反应详情

4-Iodo-2-nitrobenzoic acid. 4-Iodo-2-nitrotoluene (9.0 g, 34 mmol), KMnO4 (22.0 g, 139 mmol), and H2O (340 mL) were heated at reflux for 5 h. The resulting brown suspension was filtered through a pad of diatomaceous earth, and the filter cake was washed with H2O. The basic filtrate was acidified with concentrated HCl causing precipitation of the desired acid. The solid was collected by suction filtration and dried, affording 1.86 g of the acid. The mother liquor was extracted with DCM (3×200 mL), and the combined extracts were dried (Na2SO4) and concentrated in vacuo to afford an additional 0.16 g of the benzoic acid (total 2.02 g, 20%). 1H NMR (400 MHz, CD3OD): 8.13 (d, J=1.6 Hz, 1H), 8.01 (dd, J=8.1, 1.6 Hz, 1H), 7.50 (d, J=8.1 Hz, 1H). B. Methyl 2-amino-4-iodobenzoate. To a stirred solution of 4-iodo-2-nitrobenzoic acid (2.3 g, 7.9 mmol) in DMF (30 mL) at 0° C. was added DBU (2.4 mL, 16 mmol) followed by iodomethane (1.5 mL, 24 mmol). The reaction mixture was stirred 15 min at 0° C., then was allowed to warm to room temperature and was stirred overnight. The mixture was poured into H2O and extracted with EtOAc (2×). The combined organic extracts were washed with H2O (2×), dried (MgSO4), and concentrated in vacuo. The residue was purified by flash chromatography (hexanes/EtOAc) to afford methyl 4-iodo-2-nitrobenzoate as a pale yellow solid (2.30 g, 95%). To a solution of the nitrobenzoate (2.3 g, 7.4 mmol) in 1:1 EtOAc/DCM (10 mL) at room temperature was added SnCl2.2H2O (8.3 g, 37 mmol). The reaction mixture was allowed to stir overnight. The solvents were evaporated in vacuo, and the residue was partitioned between satd. aq. NaHCO3 and DCM. The layers were separated, and the aqueous layer was further extracted with DCM (2×). The combined organic layers were dried (MgSO4) and concentrated in vacuo to provide the pure aminobenzoate as a yellow solid (1.87 g, 91%). 1H NMR (500 MHz, CDCl3): 7.52 (d, J=8.5 Hz, 1H), 7.07 (d, J=1.6 Hz, 1H), 6.96 (dd, J=8.5, 1.6 Hz, 1H), 5.72 (br s, 2H), 3.86 (s, 3H). C. 4-Iodo-2-(Quinoxaline-5-sulfonylamino)benzoic acid methyl ester. A solution of methyl 2-amino-4-iodobenzoate (1.2 g, 4.4 mmol), quinoxaline-5-sulfonyl chloride (1.2 g, 5.3 mmol), pyridine (1.7 mL, 22 mmol) and DCM (25 mL) was maintained at 23° C. for 24 h. The reaction mixture was diluted with DCM (200 mL) and washed with satd. aq. NaHCO3, then dried and concentrated to a tan solid. This residue was chromatographed (0 to 100% EtOAc/CH2Cl2) to afford the sulfonamide as a light yellow solid (1.6 g, 77%). MS (ESI): calculated for C16H12IN3O4S, 469.0; m/z found, 470 [M+H]+. 1H NMR (500 MHz, DMSO-d6): 11.10 (s, 1H), 9.07 (d, J=1.8 Hz, 1H), 9.01 (d, J=1.8 Hz, 1H), 8.60 (dd, J=7.4, 1.3 Hz, 1H), 8.40 (dd, J=8.5, 1.3 Hz, 1H), 8.04 (dd, J=7.5, 1.0 Hz, 1H), 7.99 (d, J=1.6 Hz, 1H), 7.51 (d, J=8.3 Hz, 1H), 7.37 (dd, J=8.3, 1.6 Hz, 1H), 3.88 (s, 3H). D. 4-Iodo-2-(Quinoxaline-5-sulfonylamino)benzoic acid. A solution of LiOH·H2O (0.16 g, 3.9 mmol) in H2O (5 mL) was added to a solution of 4-iodo-2-(quinoxaline-5-sulfonylamino)benzoic acid methyl ester (0.37 mg, 0.78 mmol) and THF (10 mL), and the mixture was rapidly stirred for 16 h. The mixture was concentrated to a volume of 5 mL, then was adjusted to pH 5 with 1 M HCl. The resulting precipitate was collected by filtration to provide the acid as a white solid (0.35 g, 99%). MS (ESI): calculated for C15H10IN3O4S, 455.0; m/z found, 456 [M+H]+. 1H NMR (500 MHz, DMSO-d6): 14.0 (br s, 1H), 11.6 (s, 1H), 9.10 (d, J=1.5 Hz, 1H), 9.97 (d, J=1.5 Hz, 1H), 8.60 (d, J=7.4 Hz, 1H), 8.42 (d, J=8.4 Hz, 1H), 8.06 (t, J=7.5 Hz, 1H), 7.95 (d, J=1.2 Hz, 1H), 7.51 (d, J=8.3 Hz, 1H), 7.37 (dd, J=8.3, 1.2 Hz, 1H). E. Quinoxaline-5-sulfonic acid [5-iodo-2-(piperidine-1-carbonyl)-phenyl]-amide

1. washwashed with satd
2. dry with materialaq. NaHCO3, then dried
3. concentrationconcentrated to a tan solid
4. customThis residue was chromatographed (0 to 100% EtOAc/CH2Cl2)