Biphenylimidazo[1,2-a]pyridinone-based fluorescent probe molecules, and preparation method and application thereof

Abstract

The application provides a biphenylimidazo[1,2-alpha]pyridinone fluorescent probe molecule, a preparation method and application thereof, and belongs to the technical field of fluorescent probes, and aims to solve the technical problem of low sensitivity of organic small-molecule fluorescent dyes in pesticide detection. 1 = F, Cl, Br, I, CF3, COOMe, CN, H, Me or OMe; R 2 = Cl, Br, CF3, COOMe, H, Me or OMe; R 3 = F, Cl, Br, I, CF3, H, Me or OMe; n is a positive integer between 0 and 11. The probe molecule has good light emitting performance in a tetrahydrofuran solution, and can identify organic pesticides DCN, NF and TCA, and is expected to become a probe molecule for detecting residues of DCN, NF and TCA in actual samples.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorescent probes, and particularly relates to a biphenyl imidazo[1,2-a]pyridinone-based fluorescent probe molecule and a preparation method and application thereof. BACKGROUND

[0002] In recent years, pesticides have been widely used in modern agriculture, playing a crucial role in improving agricultural productivity and directly promoting agricultural output. However, the unreasonable use of pesticides can pollute the soil, atmosphere, water and even the ecological environment, increasing the risk of harmful substances in food and drinking water. Due to the high toxicity and non-degradability of pesticides, their long-term residual accumulation can pose a serious threat to the ecological environment and human health. In view of this situation, fluorescence detection has attracted widespread attention due to its rapid, sensitive, simple detection process, real-time monitoring and other characteristics. Organic small molecule fluorescent probes have high sensitivity, high selectivity, simple synthesis and characterization, short reaction time, multiple modification sites, and do not damage biological samples, and have attracted widespread attention from researchers. However, existing organic small molecule fluorescent dyes for organic pesticide detection generally have low sensitivity.

[0003] Imidazopyridine derivatives are a special class of nitrogen-containing fused ring compounds that are widely used in the pharmaceutical field due to their special biological activity. The pharmacological effects of imidazopyridine compounds mainly include anti-mitosis, anti-tuberculosis, anti-virus and can also act as antagonists for several receptors. In addition to having physiological significance, reasonable structural modification can make them a new type of fluorescent probe building skeleton. For example, Patent Publication No. CN 114763353A discloses a fluorescent detection reagent based on an imidazopyridine parent nucleus and its detection technology for signal molecules H2S. After the interaction of the molecular probe with the signal molecule hydrogen sulfide, the 2,4-dinitrophenyl ether group is hydrolyzed to a hydroxyl group, which emits red fluorescence in a PBS (pH = 7.4, 10 mM) buffer solution. Patent Publication No. CN 115215864A discloses a fluorescent probe for detecting the viscosity of a beverage, a preparation method and application thereof. The probe contains two electron-accepting groups, bromobenzimidazole and indolium, and a power supply group, methoxyphenyl, forming an "A-A-D" structure molecule with high electron-accepting polarity, which is conducive to the good dispersibility of the probe in the large polar water phase environment of the beverage. The free rotation characteristics of the methoxyphenyl group are conducive to the probe's sensitive response to changes in viscosity. From the above disclosure, it can be seen that different modification groups on the imidazopyridine parent nucleus have a significant impact on fluorescence performance. SUMMARY

[0004] In order to solve the problem of low sensitivity of organic small molecule fluorescent dyes in pesticide detection, the application provides a biphenyl imidazo[1,2-alpha]pyridinone fluorescent probe molecule, a preparation method and application thereof, and the compound has good fluorescence emission capacity in a solution, and can realize high-sensitivity recognition of 2,4,6-trichloroaniline (2,4,6-Trichloroaniline, referred to as TCA), 2,4-dichloro-4'-nitro diphenyl ether (Nitrofen, referred to as NF) and 2,6-dichloro-4-nitroaniline (2,6-Dichloro-4-nitroaniline, referred to as DCN).

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0006] The biphenyl imidazo[1,2-alpha]pyridinone fluorescent probe molecule has the following general structure formula:

[0007]

[0008] In the formula, R 1 =F, Cl, Br, I, CF3, COOMe, CN, H, Me or OMe; R 2 =Cl, Br, CF3, COOMe, H, Me or OMe; R 3 =F, Cl, Br, I, CF3, H, Me or OMe; n is a positive integer between 0 and 11; preferably, n is 0, 1, 2, 3, 7 or 11.

[0009] The synthesis method of the biphenyl imidazo[1,2-alpha]pyridinone fluorescent probe molecule comprises the following steps:

[0010] (1) Claisen-Schmidt reaction of 4-bromoacetophenone and benzaldehyde with R 3 substituents to obtain compound 1;

[0011] (2) cyclization reaction of 2-aminopyridine derivative with R 1 and R 2 substituents and compound 1 to obtain compound 2;

[0012] (3) Suzuki-Miyaura coupling reaction of compound 2 and 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths to obtain the target product.

[0013] The operation method of the Claisen-Schmidt reaction in the step (1) is as follows: 4-bromoacetophenone and benzaldehyde with R 3 substituents are dissolved in solvent I, and a basic catalyst is added, and the reaction is carried out at room temperature for 6-24 h.

[0014] said 4-bromoacetophenone, 2-aminopyridine derivative with R 3 The benzaldehyde with R

[0015] said 4-bromoacetophenone, 2-aminopyridine derivative with R 3 The molar ratio of the benzaldehyde with R

[0016] The operation method of the cyclization reaction in step (2) is as follows: the 2-aminopyridine derivative with R 1 and R 2 is dissolved in solvent II, and a catalyst is added, and the reaction is carried out at 60-80℃ for 12-24h.

[0017] The 2-aminopyridine derivative with R 1 and R 2 is 2-amino-4-bromopyridine, 2-amino-4-trifluoromethylpyridine, 2-amino-5-bromopyridine, 2-amino-5-trifluoromethylpyridine, 6-aminonicotinic acid methyl ester, 2-amino-5-methylpyridine, 4,5-dibromopyridin-2-amine, etc.

[0018] The molar ratio of the compound 1, 2-aminopyridine derivative with R 1 and R 2 is 1:(1-4):(2-5); and the molar volume ratio of the compound 1 to solvent II is 1:(2-5)mmol / mL.

[0019] The catalyst comprises ammonium acetate and I2 in a molar ratio of 2:1; and the solvent II is chloroform.

[0020] The operation method of the Suzuki-Miyaura coupling reaction in step (3) is as follows: compound 2 and 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths are dissolved in solvent III, and a palladium catalyst and an assistant are added, and the reaction is carried out at 70-90℃ for 12-24h in an inert gas atmosphere.

[0021] 4-(N,N-dimethylamino)phenylboronic acid pinacol ester, 4-(N,N-diethylamino)phenylboronic acid pinacol ester, 4-(N,N-dipropylamino)phenylboronic acid pinacol ester, 4-(N,N-dibutylamino)phenylboronic acid pinacol ester, 4-(N,N-dioctylamino)phenylboronic acid pinacol ester, 4-(N,N-didodecylamino)phenylboronic acid pinacol ester, etc.

[0022] The molar ratio of the compound 2, 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths, the auxiliary agent and the palladium catalyst is 1:(1.0-1.4):(1-3):(0.01-0.1), and the molar volume ratio of the compound 2 to the solvent III is 1:(4-6) mmoL / mL; the solvent III includes toluene and water in a volume ratio of 10:(1-5), or tetrahydrofuran and water; the palladium catalyst is any one of tetrakis(triphenylphosphine)palladium, palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium or dichlorobistriphenylphosphine palladium; and the auxiliary agent is any one of sodium carbonate, potassium carbonate, cesium carbonate, sodium methoxide or potassium acetate.

[0023] The application of a biphenylimidazo[1,2-alpha]pyridinone fluorescent probe molecule in pesticide detection, the probe molecule is dissolved in tetrahydrofuran solution to configure a dilute solution based on the biphenylimidazo[1,2-alpha]pyridinone compound. The dilute solution has good recognition effect on DCN, NF and TCA, and the fluorescence intensity of the compound gradually decreases when the concentration of DCN, NF and TCA in the solution gradually increases.

[0024] The beneficial effects of the present application are as follows:

[0025] The present application provides a novel biphenylimidazo[1,2-alpha]pyridinone fluorescent probe molecule, which has good luminescence performance in tetrahydrofuran solution. The probe molecule also has good solvatochromic behavior and viscosity-dependent fluorescence emission behavior. The fluorescence quantum yield of the fluorescent probe molecule M1(R 1 = R 2 = R 3 = H, n = 0) reaches 0.47, and the dilute solution thereof can be used for detecting organic pesticides DCN, NF and TCA molecules, especially the detection limit of DCN is 189 ppb, which is far lower than the requirement in the Chinese National Food Safety Standard - Maximum Residue Limits of Pesticides in Food. This has potential application value for detecting DCN, NF and TCA pesticide residues in actual samples. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without any creative effort based on these drawings also belong to the protection scope of the present application.

[0027] Figure 1 NMR hydrogen spectrum of the fluorescent probe molecule M1.

[0028] Figure 2 NMR carbon spectrum of the fluorescent probe molecule M1.

[0029] Figure 3 High-resolution mass spectrum of the fluorescent probe molecule M1.

[0030] Figure 4 Fluorescent response behavior of the probe molecule M1 (10 μM) in tetrahydrofuran solution to DCN, NF and TCA (100 μM) (I0 is the fluorescent intensity of the initial solution, and I is the fluorescent intensity of the solution after adding the pesticide).

[0031] Figure 5 Fluorescent intensity maximum of the probe molecule M1 (10 μM) in tetrahydrofuran solution as a function of the concentration of DCN.

[0032] Figure 6 Fluorescent emission normalized spectrum of the fluorescent probe molecule M1 in different solvents.

[0033] Figure 7 Double logarithmic fitting straight line of the fluorescent intensity maximum of the fluorescent probe molecule M1 and the solvent viscosity. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the protection scope of the present application.

[0035] Embodiment 1

[0036] The structural formula of the compound in the present embodiment is:

[0037]

[0038] The reaction general formula of the compound 1a is:

[0039]

[0040] The preparation method is as follows: sodium hydroxide solid (0.44 g, 11 mol) is dissolved in 9 mL of water, and then slowly added dropwise into a 4-bromoacetophenone (2 g, 10 mmol) ethanol (45 mL) solution under the condition of an ice water bath, and then benzaldehyde (1.27 g, 12 mmol) is added after stirring for 10 min. The reaction system is stirred at room temperature for 12 h, and then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, which is compound 1a (4.19 g, 73%). The product can be directly used in the next step without further purification.

[0041] The reaction general formula of compound 2a is as follows:

[0042]

[0043] The preparation method is as follows: 1a (2.87 g, 10 mmol), 2-aminopyridine (1.16 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol) and I2 (2.53 g, 10 mmol) are dissolved in 30 mL of chloroform, and the system is reacted at 70°C for 16 h. After the reaction is completed, the reaction system is cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid, which is compound 2a (0.9 g, 24%).

[0044] The reaction general formula of compound M1 is as follows:

[0045]

[0046] The preparation method is as follows: compound 2a (3.76 g, 10 mmol), 4-(N,N-dimethylamino)phenylboronic acid pinacol ester (2.97 g, 12 mmol) and tetrakis(triphenylphosphine)palladium (0.58 g, 0.5 mmol) are placed in a Schlenk flask, and 15 mL of a sodium carbonate aqueous solution (2 mol·L -1 ) and 40 mL of toluene are added under an argon atmosphere. The system is reacted at 85°C for 16 h. After the reaction is completed, the solvent is removed under reduced pressure, an appropriate amount of water is added, and then dichloromethane (20 mL x 3 times) is used for extraction. The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (ethyl acetate: petroleum ether = 1:1) to obtain a green solid, which is compound M1 (yield: 83%). The nuclear magnetic resonance spectrum is shown in Figure 1 and 2 1 ​H NMR (600MHz, CDCl3) δ8.23(d,J=8.4Hz,2H),8.11(d,J=7.0Hz,1H),7.75(d,J=9.1Hz,1H),7.62(d,J=8.4Hz,2H),7.58-7.54(m,4H),7.51 (t,J=7.6Hz,2H),7.48-7.42(m,1H),7.29(ddd,J=9.2,6.7,1.3Hz,1H),6.84(td,J=6.8,1.2Hz,1H),6.81(d,J=8.8Hz,2H),3.01(s,6H). 13 C NMR (151 MHz, CDCl3) δ 40.5, 112.6, 113.6, 119.1, 124.0, 125.6, 125.9, 127.9, 128.0, 128.4, 128.8, 129.0, 129.1, 130.4, 131.4, 135.3, 140.5, 143.9, 145.3, 150.5, 189.7. The high-resolution mass spectrum of the fluorescent probe molecule M1 is shown in Figure 5. Figure 3 As shown, HRMS (ESI) m / z calculated for [C 28 H 24 N3O + ]418.1914([M+H] + ),found 418.1913.

[0047] Example 2

[0048] The structural formula of the compound of this embodiment is:

[0049]

[0050] The general reaction formula of compound 1b is:

[0051]

[0052] Preparation: Potassium hydroxide solid (0.62 g, 11 mol) was dissolved in 9 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (45 mL) in an ice-water bath. After stirring for 10 minutes, p-trifluoromethylbenzaldehyde (2.09 g, 12 mmol) was added. The reaction system was stirred at room temperature for 12 hours, and the solid was collected by filtration. The solid was washed repeatedly with ethanol and water, and dried to yield a white solid, compound 1b (2.04 g, 58%). The product was used in the next reaction without further purification.

[0053] The general reaction formula of compound 2b is:

[0054]

[0055] The preparation method is as follows: 1b (3.54 g, 10 mmol), 2-aminopyridine (1.16 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol) and I2 (2.53 g, 10 mmol) are dissolved in 30 mL of chloroform, and the system is reacted at 70°C for 16 h. After the reaction is completed, it is cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid, which is compound 2b (0.8 g, 18%).

[0056] The reaction general formula of compound M2 is as follows:

[0057]

[0058] The preparation method is as follows: compound 2b (4.44 g, 10 mmol), 4-(N,N-dimethylamino) phenylboronic acid pinacol ester (2.97 g, 12 mmol) and tetrakis(triphenylphosphine)palladium (0.58 g, 0.5 mmol) are placed in a Schlenk flask, and 15 mL of sodium carbonate aqueous solution (2 mol·L -1 ) and 40 mL of toluene are added under an argon atmosphere. The system is reacted at 85°C for 16 h. After the reaction is completed, the solvent is removed under reduced pressure, an appropriate amount of water is added, and dichloromethane (20 mL x 3 times) is used for extraction. The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (ethyl acetate: petroleum ether = 1:1) to obtain a green solid, which is compound M2 (yield: 70%).

[0059] Example 3

[0060] The structural formula of the compound of this example is as follows:

[0061]

[0062] The reaction general formula of compound 1a is as follows:

[0063]

[0064] The preparation method is as follows: sodium hydroxide solid (0.44 g, 11 mol) is dissolved in 9 mL of water, and slowly added dropwise into a 4-bromophenylacetone (2 g, 10 mmol) ethanol (45 mL) solution under the condition of an ice water bath, and then benzaldehyde (1.27 g, 12 mmol) is added after stirring for 10 min. The reaction system is stirred at room temperature for 12 h, and then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, which is compound 1a (4.19 g, 73 %). The product can be directly used in the next step without further purification.

[0065] The reaction general formula of compound 2c is as follows:

[0066]

[0067] The preparation method is as follows: 1a (2.87 g, 10 mmol), 2-amino-5-cyanopyridine (1.43 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol) and I2 (2.53 g, 10 mmol) are dissolved in 30 mL of chloroform, and the system is reacted at 70 °C for 16 h. After the reaction is completed, the reaction system is cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid, which is compound 2c (1.1 g, 27 %).

[0068] The reaction general formula of compound M3 is as follows:

[0069]

[0070] The preparation method is as follows: compound 2c (4.01 g, 10 mmol), N, N-diethyl-4-(4, 4, 5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) aniline (3.30 g, 12 mmol) and palladium acetate (0.11 g, 0.5 mmol) are placed in a Schlenk flask, and 15 mL of sodium carbonate aqueous solution (2 mol·L -1 ) and 40 mL of tetrahydrofuran are added under an argon atmosphere. The system is reacted at 85 °C for 16 h. After the reaction is completed, the solvent is removed under reduced pressure, an appropriate amount of water is added, and dichloromethane (20 mL x 3 times) is used for extraction. The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (ethyl acetate: petroleum ether = 1:1) to obtain a green solid, which is compound M3 (yield: 78 %).

[0071] Example 4

[0072] The structural formula of the compound of the example is as follows:

[0073]

[0074] The reaction scheme of compound 1a is as follows:

[0075]

[0076] The preparation method is as follows: sodium hydroxide solid (0.44 g, 11 mol) is dissolved in 9 mL of water, and slowly added dropwise into a 4-bromoacetophenone (2 g, 10 mmol) ethanol (45 mL) solution under the condition of an ice water bath, and then benzaldehyde (1.27 g, 12 mmol) is added after stirring for 10 min. The reaction system is stirred at room temperature for 12 h, and then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, which is compound 1a (4.19 g, 73 %). The product can be directly used in the next step without further purification.

[0077] The reaction scheme of compound 2d is as follows:

[0078]

[0079] The preparation method is as follows: 1a (2.87 g, 10 mmol), 2-amino-4-methoxypyridine (1.49 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol) and I2 (2.53 g, 10 mmol) are dissolved in 30 mL of chloroform, and the system is reacted at 70 °C for 16 h. After the reaction is completed, the reaction system is cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid, which is compound 2d (0.8 g, 20 %).

[0080] The reaction scheme of compound M4 is as follows:

[0081]

[0082] The preparation method is as follows: compound 2d (4.06 g, 10 mmol), 4-(N,N-dimethylamino)phenylboronic acid pinacol ester (2.97 g, 12 mmol) and tetrakis(triphenylphosphine)palladium (0.58 g, 0.5 mmol) are placed in a Schlenk flask, and 15 mL of a sodium carbonate aqueous solution (2 mol·L -1 ) and 40 mL of toluene are added under an argon atmosphere. The system is reacted at 85 °C for 16 h. After the reaction is completed, the solvent is removed under reduced pressure, an appropriate amount of water is added, and dichloromethane (20 mL x 3 times) is used for extraction. The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (ethyl acetate: petroleum ether = 1:1) to obtain a green solid, which is compound M4 (yield: 77 %).

[0083] Example 5

[0084] The structural formula of the compound of this example is:

[0085]

[0086] The reaction general formula of compound 1a is:

[0087]

[0088] The preparation method is: sodium hydroxide solid (0.4 g, 10 mol) is dissolved in 12 mL of water, slowly added dropwise to a 4-bromoacetophenone (2 g, 10 mmol) ethanol (48 mL) solution under the condition of ice water bath, after stirring for 10 min, benzaldehyde (1.06 g, 10 mmol) is added. The reaction system is stirred at room temperature for 24 h, and then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, which is compound 1a. The product can be used in the next step reaction without further purification.

[0089] The reaction general formula of compound 2a is:

[0090]

[0091] The preparation method is: 1a (2.87 g, 10 mmol), 2-aminopyridine (0.97 g, 10 mmol), ammonium acetate (0.96 g, 13.3 mmol) and I2 (1.67 g, 6.7 mmol) are dissolved in 20 mL of chloroform, and the system is reacted at 60°C for 24 h. After the reaction is completed, it is cooled to room temperature, and the reaction system is poured into 50 mL of saturated Na2S2O3 aqueous solution, extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by silica gel chromatography column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid.

[0092] The reaction general formula of compound M1 is:

[0093]

[0094] The preparation method is: compound 2a (3.76 g, 10 mmol), 4-(N,N-dimethylamino) phenylboronic acid pinacol ester (2.48 g, 10 mmol) and tetrakis(triphenylphosphine)palladium (0.17 g, 0.1 mmol) are placed in a Schlenk flask, 5 mL of sodium carbonate aqueous solution (2 mol·L -1) and 50 mL of toluene. The system was reacted at 70°C for 24 h. After the reaction was completed, the solvent was removed under reduced pressure, and the appropriate amount of water was added and extracted with dichloromethane (20 mL x 3 times). The organic phase was combined, dried with anhydrous NaSO4, and separated with a silica gel chromatographic column (ethyl acetate: petroleum ether = 1 : 1) to obtain a green solid, which was compound Ml.

[0095] Example 6

[0096] The structural formula of the compound of this example is:

[0097]

[0098] The reaction general formula of compound la is:

[0099]

[0100] The preparation method is: sodium hydroxide solid (0.8 g, 20 mol) was dissolved in 6 mL of water, slowly added to a 4-bromoacetophenone (2 g, 10 mmol) ethanol (36 mL) solution under ice water bath conditions, stirred for 10 min, and then added benzaldehyde (1.48 g, 14 mmol). The reaction system was stirred at room temperature for 6 h, and the solid was collected by filtration, washed with ethanol and water repeatedly, and dried to obtain a white solid, which was compound la. The product was used in the next step reaction without further purification.

[0101] The reaction general formula of compound 2a is:

[0102]

[0103] The preparation method is: la (2.87 g, 10 mmol), 2-aminopyridine (3.88 g, 40 mmol), ammonium acetate (1.68 g, 23.3 mmol) and I2 (4.2 g, 16.7 mmol) were dissolved in 50 mL of chloroform, and the system was reacted at 80°C for 12 h. After the reaction was completed, the reaction system was cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The organic phase was combined, dried with anhydrous NaSO4, and separated with a silica gel chromatographic column (petroleum ether: ethyl acetate = 3: 1) to obtain a yellow solid.

[0104] The reaction general formula of compound Ml is:

[0105]

[0106] The preparation method is: compound 2a (3.76g, 10mmol), 4-(N,N-dimethylamino) phenylboronic acid pinacol ester (3.47g, 10mmol) and tetrakis(triphenylphosphine)palladium (1.7g, 1mmol) are placed in a Schlenk flask, 10mL of sodium carbonate aqueous solution (3mol·L -1 ) and 30mL of toluene are added under argon atmosphere. The system is reacted at 90℃ for 12h. After the reaction is completed, the solvent is removed under reduced pressure, an appropriate amount of water is added, and dichloromethane (20mL×3 times) is used for extraction. The organic phase is combined, dried with anhydrous NaSO4, and then separated by silica gel chromatography column (ethyl acetate: petroleum ether = 1:1) to obtain a green solid, which is compound M1.

[0107] The following application examples all use M1 prepared in Example 1 as the test object.

[0108] Application Example 1

[0109] The fluorescence intensity of the biphenylimidazo[1,2-α]pyridinone fluorescent probe molecule M1 described in the application in a tetrahydrofuran solution is greatly affected by DCN, NF and TCA Figure 4 ). When the concentration of the three pesticides in the tetrahydrofuran solution reaches 100μM, the fluorescence intensity of the compound (10μM) is reduced by 92%, 70% and 63% respectively.

[0110] Application Example 2

[0111] Dissolve the probe molecule M1 in a tetrahydrofuran solution to configure a biphenylimidazo[1,2-α]pyridinone compound dilute solution with different concentrations. When the DCN concentration in the above solution (0μM, 5μM, 10μM, 15μM, 20μM, 25μM, 30μM, 35μM, 40μM, 45μM, 50μM, 55μM, 60μM, 70μM, 80μM, 90μM, 100μM respectively) gradually increases, the fluorescence intensity of the compound (the total concentration is 10μM, and the slit width is 2) gradually decreases. And within the range of 0μM to 40μM, the compound has a good linear relationship between the maximum fluorescence intensity and the DCN concentration Figure 5 ).

[0112] Application Example 3

[0113] Prepare a 1mM stock solution of compound M1 using THF and place it for standby. Use a pipette to transfer 50μL of the above solution into a 5mL volumetric flask, add the required solvent for testing after the solvent is completely volatilized, shake well to obtain a 10μM test solution.

[0114] The biphenylimidazo[1,2-a]pyridinone fluorescent probe molecule M1 has good solvatochromic effect. Figure 6 )。

[0115] Application Example 4

[0116] The compound M1 was prepared into 1mM stock solution using dimethyl sulfoxide, and placed for standby. 50μL of the above stock solution was taken into 5mL volumetric flask using a pipette, and glycol / glycerol mixed solvent (glycerol volume was 0%, 20%, 30%, 40%, 60% and 80% respectively) was added to constant volume, and the solution was mixed thoroughly by shaking, and the fluorescence intensity of M1 molecule (total concentration was 10μM, slit width was 2) at 600nm was read.

[0117] In the above system, as the viscosity of the mixed solvent increased from 20.8cP to 620.7cP, the fluorescence intensity of the probe molecule M1 increased by 3.24 times, and the probe molecule also showed good quantitative viscosity-dependent fluorescence emission behavior Figure 7 )。

[0118] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Based on biphenyl imidazo[1,2-α]pyridone fluorescent probe molecules, characterized in that, The probe molecule has the following general structural formula: ； Where R 1 :H, CN or Me; R 2 :H, Me or OMe; R 3 : H, CF3 or Me; n is 0, 1 or 2.

2. The method for synthesizing the biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 1, characterized in that: The following steps are involved: (1) 4-bromoacetophenone and R 3 The substituted benzaldehyde undergoes Claisen-Schmidt reaction to give compound 1; (2) With R 1 and R 2 The substituted 2-aminopyridine derivative undergoes a cyclization reaction with compound 1 to obtain compound 2; (3) Compound 2 and 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths underwent Suzuki-Miyaura coupling reaction to obtain the target product.

3. The method for synthesizing a biphenylimidazo[1,2-α]pyridone fluorescent probe molecule according to claim 2, characterized in that: The operation method of the Claisen-Schmidt reaction in step (1) is: 4-bromoacetophenone and a 3 The substituted benzaldehyde is dissolved in solvent I, and a basic catalyst is added, and the reaction is carried out at room temperature for 6-24 hours.

4. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 3, wherein: The 4-bromoacetophenone, with R 3 The molar ratio of the substituted benzaldehyde and the alkaline catalyst is 1:(1-1.4):(1-2); the molar volume ratio of 4-bromoacetophenone and solvent I is 1:(4-6) mmoL / mL; the solvent I is water and / or ethanol; and the alkaline catalyst is sodium hydroxide, potassium hydroxide or cesium carbonate.

5. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 2, wherein: The operation method of the cyclization reaction in step (2) is: 1 and R 2 The substituted 2-aminopyridine derivative and compound 1 are dissolved in solvent II, and a catalyst is added, and the mixture is reacted at 60-80° C. for 12-24 hours.

6. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 5, characterized in that: The compound 1, with R 1 and R 2 The molar ratio of the substituted 2-aminopyridine derivative and the catalyst is 1:(1-4):(2-5); the molar volume ratio of compound 1 to solvent II is 1:(2-5) mmoL / mL.

7. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 6, characterized in that: The catalyst is ammonium acetate and I2 in a molar ratio of 2:1; the solvent II is chloroform.

8. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 2, wherein: The operation method of the Suzuki-Miyaura coupling reaction in step (3) is as follows: dissolving compound 2 and 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths in solvent III, adding palladium catalyst and auxiliary agent, and reacting at 70-90 ° C in a protective gas atmosphere for 12-24 h.

9. The method for synthesizing a biphenylimidazo[1,2-α]pyridone-based fluorescent probe molecule according to claim 8, characterized in that: The molar ratio of the compound 2, 4-(N,N-dialkylamino)phenylboronic acid pinacol ester with different nitrogen alkyl chain lengths, the auxiliary agent and the palladium catalyst is 1:(1.0-1.4):(1-3):(0.01-0.1); the molar volume ratio of the compound 2 and the solvent III is 1:(4-6) mmoL / mL; the solvent III is toluene and water, or tetrahydrofuran and water, in a volume ratio of 10:(1-5); the palladium catalyst is any one of tetrakis(triphenylphosphine)palladium, palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium or bistriphenylphosphinepalladium dichloro; the auxiliary agent is any one of sodium carbonate, potassium carbonate, cesium carbonate, sodium methoxide or potassium acetate.

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