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TCI Practical Example: The Metal-Free Amination of Arylboronic Acid Using the Hypervalent Iodine Compound

We are proud to present the amination of 4-(methoxycarbonyl)phenylboronic acid using 1-amino-1λ³-benzo[d][1,2]iodaoxol-3(1H)-one as an aminating reagent. The amination reaction can proceed without any metal reagents.

Used Chemicals

• 4-(Methoxycarbonyl)phenylboronic Acid [M1907]
• 1-Amino-1λ³-benzo[d][1,2]iodaoxol-3(1H)-one [A3839]
• Cesium Carbonate [C2160]
• THF

Procedure

1-Amino-1λ³-benzo[d][1,2]iodaoxol-3(1H)-one (1.61 g, 6.11 mmol) was added to a suspension of 4-(methoxycarbonyl)phenylboronic acid (1.00 g, 5.56 mmol) and cesium carbonate (2.16 g, 6.67 mmol) in dry THF (28 mL) at room temperature and the mixture was stirred at 50 °C for two days. The reaction mixture was quenched with sat. NaHCO₃ aq. (40 mL) at room temperature and the aqueous layer was extracted with dichloromethane (4 x 20 mL). The combined organic layer was washed with brine (50 mL), dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography (ethyl acetate:hexane = 0:100 – 30:70 on NH-silica gel) to give methyl 4-aminobenzoate as a pale yellow solid (730 mg, 87% yield).

Experimenter's Comments

The reaction mixture was monitored by UPLC.
1-Amino-1λ³-benzo[d][1,2]iodaoxol-3(1H)-one should be avoided in contact with metals due to its potential explosive nature.

Analytical Data

Methyl 4-Aminobenzoate

¹H NMR (400 MHz, CDCl₃); δ 7.82 (d, J = 8.0 Hz, 2H), 6.15 (m, 2H), 4.04 (brs, 2H), 3.03 (s, 3H).

Lead Reference

• Amino-λ³-iodane-Enabled Electrophilic Amination of Arylboronic Acid Derivatives
  • K. Kiyokawa, K. Kawanaka, S. Minakata, Angew. Chem. Int. Ed. 2024, 63, e202319048.