Synlett 2018; 29(12): 1572-1577
DOI: 10.1055/s-0037-1610188
letter
© Georg Thieme Verlag Stuttgart · New York

Visible-Light-Induced Decarboxylative Iodination of Aromatic Carboxylic Acids

Min Jiang
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China   Email: fuhua@mail.tsinghua.edu.cn
,
Haijun Yang
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China   Email: fuhua@mail.tsinghua.edu.cn
,
Yunhe Jin
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China   Email: fuhua@mail.tsinghua.edu.cn
,
Lunyu Ou
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China   Email: fuhua@mail.tsinghua.edu.cn
,
Hua Fu  *
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China   Email: fuhua@mail.tsinghua.edu.cn
› Author Affiliations
We thank the National Natural Science Foundation of China (Grant No. 21772108) for financial support.
Further Information

Publication History

Received: 17 April 2018

Accepted after revision: 24 May 2018

Publication Date:
18 June 2018 (online)


Abstract

A convenient, efficient and practical visible-light-induced decarboxylative iodination of aromatic carboxylic acids has been developed, and the corresponding aryl iodides were obtained in good yields. The method shows some advantages including the use of readily available aromatic carboxylic acids as the starting materials, simple and mild conditions, high efficiency, wide substrate scope and tolerance of various functional groups.

Supporting Information

 
  • References

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  • 24 General procedures for the iodination of aromatic carboxylic acids General procedure A: To a 15 mL test tube with septum, Cs2CO3 (0.6 mmol, 195 mg), aromatic carboxylic acid (1; 0.3 mmol), [Ir(dF(CF3)ppy)2dtbbpy]PF6 (D; 6 μmmol, 6.7 mg), N-iodosuccinimide (NIS; 0.9 mmol, 202.5 mg), and I2 (15 μmol, 5 mol%) were added. The tube was evacuated and backfilled with argon three times, and then 3 mL of anhydrous 1,2-dichloroethane (DCE) was added through a syringe under argon. The tube was sealed with Parafilm M® and placed in an oil bath with a contact thermometer, and the reaction was carried out at 50 °C under irradiation with 6 × 5 W blue LEDs (λmax = 455 nm). After 24 or 36 h, the resulting mixture was filtered through a 2 cm thick pad of silica, and the silica was washed with dichloromethane (50 mL). The filtrate was collected and the solvent was removed in vacuo. The crude residue was purified by silica gel flash column chromatography to provide the target product 2 (Note: The reaction was very sensitive to moisture, and the yields sharply decreased to less than 5% when 0.01 equivalent of H2O was added to the reaction system).General procedure B: To a 15 mL test tube with septum, Cs2CO3 (0.6 mmol, 195 mg), aromatic carboxylic acid (1; 0.3 mmol), [Ir(dF(CF3)ppy)2dtbbpy]PF6 (D; 6 μmol, 6.7 mg), NIS (1.5 mmol, 337.5 mg) and I2 (60 μmol, 20 mol%) were added. The tube was evacuated and backfilled with argon three times, and then 3 mL of anhydrous DCE was added through a syringe under argon. The tube was sealed with Parafilm M® and placed in an oil bath with a contact thermometer, and the reaction was carried out at 50 °C under irradiation with 6 × 5 W blue LEDs (λmax = 455 nm). After 24 h or 36 h, the resulting mixture was filtered through a 2 cm thick pad of silica, and the silica was washed with CH2Cl2 (50 mL). The filtrate was collected and the solvent was removed in vacuo. The crude residue was purified by silica gel flash column chromatography to provide the target product 2 (Note: The reaction was very sensitive to moisture, and the yields sharply decreased to less than 5% when 0.01 equivalent of H2O was added to the reaction system).General procedure C: To a 15 mL test tube with septum, Cs2CO3 (0.6 mmol, 195 mg), aromatic carboxylic acid (1; 0.3 mmol), [Ir(dF(CF3)ppy)2dtbbpy]PF6 (D; 6 μmol, 6.7 mg), NIS (1.5 mmol, 337.5 mg) and I2 (60 μmol, 20 mol%) were added. The tube was evacuated and backfilled with argon for times, and then 3 mL of anhydrous CH3CN was added through a syringe under argon. The tube was sealed with Parafilm M® and placed in an oil bath with a contact thermometer, and the reaction was carried out at 50 °C under irradiation with 6 × 5 W blue LEDs (λmax = 455 nm). After 24 h, the resulting mixture was filtered through a 2 cm thick pad of silica, and the silica was washed with CH2Cl2 (50 mL). The filtrate was collected and the solvent was removed in vacuo. The crude residue was purified by silica gel flash column chromatography to provide the target product 2 (Note: The reaction was very sensitive to moisture, and the yields sharply decreased to less than 5% when 0.01 equivalent of H2O was added to the reaction system).Three representative examples are shown as follows:1-Iodo-3-methoxybenzene (2f)25Eluent: pentane/diethyl ether 50:1, the solvent was removed under reduced pressure. Yield: 52.7 mg (75%) by following general procedure A. Colorless oil. 1H NMR (CDCl3, 400 MHz): δ = 7.29 (d, J = 8.24 Hz, 1 H), 7.26 (s, 1 H), 7.0 (t, J = 8.24 Hz, 1 H), 6.87 (d, J = 8.70 Hz, 1 H), 3.78 (s, 3 H). 13C NMR (CDCl3, 100 MHz): δ = 160.2, 130.9, 129.9, 123.1, 113.8, 94.5, 55.5. EI-MS: M+ m/z 234.Methyl 4-iodobenzoate (2s)25Eluent: pentane/diethyl ether 50:1, the solvent was removed under reduced pressure. Yield: 59.7 mg (76%) by following general procedure B. White solid; mp 113–115 °C. 1H NMR (CDCl3, 400 MHz): δ = 7.79 (d, J = 8.24 Hz, 2 H), 7.64 (d, J = 8.24 Hz, 2 H), 3.95 (s, 3 H). 13C NMR (CDCl3, 100 MHz): δ = 167.0, 137.2, 130.6, 129.2, 100.4, 52.2. EI-MS: m/z = 262 [M+].3-Iodopyridine (2ab)26Eluent: pentane/diethyl ether 5:1, the solvent was removed at 0 °C under reduced pressure. Yield: 45.5 mg (65%) by following general procedure C. Yellow oil. 1H NMR (CDCl3, 400 MHz): δ = 8.86 (s, 1 H), 8.79 (d, J = 5.04 Hz, 1 H), 7.94 (d, J = 8.24 Hz, 1 H), 7.42 (t, J = 6.87 Hz, 1 H). 13C NMR (CDCl3, 100 MHz): δ = 146.7, 144.3, 139.6, 130.2, 129.4, 128.9, 128.2, 120.1, 127.7, 98.8. EI-MS: m/z = 205 [M+]
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