Synlett 2024; 35(01): 101-108
DOI: 10.1055/s-0042-1752719
cluster
Functional Dyes

A Practical Synthesis of Near-Infrared Benzannulated Xanthenoid Dyes

Jin Li
a   State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, P. R. of China
,
Ruwei Wei
a   State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, P. R. of China
,
Xiaodong Zhang
a   State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, P. R. of China
,
Xiao Luo
b   Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Dongchuan Road 500, Shanghai 200241, P. R. of China
,
Xuhong Qian
a   State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, P. R. of China
b   Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Dongchuan Road 500, Shanghai 200241, P. R. of China
,
Youjun Yang
a   State Key Laboratory of Bioreactor Engineering, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, P. R. of China
› Author Affiliations
This work was supported by the National Key Research and Development Program of China (2022YFD17800), the National Natural Science Foundation of China (21908065, 22078098, and 22278138), the Shanghai Academic Technology Research Leader (22XD1421000), the Research Funds of Happiness Flower ECNU (2020JK2103), and the Open Funding Project of the State Key Laboratory of Bioreactor Engineering.


Jin Li and Ruwei Wei contributed equally.

Abstract

Near-infrared dyes are sought after for their potential in biomedical applications. Benzoxanthene dyes with a non-oxygen bridging atom are expected to exhibit longer absorption and emission wavelengths than their oxygen-containing counterparts, yet their synthesis remains unaddressed. Herein, we report the first syntheses of non-oxygen-bridged benzoxanthenes starting from a 7-bromo-2-aminonaphthalene derivative, and discuss their photophysical properties as well as their potential for in vivo imaging.

Supporting Information



Publication History

Received: 31 March 2023

Accepted after revision: 22 May 2023

Article published online:
07 August 2023

© 2023. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 
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  • 47 Compound 4 DMF (1.64 mL, 21 mmol, 1.2 equiv.) was mixed with 1,2-dichloroethane (10 mL) and cooled to 0 °C before dropwise addition of POCl3 (1.98 mL, 21 mmol, 1.2 equiv.) and stirring for 30 min. The resulting mixture was added to a solution of compound 3 (3.5 g, 10 mmol, 1 equiv.) in anhydrous CH2Cl2 (10 mL) at 75 °C , and the obtained mixture was stirred for 3 h. The reaction was allowed to cool to the R.T. and quenched by adding saturated Na2CO3 solution. The aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo. The crude extract was purified by column chromatography (EtOAc/PE = 1:50 to 1:25, v/v) to give 4 (2.2 g, 39%) as a yellow solid. Mp 106.9–108.0 °C. 1H NMR (400 MHz, CDCl3): δ = 10.35 (s, 1 H), 8.24 (s, 1 H), 7.89 (s, 1 H), 7.66 (d, J = 9.2 Hz, 1 H), 7.11 (d, J = 9.2 Hz, 1 H), 3.69–3.56 (m, 4 H), 3.47–3.35 (m, 2 H), 2.98 (t, J = 6.5 Hz, 2 H), 2.11 (dd, J = 12.6, 5.2 Hz, 4 H). 13C NMR (101 MHz, CDCl3): δ = 191.76, 146.02, 137.14, 132.32, 130.07, 125.98, 125.59, 124.30, 122.17, 115.65, 111.19, 49.59, 49.00, 42.50, 30.09, 23.44, 21.45. HRMS (ESI): m/z [M]+ calcd for C17H17BrClNO: 336.0255; found 336.0254.
  • 48 Compound 5 Compound 4 (1 g, 2.8 mmol, 1 equiv.) was dissolved in anhydrous THF (20 mL) under an argon atmosphere and cooled to 0 °C before o-tolylmagnesium bromide (5.45 mL, 5.6 mmol, 2 equiv.) was added dropwise. The reaction was quenched after 30 min. Then the reaction was quenched with saturated NH4Cl aqueous solution (50 mL), and extracted with EtOAc (3 × 20 mL). The organic layer was combined, dried over anhydrous Na2SO4, filtered and evaporated to a yellow residue. The crude product was purified by column chromatography (PE/CH2Cl2 = 6:1, v/v) to yield 5 (1.18 g, 98%) as a white solid. Mp 101.0–102.4 °C. 11H NMR (400 MHz, CDCl3) δ 7.94 (s, 1H), 7.53 (s, 1H), 7.45 (d, J = 9.1 Hz, 1H), 7.31 (d, J = 7.4 Hz, 1H), 7.18 (dd, J = 15.7, 7.4 Hz, 3H), 7.04 (d, J = 9.1 Hz, 1H), 6.32 (s, 1H), 3.61 (t, J = 6.1 Hz, 2H), 3.51 (td, J = 6.8, 3.2 Hz, 2H), 3.31 (dd, J = 6.2, 4.8 Hz, 2H), 2.95 (t, J = 6.5 Hz, 2H), 2.36 (s, 1H), 2.29 (s, 3H), 2.10 – 2.01 (m, 4H). 13C NMR (101 MHz, CDCl3) δ 143.57, 140.40, 136.10, 134.19, 133.95, 130.44, 128.16, 127.66, 127.61, 126.49, 126.05, 125.51, 125.36, 122.38, 115.52, 111.65, 72.17, 49.48, 49.22, 42.82, 30.15, 23.63, 21.75, 19.24. HRMS (ESI): m/z [M + H]+ calcd for C24H26BrClNO: 458.0881; found: 458.0882.
  • 49 Compound 7 Compound 5 (2 g, 2.25 mmol, 1 equiv.), 8-bromo-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline (6) (0.68 g, 2.7 mmol, 1.2 equiv.) and H2SO4 (0.5 mL) (catalytic quantity) were dissolved in AcOH (20 mL) and the resulting mixture was stirred at 70 °C for 8 h. The reaction was allowed to cool to R.T. and quenched by adding saturated NaHCO3 solution (30 mL). The aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified by column chromatography (PE/CH2Cl2 = 8:1, v/v) to give 7 (2 g, 73%) as a white solid. Mp 156–157 °C. 1H NMR (400 MHz, CDCl3) δ 7.98 (s, 1H), 7.39 (d, J = 9.1 Hz, 1H), 7.17 – 7.11 (m, 2H), 7.09 – 6.98 (m, 3H), 6.73 (d, J = 7.6 Hz, 1H), 6.22 (s, 1H), 6.16 (s, 1H), 3.63 (t, J = 6.1 Hz, 2H), 3.53 (t, J = 6.9 Hz, 2H), 3.36 – 3.29 (m, 2H), 3.10 (s, 4H), 2.98 (t, J = 6.5 Hz, 2H), 2.80 (t, J = 6.6 Hz, 2H), 2.55 (t, J = 6.1 Hz, 2H), 2.21 (s, 3H), 2.07 (dt, J = 12.8, 6.3 Hz, 4H), 2.04 – 1.90 (m, 4H). 13C NMR (101 MHz, CDCl3): δ = 143.17, 143.15, 141.64, 137.19, 135.52, 133.31, 130.28, 130.19, 129.09, 129.00, 128.91, 127.37, 126.69, 126.30, 125.62, 125.56, 125.49, 125.49, 121.56, 120.17, 115.25, 111.81, 52.95, 50.14, 49.61, 49.54, 49.29, 42.89, 30.23, 29.63, 27.73, 23.74, 22.33, 22.00, 21.89, 19.78. HRMS (ESI): m/z [M + H]+ calcd for C36H38Br2ClN2: 691.1085; found: 691.1091.
  • 50 EC4 Compound 7 (R1 = H, R2 = Me) (0.2 g, 0.29 mmol, 1 equiv.) was dissolved in anhydrous THF (10 mL) under an argon atmosphere and cooled to –78 °C before sec-BuLi (0.49 mL, 1.3 M in hexane, 0.64 mmol, 2.2 equiv.) was added dropwise. After stirring for 30 min, the mixture was added to a solution of methyl 2-phenoxybenzoate (0.13 g, 0.58 mmol, 2 equiv.) in THF (10 mL), and stirring was continued at 0 °C for 30 min. The reaction was quenched by adding saturated NH4Cl aqueous solution (50 mL), and extracted with EtOAc (3 × 20 mL). The organic layer was combined, dried over anhydrous Na2SO4, filtered and concentrated in vacuo The crude residue from concentrating the organic extract was dissolved in CH2Cl2 (20 mL) containing MeSO3H (1 mL). After 2 h, chloranil (0.1 g) was added and the mixture was stirred for 4 h. The aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo The residue was purified by column chromatography (CH2Cl2/MeOH = 10:1, v/v) to give EC4 (50 mg, 25%) as a green solid. Mp 209.7–209.9 °C. 1H NMR (400 MHz, CDCl3) δ 7.55 (d, J = 7.3 Hz, 1H), 7.49 (d, J = 7.4 Hz, 2H), 7.40 (s, 1H), 7.30 (dd, J = 10.5, 6.8 Hz, 5H), 7.23 (s, 1H), 6.92 (d, J = 8.7 Hz, 3H), 6.88 (s, 1H), 6.78 (d, J = 7.2 Hz, 1H), 6.73 (d, J = 7.9 Hz, 1H), 3.87 (s, 2H), 3.62 (s, 2H), 3.55 (t, J = 6.1 Hz, 4H), 3.38 – 3.30 (m, 2H), 2.69 (t, J = 5.6 Hz, 2H), 2.60 (t, J = 6.4 Hz, 2H), 2.21 (s, 3H), 2.14 (dd, J = 15.9, 8.2 Hz, 2H), 2.01 (dd, J = 12.9, 6.5 Hz, 4H), 1.98 – 1.93 (m, 2H), 1.50 (d, J = 4.9 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ = 161.55, 156.10, 149.55, 148.64, 148.61, 147.38, 147.24, 136.07, 134.98, 134.76, 130.83, 130.67, 129.49, 128.99, 127.69, 127.38, 126.83, 124.83, 124.53, 117.13, 117.04, 115.48, 112.58, 53.89, 52.56, 48.99, 47.54, 42.26, 30.00, 27.45, 25.28, 22.76, 21.18, 20.22, 19.79, 19.54. HRMS (ESI): m/z [M]+ calcd for C49H44ClN2O: 711.3137; found: 711.3132.
  • 51 ESi4 Compound 7 (R1 = H, R2 = Me) (0.2 g, 0.29 mmol, 1 equiv.) was dissolved in anhydrous THF (10 mL) under an argon atmosphere and cooled to –78 °C before sec-BuLi (0.49 mL, 1.3 M in hexane, 0.64 mmol, 2.2 equiv.) was added dropwise. After stirring for 30 min, the resulting mixture was added to a solution of dichlorodimethylsilane (0.05 mL, 0.44 mmol, 1.5 equiv.) in THF (10 mL) and the obtained mixture was stirred at 0 °C for 30 min. The reaction was quenched by adding saturated NH4Cl aqueous solution and extracted with EtOAc (3 × 20 mL). The organic layer was combined, dried over anhydrous Na2SO4, filtered and evaporated to a yellow residue. The residue from the organic extract was dissolved in CH2Cl2 (20 mL) containing chloranil (0.1 g) and the mixture was stirred for 4 h. The aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified by column chromatography (CH2Cl2/MeOH = 10:1, v/v) to give ESi4 (100 mg, 58%) as a green solid. Mp 241.5–241.9 °C. 1H NMR (400 MHz, CDCl3) δ 7.97 (s, 1H), 7.47 (t, J = 7.4 Hz, 1H), 7.37 (d, J = 7.7 Hz, 2H), 7.33 (d, J = 9.2 Hz, 2H), 7.12 (d, J = 7.6 Hz, 1H), 7.05 (d, J = 9.2 Hz, 1H), 6.80 (s, 1H), 3.99 (d, J = 17.2 Hz, 4H), 3.71 – 3.58 (m, 4H), 3.53 – 3.47 (m, 2H), 3.11 (dd, J = 13.2, 6.4 Hz, 4H), 2.57 (s, 2H), 2.23 (s, 2H), 2.13 (dd, J = 12.7, 5.9 Hz, 4H), 2.03 (s, 3H), 2.03 – 1.97 (m, 2H), 0.70 (s, 3H), 0.67 (s, 3H). 13NMR (151 MHz, CDCl3) δ 165.69, 153.32, 147.51, 143.76, 140.14, 139.17, 138.95, 136.09, 135.66, 134.47, 133.94, 131.70, 130.29, 129.62, 129.54, 128.77, 126.47, 125.96, 125.71, 115.51, 113.32, 53.62, 52.94, 49.84, 49.15, 42.35, 31.44, 29.99, 28.70, 27.43, 23.27, 20.90, 20.44, 19.58, 0.24, 0.21.
  • 52 EP4 Compound 7 (R1/R2 = Me) (0.2 g, 0.29 mmol, 1 equiv.) was dissolved in anhydrous THF (10 mL) under an argon atmosphere and cooled to –78 °C before sec-BuLi (0.49 mL, 1.3 M in hexane, 0.64 mmol, 2.2 equiv.) was added dropwise. After stirring for 30 min, the resulting mixture was added to a solution of dichlorophenylphosphine (0.17 g, 0.7 mmol, 2 equiv.) in THF (10 mL) and the obtained mixture was stirred at 0 °C for 30 min. The reaction was quenched by adding saturated NH4Cl aqueous solution and extracted with EtOAc (3 × 20 mL). The organic layer was combined, dried over anhydrous Na2SO4, filtered and concentrated in vacuo. The organic residue was dissolved in CH2Cl2 (20 mL) containing chloranil (0.1 g) and the mixture was stirred for 4 h. The aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo The residue was purified by column chromatography (CH2Cl2/MeOH = 10:1, v/v) to give EP4 (51 mg, 21%) as a green solid. Mp 248.8–249.5 °C. 1H NMR (600 MHz, CDCl3) δ 8.26 (d, J = 16.0 Hz, 1H), 7.72 (dd, J = 12.6, 7.5 Hz, 2H), 7.53 (d, J = 6.9 Hz, 1H), 7.49 (d, J = 5.2 Hz, 2H), 7.43 – 7.37 (m, 2H), 7.25 (d, J = 7.2 Hz, 3H), 7.10 (d, J = 9.3 Hz, 1H), 6.76 (d, J = 5.0 Hz, 1H), 4.30 (d, J = 12.4 Hz, 1H), 4.07 (d, J = 12.9 Hz, 1H), 3.83 (s, 2H), 3.76 (d, J = 15.0 Hz, 1H), 3.67 (d, J = 7.1 Hz, 2H), 3.61 (t, J = 5.8 Hz, 2H), 3.49 (dd, J = 10.6, 5.2 Hz, 2H), 3.09 (dd, J = 19.3, 9.6 Hz, 1H), 2.97 – 2.90 (m, 1H), 2.80 – 2.68 (m, 2H), 2.60 (d, J = 8.6 Hz, 1H), 2.10 (s, 3H), 2.10 – 2.02 (m, 8H), 2.02 (s, 3H). 13C NMR (151 MHz, CDCl3) δ 160.64, 154.11, 148.82, 137.30, 137.24, 136.67, 136.43, 136.13, 135.94, 135.78, 134.35, 134.26, 133.87, 133.16, 132.49, 130.05, 129.98, 129.39, 129.31, 128.72, 128.13, 128.00, 127.82, 126.99, 125.80, 116.70, 115.69, 54.16, 52.94, 49.98, 49.22, 42.23, 29.90, 29.70, 27.38, 25.67, 25.62, 23.17, 22.62, 20.91, 19.93. 31P NMR (243 MHz, CDCl3): δ = 8.07. HRMS (ESI): m/z [M]+ calcd for C43H43ClN2OP: 669.2796; found: 669.2797. The exact mass calculated with the ChemDraw for EP4 is 669.2797.
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