Boron difluoride compound capable of realizing long-wavelength absorption and preparation method thereof

Abstract

The invention discloses a boron difluoride compound capable of realizing long-wavelength absorption and a preparation method of the boron difluoride compound. The boron difluoride compound is a compound with a structure as shown in a formula (I) or a salt of the compound. Compared with the traditional boron dipyrromethene dye, the boron difluoride compound has larger Stokes shift, and shows potential application value in the fields of cell detection, biomarkers and the like. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of long-wavelength absorbing BF2 complexes, and specifically relates to a ligand with 1-azaazulene as a structural unit and a preparation method and photophysical properties of the complex. Background Art

[0002] Boron dipyrromethene (BODIPY) dyes have attracted extensive attention in related fields such as chemistry, materials science, and life sciences due to their advantages such as easy synthesis and functional modification, excellent and adjustable photophysical properties, and good light and chemical stability. However, traditional BODIPY molecules have a symmetrical rigid conjugated skeleton, and the excited equilibrium state structure formed after the molecule is excited by light is similar to the ground state structure. Therefore, this type of dye usually has a small Stokes shift, and the absorption spectrum and emission spectrum have a large cross-overlap. This will bring a series of problems to practical applications, such as: the generated fluorescence is reabsorbed by the surrounding molecules, resulting in fluorescence self-quenching; the excitation light and the fluorescence generated by the dye interfere with each other, so the detection sensitivity and imaging contrast are reduced. In recent years, in order to overcome the disadvantage of the small Stokes shift of traditional BODIPY dyes, its analogs - boron difluoride compounds. The ultraviolet absorption value of traditional BF2 complexes containing phenolic skeletons is mostly below 400 nanometers, and the ultraviolet absorption value of compound G of the present invention reaches 479 nanometers.

[0003] Boron difluoride compounds are formed by the chelation of boron difluoride groups (BF2) and bidentate ligands. According to the coordinated atoms, they can be mainly divided into three categories: N,N-, N,O- and O,O-bidentate. Similar to traditional BODIPY, boron difluoride compounds are a class of strong luminescent fluorescent molecules with long fluorescence lifetime and high fluorescence quantum yield due to the coordination effect of the BF2 group. Due to the asymmetry of the ligand structure, there is a big difference in the shape of the potential energy curve between the ground state and the excited state of boron difluoride compounds. Therefore, the geometric configuration when reaching the excited equilibrium state will change significantly compared with the ground state, which is manifested as a large Stokes shift. However, the boron difluoride compounds reported so far usually have the characteristics of short absorption wavelength, which has become a key problem limiting their application in many fields. Compared with dyes in the visible light region, near-infrared dyes have the characteristics of strong cell penetration, strong photothermal properties, low interference and toxicity to biological tissues, etc., and have shown great application value in the fields of cell analysis and detection, biomolecule labeling, photothermal / photodynamic therapy, etc. Therefore, the design and research of new boron difluoride dyes with near-infrared absorption characteristics have received much attention and have important academic research and practical application value. Summary of the invention

[0004] One of the purposes of the present invention is to disclose a boron difluoride complex capable of achieving long-wavelength absorption, which is a compound or a salt thereof having a structure as shown in formula (I):

[0005]

[0006] Among them, R 1 H, C 1-3 Alkyl, C 1-3 Alkoxy, halogen, hydroxyl, mercapto, cyano, amino, acetyl, formaldehyde, p-toluenesulfonyloxy, substituted or unsubstituted phenyl, the substituent on the phenyl is C 1-3 Alkoxy or dimethylamino;

[0007] R 2 H, C 1-6 Alkyl, C 1-3 Alkoxy, halogen, substituted or unsubstituted phenyl, the substituent on the phenyl is halogen, C 1-3 Alkoxy, nitro, amino, hydroxy, cyano or acetyl;

[0008] Ar is an aromatic group.

[0009] As a preference, R 1 For H.

[0010] As the preferred 2 For H.

[0011] Preferably, Ar is phenyl, indolyl or benzofuranyl.

[0012] As further preferred, it is the following specific compound or its salt:

[0013]

[0014] The second object of the present invention is to disclose a method for preparing the above-mentioned organic small molecule with 1-azaazulene as a structural unit, comprising the following steps:

[0015] 1) Dissolve a mixture of pyridine and 2-bromo-1-(2-nitrophenyl)ethane-1-one in acetonitrile, and stir in an oil bath for 4 hours after the addition is complete. After the reaction is complete, wash with acetonitrile and purify to obtain compound A;

[0016] 2) Under nitrogen protection, acetic acid was added to compound A and ammonium acetate, and cycloheptatrienone was added dropwise at 118° C. After the addition was completed, the reaction solution was stirred in an oil bath for 12 h, the solvent was removed under reduced pressure, and the reaction solution was separated and purified by silica gel chromatography to obtain a red solid to obtain compound B;

[0017] 3) Under nitrogen protection, isopropanol was added to the reaction bottle containing compound B, bis(pinacolato)diboron and potassium tert-butyl alcohol, and the mixture was stirred overnight in an oil bath at 80°C. After cooling to room temperature, the reaction mixture was extracted, washed and dried, concentrated under reduced pressure, and separated and purified by silica gel chromatography to obtain a red solid to obtain compound C;

[0018] 4) Under nitrogen protection, compound C, tris(dibenzylideneacetone)dipalladium(0), X-PHOS and sodium tert-butyl alcohol were dissolved in 1,4-dioxane, and 2-bromo-1,3,5-trimethylbenzene was added dropwise to the mixture. After the addition was completed, the mixture was stirred in an oil bath at 110°C for 12 hours. After cooling to room temperature, the reaction mixture was extracted, washed and dried, concentrated under reduced pressure, and separated and purified by silica gel chromatography to obtain a red solid to obtain compound D;

[0019] 5) Under nitrogen protection, compound D is dissolved in anhydrous 1,2-dichloroethane, and triethylamine is added dropwise to the mixture. After the addition is complete, the mixture is stirred at room temperature for 1 hour, and then boron trifluoride ether is added dropwise, and stirring is continued for 2 hours at room temperature. After the reaction is completed, it is quenched, extracted, washed, dried, and concentrated under reduced pressure. The residue is purified by recrystallization with methanol to obtain a black solid, namely compound E, which is an organic small molecule with 1-azaazulene as a structural unit. Preferably, in step 1), the molar ratio of compound 3,6-di-tert-butylcarbazole and ferric chloride is 1:1.

[0020] Preferably, in step 1), the molar ratio of the compound pyridine to 2-bromo-1-(2-nitrophenyl)ethane-1-one is 1:1.

[0021] Preferably, in step 2), the molar ratio of tropone, compound A and ammonium acetate is 1:2:15.

[0022] Preferably, in step 2), the silica gel column chromatography separation conditions are ethyl acetate:n-hexane=1:1.25.

[0023] Preferably, in step 3), the molar ratio of compound B, bis(pinacol)diboron and potassium tert-butyl alcohol is 1:3:2.

[0024] Preferably, in step 3), the silica gel column chromatography separation conditions are ethyl acetate:n-hexane=3:10.

[0025] Preferably, in step 4), the molar ratio of compound C, tris(dibenzylideneacetone)dipalladium(0), X-PHOS, sodium tert-butyl alcohol and 2-bromo-1,3,5-trimethylbenzene is 1:0.05:0.2:2:2.

[0026] Preferably, in step 4), the silica gel column chromatography separation conditions are ethyl acetate:n-hexane=1:20.

[0027] Preferably, in step 5), the molar ratio of compound D, triethylamine and boron trifluoride diethyl ether is 1:8.3:10.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) Boron difluoride dyes have a larger Stokes shift than traditional fluoroboron dipyrromethene dyes and show potential application value in the fields of cell detection and biomarkers.

[0030] (2) Compared with the isomers with quinoline (alternating conjugation) as ligands, the non-alternating conjugated structure of organic small molecules with 1-azaazulene as the structural unit can cause the absorption wavelength of fluoroboron dyes to red-shift. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 For compound B 1 H NMR spectrum.

[0032] Figure 2 For compound B 13 C NMR spectrum.

[0033] Figure 3 For compound C 1 H NMR spectrum.

[0034] Figure 4 For compound C 13 C NMR spectrum.

[0035] Figure 5 For compound D 1 H NMR spectrum.

[0036] Figure 6 For compound D 13 C NMR spectrum.

[0037] Figure 7 For compound E 1 H NMR spectrum.

[0038] Figure 8 For compound E 13 C NMR spectrum.

[0039] Fig. 9 For compound E 19 F NMR spectrum.

[0040] Fig.10 For compound E 11 B NMR spectrum.

[0041] Fig.11 For compound G 1 H NMR spectrum.

[0042] Fig.12 For compound G 13 C NMR spectrum.

[0043] Fig.13 For compound G19 F NMR spectrum.

[0044] Fig.14 For compound G 11 B NMR spectrum.

[0045] Fig.15 UV-visible absorption (red) and fluorescence (blue) spectra of compound B.

[0046] Fig.16 The UV-visible absorption (red) and fluorescence (blue) spectra of the isomeric structure of compound G with quinoline (alternating conjugation) as a ligand. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatus.

[0049] The present invention is further described in detail below with reference to the accompanying drawings.

[0050] Example 1

[0051] 1. The organic small molecule with 1-azaazulene as the structural unit of the present invention can be prepared by the following steps:

[0052] Step 1:

[0053]

[0054] A mixture of pyridine (0.16 g, 2.0 mmol) and 2-bromo-1-phenylethanone (0.44 g, 2.2 mmol) was stirred in MeCN (5.0 mL) at 40°C for 4 hours. After the reaction was completed, the mixture was purified with acetonitrile to obtain compound A. Yield: 86%.

[0055] Step 2:

[0056]

[0057] Under nitrogen protection, 3.5 mL of acetic acid was injected into a reaction bottle containing compound A (581.6 mg, 1.8 mmol) and ammonium acetate (1.085 g, 14.08 mmol). Cycloheptatrienone (0.091 mL, 0.94 mmol) was added dropwise to the mixture. The mixture was stirred at 118 ° C (in an oil bath) for 12 hours. After cooling to room temperature, the mixture was poured into a NaHCO3 aqueous solution, extracted with dichloromethane, washed with a thiosulfate solution and brine, dried over anhydrous Na2SO4, and the solvent was removed under reduced pressure. The red solid, i.e., compound B, was separated and purified by column chromatography. Yield: 50%. 1 H NMR(500MHz, CDCl3)δ=8.77(d,J=9.8Hz,1H),8.59(d,J=9.8Hz,1H),8.09(d,J=7.7Hz,1H),7.92(t, 13C NMR (126MHz, CDCl3): δ=162.3,157.7,150.0,147.7,138.5,137.3,136.6,132.4,132.2,130.2,130.2,129.8,129.4,124.1,112.8ppm

[0058] Step 3:

[0059]

[0060] Under nitrogen protection, 15 mL of isopropanol was added to a reaction flask containing compound B (250 mg, 1.0 mmol), bis(pinacolato)diboron (787 mg, 3.1 mmol) and potassium tert-butyl alcohol (224 mg, 2.0 mmol). The mixture was stirred at 80 ° C (in an oil bath) overnight. After cooling to room temperature, the reactant was extracted with ethyl acetate, washed with water and brine, dried over anhydrous Na2SO4, and the solvent was removed under reduced pressure. A red solid was obtained by column chromatography, i.e., compound C. Yield: 89%. 1H NMR (500MHz, CDCl3) δ = 8.57 (d, J = 8.7Hz, 1H), 8.44 (d, J = 10.1Hz, 1H), 7.93 (d, J = 7.9Hz, 1H), 7.70 ( dd,J=14.6,6.8Hz,3H),7.56(t,J=9.5Hz,1H),7.20(t,J=7.7Hz,1H),6.79(d,J=8.5Hz,2H)ppm; 13C NMR (126MHz, CDCl3): δ=168.8,157.8,148.7,146.4,135.8,134.0,133.6,131.2,130.6,129.8,129.0,117.2,117.2,117.0,111.6ppm

[0061] Step 4:

[0062]

[0063] Under nitrogen protection, compound C (443 mg, 2.01 mmol), tris(dibenzylideneacetone)dipalladium (0) (92 mg, 0.1 mmol), X-PHOS (190 mg, 0.4 mmol) and sodium tert-butyl alcohol (386 mg, 4.02 mmol) were dissolved in 25 mL 1,4-dioxane. 2-Bromo-1,3,5-trimethylbenzene (0.615 mL, 4.02 mmol) was added dropwise to the mixture. After the addition was complete, the mixture was stirred at 110°C (in an oil bath) for 12 hours. After cooling to room temperature, the reaction mixture was diluted with water, extracted with ethyl acetate, washed with water and brine, dried over anhydrous Na2SO4, and the solvent was removed under reduced pressure. A red solid was obtained by column chromatography, that is, compound D. Yield: 43%. 1H NMR (500MHz, CD2Cl2)δ=11.27(s,1H),8.48(dd,J=13.5,9.5Hz,2H),8.03(d,J=6.4Hz,1H),7.82(s,1H),7.75–7.65(m,2H),7.59(t ,J=9.5Hz,1H),7.12(t,J=7.7Hz,1H),7.00(s,2H),6.74(t,J=7.4Hz,1H),6.29(d,J=8.4Hz,1H),2.33(s,3H),2.22(s,6H)ppm; 13C NMR (126MHz, CD2Cl2): δ=169.5,158.1,148.7,146.4,136.8,136.4,135.8,134.1,13 3.6,131.6,130.8,130.0,129.4,129.2,116.7,116.3,113.1,111.5,21.1,18.6ppm.

[0064] Step 5:

[0065]

[0066] Under nitrogen protection, compound D (440 mg, 1.3 mmol) was dissolved in 110 mL 1,2-dichloroethane. Then 1.5 mL triethylamine (10.79 mmol) was slowly added dropwise, and the mixture was stirred at room temperature for 1 h. Then boron trifluoride ether (3.3 mL, 48% BF3, 13 mmol) was added dropwise, and stirred at room temperature for 2 h. The reaction mixture was quenched with an aqueous solution of NaHCO3, extracted with ethyl acetate, washed with water and brine, dried with anhydrous Na2SO4, and the solvent was removed under reduced pressure. The residue was purified by recrystallization with methanol to obtain a black solid, which was the organic small molecule with 1-azaazulene as the basic unit. Yield: 53%. 1H NMR(500MHz, CDCl3)δ=9.15(d,J=10.5Hz,1H),8.43(d,J=10.3Hz,1H),7.88(d,J=8.0Hz,1H),7.85–7.77(m,2H),7.76–7.71(m,1H) 13C NMR (126MHz, CD2Cl2): δ=157.7,150.1,149.3,146.3,139.1,138.5,137.3,136.6,136.5,135.0,133 .8,133.7,132.0,132.0,131.9,129.7,128.7,116.1,114.7,110.6,107.3,21.1,18.4,18.4ppm; 11B NMR (160MHz, CD2Cl2) δ = 2.37 (t, J = 31.2Hz) ppm; 19F NMR (470MHz, CD2Cl2) δ = -135.0 (dd, J = 63.6, 27.4Hz) ppm

[0067] The reaction formula is as follows:

[0068]

[0069] Example 2

[0070] Step 1:

[0071]

[0072] Wherein compound D is replaced by compound F to obtain red solid G with a yield of 94%. 1H NMR (500MHz, d6-DMSO) δ = 9.13 (d, J = 9.7Hz, 1H), 9.01 (d, J = 10.1Hz, 1H), 8.43–8.36 (m, 1H), 8.36–8.29 (m, 1H), 8 13C NMR (126MHz, d6-DMSO): δ=155.9, 154.3, 148.3, 146.1, 142.4, 139.6, 135.4, 135.2, 134.6, 132.9, 127.7, 120.1, 119.0, 114.0, 107.4ppm; 11B NMR (160MHz, CD2Cl2) δ = 1.45 (t, J = 17.3Hz) ppm; 19F NMR (470MHz, CD2Cl2) δ = -137.8 (dd, J = 34.2, 16.9Hz) ppm.

[0073] Test Example 1

[0074] In the UV-visible absorption spectrum measurement, a high-resolution UV-visible spectrophotometer was used. First, compound B was dissolved in dichloromethane (DCM), tetrahydrofuran (THF), hexane (Hexane), toluene (Toluene), methanol (MeOH) and acetonitrile (CH3CN) solvents, respectively, and placed in the sample cell of the UV-visible spectrophotometer. Then, the sample was scanned in the wavelength range of 300-900nm to obtain the absorption spectrum of the sample. In order to eliminate the absorption of the solvent, the absorption spectrum of the blank solvent was used as a reference and calibrated before the measurement.

[0075] In the fluorescence spectrometry, the dissolved compound B is also placed in the sample cell of the fluorescence spectrophotometer. In order to excite the fluorescence of the sample, an appropriate excitation wavelength is selected and the emission spectrum is recorded in the wavelength range of 400-800nm. In order to correctly interpret and analyze the emission spectrum, background correction is also required to eliminate background scattering and fluorescence.

[0076] from Fig.16In the ultraviolet absorption spectrum, the difference between the ultraviolet absorption of compound G and the isomeric structure with quinoline (alternating conjugation) as the ligand was compared. Compound G showed a stronger red-shifted absorption band, which was 99nm red-shifted compared with the isomeric structure with quinoline as the ligand. In the fluorescence emission spectrum, the difference between the fluorescence properties of compound G and the isomeric structure with quinoline (alternating conjugation) as the ligand was compared. Comparing the fluorescence emission data of compound G and the isomeric structure with quinoline as the ligand, the maximum emission wavelength of compound G is located at 550nm, and the maximum emission wavelength of the isomeric structure with quinoline as the ligand is located at 470nm, and the Stokes shift of compound G is larger. Through the above comparison, it is shown that the cross-overlap between the absorption spectrum and the emission spectrum of compound G is smaller, which reduces the reabsorption of the generated fluorescence by the surrounding molecules and reduces the possibility of fluorescence self-quenching; it reduces the mutual interference between the excitation light and the fluorescence generated by the dye in practical applications, thereby reducing the possibility of reduced detection sensitivity and imaging contrast.

[0077] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A boron difluoride composite capable of achieving long-wavelength absorption, characterized in that: It is a compound or a salt thereof having a structure as shown in formula (I): Among them, R 1 H, C 1-3 Alkyl, C 1-3 Alkoxy, halogen, hydroxyl, mercapto, cyano, amino, acetyl, formaldehyde, p-toluenesulfonyloxy, substituted or unsubstituted phenyl, the substituent on the phenyl is C 1-3 Alkoxy or dimethylamino; R 2 H, C 1-6 Alkyl, C 1-3 Alkoxy, halogen, substituted or unsubstituted phenyl, the substituent on the phenyl is halogen, C 1-3 Alkoxy, nitro, amino, hydroxy, cyano or acetyl; Ar is an aromatic group.

2. The boron difluoride composite capable of achieving long-wavelength absorption according to claim 1, characterized in that: R 1 For H.

3. The boron difluoride composite capable of achieving long-wavelength absorption according to claim 1, characterized in that: R 2 For H.

4. The boron difluoride composite capable of achieving long-wavelength absorption according to claim 1, characterized in that: The Ar is phenyl, indolyl or benzofuranyl.

5. The boron difluoride composite capable of achieving long-wavelength absorption according to claim 1, characterized in that: The following compound or its salt:

6. A method for preparing the boron difluoride complex as claimed in claim 5, characterized in that: The following steps are involved: 1) A mixture of pyridine and 2-bromo-1-(2-nitrophenyl)ethane-1-one was dissolved in acetonitrile, and then stirred in an oil bath for 3 to 10 hours. After the reaction was completed, the mixture was washed and purified with acetonitrile to obtain compound A; 2) Under nitrogen protection, acetic acid was added to compound A and ammonium acetate, and cycloheptatrienone was added dropwise at 110-120° C. After the addition was completed, the reaction solution was stirred in an oil bath for 10-15 hours, the solvent was removed under reduced pressure, and the reaction solution was separated and purified by silica gel chromatography to obtain a red solid to obtain compound B; 3) Under nitrogen protection, isopropanol is added to a reaction flask containing compound B, bis(pinacolato)diboron and potassium tert-butyl alcohol, and the mixture is stirred at 70-90° C. overnight; after cooling to room temperature, the reaction mixture is extracted, washed and dried, concentrated under reduced pressure, and separated and purified by silica gel chromatography to obtain a red solid to obtain compound C; 4) Under nitrogen protection, compound C, tris(dibenzylideneacetone)dipalladium(0), X-PHOS and sodium tert-butyl alcohol are dissolved in 1,4-dioxane, and 2-bromo-1,3,5-trimethylbenzene is added dropwise to the mixture; after the addition is complete, the mixture is stirred in an oil bath at 100-120° C. for 10-15 hours; after cooling to room temperature, the reaction mixture is extracted, washed and dried, concentrated under reduced pressure, and separated and purified by silica gel chromatography to obtain a red solid to obtain compound D; 5) Under nitrogen protection, compound D is dissolved in anhydrous 1,2-dichloroethane, and triethylamine is added dropwise to the mixture; after the addition is completed, the mixture is stirred at room temperature for 1 to 5 hours, and then boron trifluoride ether is added dropwise, and stirring is continued at room temperature for 1 to 5 hours; after the reaction is completed, the reaction is quenched, extracted, washed, dried, and concentrated under reduced pressure; the residue is purified by recrystallization with methanol to obtain a black solid, namely compound E, which is the boron difluoride complex.

7. The method for preparing an organic small molecule containing a boron-nitrogen covalent bond according to claim 6, characterized in that: In step 1), the molar ratio of the compound pyridine to 2-bromo-1-(2-nitrophenyl)ethane-1-one is 1:1 to 1.

2.

8. The method for preparing an organic small molecule containing a boron-nitrogen covalent bond according to claim 6, characterized in that: In step 2), the molar ratio of cycloheptatrienone, compound A and ammonium acetate is 1:2-2.4:15-18, and the silica gel column chromatography separation conditions are ethyl acetate:n-hexane=1:1.25-1.

5.

9. The method for preparing an organic small molecule containing a boron-nitrogen covalent bond according to claim 6, characterized in that: In step 3), the molar ratio of compound B, bis(pinacolato)diboron and potassium tert-butyl alcohol is 1:3-4:2-3, and the silica gel column chromatography separation condition is ethyl acetate:n-hexane=3:10-12.

10. The method for preparing an organic small molecule containing a boron-nitrogen covalent bond according to claim 6, characterized in that: In step 4), the molar ratio of compound C, tris(dibenzylideneacetone)dipalladium(0), X-PHOS, sodium tert-butyl alcohol and 2-bromo-1,3,5-trimethylbenzene is 1:0.05-0.06:0.2-0.3:2-2.4:2-2.4, and the silica gel column chromatography separation condition is ethyl acetate:n-hexane=1:10-30; In step 5), the molar ratio of compound D, triethylamine and boron trifluoride diethyl ether is 1:8.0-8.5:10-15.

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