Quinoline cyanine analogue near-infrared fluorescent dye and preparation method thereof

Abstract

The invention relates to a quinoline cyanine analogue near-infrared fluorescent dye and a preparation method thereof. The method comprises the following steps: refluxing 4-methylquinoline and halogenated hydrocarbon in an organic solvent, cooling, adding tert-butyl methyl ether for precipitation, carrying out suction filtration, and washing with tert-butyl methyl ether; and refluxing the product, N, N '-dibenzamidine and triethyl orthoformate in an ethanol solvent, cooling, carrying out reduced pressure spin-drying on the solvent, adding ethyl acetate to wash the remaining solid, carrying out suction filtration, leaching with ethyl acetate, suspending ethyl chromate in anhydrous and oxygen-free tetrahydrofuran, adding methyl magnesium bromide under the protection of N2, then adding methanol for quenching, and carrying out reduced pressure removal on the solvent to obtain the ethyl chromate. Obtaining a crude product; and eluting the crude product with ethyl acetate, dissolving the crude product in dichloromethane, adding triethylamine, stirring overnight at room temperature, after the reaction is finished, spin-drying the solvent, and purifying the product through column chromatography to obtain the quinoline cyanine analogue near-infrared fluorescent dye. The dye is synthesized into the dye with excitation emission wavelengths in near infrared (more than 700nm), can effectively avoid biological background fluorescence interference, and is large in molar extinction coefficient and good in fluorescence property.

Description

Technical Field

[0001] The invention belongs to the field of organic dye synthesis, and in particular relates to a method for preparing a quinoline cyanine analog near-infrared fluorescent dye. Background Art

[0002] Quinoline cyanine dyes are an important branch of cyanine dyes. This type of dye has a high molar extinction coefficient, the fluorescence emission wavelength is easy to adjust, the maximum absorption wavelength can be tuned in a wide range, it is easy to synthesize and has relatively high stability. In recent years, it has been widely used in the field of biological probes, optical storage materials, and biomolecule labeling.

[0003] The quinoline dyes that are currently used more often have shorter maximum absorption wavelengths and fluorescence emission wavelengths, and the sensitivity of fluorescence detection is low. By modifying asymmetric quinoline cyanine dyes, that is, by changing the electron transfer ability of the molecule, the synthesis of quinoline cyanine analogs can make the excitation and emission of this type of dye exceed 700nm. In this near-infrared region, the interference of biological background fluorescence and scattered light is very weak, so the imaging signal-to-noise ratio is high. In addition, this type of dye has good photostability, a high molar extinction coefficient, and a simple synthesis process. It can be directly applied to the labeling of biological molecules or solar cells and other fields, and has a broad application prospect. Summary of the invention

[0004] The object of the present invention is to provide a quinoline cyanine analogue near-infrared fluorescent dye and a preparation method thereof. The method comprises the following steps: reflux 4-methylquinoline and halogenated alkane in an organic solvent, cool the mixture, add tert-butyl methyl ether to precipitate a solid, filter the mixture by suction, and repeatedly wash the mixture with tert-butyl methyl ether; reflux the product with N,N'-diphenylformamidine and triethyl orthoformate in an ethanol solvent, cool the mixture, decompress and spin-dry the solvent, add ethyl acetate to wash the remaining solid, filter the mixture by suction, rinse the mixture with ethyl acetate, suspend ethozone in anhydrous and oxygen-free tetrahydrofuran, and precipitate the solid by filtration. 2 Under protection, methylmagnesium bromide is added, and then methanol is added to quench, and the solvent is removed under reduced pressure to obtain a crude product; the product obtained by eluting with ethyl acetate and the crude product are dissolved in dichloromethane, triethylamine is added, and the reaction is stirred overnight at room temperature. After the reaction is completed, the solvent is spin-dried, and the product is purified by column chromatography to obtain a quinoline cyanine analog near-infrared fluorescent dye. The dye synthesizes a dye with excitation and emission wavelengths both in the near infrared (>700nm), can effectively avoid biological background fluorescence interference, has a large molar extinction coefficient, and has good fluorescence performance. Organic small molecule dyes. This type of dye can emit near-infrared fluorescence with a maximum absorption wavelength of>700nm in organic solvents such as toluene, dichloromethane, methanol, and ethanol. The synthesis method of the present invention is simple, the conditions are mild, and the yield is high, which provides good application prospects for the fields of biological molecule labeling, solar cells, and fluorescence imaging.

[0005] The quinoline cyanine analogue near-infrared fluorescent dye described in the present invention has a molecular structure formula as follows:

[0006]

[0007] Where R = (CH 2 ) n CH 3 , n=0-6 integer, X is iodine or bromine.

[0008] The preparation method of the quinoline cyanine analog near-infrared fluorescent dye is carried out according to the following steps:

[0009] a. Add dry acetonitrile to 4-methylquinoline, add alkyl halide such as iodoalkane or bromoalkane after it dissolves, and heat under reflux for 8-16h. After the reaction is complete, remove part of the acetonitrile under reduced pressure, and then add tert-butyl methyl ether. A yellow solid precipitates, and the filter cake is filtered and rinsed with methyl tert-butyl ether for 3 times to obtain the product;

[0010] b. Mix the product obtained in step a with N,N'-dibenzamide and triethyl orthoformate, and reflux in ethanol for 1-4 hours. Remove the ethanol under reduced pressure, add ethyl acetate to wash the remaining solid, filter, and rinse the filter cake with ethyl acetate 3 times to obtain a reddish brown solid;

[0011] c. Suspend ethoxycarbonyl in anhydrous and oxygen-free tetrahydrofuran under N 2 Under protection, methylmagnesium bromide was added, and methanol was added to reflux for 2-4 hours to quench, and tetrahydrofuran and methanol solvents were removed under reduced pressure to obtain a crude product;

[0012] d. Dissolve the crude product obtained in step c in dichloromethane, add the product obtained in step b, then add triethylamine, and stir at room temperature overnight;

[0013] e. After the reaction is completed, the solvent is dried by spin drying, and the product is purified by column chromatography with dichloromethane:methanol in a volume ratio of 20:1 to obtain a quinoline cyanine analog near-infrared fluorescent dye with an absorption wavelength of 600-800 and an emission wavelength of 700-900.

[0014] The present invention provides a method for synthesizing a quinoline cyanine analog near-infrared fluorescent dye, wherein the dye has the following structure:

[0015]

[0016] The synthetic route of a quinoline cyanine analogue near-infrared fluorescent dye described in the present invention is:

[0017]

[0018] Wherein, R is a C1-C6 alkyl chain, and X is iodine or bromine.

[0019] The quinoline cyanine analogue near-infrared fluorescent dye of the present invention has excitation and emission wavelengths greater than 700 nm, and changing the alkyl chain length will not affect the fluorescence wavelength and brightness. Different alkyl chains can meet different usage requirements, making the dye more widely used.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The quinoline cyanine analogue near-infrared fluorescent dye provided by the present invention has excitation and emission wavelengths greater than 700 nm, good penetration ability, high molar extinction coefficient, good photostability, and can be used for biomolecule labeling or in vitro sensors and the like. The dye has a simple synthesis method, mild conditions, cheap and readily available raw materials, high yield, and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the ultraviolet absorption spectrum of the quinoline cyanine analogue near-infrared fluorescent dye of the present invention;

[0023] Figure 2 It is the fluorescence spectrum of the quinoline cyanine analogue near-infrared fluorescent dye of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described with the following specific embodiments, but is not limited to the given embodiments.

[0025] Example 1

[0026] a. Weigh 3 g of 4-methylquinoline into a 100 ml round-bottom flask, add 25 ml of dry acetonitrile, add 3.9 g of methyl iodide and mix, heat under reflux for 8 h, after the reaction is complete, remove part of the acetonitrile under reduced pressure, add tert-butyl methyl ether to precipitate a yellow solid, filter, and rinse the filter cake with methyl tert-butyl ether 3 times to obtain a pure product with a yield of 98%;

[0027] b. Weigh 2.85 g of the product obtained in step a, add 2.16 g of N,N'-dibenzamide and 1 ml of triethyl orthoformate, mix, reflux in ethanol for 1 hour, after the reaction is complete, remove ethanol under reduced pressure, add ethyl acetate to wash the remaining solid, filter, and rinse the filter cake with ethyl acetate 3 times to obtain a reddish brown solid with a yield of 70%;

[0028] c. Weigh 1.46 g of ethazole and suspend it in 10 ml of anhydrous tetrahydrofuran. 2Under protection, 1 ml of 4M methylmagnesium bromide was added dropwise, and the reaction was refluxed for 4 h, and then methanol was added to quench the reaction. The tetrahydrofuran and methanol solvents were removed under reduced pressure to obtain a crude product;

[0029] d. Dissolve the crude product obtained in step c in 10 ml of dichloromethane, add 2 g of the reddish brown product obtained in step b, then add 1 ml of triethylamine, and stir the mixture at room temperature for 16 h;

[0030] e. After the reaction was completed, the solvent was dried by spin drying, and the product was purified by column chromatography with dichloromethane:methanol in a volume ratio of 20:1 to obtain a quinoline cyanine analogue near-infrared fluorescent dye with a yield of 45%;

[0031] 1 H NMR (500 MHz, CDCl 3 )δ8.27(d,J=6.6Hz,1H),8.01(dd,J=7.5,1.1Hz,1H),7.96(td,J=7.1,1.3H z,1H),7.91(td,J=7.2,1.5Hz,2H),7.74–7.52(m,5H),7.31(ddd,J=15.2,8. 4,0.9Hz,1H),7.19(dq,J=7.3,1.1Hz,1H),7.00(td,J=8.3,1.5Hz,1H),6.8 8(dt,J=8.4,1.3Hz,1H), 6.71(dt,J=7.3,1.2Hz,1H), 3.72(d,J=1.1Hz,3H).

[0032] Example 2

[0033] a. Weigh 3 g of 4-methylquinoline into a 100 ml round-bottom flask, add 25 ml of dry acetonitrile, add 3.7 g of ethyl iodide and mix, heat under reflux for 8 h, after the reaction is complete, remove part of the acetonitrile under reduced pressure, add tert-butyl methyl ether to precipitate a yellow solid, filter, and rinse the filter cake with methyl tert-butyl ether 3 times to obtain a pure product with a yield of 95%;

[0034] b. 3 g of the product obtained in step a was added with 2.16 g of N, N'-dibenzamide and 1 ml of triethyl orthoformate, and the mixture was refluxed in ethanol for 2 hours. After the reaction was complete, all ethanol was removed under reduced pressure, and ethyl acetate was added to wash the remaining solid. The filter cake was filtered and rinsed with ethyl acetate for 3 times to obtain a reddish brown solid with a yield of 68%;

[0035] c. Weigh 1.46 g of ethazole and suspend it in 10 ml of anhydrous tetrahydrofuran. 2Under protection, 1 ml of 4M methylmagnesium bromide was added dropwise, and the reaction was refluxed for 4 h, and then methanol was added to quench the reaction. The tetrahydrofuran and methanol solvents were removed under reduced pressure to obtain a crude product;

[0036] d. Dissolve the crude product obtained in step c in 10 ml of dichloromethane, add 2 g of the reddish brown product obtained in step b, and then add 1 ml of triethylamine, and stir at room temperature overnight;

[0037] e. After the reaction was completed, the solvent was dried by spin drying, and the product was purified by column chromatography with dichloromethane:methanol in a volume ratio of 20:1 to obtain a quinoline cyanine analogue near-infrared fluorescent dye with a yield of 42%;

[0038] 1 H NMR (500 MHz, CDCl 3 )δ8.32(d,J=6.6Hz,1H),8.18–7.88(m,3H),7.80–7.76(m,4H),7.54–7.32(m,3H),7.24(d,J=7.5Hz,1H),7.17–6. 98(m,1H),6.85(dt,J=8.4,1.3Hz,1H),6.67(dt,J=7.5,1.3Hz,1H),4.29(q,J=7.3Hz,2H),1.38(t,J=7.4Hz,3H).

[0039] Example 3

[0040] a. Weigh 3 g of 4-methylquinoline into a 100 ml round-bottom flask, add 25 ml of dry acetonitrile, add 2.7 g of 1-bromopropane and mix after dissolving, heat and reflux for 16 h, after the reaction is complete, remove part of the acetonitrile under reduced pressure, add tert-butyl methyl ether, and a yellow solid precipitates, filter, and rinse the filter cake with methyl tert-butyl ether 3 times to obtain a pure product with a yield of 90%;

[0041] b. 2.65 g of the product obtained in step a was added with 2.16 g of N, N'-dibenzamide and 1 ml of triethyl orthoformate, and the mixture was refluxed in ethanol for 4 hours. After the reaction was complete, all ethanol was removed under reduced pressure, ethyl acetate was added to wash the remaining solid, and the filter cake was washed with ethyl acetate 3 times to obtain a reddish brown solid with a yield of 65%;

[0042] c. Weigh 1.46 g of ethazole and suspend it in 10 ml of anhydrous tetrahydrofuran. 2 Under protection, 1 ml of 4M methylmagnesium bromide was added dropwise, and the reaction was refluxed for 4 h, after which methanol was added to quench the reaction, and tetrahydrofuran and methanol solvents were removed under reduced pressure to obtain a crude product;

[0043] d. Dissolve the crude product obtained in step c in 10 ml of dichloromethane, add 2 g of the reddish brown product obtained in step b, and then add 1 ml of triethylamine, and stir at room temperature overnight;

[0044] e. After the reaction was completed, the solvent was dried by spin drying, and the product was purified by column chromatography with dichloromethane:methanol in a volume ratio of 20:1 to obtain a quinoline cyanine analogue near-infrared fluorescent dye with a yield of 43%;

[0045] 1 H NMR (500 MHz, CDCl 3 )δ8.24(d,J=6.6Hz,1H),8.08–7.85(m,3H),7.80–7.57(m,4H),7.46–7.28(m,3H),7.24(dd,J=7.6,1.4Hz,1H),7.05(td,J=8.2,1. 4Hz, 1H), 6.83 (dt, J = 8.4, 1.3Hz, 1H), 6.63 (dt, J = 7.3, 1.2Hz, 1H), 4.12 (t, J = 6.5Hz, 2H), 1.92–1.78 (m, 2H), 0.94 (t, J = 7.2Hz, 3H).

Claims

1. A quinoline cyanine analog near-infrared fluorescent dye, characterized in that: The molecular structure of the dye is as follows: Where R=(CH2) n CH3, n=0-6 integer, X is iodine or bromine.

2. The method for preparing the quinoline cyanine analog near-infrared fluorescent dye according to claim 1, characterized in that Follow these steps: a. Add dry acetonitrile to 4-methylquinoline, add alkyl halide such as iodoalkane or bromoalkane after it dissolves, and heat under reflux for 8-16h. After the reaction is complete, remove part of the acetonitrile under reduced pressure, and then add tert-butyl methyl ether. A yellow solid precipitates, and the filter cake is filtered and rinsed with methyl tert-butyl ether for 3 times to obtain the product; b. Mix the product obtained in step a with N,N'-dibenzamide and triethyl orthoformate, and reflux in ethanol for 1-4 hours. Remove the ethanol under reduced pressure, add ethyl acetate to wash the remaining solid, filter, and rinse the filter cake with ethyl acetate 3 times to obtain a reddish brown solid; c. Suspend ethoxycarbonyl in anhydrous and oxygen-free tetrahydrofuran, add methylmagnesium bromide under N2 protection, reflux for 2-4 hours, then add methanol to quench, remove tetrahydrofuran and methanol solvents under reduced pressure to obtain a crude product; d. Dissolve the crude product obtained in step c in dichloromethane, add the product obtained in step b, then add triethylamine, and stir at room temperature overnight; e. After the reaction is completed, the solvent is dried by spin drying, and the product is purified by column chromatography with dichloromethane:methanol in a volume ratio of 20:1 to obtain a quinoline cyanine analog near-infrared fluorescent dye with an absorption wavelength of 600-800 and an emission wavelength of 700-900.

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