[Synthesis]
General procedure for the synthesis of 5-iodo-2-nitrophenol and 3-iodo-4-nitrophenol from 3-iodophenol: 3.0 mL of fuming nitric acid (75 mmol) in 12 mL of glacial acetic acid was slowly added dropwise to 15.03 g (68.3 mmol) of 3-iodophenol dissolved in 60 mL of glacial acetic acid over a 25-minute period and the reaction flask was placed in an ice bath to cool. After the dropwise addition was completed, the reaction mixture was continued to be stirred at room temperature for 30 min. Subsequently, the reaction solution was poured into ice water and concentrated under vacuum to remove most of the solvent. The residue was dissolved in 150 mL of water and then extracted with dichloromethane (2 x 300 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure to give 17 g of crude product. Separation by silica gel medium-pressure chromatography (eluent ratio 1:2 ethyl acetate:hexane) afforded 3-iodo-4-nitrophenol (6.93 g, 26.1 mmol, 38% yield), melting point 121-123 °C; 1H NMR (CDCl3, 300 MHz) δ 7.98 (d, 1H, J = 9 Hz), 7.54 (d, 1H, J = 3 Hz) 6.92 (dd, 1H, J = 9, 3 Hz), 5.54 (bs, 1H); IR (KBr) 3150 (wide), 1600, 1580, 1512, 1404, 1336, 1298, 1212, 1121, 1023, 870 cm?1; and 3-iodo-6-nitrophenol (3.07 g, 11.6 mmol, yield 17%), melting point 92-94 °C after recrystallization from dichloromethane/hexane (literature value 96 °C; Hodgson, H.H. et al., 1927); 1H NMR (CDCl3, 300 MHz) δ 10.53 (s, 1H), 7.76 (d, 1H, J = 9.0 Hz), 7.59 (d, 1H, J = 2.0 Hz), 7.33 ( dd, 1H, J = 9.0, 2.0 Hz); 13C NMR (CDCl3; assisted attribution by HMQC) δ 105.2 (C-3), 125.6 (C-5), 129.2 (C-2), 129.7 (C-4), 133.4 (C-6), 154.6 (C-1); IR (KBr) 3430 (broad), 1604, 1671, 1518, 1463 1571, 1518, 1463, 1317, 1225, 1172, 1055, 888 cm?1; Calculated elemental analysis (C6H4INO3): C, 27.19; H, 1.52; N, 5.29. Measured values: C, 27.36; H, 1.57; N, 5.15. |