A fluoran-based compound, a thermosensitive dye dispersion liquid, and a method for producing the same

Abstract

The present application relates to a kind of fluorane compound, thermosensitive dye dispersion and its preparation method, the fluorane compound has the structure shown in formula I, wherein, R is selected from 4-trifluoromethylphenyl, n-hexyl, aminomethyl, -CH2CH2OH, -CH2CH2Br, -CH2OCH3 Or one of esterified PEO groups.The fluorane compound of the present application can be used as thermosensitive dye, and the 1,2,3-triazole structure can enhance the color ability of fluoran mother nucleus.

Description

[0001] This application is a divisional application of the parent application filed on January 12, 2022, with application number 202210031922.3 and invention title "A fluorane compound, its preparation method and application". Technical Field

[0002] This invention relates to the field of thermosensitive dye technology, and in particular to a fluorane compound, a thermosensitive dye dispersion, and a method for preparing the same. Background Technology

[0003] Due to their unique chemical structure, fluorane compounds are widely used in thermal and pressure-sensitive printing. Their working principle is that when printing materials containing dye and developer coatings are stimulated by external factors, the dye and developer come into contact. The protons released by the developer open the lactone ring in the fluorane structure to form a larger planar structure, which extends the conjugation length in the original structure. A strong absorption band appears in the visible light region, macroscopically displaying color, thereby realizing the function of printing text and patterns.

[0004] To achieve color diversity in thermal printing materials, high-performance thermal dyes with different colors are needed. Color modulation of thermal dyes requires controlling the wavelength of their visible light absorption band after color development to achieve complementary color modulation. Traditional chemical modification of thermal dyes mainly involves using aromatic substituents in the precursor prepared from fluoranes. However, some specific substituents cannot withstand the synthetic conditions during the preparation process, limiting the preparation of the fluorane core and requiring prior chemical protection. This can affect the conversion rate or selectivity of the preparation. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a fluorane compound, a thermosensitive dye dispersion, and a method for preparing the same, in order to solve the problems of low conversion rate or cumbersome process of fluorane compounds prepared by existing methods.

[0006] On one hand, one embodiment of the present invention provides a fluorane compound having the structure shown in Formula I:

[0007]

[0008] Wherein, R is selected from hydrogen, C1-C8 alkyl, C1-C4 alkoxy, phenyl, substituted phenyl, C1-C6 aminoalkyl, C1-C6 hydroxyalkyl, C1-C6 haloalkyl and groups containing polyethylene oxide chains.

[0009] According to one embodiment of the present invention, the C1-C6 aminoalkyl group is -(CH2). m -NH2, wherein the C1-C6 hydroxyalkyl group is -(CH2). n-OH, m and n are integers selected from 1 to 6; and / or,

[0010] The group containing the polyethylene oxide chain is -R1-O-PEO or -R2-COO-PEO; PEO is a polyethylene oxide group, R1 is an alkylene group containing 2 to 4 carbon atoms, and R2 is an alkylene group containing 1 to 3 carbon atoms; and / or,

[0011] The weight-average molecular weight of the groups containing the polyethylene oxide chain is 800 to 5000.

[0012] According to one embodiment of the present invention, R is selected from hydrogen, C1-C8 straight-chain alkyl, phenyl, C1-C4 alkoxy, and the group containing the polyethylene oxide chain.

[0013] According to one embodiment of the present invention, R is selected from hydrogen, methyl, ethyl, phenyl, methoxy, ethoxy, and the group containing the polyethylene oxide chain.

[0014] According to one embodiment of the present invention, R is phenyl or methoxy.

[0015] On the other hand, one embodiment of the present invention provides a method for preparing the above-mentioned fluorane compounds, comprising reacting the compound shown in Formula II with an alkynyl compound HC≡CR via a click chemistry reaction to obtain the fluorane compounds;

[0016]

[0017] Wherein, R is selected from hydrogen, C1-C8 alkyl, C1-C4 alkoxy, phenyl, substituted phenyl, C1-C6 aminoalkyl, C1-C6 hydroxyalkyl, C1-C6 haloalkyl and groups containing polyethylene oxide chains.

[0018] According to one embodiment of the present invention, the method includes: dissolving the compound of formula II and the alkynyl compound in an organic solvent, and carrying out the click chemical reaction under the action of cuprous halide and ligand, wherein the reaction temperature is 0-60°C and the reaction time is 0.5-5.0 hours.

[0019] According to one embodiment of the present invention, the organic solvent includes one or more of tetrahydrofuran, dioxane, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; and / or,

[0020] The ligand comprises one or more of triethylamine, pentamethyldiethylenetriamine, and triethylenediamine; and / or,

[0021] The cuprous halide includes one or more of cuprous chloride, cuprous bromide, and cuprous iodide; and / or,

[0022] The reaction temperature is 10–20°C.

[0023] One embodiment of the present invention also provides a thermosensitive dye dispersion, comprising the following raw materials by weight: 10.00 parts of fluorane compound, 1.25 parts of PVA-205, and 20.00 parts of deionized water;

[0024] The fluorescent compound described herein has the structure shown in Formula I:

[0025]

[0026] Wherein, R is selected from one of phenyl, 4-trifluoromethylphenyl, n-hexyl, aminomethyl, -CH2CH2OH, -CH2CH2Br, -CH2OCH3 or esterified PEO group.

[0027] One embodiment of the present invention also provides a method for preparing a thermosensitive dye dispersion, wherein the raw materials are weighed according to the weight parts, mixed and ground until a dispersion is obtained. 50 The desired dispersion of the thermosensitive dye was obtained by setting the particle size to 0.80 ± 0.05 μm.

[0028] One embodiment of the present invention also provides a thermosensitive dye, comprising the above-mentioned fluorane compounds.

[0029] An embodiment of the present invention further provides the application of the above-mentioned fluorane compounds in thermal paper.

[0030] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0031] 1. The fluorane compound of one embodiment of the present invention can be used as a thermosensitive dye, and its 1,2,3-triazole structure can enhance the color-emitting ability of the fluorane core.

[0032] 2. The preparation method of one embodiment of the present invention is universal. By controlling the chemical structure of the fluorane compound through the substituents of the reactant alkynyl compound, the color can be adjusted. Moreover, the click chemistry reaction used in this method is based on the cyclization reaction of alkynyl and azide. The reaction conditions are mild, the selectivity is high, and the tolerance to various functional groups is strong. It can be used to prepare a series of thermosensitive dyes of different colors.

[0033] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0034] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0035] Figure 1 The 1H NMR spectrum of the fluorane compounds prepared in Example 1;

[0036] Figure 2 The UV-Vis absorption spectra of the chromatic and leuco states of the fluorane compounds prepared in Example 1 are shown.

[0037] Figure 3 The static color development properties of the fluorane compounds prepared in Example 1 and the fluoranes in the comparative example are shown in the test graph. Detailed Implementation

[0038] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0039] One embodiment of the present invention provides a fluorane compound containing a 1,2,3-triazole structure, having the structure shown in Formula I:

[0040]

[0041]

[0042] Wherein, R is selected from hydrogen, C1-C8 alkyl, C1-C4 alkoxy, phenyl, substituted phenyl, C1-C6 aminoalkyl, C1-C6 hydroxyalkyl, C1-C6 haloalkyl and groups containing polyethylene oxide chains.

[0043] In one embodiment, the groups containing the polyethylene oxide chain may be esterified or etherified polyethylene oxide groups.

[0044] In one embodiment, the esterified or etherified vinyl oxide group can be -R1-O-PEO or -R2-COO-PEO; wherein, PEO can be a vinyl oxide group terminated with hydrogen or other groups (e.g., methyl), such as -(CH2CH2O). x -H or -(CH2CH2O) x -CH3; R1 is an alkylene group containing 2 to 4 carbon atoms, such as -(CH2)2-, -(CH2)3- or -(CH2)4-; R2 is an alkylene group containing 1 to 3 carbon atoms, such as -CH2-, -(CH2)2- or -(CH2)3-.

[0045] In one embodiment, the number of carbon atoms contained in the C1 to C8 alkyl group can be 1, 2, 3, 4, 5, 6, 7 or 8.

[0046] In one embodiment, the C1 to C8 alkyl groups can be straight-chain alkyl groups, such as n-propyl, isopropyl, n-butyl, n-pentyl, etc.

[0047] In one embodiment, the number of carbon atoms contained in the C1 to C4 alkoxy group can be 1, 2, 3 or 4.

[0048] In one embodiment, the alkoxy group of C1 to C4 can be methoxy, ethoxy, n-propoxy, or n-butoxy.

[0049] In one embodiment, the substituent in the substituted phenyl group can be methoxy, methyl, nitro, or trifluoromethyl. For example, the substituted phenyl group can be -C6H4-OCH3, -C6H4-CH3, -C6H4-NO2, or -C6H4-CF3.

[0050] In one embodiment, the number of carbon atoms contained in the C1 to C6 aminoalkyl group can be 1, 2, 3, 4, 5 or 6.

[0051] In one embodiment, the C1-C6 aminoalkyl group is -(CH2). m -NH2, m is an integer selected from 1 to 6, for example 2, 3, 4, 5 or 6.

[0052] In one embodiment, the C1-C6 hydroxyalkyl group is -(CH2). n -OH, where n is an integer selected from 1 to 6, for example, 1, 2, 3, 4, 5 or 6.

[0053] In one embodiment, the number of carbon atoms contained in the C1 to C6 haloalkyl group can be 1, 2, 3, 4, 5 or 6.

[0054] In one embodiment, the halogen atom in the C1 to C6 haloalkyl group can be F, Cl, Br, or I, and the number of halogen atoms can be one or more, such as two, three, or four.

[0055] In one embodiment, the C1 to C6 haloalkyl group can be a haloed straight-chain alkyl group, such as -CH2Br, -CH2CH2Br, or -CH2CH2CH2Br.

[0056] In one embodiment, the weight-average molecular weight of the esterified or etherified polyethylene oxide groups can be 800 to 5000, for example 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500.

[0057] In one embodiment, R can be hydrogen, a C1-C8 linear alkyl group, a phenyl group, a C1-C4 alkoxy group, or a polyoxyethylene group.

[0058] In one embodiment, R can be hydrogen, methyl, ethyl, phenyl, methoxy, ethoxy, or polyoxyethylene.

[0059] One embodiment of the present invention provides a method for preparing the fluorane compound of the claims above, comprising reacting the compound shown in Formula II (2-azido-3-methyl-6-dibutylaminofluorane) with the alkynyl compound HC≡CR via a click chemistry reaction to obtain the fluorane compound;

[0060]

[0061] In this case, the R group in the alkynyl compound HC≡CR is subject to the limitations specified in Formula I above.

[0062] The preparation method of one embodiment of the present invention allows for the modification of a series of different substituents onto a fluorane core containing an azide group via a click chemistry reaction. The substituents are linked to the fluorane core via 1,2,3-triazoles, and the introduced triazoles also enhance the color-emitting ability of the fluorane core. The color of the thermosensitive dye prepared using this method is related to the type of substituent introduced, but because they are all based on a triazole structure, they have high chemical structural similarity and better compatibility.

[0063] In one embodiment, the alkynyl compound includes one or more of 1-pentyne, methylpropynyl ether, 3-bromopropyne, 2-propyn-1-ol, phenylacetylene, 4-methoxyphenylacetylene, benzylpropynyl ether, and mono-alkynyl-terminated polyethylene oxide, preferably phenylacetylene or methylpropynyl ether.

[0064] In one embodiment, the mono-alkynyl-terminated polyethylene oxide can be HC≡C-R1-O-PEO or HC≡C-R2-COO-PEO; wherein, PEO can be a polyethylene oxide group terminated with hydrogen or other groups (e.g., methyl), such as -(CH2CH2O). x -H or -(CH2CH2O) x -CH3; R1 is an alkylene group containing 2 to 4 carbon atoms, such as -(CH2)2-, -(CH2)3- or -(CH2)4-; R2 is an alkylene group containing 1 to 3 carbon atoms, such as -CH2-, -(CH2)2- or -(CH2)3-.

[0065] In one embodiment, the compound represented by Formula II reacts with an alkynyl compound in the presence of a cuprous halide catalyst and a ligand, as shown in the following equation:

[0066]

[0067] In one embodiment, the preparation method includes: dissolving the compound of formula II and the alkynyl compound in an organic solvent, adding a ligand thereto, subjecting the reaction system to multiple cycles of liquid nitrogen cooling-vacuuming-thawing, adding cuprous halide thereto, controlling the reaction temperature at 0-60°C, and the reaction time at 0.5-5.0 hours.

[0068] In one embodiment, the molar ratio of the compound of formula II to the alkynyl compound is 1:(0.8 to 1.2), for example 1:0.9, 1:1, or 1:1.1.

[0069] In one embodiment, the molar ratio of the compound of formula II, the alkynyl compound, the cuprous halide, and the ligand is: compound of formula II: alkynyl compound: cuprous halide: ligand = 1.00:(0.8-1.2):(0.01-0.10):(0.01-0.20).

[0070] In one embodiment, the organic solvent may be one or more of tetrahydrofuran, dioxane, acetone, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), preferably tetrahydrofuran and / or N,N-dimethylformamide.

[0071] In one embodiment, the ligand may be one or more of triethylamine (TEA), pentamethyldiethylenetriamine (PMDETA), and triethylenediamine (DABCO), preferably pentamethyldiethylenetriamine.

[0072] In one embodiment, the cuprous halide may be one or more of cuprous chloride (I), cuprous bromide (I), and cuprous iodide (I), preferably cuprous bromide (I).

[0073] In one embodiment, the purpose of using liquid nitrogen cooling-vacuuming-thawing cycle is to remove oxygen from the reaction vessel and dissolved oxygen from the reaction solvent, and to prevent cuprous halide (I) from being oxidized to divalent copper (II). Preferably, three liquid nitrogen cooling-vacuuming-thawing cycles are performed.

[0074] In one embodiment, the reaction temperature can be 10°C, 12°C, 15°C, 16°C, 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, etc.; the reaction time can be 0.5 hours, 0.6 hours, 0.8 hours, 1 hour, 1.5 hours, 2 hours, 3 hours, 4 hours, 4.5 hours, etc.

[0075] In one embodiment, the reaction temperature is 10–20°C and the reaction time is 0.5 hours.

[0076] In one embodiment, after the click chemical reaction is completed, neutral alumina is used to remove the cuprous halide, and the concentrated solvent is used to precipitate the product of compound I.

[0077] In one embodiment, the neutral alumina is in powder form, preferably 100-200 mesh.

[0078] The fluorane compound of one embodiment of the present invention can be used in thermal printing paper, where it develops color under the action of phenolic color developers and can display different patterns.

[0079] The preparation method of one embodiment of the present invention introduces a 1,2,3-triazole structure into a traditional fluorane compound, forming a larger conjugated planar structure with the fluorane structure in the parent core. At the same time, the melting point and visible light absorption band of the thermosensitive dye can be controlled by the structure of the substituent R, enabling the preparation of a series of fluorane thermosensitive dye derivatives of different colors based on a universal parent core structure.

[0080] The preparation method of one embodiment of the present invention can efficiently and simply achieve directional modification of the fluorane core to form a series of thermosensitive dye compounds that can be applied to different thermosensitive materials.

[0081] The preparation method of one embodiment of the present invention has the advantages of mild reaction conditions, fast reaction rate, high atom economy and high yield.

[0082] The preparation and application of the fluorane compounds according to an embodiment of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, all raw materials used are commercially available.

[0083] Example 1R is phenyl

[0084] Preparation of fluorane compounds

[0085] In a Schlenk flask, 2 mL of distilled tetrahydrofuran, 0.0966 g of 2-azido-3-methyl-6-dibutylaminofluorane (compound II), 0.0035 g of PMDETA, and 0.0245 g of phenylacetylene were added. After complete dissolution with magnetic stirring, the mixture was subjected to three cycles of liquid nitrogen cooling-vacuuming-thawing. The temperature was slowly increased to 15°C, and 0.0029 g of cuprous bromide was added under nitrogen protection. The mixture was stirred at this temperature for 0.5 hours. Then, 5 mL of distilled tetrahydrofuran was added to dilute the reaction solution. The cuprous bromide was adsorbed using 100–200 mesh neutral alumina. The remaining liquid was distilled under reduced pressure to remove all solvents. The remaining solid was the prepared fluorane compound, with a mass of approximately 0.1121 g, a yield of approximately 95.6%, and a purity of 98.6% (HPLC area method). The pre-acid colorimetric result was pink.

[0086] Applications of fluorane compounds in thermal paper

[0087] The fluorane dye with R being phenyl was used as a thermosensitive dye, bisphenol A (BPA) as a color developer, and benzyl-2-naphthyl ether (BON) as a sensitizer. Static color development was compared with 2-phenylamino-3-methyl-6-dibutylaminofluorane (ODB-2). 10.00 parts of the fluorane dye with R being phenyl, 1.25 parts of PVA-205, and 20.00 parts of deionized water were ground to a dispersion. 50 The dispersion of the thermosensitive dye was prepared with a particle size of 0.80 ± 0.05 μm. 10.00 parts of bisphenol A, 1.50 parts of PVA-205, and 20.00 parts of deionized water were ground to a dispersion consistency of d. 50 The dispersion of the colorimetric reagent was 0.80±0.05μm; 10.00 parts of benzyl-2-naphthyl ether, 1.80 parts of PVA-205, and 20.00 parts of deionized water were ground to a dispersion consistency of d. 50 The particle size was 0.80±0.05μm, which was used as a sensitizer dispersion.

[0088] 10.00 parts of the above-mentioned thermosensitive dye dispersion, 15.00 parts of the color developer dispersion, 7.50 parts of the sensitizer, 9.00 parts of kaolin, and 10.00 parts of deionized water were mixed and dispersed mechanically for 1 hour. The mixture was then coated onto paper to prepare thermosensitive paper. Static color development tests were conducted at 60–150°C, and color density values ​​were recorded at 10°C intervals. The test results are shown in [reference needed]. Figure 3 .

[0089] Comparative Example

[0090] The thermal paper was prepared and tested according to the same steps and conditions as in Example 1, "Application of Fluorane Compounds in Thermal Paper," with the only difference being that the fluorane compound with R being phenyl was replaced with 2-phenylamino-3-methyl-6-dibutylaminofluorane. The test results are shown in [reference needed]. Figure 3 .

[0091] according to Figure 3 As can be seen from the curve, between 110°C and 150°C, the color density of the thermal paper of Example 1 is higher than that of the thermal paper of the comparative example, indicating that the fluorane compound of Example 1 has a stronger color development ability.

[0092] Example 2R is phenyl

[0093] Add 100 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 5.11 g of phenylacetylene to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 90 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Add 30 mL of n-hexane, stir for 15 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 21.69 g, a yield of approximately 92.7%, and a purity of 99.3% (HPLC area method).

[0094] Example 3R is phenyl

[0095] Add 30 mL of DMF, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, and 5.11 g of phenylacetylene to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, maintain this temperature and stir for 1 hour. Dilute with 50 mL of tetrahydrofuran, then adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove all tetrahydrofuran by vacuum distillation. Add the remaining liquid to 100 mL of deionized water to precipitate the solid. Filter the solid obtained, which is the prepared fluorane compound. The dried mass is approximately 18.53 g, the yield is approximately 79.23%, and the purity is 98.2% (HPLC area method).

[0096] Example 4R is 4-trifluoromethylphenyl

[0097] Add 60 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 9.31 g of 4-trifluoromethylphenylacetylene to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 50 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Add 30 mL of n-hexane, stir for 15 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 25.45 g, a yield of approximately 95.1%, and a purity of 99.2% (HPLC area method).

[0098] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0099] 1 H NMR(500MHz,Chloroform-d)δ8.14(s,1H),8.04–7.98(m,2H),7.92(dd,J=7.3,1.6Hz,1H ),7.74–7.69(m,2H),7.68(dd,J=7.5,1.6Hz,1H),7.56–7.49(m,2H),7.44(s,1H),7.34(d ,J=7.5Hz,1H),6.92–6.88(m,1H),6.71(dd,J=7.5,1.6Hz,1H),6.41(d,J=1.5Hz,1H),3.1 7–3.03(m,4H),2.41(s,3H),1.69–1.48(m,4H),1.48–1.23(m,4H),0.94(t,J=8.0Hz,6H).

[0100] Example 5R is n-hexyl

[0101] Add 60 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 5.51 g of 1-octyne to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 50 mL of tetrahydrofuran from the remaining liquid by vacuum distillation, add 30 mL of n-hexane, cool to -20 °C, stir for 60 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 20.14 g, a yield of approximately 84.9%, and a purity of 99.7% (HPLC area method).

[0102] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0103] 1H NMR(500MHz,Chloroform-d)δ8.37(s,1H),7.94(dd,J=7.3,1.7Hz,1H),7.69(td,J=7.5,1.5Hz,1H),7. 56–7.49(m,2H),7.40(s,1H),7.33(d,J=7.5Hz,1H),6.88(d,J=0.6Hz,1H),6.71(dd,J=7.5,1.6Hz,1H) ,6.41(d,J=1.5Hz,1H),3.17–3.03(m,4H),2.85(dt,J=12.5,7.1Hz,1H),2.74(dt,J=12.4,7.1Hz,1H), 2.41(s,3H),1.87–1.71(m,2H),1.69–1.48(m,4H),1.48–1.24(m,10H),0.97–0.88(m,9H),0.87(s,1H).

[0104] Example 6R is aminomethyl

[0105] Add 60 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 2.75 g of propargylamine to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 50 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Add 30 mL of n-hexane, stir for 15 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 20.72 g, a yield of approximately 96.3%, and a purity of 98.9% (HPLC area method).

[0106] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0107] 1H NMR(500MHz,Chloroform-d)δ8.48(s,1H),7.96(dd,J=7.3,1.5Hz,1H),7.68(td,J=7.5, 1.6Hz,1H),7.56–7.49(m,2H),7.39(s,1H),7.34(d,J=7.5Hz,1H),6.88(s,1H),6.71(dd ,J=7.5,1.6Hz,1H),6.41(d,J=1.5Hz,1H),4.29–4.16(m,2H),3.60(t,J=7.1Hz,2H),3.1 7–3.03(m,4H),2.41(s,3H),1.69–1.48(m,4H),1.48–1.26(m,4H),0.94(t,J=8.0Hz,6H).

[0108] Example 7R is hydroxyethyl (-CH2CH2OH).

[0109] Add 60 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 3.50 g of 3-butyn-1-ol to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 50 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Add 30 mL of n-hexane, stir for 15 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 20.16 g, a yield of approximately 91.2%, and a purity of 99.7% (HPLC area method).

[0110] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0111] 1H NMR(500MHz,Chloroform-d)δ8.15(s,1H),7.96(dd,J=7.3,1.5Hz,1H),7.68(td,J=7.5, 1.6Hz,1H),7.56–7.49(m,2H),7.42(s,1H),7.34(d,J=7.5Hz,1H),6.88(s,1H),6.71(dd ,J=7.5,1.6Hz,1H),6.41(d,J=1.5Hz,1H),4.63–4.52(m,2H),4.24(t,J=6.9Hz,1H),3.1 7–3.03(m,4H),2.41(s,2H),1.69–1.49(m,4H),1.49–1.26(m,4H),0.94(t,J=8.0Hz,6H).

[0112] Example 8R is 2-bromoethyl(-CH2CH2Br)

[0113] Add 60 mL of distilled tetrahydrofuran, 19.30 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.69 g of PMDETA, and 6.65 g of 4-bromo-1-butyne to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.57 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 1 hour. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 50 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Add 30 mL of n-hexane, stir for 15 minutes, and filter. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 22.21 g, a yield of approximately 90.2%, and a purity of 99.3% (HPLC area method).

[0114] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0115] 1H NMR(500MHz,Chloroform-d)δ8.40(s,1H),7.94(dd,J=7.4,1.6Hz,1H),7.68(td,J=7.5,1.6Hz, 1H),7.56–7.49(m,2H),7.39(s,1H),7.33(d,J=7.5Hz,1H),6.90–6.86(m,1H),6.70(dd,J=7.5,1 .5Hz,1H),6.41(d,J=1.5Hz,1H),3.86(td,J=7.0,1.4Hz,2H),3.17–3.08(m,2H),3.11–3.05(m,2 H),3.07–2.97(m,2H),2.41(s,2H),1.69–1.48(m,4H),1.48–1.25(m,4H),0.94(t,J=7.9Hz,6H).

[0116] Example 9R is methoxymethyl (-CH2OCH3).

[0117] Add 30 mL of distilled tetrahydrofuran, 9.6516 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.3466 g of PMDETA, and 1.7523 g of methylpropynyl ether to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.2869 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 3.0 hours. Adsorb cuprous bromide using 100-200 mesh neutral alumina. Remove all solvent from the remaining liquid by vacuum distillation. The resulting solid is the prepared fluorane compound, with a dry mass of approximately 10.21 g, a yield of approximately 92.4%, and a purity of 99.0% (HPLC area method).

[0118] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0119] 1H NMR (400MHz, DMSO-d6) δ8.11(s,1H),7.94(dd,J=7.4,1.6Hz,1H),7.68(td,J=7.5,1. 5Hz,1H),7.57–7.49(m,2H),7.42(s,1H),7.33(d,J=7.5Hz,1H),6.88(s,1H),6.71(d d,J=7.5,1.6Hz,1H),6.41(d,J=1.6Hz,1H),4.57–4.45(m,2H),3.39(s,2H),3.17–3. 03(m,4H),2.40(s,3H),1.69–1.49(m,4H),1.49–1.26(m,5H),0.94(t,J=7.9Hz,6H).

[0120] Example 10R is an esterified PEO group

[0121] Use M w Mono-hydroxy-terminated PEO of approximately 1000 and 2-butynic acid were reacted with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC hydrochloride) to prepare mono-alkynyl-terminated PEO. The mixture was precipitated multiple times in cold diethyl ether and centrifuged to obtain mono-alkynyl-terminated PEO.

[0122] Add 60 mL of distilled tetrahydrofuran, 9.6516 g of 2-azido-3-methyl-6-dibutylaminofluorane, 0.3813 g of PMDETA, and 17.1000 g of mono-alkynyl-terminated PEO to a Schlenk flask. After complete dissolution with magnetic stirring, perform three cycles of liquid nitrogen cooling-vacuuming-thawing. Slowly raise the temperature to 15 °C, add 0.3156 g of cuprous bromide under nitrogen protection, and maintain this temperature while stirring for 4.0 hours. Adsorb the cuprous bromide using 100-200 mesh neutral alumina. Remove 40 mL of tetrahydrofuran from the remaining liquid by vacuum distillation. Precipitate in 50 mL of cold diethyl ether, centrifuge, and dry. The resulting powdery solid is the prepared fluorane compound. The dried mass is approximately 20.59 g, with a yield of approximately 72.32%. Infrared spectroscopy shows that the product contains no alkynyl group (-C≡CH, 3310 cm⁻¹). -1 The stretching vibration peak of azide (-N3, 2115 cm⁻¹) and the stretching vibration peak of azide (-N3, 2115 cm⁻¹) -1 The specific reaction formula is as follows:

[0123]

[0124] The obtained fluorane compounds were subjected to NMR analysis, and the specific results are as follows:

[0125] 1H NMR(400MHz, DMSO-d6)δ8.09(s,1H),7.94(dd,J=7.3,1.5Hz,1H),7.69(td,J=7.5,1.5Hz, 1H),7.56–7.48(m,2H),7.37(s,1H),7.31(d,J=7.4Hz,1H),6.88(s,1H),6.71(dd,J=7.5, 1.6Hz,1H),6.41(d,J=1.5Hz,1H),4.42–4.26(m,2H),3.79–3.54(m,89H),3.38(s,2H),3. 17–3.03(m,4H),2.41(s,2H),1.68–1.48(m,4H),1.48–1.22(m,4H),0.94(t,J=7.9Hz,6H).

[0126] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluoran-based compound, characterized by, A compound having a structure shown in Formula I: ； Formula I R is selected from one of 4-trifluoromethylphenyl, n-hexyl, aminomethyl, -CH2CH2OH, -CH2CH2Br or -CH2OCH3.

2. A method for preparing a fluoran-based compound, characterized by, The compound of Formula II and the alkyne compound HC≡C-R are dissolved in an organic solvent, a ligand is added, the reaction system is subjected to multiple liquid nitrogen cooling-vacuum extraction-thawing cycles, cuprous halide is added, the reaction temperature is controlled at 10-20 DEG C, and the reaction time is 0.5-5.0 hours; ； Formula II R is selected from one of 4-trifluoromethylphenyl, n-hexyl, aminomethyl, -CH2CH2OH, -CH2CH2Br or -CH2OCH3. The ligand is one or more of triethylamine, pentamethyldiethylene triamine and triethylene diamine. The organic solvent includes one or more of tetrahydrofuran, dioxane, acetone, N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl pyrrolidone. The purpose of the liquid nitrogen cooling-vacuum extraction-thawing cycle is to remove oxygen in the reaction vessel and dissolved oxygen in the reaction solvent, so as to avoid oxidation of cuprous halide into divalent copper.

3. The preparation method of the fluorane compound according to claim 2, characterized in that, The cuprous halide includes one or more of cuprous chloride, cuprous bromide and cuprous iodide; and / or.

4. A heat-sensitive dye dispersion liquid characterized by comprising: The fluorane compound is prepared by using the following raw materials by weight: fluorane compound 10.00 parts, PVA-205 1.25 parts and deionized water 20.00 parts. The fluorane compound has a structure shown in Formula I: ； Formula I R is selected from one of 4-trifluoromethylphenyl, n-hexyl, aminomethyl, -CH2CH2OH, -CH2CH2Br or -CH2OCH3.

5. A method for producing the heat-sensitive dye dispersion liquid according to claim 4, characterized by, The raw materials were weighed out in parts by weight, mixed and ground to a dispersion d 50 0.80 ± 0.05 μm, to obtain the heat-sensitive dye dispersion.

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