carbon signals (δ 102–133 ppm): Higher field signals (102.90–113.58 ppm) correspond to protonated carbons on the aromatic ring with strong substituent shielding effects, possibly located far from strongly electronegative substituents. Signals at 132.79 ppm and 129.48 ppm belong to CH carbons on the aromatic ring with strong deshielding, possibly adjacent to halogen or lactone rings.

[0108] The number of spectral signals corresponds to the structure: the molecular formula of the compound is C. 20 H6O3Cl2F4 contains 20 carbon atoms. The spectrum shows 17 distinct signals. However, due to the highly similar chemical environments of some aromatic quaternary carbons or fluorine coupling, signal overlap / broadening occurs, and not all 20 independent signals are fully resolved. This is a common phenomenon in multi-substituted aromatic systems.

[0109] The effect of fluorine and chlorine substitution: no obvious effect was observed in the spectrum. 13 C– 19 F-coupled splitting (usually multiple or broad peaks) may be suppressed by coupling under test conditions or the spectral resolution may be insufficient to show fine splitting, but the chemical shift range is sufficient to support fluorine and chlorine substituted aromatic structures.

[0110] In conclusion, 13The C10 NMR spectrum shows a typical lactone carbonyl signal at 163.01 ppm, with dense aromatic quaternary carbon signals appearing in the 145–162 ppm region, corresponding to the COC ether bond carbon and CF / C-Cl substituted aromatic carbons in the structure. Signals in the 102–133 ppm range are attributed to CH carbons and some quaternary carbons on the aromatic ring. The overall spectral characteristics are completely consistent with the highly substituted spirocyclic lactone structure of 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one, further verifying the structure of this compound.

[0111] 4. 19 F NMR spectral analysis: intermediate product 2 19 F NMR spectrum as shown Figure 10 As shown in Table 11, the peak-shaped coupling characteristic analysis table is presented.

[0112] Table 11 Intermediate Product 2 19 F NMR Spectral Peak Shape Coupling Characteristic Analysis Table Spectrum Analysis Explanation Signal Quantity and Peak Shape: The spectrum clearly shows four independent fluorine signals, labeled A, B, C, and D, all exhibiting a singlet (s) shape. This is perfectly consistent with the number of four fluorine atoms (C4, C5, C6, C7-tetrafluorosubstituted) in the molecule. The fact that all signals are singlets indicates that no significant fluorine fluoride was observed under the current spectral resolution or testing conditions. 19 F– 19 F spin coupling or 19 F– 1 Peak splitting caused by H coupling is common in some aromatic fluorine spectra. This may be due to the small coupling constant, the setting of the spectrum resolution, or the fact that the coupling effect is not significant in the spatial and electronic environment of fluorine atoms.

[0113] Chemical shift range and electronic environment: The chemical shifts of the four fluorine signals range from -136.09 to -152.07 ppm, which is typical for aromatic fluorides (approximately -110 to -160 ppm), and is significantly biased towards a higher field (more negative). This indicates that the fluorine atom is attached to a highly electron-deficient benzofuran aromatic ring, consistent with the presence of strong electron-withdrawing groups in the structure (lactone carbonyl, spiro ring strain, ortho-chlorine atom). The distribution of the four signals spans approximately 16 ppm, indicating that the four fluorine atoms are located in different local chemical environments with varying electron shielding effects, consistent with the asymmetric substitution pattern on the benzofuran ring.

[0114] Shielding sequence and structure inference: Signal C (δ-152.07) is at the highest field, indicating that the fluorine atom is subjected to the strongest shielding effect, possibly located at C7, closest to the lactone carbonyl or spirocarbon, and strongly influenced by ring current and substituents.

[0115] Signal D (δ-136.09) is at the lowest field and has weak shielding, possibly located at C4 or C5, and is relatively less affected by the electronic effects of adjacent substituents and the space environment. Signals A and B are located in the middle, possibly corresponding to C5 and C6 positions respectively; their specific assignments need to be further confirmed by combining two-dimensional spectra or calculations.

[0116] Spectral integrity confirmation: The horizontal axis (f1) of the spectrum shows the complete chemical shift range with no missing signals, the four peaks have moderate intensities, and the baseline is stable, indicating that the spectrum acquisition quality is good and can fully reflect the resonance information of all fluorine atoms in the molecule.

[0117] In conclusion, 19 The 1F NMR spectrum clearly shows four singlet fluorine signals, corresponding to four fluorine atoms in different chemical environments on the benzofuran ring of the compound. The chemical shift range (δ -136.09 to -152.07 ppm) is consistent with the characteristics of highly electron-deficient aromatic fluorine, and the signal distribution span confirms the asymmetry of the substitution mode on the ring. The number of signals and peak shape in the spectrum are completely consistent with the structure of the target intermediate 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one, further verifying the correctness of the tetrafluoro substitution structure from the perspective of fluorine NMR.

[0118] 5. Ultraviolet-Vis absorption spectroscopy analysis: The UV-Vis absorption spectrum of intermediate product 2 is as follows: Figure 11 As shown, its maximum absorption wavelength is 285nm, which is consistent with the expected characteristics of the target product.

[0119] 6. HPLC chromatographic analysis: The HPLC detection wavelength for intermediate product 2 was 285 nm, and other detection parameters were the same as in Table 6. The chromatogram is shown below. Figure 12 As shown in Table 12, the information of each chromatographic peak in the chromatogram is as follows.

[0120] Table 12 Information on each chromatographic peak in the HPLC chromatogram The purity of 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one was calculated to be 98.99% based on the area normalization method.

[0121] The final identification conclusion combines FT-IR,1 H NMR, 13 C NMR, 19 Data from F NMR, UV and HPLC are highly consistent with the structure of 3',6'-dichloro-4,5,6,7-tetrafluoro-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0122] (3) Testing and identification of intermediate product 3: 1. Infrared spectroscopy analysis: The FT-IR spectrum of intermediate product 3 in this embodiment is as follows: Figure 13 As shown in Table 13, the main absorption peaks in the spectrum and their assignments are as follows: Table 13. Assignment of major absorption peaks and functional groups in the infrared spectrum of intermediate product 3. It can be seen that the most significant feature in the spectral data is located at 1641.28 cm⁻¹. -1 The strong carbonyl absorption peak clearly points to the spirocyclic lactone structure. Simultaneously, the characteristic absorption peaks of alkyl CH, aromatic ring C=C, CN, CF, COC, and C-Cl are all present, preliminarily confirming the functional group composition of the target molecule.

[0123] 2. 1 H NMR spectral analysis: intermediate product 3 1 H NMR spectrum as shown Figure 14 As shown, 1 The proton peak assignments in the H NMR spectra are shown in Table 14.

[0124] Table 14 Intermediate Product 3 1 Table of proton peak assignments in 1H NMR spectra It can be seen that, 1 The 1H NMR spectrum reveals all types of protons in the molecule. The aromatic region (δ7.65–6.90) has a total of 9H protons, corresponding to the aromatic hydrogens of the xanthracene ring (6H) and the indoline ring (3H). The high-field region (δ2.08–1.34) has a total of 11H protons, corresponding to the methylene group and three methyl groups of the indoline ring. The total integral is approximately 20H, corresponding to the molecular formula C1. 31 H 20 The number of hydrogen atoms (20H) substituted by non-fluorine / chlorine atoms in ClF4NO3 is completely consistent.

[0125] 3. 13 C NMR spectral analysis: intermediate product 3 13 C NMR spectra as follows Figure 15 As shown in Table 15, the carbon peak attribution table is as follows.

[0126] Table 15 Intermediate Product 3 13 C NMR Spectrum Carbon Peak Assignment Table visible, 13 The most crucial signal in the C10 NMR spectrum is the central quaternary carbon (C-spiro) of the spirocyclic ring at 66.00 ppm, which is one of the decisive pieces of evidence confirming the spironolactone structure. The abundant carbon signals in the aromatic region correspond perfectly to the carbon skeletons of the tetrafluoro-substituted benzene ring, the oxanthracene ring, and the indoline ring. The methyl carbon signals in the high-field region are consistent with the three methyl groups in the structure.

[0127] 4. 19 F NMR spectral analysis: intermediate product 3 19 F NMR spectrum as Figure 16 As shown in Table 16, the peak-shaped coupling characteristic analysis table is as follows: Table 16 Intermediate Product 3 19 F NMR Spectral Peak Shape Coupling Characteristic Analysis Table It can be seen that, 19 The F NMR spectrum showed four independent fluorine signals, which corresponded perfectly to the four fluorine atoms in the 4,5,6,7-tetrafluoro-substituted benzene ring in the structure. The chemical shift range of the fluorine signals (-139 to -152 ppm) is consistent with the typical characteristics of aromatic fluorines.

[0128] 5. Ultraviolet-Vis absorption spectroscopy analysis: The UV-Vis absorption spectrum of intermediate product 3 is as follows: Figure 17 As shown, the maximum absorption wavelength is 275 nm, which is consistent with the expected characteristics of the target product.

[0129] 6. HPLC chromatographic analysis: The HPLC chromatographic detection parameters for intermediate product 3 are the same as those in Table 6, and the chromatogram is shown below. Figure 18 As shown in Table 17, the information of each chromatographic peak in the chromatogram is as follows.

[0130] Table 17 Information on each chromatographic peak in the HPLC chromatogram The purity of 6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one was calculated using the area normalization method and found to be 98.58%.

[0131] Integrating FT-IR, 1 H NMR, 13 C NMR, 19 Data from F NMR, UV and HPLC all show a high degree of consistency with the structure of 6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one.

[0132] (4) Testing and identification of the target product: 1. Infrared spectroscopy analysis: FT-IR spectroscopy is used to identify functional groups in molecules. The FT-IR spectrum of the target product in this embodiment is as follows: Figure 19 As shown in Table 18, the main absorption peaks in the spectrum and their assignments are as follows: Table 18. Assignment of major absorption peaks and functional groups in the infrared spectrum of the target product. It can be seen that the most significant feature in the spectral data is located at 1772.63 cm⁻¹. -1 The carbonyl absorption peak clearly points to the spirocyclic lactone structure. Simultaneously, the characteristic absorption peaks of alkyl CH, aromatic ring C=C, CN, CF, and COC are all present, preliminarily confirming the functional group composition of the target molecule.

[0133] 2. 1 H NMR spectral analysis: target product 1 H NMR spectrum as Figure 20 As shown in Table 19, the proton peak assignment table is shown in Table 19.

[0134] Table 19 Target Product 1 Table of proton peak assignments in 1H NMR spectra It can be seen that, 1 The 1H NMR spectrum reveals all types of protons in the molecule. The aromatic region (δ8.01–6.45) has a total of 13 H protons, corresponding to the aromatic hydrogens and one NH proton in the three aromatic ring systems (oxanthracene, dimethylaniline, and indoline). The high-field region (δ3.75–1.30) has a total of 17 H protons, corresponding to the methylene and methyl groups on the indoline ring, and the two methyl groups on the dimethylaniline ring. The total integral is approximately 30 H, corresponding to the molecular formula C1. 39 The number of hydrogen atoms in H30N2O3F4 matches.

[0135] 3. 13 C NMR spectral analysis: target product 13 C NMR spectra as follows Figure 21 As shown in Table 20, the carbon peak attribution table is as follows.

[0136] Table 20 Target Product 13 C NMR Spectrum Carbon Peak Assignment Table It can be seen that, 13 The most crucial signal in the C10 NMR spectrum is the central quaternary carbon (C-spiro) of the spirocyclic ring at 65.97 ppm, which is one of the decisive pieces of evidence confirming the spironolactone structure (the carbonyl carbon signal may be masked by solvent peaks or noise). The abundant carbon signals in the aromatic region correspond perfectly to the carbon skeletons of the tetrafluorosubstituted benzene ring, oxanthracene ring, dimethylaniline ring, and indoline ring. The methyl carbon signals in the high-field region are consistent with the five methyl groups in the structure.

[0137] 4. 19 F NMR spectral analysis: target product 19 F NMR spectrum as Figure 22 As shown in Table 21, the peak value analysis is presented in the table.

[0138] Table 21 Target Product 19 F NMR Spectral Peak Analysis Table It can be seen that, 19 The F NMR spectrum showed four independent fluorine signals, which corresponded perfectly to the four fluorine atoms in the 4,5,6,7-tetrafluoro-substituted benzene ring in the structure. The chemical shift range of the fluorine signals (-140 to -155 ppm) is typical of aromatic fluorines. The signal broadening may be due to coupling or relaxation effects between fluorine atoms.

[0139] 5. Ultraviolet-Vis absorption spectroscopy analysis: The UV-Vis absorption spectrum of the target product is as follows: Figure 23 As shown, its maximum absorption wavelength is 275 nm, which is consistent with the expected characteristics of the target product.

[0140] 6. HPLC chromatographic analysis: The HPLC chromatographic detection parameters for the target product are the same as those in Table 6, and the chromatogram is shown below. Figure 24 As shown in Table 22, the information of each chromatographic peak in the chromatogram is as follows.

[0141] Table 22 Information on each chromatographic peak in the HPLC chromatogram The purity of 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one was calculated using the area normalization method and found to be 98.68%.

[0142] In summary, the spironolactone core is represented by 1772.63 cm⁻¹ in FT-IR. -1 carbonyl absorption peak and 13 The presence of 65.97 ppm spirocyclic quaternary carbons was confirmed by C NMR. The tetrafluoro-substituted benzene ring was determined by... 13 CF carbon signals at δ141.66–137.01 in C NMR and 19 The results were confirmed by four independent fluorine signals (δ-140.25, -143.93, -144.24, -152.05) in F NMR.

[0143] Regarding substituents 1 The 1H NMR data clearly showed the presence of the 2,4-dimethylaniline group (methyl singlet at δ 2.29 and 2.25) and the indoline ring (methylene at δ 3.75–3.70, methyl at δ 2.17 and 1.30), with integral values ​​consistent with the structure.

[0144] All spectral data are highly consistent and without contradictions, forming a complete chain of evidence. (This is in conjunction with FT-IR...) 1 H NMR, 13 CNMR, 19 Cross-validation using 1F NMR, UV, and HPLC data confirmed the product's structure as 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one, with the molecular formula: C 39 H 30 N2O3F4.

[0145] Example 2 In this embodiment, the cyan product from the third step of Example 1 (i.e., 6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthon]-3-one) was used for further preparation. The reaction conditions of the fourth step synthesis process were optimized, and the effect of the target product was verified.

[0146] The specific preparation process for the fourth step is as follows: The cyan product from the third step of Example 1 (0.1 g, 0.17 mmol) was dissolved in sulfolane (2 ml) along with zinc chloride (0.08 g, 0.59 mmol), zinc oxide (0.016 g, 0.20 mmol), and 2,4-dimethylaniline (0.048 g, 0.40 mmol). The mixture was heated to 160 °C and stirred for 10 hours under nitrogen protection.

[0147] After the reaction was complete, the reaction mixture was poured into an ice / water / hydrochloric acid mixture and stirred for 0.5 hours. A solid precipitated, which was then filtered and dried. The crude product was dissolved in dichloromethane, treated with a saturated sodium bicarbonate aqueous solution, evaporated to dryness, and purified by silica gel column chromatography.

[0148] The eluent was dichloromethane and ethyl acetate in a volume ratio of 3:1. The target fraction obtained by elution was collected and evaporated to dryness to obtain the target product 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one in pure form.

[0149] The target product in this embodiment is a dark blue solid powder. According to HPLC analysis (C18 column, methanol as mobile phase, flow rate 0.5 mL / min, detection wavelength 275 nm, column temperature 35 °C), the purity of the product is 98.68% calculated by the area normalization method.

[0150] Verification of the effectiveness of the target product: The obtained dye was formulated into ink according to a conventional thermal transfer ribbon coating formula, and printing tests were conducted using a Zebra printer (print density 30, print speed 5). The optical density (OD value) of the printed samples was measured using a colorimeter. The results showed that the maximum OD value of this cyan dye was 0.5, indicating pure and deep color with high image contrast. Furthermore, sunlight and heat stability tests demonstrated that the dye possesses good lightfastness and heat resistance, meeting the application requirements of thermal transfer printing.

[0151] Example 3 This embodiment reduces the reaction temperature range in step four to 145°C, based on Example 2. Correspondingly, the reaction time is extended to 16 hours. All other raw materials, proportions, post-treatment methods, and purification steps are the same as in Example 2. The target product in this embodiment has a purity of 97.5% as determined by HPLC, and the yield is slightly lower than that in Example 2.

[0152] The target product of this embodiment was printed and tested under the same conditions as in Example 2, and the maximum OD value of the printed sample was measured to be 0.48.

[0153] The above test results show that, although the reaction activity decreases at slightly lower reaction temperatures, resulting in a slight reduction in yield and product purity, the obtained dye still exhibits excellent optical density performance, approaching the target OD value of 0.5. This demonstrates that the synthesis process conditions of this invention have a certain range of practicality and adjustability.

[0154] Example 4 This embodiment differs from Example 2 by altering the proportions of the zinc salt system in the fourth step. Specifically, the amount of zinc chloride in the fourth step is increased to 0.10 g (0.73 mmol), while the amount of zinc oxide is decreased to 0.010 g (0.12 mmol). All other raw materials, reaction temperature, time, and post-treatment methods remain the same as in Example 2. The target product obtained in this embodiment has a purity of 98.1% as determined by HPLC.

[0155] The target product was printed under the same conditions as in Example 2, and the maximum OD value of the printed sample was measured to be 0.5.

[0156] The above test results show that, in the zinc salt system, the relative amounts of zinc chloride and zinc oxide can be adjusted within a certain range to still efficiently catalyze the aromatic amination reaction and obtain the target product with high purity. Moreover, the product exhibits stable optical density in printing applications, verifying the adaptability of the synthesis system to changes in the raw material ratio.

[0157] Example 5 This embodiment, based on Example 2, shortens the reaction time of the fourth step to 8 hours, and maintains the reaction temperature at 160-175℃. The remaining raw material amounts, feed ratios, post-processing, and purification methods are the same as in Example 2. The target product obtained in this embodiment, as determined by HPLC, has a purity of 96.4%, and the yield is lower than that of Example 2 (approximately 72%).

[0158] The target product of this embodiment was printed and tested under the same conditions as in Example 2, and the maximum OD value of the printed sample was measured to be 0.47.

[0159] The test results above show that the target product can still be obtained by shortening the reaction time to 8 hours, and its OD value is still significantly better than that of the cyan dye in the prior art. This example also shows that a reaction time of 10 hours is a more preferred condition, which can obtain higher yield, purity, and optimal OD value.

[0160] Example 6 This embodiment is based on Example 2, except that the amount of 2,4-dimethylaniline in step four is reduced to 0.036 g (0.30 mmol, or approximately 1.8 equivalents). The amounts of other raw materials, reaction temperature, time, and post-treatment methods are the same as in Example 2. The purity of the target product in this embodiment was determined to be 98.0% by HPLC.

[0161] The target product was printed under the same conditions as in Example 2, and the maximum OD value of the printed sample was measured to be 0.5. The results show that even with an appropriate reduction in the amount of aromatic amine, the reaction can still proceed efficiently, and the product purity and printing performance are not significantly affected. This result demonstrates that the method of the present invention has a certain tolerance for the amount of amine raw materials, which helps to reduce raw material costs and further reflects the industrial feasibility of the process.

[0162] Comparative Example 1 This comparative example uses Kayaset Blue 714 (CI Solvent Blue 70), a commercially available cyan dye manufactured by Nippon Kayaku Co., Ltd. This cyan dye is used for thermal transfer ribbons, and its main components are not the compounds described in this invention. Coating and printing tests were conducted using the exact same coating formulation and printing conditions (Zebra printer, concentration 30, speed 5) as in Example 2.

[0163] Test results show that the maximum OD value of the commercially available cyan dye is 0.35. Compared with the OD value of 0.5 in Example 1 of this invention, the cyan dye of this invention improves optical density by approximately 42.9%. In actual visual perception, the color depth and image contrast of the printed blocks printed with the dye of this invention are far superior to those of the commercially available product. This comparative example clearly demonstrates that existing commercially available cyan dyes generally suffer from insufficient optical density, and this invention, through innovation in a specific molecular structure, has successfully achieved a significant breakthrough in OD value.

[0164] Comparative Example 2 This comparative example uses a monosubstituted indoline intermediate as the dye, which is the intermediate 3 of the third step product of this invention: 6'-chloro-4,5,6,7-tetrafluoro-3'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthones]-3-one. This compound only completes the aromatic amination modification on one side of the xanthones ring, while the other side retains the chlorine atom substitution.

[0165] Tests were conducted using the exact same coating formulation and printing conditions as in Example 2. The results showed that the maximum OD value of intermediate product 3 was only 0.22. This is because the molecular structure contains only one strong electron-donating group (indoline group), while the other side is an electron-withdrawing chlorine atom, failing to form a sufficiently extended push-pull electron conjugated system, resulting in weak spectral absorption and an unexpected cyan color. This comparative example demonstrates that double modification at the 3' and 6' positions of the xanthonium ring, introducing two different electron-donating groups, is a key structural requirement for constructing an efficient cyan chromogenic system and achieving high optical density.

[0166] Comparative Example 3 This comparative example refers to the disclosed conventional method and attempts to replace the zinc salt in step four of this invention with the Ullmann condensation method to promote the aromatic amination reaction. The specific steps are as follows: The product from step three (0.1 g, 0.17 mmol), 2,4-dimethylaniline (0.048 g, 0.40 mmol), cuprous iodide (0.033 g, 0.17 mmol), and potassium carbonate (0.07 g, 0.51 mmol) were dissolved in sulfolane (2 ml) and reacted at 170 °C for 20 hours under nitrogen protection. The post-treatment procedure was the same as in Example 2.

[0167] HPLC monitoring revealed no obvious formation of the target product in the reaction system; most of the raw materials remained unconverted, resulting in a small amount of complex degradation products. TLC analysis showed extremely faint, complex tailings of the product spots, making it impossible to obtain a pure target compound through simple column chromatography.

[0168] This comparative example demonstrates that, due to the unique steric hindrance and complex electronic environment of the remaining chlorination sites in the substrate of this invention, traditional Ullmann condensation reactions are almost ineffective on this substrate, failing to yield the target product. However, the zinc chloride / zinc oxide synergistic activation system employed in this invention, through the synergistic effect of a Lewis acid and a solid base, is a key innovation for successfully achieving mild and efficient aromatic amination at this site, obtaining the target product in high yield and high purity.

[0169] Comparative Example 4 This comparative example follows the procedure of Example 2, except that the zinc salt system lacks zinc oxide, and in the fourth step, only zinc chloride (0.08 g, 0.59 mmol) is used without adding zinc oxide. The other raw materials, reaction temperature, time, and post-treatment methods are the same as in Example 2.

[0170] HPLC monitoring revealed only a small amount of the target product (approximately 18% HPLC area percentage) in the reaction system, with most of the raw materials remaining unconverted. Extending the reaction time to 20 hours did not significantly improve the conversion rate and instead increased the amount of byproducts. Silica gel column chromatography yielded only 15% of the target product with a purity of 91.2%. Printing tests were performed on this product under the same conditions as in Example 2, and the maximum OD value was measured to be only 0.31.

[0171] This comparative example demonstrates that the aromatic amination efficiency is extremely low when using zinc chloride as the sole activator. In the system of this invention, zinc oxide not only serves as a Lewis acid donor but, more importantly, acts as a solid base to assist in the deprotonation of the NH4+ in aromatic amines, enhancing the nucleophilicity of the amine. Without zinc oxide, this synergistic activation cannot be achieved, resulting in extremely low reaction yields. This proves that the zinc chloride / zinc oxide synergistic catalytic system of this invention is a key innovation for successfully achieving highly efficient aromatic amination.

[0172] Comparative Example 5 This comparative example follows the procedure of Example 2, except that 2,4-dimethylaniline in step four is replaced with an equimolar amount of 2,6-dimethylaniline (0.048 g, 0.40 mmol). All other raw materials, reaction temperature, time, and post-treatment methods are the same as in Example 2.

[0173] HPLC monitoring revealed the formation of a new product in the reaction system, but the reaction rate was significantly slow. After 10 hours of reaction, the product was obtained by silica gel column chromatography with a yield of only 38% and an HPLC purity of 94.5%. The product was then subjected to printing tests under the same conditions as in Example 1, and the maximum OD value was measured to be only 0.35.

[0174] The two ortho-methyl groups in 2,6-dimethylaniline exhibit significant steric hindrance, making it difficult for the nitrogen atom to undergo SNAr nucleophilic attack on the chloroaromatic carbon, resulting in a substantial decrease in both reaction rate and conversion. Furthermore, because the electronic and steric effects of the two ortho-methyl groups differ from those of the 2,4-dimethylaniline of this invention, the absorption spectral properties of the final product change, with a significant decrease in the OD value.

[0175] This comparative example strongly demonstrates that the choice of 2,4-dimethylaniline as the electron-donating group of the aromatic amine in this invention is the optimal choice in terms of reactivity, spatial matching, and optical properties, and is not something that can be arbitrarily replaced.

[0176] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a novel cyan dye compound, characterized in that, Using meta-substituted diphenolic compounds and tetrafluorophthalic anhydride as raw materials, an intermediate containing a spiro[benzofuran-xanthones]one skeleton and two phenolic hydroxyl groups was obtained by acid-catalyzed condensation. The two phenolic hydroxyl groups were then dichlorosubstituted to obtain a dichloro intermediate. The dichloro intermediate was reacted with 3,3,5-trimethylindoline via a Lewis acid catalysis to undergo a one-sided nucleophilic aromatic substitution reaction, in which one chlorine substituent was replaced with an indoline group. Then, an aromatic amination reaction was promoted with an aromatic primary amine compound via a zinc salt-solid base synergistic catalysis system, in which the other chlorine substituent was replaced with an aromatic amine group, to obtain the novel cyan dye compound.

2. The method for preparing a novel cyan dye compound according to claim 1, characterized in that, The aromatic amination reaction is carried out at a temperature of 140-180℃ for 8-20 hours, and the solvent is a high-boiling-point polar aprotic solvent. The zinc salt-solid base synergistic catalytic system includes zinc chloride and zinc oxide.

3. The method for preparing a novel cyan dye compound according to claim 2, characterized in that, The aromatic primary amine compound is one of aniline, 2-methylaniline, 3,4-dimethylaniline, 2,5-dimethylaniline, 2-methoxy-4-methylaniline, 4-methoxy-2-methylaniline, 4-ethoxyaniline, 2,4-dimethylaniline, 2,4-diethylaniline, and 2,4-diisopropylaniline.

4. A method for preparing a novel cyan dye compound according to any one of claims 1-3, characterized in that, The acid-catalyzed condensation reaction temperature is 100-160℃, and the reaction time is 1-5 hours; the acid used in the acid-catalyzed condensation is methanesulfonic acid. The meta-substituted diphenolic compounds include one of resorcinol, 3-methoxyphenol, 3-ethoxyphenol, and 3,5-dihydroxybenzoate.

5. A method for preparing a novel cyan dye compound according to any one of claims 1-3, characterized in that, The dichlorination was carried out using a chlorinating agent under the catalysis of a catalyst at a reaction temperature of 120-150℃ for 12-20 hours. The chlorination reagent is phosphorus oxychloride, a combination of phosphorus trichloride and chlorine, phosphorus pentachloride, oxalyl chloride, or thionyl chloride.

6. A method for preparing a novel cyan dye compound according to any one of claims 1-3, characterized in that, The one-sided nucleophilic aromatic substitution reaction is carried out in a reaction system containing aluminum trichloride and a catalytic amount of organic base, at a temperature of 100-140℃ and a time of 15-25 hours. The Lewis acid is one of aluminum trichloride, boron trifluoride ether, titanium tetrachloride, tin tetrachloride, zinc chloride, and scandium trifluoromethanesulfonate; the catalytic organic base is one of 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, N,N-diisopropylethylamine, triethylamine, N-methylmorpholine, pyridine, potassium carbonate, and cesium carbonate.

7. A method for preparing a novel cyan dye compound according to any one of claims 1-3, characterized in that, The method also includes a post-processing step for the novel cyan dye compound; the post-processing involves cooling, filtering and drying the product to obtain a crude product, dissolving, washing and evaporating the crude product, and separating and purifying the resulting organic phase residue by silica gel column chromatography.

8. A novel cyan dye compound, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. A novel cyan dye compound according to claim 9, characterized in that, The chemical name of the compound is 3'-[(2,4-dimethylphenyl)amino]-4,5,6,7-tetrafluoro-6'-(3,3,5-trimethyl-2,3-dihydro-1H-indol-1-yl)-3H-spiro[2-benzofuran-1,9'-xanthanene]-3-one, and its molecular formula is C2. 39 H 30 N2O3F4, chemical formula as shown in formula (1): Equation (1).

10. The application of the novel cyan dye compound as described in claim 8 or 9 in the preparation of heat transfer cyan dye.

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