A benzoxazine fluorescent material, its preparation method and application

Abstract

The present invention belongs to the technical field of fluorescent materials, and specifically relates to a benzoxazine fluorescent material, a preparation method thereof and an application thereof. The preparation method of the benzoxazine fluorescent material is specifically to add reactants, namely an oxazine compound, a sulfonium ylide compound, a rhodium catalyst and an additive, into a solvent under an inert atmosphere for heating reaction, and after the reaction is completed, the benzoxazine fluorescent material is obtained through purification and separation. The fluorescent material can achieve a reversible change in fluorescence color under acid-base stimulation, specifically, the solution changes from green fluorescence to red after adding alkali, and then changes back to green fluorescence after adding acid again. It utilizes the response of secondary amine to acid-base stimulation, specifically the protonation and neutralization reactions of secondary amine, to achieve the reversible acid-base response of the benzophenoxazine fluorescent material. The method of the present invention has the advantages of less amount of reaction catalyst used, simple separation operation, atom economy, step economy, strong functional group tolerance, and no need for metal oxidants such as silver salts.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent materials, and in particular relates to a benzoxazine fluorescent material and a preparation method and application thereof. Background Art

[0002] In recent decades, information technology has developed rapidly, and fluorescent sensors have stood out from many sensors due to their high sensitivity, good selectivity, and easy analysis. Stimulus responsiveness is the core performance of the sensor. As a stimulus-responsive functional molecule, the switch molecule can achieve reversible transformation under the action of external stimuli. Large conjugated fluorophores have broad application prospects in the fields of bioimaging, chemical sensing, photodynamic therapy, etc. due to their good photothermal stability, good biocompatibility, and strong modifiability. Fluorescent probes made with large conjugated rings as the parent core structure have the advantages of simple operation, strong visualization, and high sensitivity. They can convert signals into fluorescent signals, and can be visualized and identified through the fluorescence "off-on" or "on-off" mode.

[0003] Among them, the fluorescence color and spectrum of the acid-base stimulus responsive fluorescent material change significantly after being stimulated by external acid and base, which can realize the visual identification of fluorescence. The acid-base stimulus responsive fluorescent materials mainly include Schiff base type, pyridinium salts, thiazoles, indoles, etc. These fluorescent materials can react with acids and bases through their own specific groups, that is, they have a structure that can donate or accept protons. Utilizing the characteristics of acid-base stimulus responsive fluorescent materials, chemical devices such as pH probes, acid-base steam exhaust gas detection probes, and acid-base responsive electrochromic films can be made. Therefore, it is of great research significance to use a new method to prepare acid-base responsive fluorescent materials. Summary of the invention

[0004] The object of the present invention is to provide a benzoxazine fluorescent material and a preparation method and application thereof. The present invention pioneers the selection of a transition metal Rh-catalyzed CH bond activation reaction to prepare an acid-base responsive fluorescent material. The direct conversion of the CH bond can avoid the pre-functionalization of the reaction raw materials, shorten the synthesis reaction route, save economic costs, reduce the generation of harmful by-products, etc. It is a method for constructing carbon-carbon and carbon-heteroatom bonds with great application prospects and high atom economy.

[0005] The implementation process of the present invention is as follows:

[0006] A benzoxazine fluorescent material, the chemical structure of which is shown below:

[0007]

[0008] Among them, R 1 R is selected from any one of a hydrogen group, a halogen group or an alkyl group having 1 to 8 carbon atoms; 2Selected from any one of a hydrogen group or an alkoxy group having 1 to 8 carbon atoms; R 3 Selected from any one of a hydrogen group or a halogen group.

[0009] The preparation method of the above benzoxazine fluorescent material is to add the reactant oxazine compound, sulfonium ylide compound, rhodium catalyst and additive into a solvent together under an inert atmosphere for heating reaction, and after the reaction is completed, the benzoxazine fluorescent material is obtained through purification and separation; the reaction formula is as follows,

[0010]

[0011] Furthermore, the chemical structural formula of the oxazine compound is as follows,

[0012]

[0013] wherein, R 1 is selected from any one of a hydrogen group, a halogen group or an alkyl group having 1 to 8 carbon atoms; R 2 is selected from any one of a hydrogen group or an alkoxy group having 1 to 8 carbon atoms;

[0014] The chemical structural formula of the sulfonium ylide compound is as follows:

[0015]

[0016] wherein, R 3 is selected from any one of a hydrogen group or a halogen group.

[0017] Furthermore, the rhodium catalyst is dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer.

[0018] Furthermore, the additive is selected from cesium acetate, sodium acetate or lithium acetate.

[0019] Furthermore, the solvent is hexafluoroisopropanol.

[0020] Furthermore, the reaction temperature of the reaction is 40°C - 100°C, the reaction time is 1h - 12h, and the inert atmosphere is a nitrogen atmosphere.

[0021] Furthermore, the molar ratio of the oxazine compound, the sulfonium ylide compound, the rhodium catalyst and the additive is 1:(1.1 - 1.5):(0.1 - 0.2):(1.0 - 2.0).

[0022] Furthermore, the concentration of the oxazine compound in the solvent is 0.1 - 0.2 mol·L -1 .

[0023] The application of the above benzoxazine fluorescent material in terms of acid-base stimulation response.

[0024] The reaction mechanism of the present invention is shown as follows:

[0025]

[0026] Rhodium reacts with the benzoxazine compound to obtain a rhodium complex B with a five-membered ring structure. The sulfur ylide compound migrates and inserts, and through coordination, an intermediate C is obtained. Intermediate C eliminates one molecule of DMSO to generate intermediate D. Subsequently, intermediate D is protonated to obtain E. Then, a nucleophilic attack is carried out on the C 2 site, and the rhodium catalyst dissociates from the coordinating atom to achieve a regeneration cycle, and at the same time, the target product 3 is obtained.

[0027] Positive effects of the present invention:

[0028] (1) Through the C-H bond activation reaction catalyzed by transition metals, the present invention uses easily available benzoxazine compounds and sulfur ylide compounds to react, and realizes the construction of a novel fused ring skeleton in one step through [4+2] cycloaddition, providing a simple and effective synthesis method for the construction of complex fused rings.

[0029] (2) The method of the present invention has the advantages of less catalyst dosage, simple separation operation, atom economy, step economy, strong functional group tolerance, and no need for metal oxidants such as silver salts.

[0030] (3) The fluorescent material of the present invention can realize reversible changes in fluorescence color under acid-base stimulation. Specifically, the solution changes from green fluorescence to red after adding alkali, and then changes back to green fluorescence after adding acid. It utilizes the response of secondary amines to acid-base stimulation, specifically the protonation and neutralization reactions of secondary amines, to achieve reversible acid-base response of the benzophenoxazine fluorescent material.

[0031] (4) When the ratio of organic solvent is H 2 O:DMSO = 9:1, the fluorescent material of the present invention can realize responses to different pH values, specifically manifested as a quenching phenomenon, that is, when the pH reaches a certain value, the fluorescence disappears, realizing the "on-off" response to the alkaline environment. Description of the Drawings

[0032] Figure 1 is the reversible response ultraviolet absorption diagram of compound 3aa;

[0033] Figure 2 is the pH response fluorescence emission diagram of compound 3aa;

[0034] Figure 3It is the reversible response color change diagram of compound 3aa; where a is the solution of compound 3aa under sunlight, b is the solution after adding base to a under sunlight, c is the solution after adding acid to b under sunlight, d is the solution of compound 3aa under 365 nm, e is the solution after adding base to d under 365 nm, and f is the solution after adding acid to d under 365 nm;

[0035] Figure 4 It is the pH response color change diagram of compound 3aa; where a is the solution of compound 3aa under 365 nm, and b is the fluorescence quenching phenomenon of compound 3aa solution when pH = 14 under 365 nm;

[0036] Figure 5 It is the reversible response ultraviolet absorption diagram of compound 3ba;

[0037] Figure 6 It is the pH response fluorescence emission diagram of compound 3ba;

[0038] Figure 7 It is the reversible response color change diagram of compound 3ba; where a is the solution of compound 3ba under sunlight, b is the solution after adding base to a under sunlight, c is the solution after adding acid to b under sunlight, d is the solution of compound 3ba under 365 nm, e is the solution after adding base to d under 365 nm, and f is the solution after adding acid to d under 365 nm;

[0039] Figure 8 It is the pH response color change diagram of compound 3ba; where a is the solution of compound 3ba under 365 nm, and b is the fluorescence quenching phenomenon of compound 3ba solution when pH = 13 under 365 nm;

[0040] Figure 9 It is the reversible response ultraviolet absorption diagram of compound 3ca;

[0041] Figure 10 It is the pH response fluorescence emission diagram of compound 3ca;

[0042] Figure 11 It is the reversible response color change diagram of compound 3ca; where a is the solution of compound 3ca under sunlight, b is the solution after adding base to a under sunlight, c is the solution after adding acid to b under sunlight, d is the solution of compound 3ca under 365 nm, e is the solution after adding base to d under 365 nm, and f is the solution after adding acid to d under 365 nm;

[0043] Figure 12 It is the pH response color change diagram of compound 3ca; where a is the solution of compound 3ca under 365 nm, and b is the fluorescence quenching phenomenon of compound 3ca solution when pH = 13.5 under 365 nm;

[0044] Figure 13 It is the 1H NMR spectrum of compound 3aa; 1 H spectrum;

[0045] Figure 14 It is the 1H NMR spectrum of compound 3aa; 13 C spectrum;

[0046] Figure 15 It is the 1H NMR spectrum of compound 3ba; 1 H spectrum;

[0047] Figure 16 It is the 1H NMR spectrum of compound 3ba; 13 C spectrum;

[0048] Figure 17 It is the 1H NMR spectrum of compound 3ca; 1 H spectrum;

[0049] Figure 18 It is the 1H NMR spectrum of compound 3ca; 13 C spectrum;

[0050] Figure 19 It is the 1H NMR spectrum of compound 3da; 1 H spectrum;

[0051] Figure 20 It is the 1H NMR spectrum of compound 3da; 13 C spectrum;

[0052] Figure 21 It is the 1H NMR spectrum of compound 3ea; 1 H spectrum;

[0053] Figure 22 It is the 1H NMR spectrum of compound 3ea; 13 C spectrum;

[0054] Figure 23 It is the 1H NMR spectrum of compound 3fa; 1 H spectrum;

[0055] Figure 24 It is the 1H NMR spectrum of compound 3fa; 13 C spectrum. Detailed implementation manners

[0056] The present invention will be further described below in conjunction with embodiments.

[0057] The present invention provides a benzoxazine-based fluorescent material, a preparation method thereof, and an application thereof in acid-base response. The fluorescent material can achieve a reversible change in fluorescence color under acid-base stimulation, specifically, the solution changes from green fluorescence to red after adding alkali, and then changes back to green fluorescence after adding acid. It utilizes the response of secondary amine to acid-base stimulation, specifically the protonation and neutralization reactions of secondary amine, to achieve the reversible acid-base response of the benzophenoxazine fluorescent material. At the same time, when the proportion of organic solvent is H 2 O:DMSO = 9:1, the fluorescent material can achieve responses to different pH values, specifically, a quenching phenomenon, that is, when the pH reaches a certain value, the fluorescence disappears, realizing the "on-off" response to the alkaline environment. The present invention innovatively utilizes the C-H bond activation strategy catalyzed by transition metals to achieve the construction of a novel fused ring skeleton in one step through [4+2] under the action of a rhodium metal catalyst, providing a simple and effective synthesis method for the construction of complex fused rings. At the same time, the synthesis method of the fluorescent material of the present invention has the advantages of less catalyst dosage, simple separation operation, atom economy, step economy, strong functional group tolerance, and no need for metal oxidants such as silver salts.

[0058] Example 1 Preparation of Fluorescent Material 3aa

[0059]

[0060] Under nitrogen atmosphere, oxazine compound 1a (0.20 mmol), sulfonium ylide compound 2a (0.30 mmol), [Cp*RhCl 2 2 (0.04 mmol), LiOAc (0.20 mmol) and solvent HFIP (2.0 mL) were added to a 38 mL sealed tube and reacted in a reaction module at 100 °C for 12 h. After the reaction, the solvent was removed under reduced pressure, and the target product (3aa) was separated by silica gel column. All eluents were prepared by mixing petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 86% yield. The NMR spectra are as shown in Figure 13 and 14 . 1 H NMR (400 MHz, DMSO-d 6 ) δ 8.50 (s, 1H), 7.98 (d, J = 8.6 Hz, 1H), 7.79 (d, J = 8.2 Hz, 1H), 7.57 (d, J = 7.6 Hz, 2H), 7.51–7.44 (m, 3H), 7.43–7.35 (m, 2H), 7.33 (s, 1H), 6.61 (dd, J = 9.8, 3.0 Hz, 1H), 6.50 (dd, J = 8.7, 5.2 Hz, 1H), 6.38 (td, J = 8.6, 3.0 Hz, 1H). 13 ​13C NMR (101 MHz, DMSO) δ 158.8 (d, J = 237.2 Hz), 139.55, 139.53, 136.85, 135.82, 134.40 (d, J = 11.7 Hz), 130.21, 129.52, 129.36, 128.50, 128.23, 127.50, 125.73, 125.22, 125.01, 121.46, 120.93, 120.29, 115.63 (d, J = 9.8 Hz), 106.27 (d, J = 23.2 Hz), 101.29 (d, J = 28.1 Hz). HRMS: [M] calculated for C 22 H 14 FNO: 327.1059, found: 327.1064.

[0061] Experiment on the Reversible Response of Fluorescent Material 3aa to Acids and Bases

[0062] (1) Prepare a solution of fluorescent material 3aa with a concentration of 2×10 -4 mol·L -1 in DMSO:H 2 O = 9:1. Additionally, prepare 4.5 mol·L -1 aqueous NaOH solution and 4.5 mol·L -1 aqueous HCl solution for the subsequent exploration of the reversible acid-base response experiment.

[0063] (2) Take 2 ml of the above solution and successively add 1 - 2 μl of 4.5 mol·L -1 aqueous NaOH solution, and measure its ultraviolet absorption spectrum. As shown in Figure 1 , it can be found that an obvious red shift phenomenon occurs after adding the base. As shown in Figure 3 e, a new absorption peak slowly appears at around 545 nm.

[0064] (3) Then add 1 - 10 μl of 4.5 mol·L -1 aqueous HCl solution to the solution in (2), and measure its ultraviolet absorption spectrum. As shown in Figure 1 , it can be found that an obvious blue shift phenomenon occurs after adding the acid. As shown in Figure 3 f, the new peak slowly disappears, indicating that the acid-base response is reversible.

[0065] Figure 3 Among them, a is the solution of compound 3aa under sunlight, b is the solution of a after adding base under sunlight, c is the solution of b after adding acid under sunlight, d is the solution of compound 3aa under 365 nm, e is the solution of d after adding base under 365 nm, and f is the solution of d after adding acid under 365 nm.

[0066] Experiment on the pH Response of Fluorescent Material 3aa

[0067] (1) Prepare a DMSO solution with a concentration of 1×10 -3 mol·L -1 . Additionally, prepare aqueous solutions with pH = 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, and 14.0.

[0068] (2) Take 200 μl of the DMSO solution of fluorescent material 3aa with a concentration of 1×10 -3 mol·L -1 and add it to 1800 μl of the above pH solutions respectively to obtain a solution with a DMSO:H -4 mol·L -1 O ratio of 1:9. Measure its fluorescence emission spectrum. As shown in 2 Figure 2 , it is found that when pH = 14, fluorescence quenching occurs and the fluorescence disappears. As shown in Figure 4 b, an "on - off" response to the alkaline environment is achieved.

[0069] Example 2 Preparation of Fluorescent Material 3ba

[0070]

[0071] Under nitrogen conditions, oxazine compound 1b (0.20 mmol), sulfonium ylide compound 2a (0.22 mmol), [Cp*RhCl 2 2 (0.02 mmol of the oxazine compound), NaOAc (0.40 mmol) and the solvent HFIP (2.0 mL) are added to a 38 mL sealed tube and reacted in a reaction module at 100 °C for 12 h. After the reaction, the solvent is removed under reduced pressure, and the target product (3ba) is separated by silica gel column chromatography. All eluents are prepared from petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 75% yield. The NMR spectra are as shown in Figure 15 and 16 and 16 shown, 1 H NMR (400 MHz, DMSO - d 6)δ8.47(s,1H),7.95(d,J=8.6Hz,1H),7.78(dd,J=8.3,1.3Hz,1H),7.58–7.52(m,2H),7.50–7.43(m,3H),7.42–7.34(m,2H),7.31(s,1H),6.79(d,J=2.5Hz,1H),6.60(dd,J=8.4,2.5Hz,1H),6.48(d,J=8.4Hz,1H). 13 C NMR(101MHz,DMSO)δ142.3,136.8,135.6,134.5,130.3,129.5,129.4,128.5,128.3,127.7,127.5,125.8,125.4,125.1,121.5,121.0,120.4,120.3,116.3,113.5.HRMS:[M]calculated for C 22 H 14 ClNO:343.0764,found:343.0762

[0072] Experiment on the Reversible Response of Fluorescent Material 3ba to Acids and Bases

[0073] (1) Prepare a solution of fluorescent material 3ba with a concentration of 2×10 -4 mol·L -1 in DMSO:H 2 O = 9:1. Prepare 4.5 mol·L -1 aqueous NaOH solution and 4.5 mol·L -1 aqueous HCl solution for the subsequent exploration of the reversible response experiment to acids and bases.

[0074] (2) Take 2 ml of the above solution and sequentially add 1 - 2 μl of 4.5 mol·L -1 aqueous NaOH solution, and measure its ultraviolet absorption spectrum. See Figure 5 . It can be found that there is an obvious red - shift phenomenon after adding the base. See Figure 7 e, and a new absorption peak slowly appears at 559 nm.

[0075] (3) Then add 1 - 4 μl of 4.5 mol·L -1 aqueous HCl solution to the solution in (2), and measure its ultraviolet absorption spectrum. See Figure 5 . It can be found that there is an obvious blue - shift phenomenon after adding the acid. See Figure 7 f, and the new peak slowly disappears, indicating that the acid - base response is reversible.

[0076] Figure 7Among them, a is the solution of compound 3ba under sunlight, b is the solution after adding alkali to a under sunlight, c is the solution after adding acid to b under sunlight, d is the solution of compound 3ba under 365 nm, e is the solution after adding alkali to d under 365 nm, and f is the solution after adding acid to d under 365 nm.

[0077] Experiment on the pH response of fluorescent material 3ba

[0078] (1) Prepare a DMSO solution with a concentration of 1×10 -3 mol·L -1 of fluorescent material 3ba. Prepare aqueous solutions with pH = 10.0, 11.0, 12.0, 12.5, 13.0, 13.5, and 14.0 respectively.

[0079] (2) Take 200 μl of the DMSO solution of fluorescent material 3ba with a concentration of 1×10 -3 mol·L -1 and add it to 1800 μl of the above-mentioned pH solution respectively to obtain a solution with a DMSO:H -4 mol·L -1 O ratio of 1:9. Measure its fluorescence emission spectrum. See 2 Figure 6 . It is found that when pH = 13, fluorescence quenching occurs and the fluorescence disappears. See Figure 6 Figure 8 b, realizing the "on-off" response to the alkaline environment.

[0080] Example 3 Preparation of fluorescent material 3ca

[0081]

[0082] Under nitrogen atmosphere, oxazine compound 1c (0.2 mmol), sulfonium ylide compound 2a (0.30 mmol), [Cp*RhCl 2 2 (0.04 mmol of oxazine compound), LiOAc (0.40 mmol) and solvent HFIP (2.0 mL) are added to a 38 mL sealed tube and reacted in a reaction module at 100 °C for 12 h. After the reaction, the solvent is removed under reduced pressure, and the target product (3ca) is separated by silica gel column chromatography. All eluents are prepared from petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 70% yield. The NMR spectra are as shown in Figure 17 and 18 shown, 1 H NMR (400 MHz, DMSO-d 6)δ8.28(s,1H),7.97(d,J=9.2Hz,1H),7.57(d,J=7.6Hz,2H),7.47(t,J=7.5Hz,2H),7.42–7.35(m,1H),7.24–7.17(m,2H),7.13(dd,J=9.2,2.4Hz,1H),6.79(d,J=3.7Hz,2H),6.65–6.58(m,1H),6.50(d,J=7.8Hz,1H),3.84(s,3H). 13 C NMR(101MHz,DMSO)δ156.5,143.4,137.2,134.1,132.9,131.5,129.9,129.3,128.1,127.3,126.7,124.0,122.2,121.2,119.4,117.9,116.3,114.9,114.1,106.5,55.1.HRMS:[M]calculated for C 23 H 17 NO 2 :339.1259,found:339.1264

[0083] Experiment on the Reversible Response of Fluorescent Material 3ca to Acids and Bases

[0084] (1) Prepare a solution of fluorescent material 3ca with a concentration of 2×10 -4 mol·L -1 in DMSO:H 2 O = 9:1. Additionally, prepare 4.5 mol·L -1 aqueous NaOH solution and 4.5 mol·L -1 aqueous HCl solution for the subsequent exploration of the reversible response experiment to acids and bases.

[0085] (2) Take 2 ml of the above solution and successively add 1 - 5 μl of 4.5 mol·L -1 aqueous NaOH solution, and measure its ultraviolet absorption spectrum. As shown in Figure 9 , it can be found that there is an obvious red - shift phenomenon after adding the base. As shown in Figure 11 e, a new absorption peak slowly appears at 534 nm.

[0086] (3) Then add 1 - 8 μl of 4.5 mol·L -1 aqueous HCl solution to the solution in (2), and measure its ultraviolet absorption spectrum. As shown in Figure 9 , it can be found that there is an obvious blue - shift phenomenon after adding the acid. As shown in Figure 11 , the new peak slowly disappears, indicating that the acid - base response is reversible.

[0087] Figure 11Among them, a is the solution of compound 3ca under sunlight, b is the solution after adding base to a under sunlight, c is the solution after adding acid to b under sunlight, d is the solution of compound 3ca under 365 nm, e is the solution after adding base to d under 365 nm, and f is the solution after adding acid to d under 365 nm.

[0088] Experiment on the pH response of fluorescent material 3ca

[0089] (1) Prepare a DMSO solution with a concentration of 1×10 -3 mol·L -1 of fluorescent material 3ca. Prepare aqueous solutions with pH = 10.0, 11.0, 12.0, 12.5, 13.0, 13.5, and 14.0 respectively.

[0090] (2) Take 200 μl of the DMSO solution of fluorescent material 3ca with a concentration of 1×10 -3 mol·L -1 and add it to 1800 μl of the above pH solutions respectively to obtain a solution of DMSO:H -4 mol·L -1 O = 1:9 with a concentration of 1×10 2 of fluorescent material 3ca. Measure its fluorescence emission spectrum, as shown in Figure 10 . It is found that when pH = 13.5, fluorescence quenching occurs and the fluorescence disappears, as shown in Figure 12 b, realizing the "on-off" response to the alkaline environment.

[0091] Example 4 Preparation of fluorescent material 3da

[0092]

[0093] Under nitrogen atmosphere, oxazine compound 1d (0.2 mmol), sulfonium ylide compound 2a (0.30 mmol), [Cp*RhCl 2 2 (0.04 mmol), LiOAc (0.40 mmol) and solvent HFIP (2.0 mL) were added to a 38 mL sealed tube and reacted in a reaction module at 40 °C for 12 h. After the reaction, the solvent was removed under reduced pressure, and the target product (3da) was separated by silica gel column chromatography. All eluents were prepared with petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 50% yield. The NMR spectra are as shown in Figure 19 and 20 , 1 H NMR (400 MHz, DMSO-d 6 ​)δ8.22(s,1H),8.03(d,J=8.4Hz,1H),7.77(d,J=8.0Hz,1H),7.57(d,J=7.5Hz,2H),7.51–7.42(m,3H),7.42–7.32(m,2H),7.28(s,1H),6.63(s,1H),6.46–6.33(m,2H),2.13(s,3H). 13 C NMR(101MHz,CDCl 3 )δ141.1,137.1,135.8,133.0,132.5,130.1,129.5,129.3,128.4,128.1,127.3,126.3,125.4,124.8,121.3,121.0,120.7,120.5,114.8,114.6,20.5.HRMS:[M]calculated for C 23 H 17 NO:323.1310,found:323.1311

[0094] Preparation of Fluorescent Material 3ea in Example 5

[0095]

[0096] Under nitrogen atmosphere, oxazine compound 1e (0.2 mmol), sulfonium ylide compound 2a (0.30 mmol), [Cp*RhCl 2 2 (0.04 mmol), CsOAc (0.40 mmol) and solvent HFIP (1.0 mL) were added to a 38 mL sealed tube and reacted in a reaction module at 100 °C for 1 h. After the reaction, the solvent was removed under reduced pressure, and the target product (3ea) was obtained by silica gel column chromatography. All eluents were prepared from petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 80% yield. The NMR spectra are as shown in Figure 21 and 22 shown 1 H NMR(400MHz,DMSO-d 6 )δ8.44(s,1H),8.00(d,J=8.5Hz,1H),7.78(d,J=8.1Hz,1H),7.57(d,J=7.2Hz,2H),7.52–7.43(m,3H),7.42–7.34(m,2H),7.31(s,1H),6.96(dd,J=8.3,2.2Hz,1H),6.73(d,J=8.4Hz,1H),6.65(d,J=2.2Hz,1H). 13 ​¹³C NMR (101 MHz, DMSO) δ 144.2, 136.7, 135.3, 132.5, 130.3, 129.4, 129.3, 128.4, 128.2, 127.4, 126.8, 125.9, 125.6, 125.1, 121.1, 120.9, 120.45, 117.6, 115.4, 111.2. HRMS: [M] calculated for C 22 H 14 BrNO: 387.0259, found: 387.0257

[0097] Example 6 Preparation of Fluorescent Material 3fa

[0098]

[0099] Under nitrogen, oxazine compound 1f (0.2 mmol), sulfonium ylide compound 2a (0.30 mmol), [Cp*RhCl 2 2 (0.04 mmol), LiOAc (0.40 mmol) and solvent HFIP (2.0 mL) were added to a 38 mL sealed tube and reacted in a reaction module at 100 °C for 1 h. After the reaction, the solvent was removed under reduced pressure, and the target product (3fa) was obtained by silica gel column separation. All eluents were prepared from petroleum ether and dichloromethane in a ratio of 3:1. Product data characterization: yellow solid, 56% yield. The NMR spectra are as Figure 23 and 24 shown 1 ¹H NMR (400 MHz, DMSO-d 6 ) δ 8.31 (s, 1H), 8.05 (d, J = 8.5 Hz, 1H), 7.77 (d, J = 8.2 Hz, 1H), 7.61–7.54 (m, 1H), 7.52–7.42 (m, 4H), 7.41–7.35 (m, 1H), 7.17 (s, 1H), 6.83–6.74 (m, 2H), 6.58 (td, J = 7.3, 6.7, 2.3 Hz, 1H), 6.39 (d, J = 7.9 Hz, 1H). 13 ¹³C NMR (101 MHz, DMSO) δ 143.4, 136.2, 136.0, 133.0, 132.9, 131.8, 130.0, 129.4, 129.1, 128.4, 127.5, 127.1, 126.2, 125.7, 124.9, 124.1, 121.3, 121.3, 120.9, 120.5, 115.2, 114.2. HRMS: [M] calculated for C 22 H​15 ClNO + : 343.0764, found: 343.0770

[0100] The benzophenoxazine fluorescent material obtained in the present invention has a secondary amine site sensitive to the alkaline environment. After neutralization with hydroxyl groups, the structure changes, resulting in changes in the ultraviolet absorption spectrum and fluorescence emission spectrum. When the organic solvent is DMSO:H 2 O = 9:1, after adding 0 - 6 μl of 4.5 mol·L -1 NaOH solution, an obvious red shift phenomenon occurs, and a new absorption peak slowly appears around 537 nm. Then, after adding 1 - 6 μl of 4.5 mol·L -1 HCl, the new peak slowly disappears, indicating that the acid-base response is reversible. When the organic solvent is DMSO:H 2 O = 1:9, fluorescence quenching occurs at pH = 14. The reversible fluorescence response property of the material to acid-base substances can be used to detect acid-base vapor waste gas, acid-base, and garbage concentrated liquid degradation wastewater in industry. At the same time, its "on-off" response to pH can be used as a new type of pH probe for accurate pH measurement.

[0101] The reaction module mentioned in the present invention is a parallel reaction tube heating aluminum reaction module, but other instruments capable of achieving this reaction condition can also be used.

[0102] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A benzoxazine fluorescent material, characterized in that, its chemical structural formula is as follows: Among them, R 1 is selected from any one of a hydrogen group, a halogen group or an alkyl group having 1 to 8 carbon atoms; R 2 is selected from any one of a hydrogen group or an alkoxy group having 1 to 8 carbon atoms; R 3 is selected from any one of a hydrogen group or a halogen group.

2. The preparation method of the benzoxazine fluorescent material according to claim 1, characterized in that: Under an inert atmosphere, the reactants, namely oxazine compounds, sulfonium ylide compounds, rhodium catalysts and additives, are added together to a solvent for heating reaction, and after the reaction is completed, the benzoxazine fluorescent material is obtained through purification and separation; wherein, the additive is selected from cesium acetate, sodium acetate or lithium acetate; The reaction formula is as follows, 3. According to the preparation method of the benzoxazine fluorescent material described in claim 2, characterized in that: The solvent is hexafluoroisopropanol.

4. According to the preparation method of the benzoxazine fluorescent material described in claim 2, characterized in that: The reaction temperature of the reaction is 40°C - 100°C, the reaction time is 1h - 12h, and the inert atmosphere is a nitrogen atmosphere.

5. According to the preparation method of the benzoxazine fluorescent material described in claim 2, characterized in that: The molar ratio of the oxazine compound, sulfonium ylide compound, rhodium catalyst and additive is 1:(1.1 - 1.5):(0.1 - 0.2):(1.0 - 2.0).

6. According to the preparation method of the benzoxazine fluorescent material described in claim 2, characterized in that: The concentration of oxazine compounds in the solvent is 0.1 - 0.2 mol·L -1 .

7. The application of the benzoxazine fluorescent material described in claim 1 in terms of acid-base stimulation response.

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