5-Chloro-2-nitroaniline → 5-Chloro-4-iodo-2-nitroaniline

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Reaction Steps

To a solution of 5-chloro-2-nitroaniline (50 g, 289.74 mmol) in AcOH (200 ml) was added NIS (63 g, 280.02 mmol) with stirring overnight at room temperature. Then the solids were collected by filtration and washed with water (50 ml). The solid was dried in an oven under reduced pressure to afford 5-chloro-4-iodo-2-nitroaniline as a yellow solid (70 g, 81%). Next, to a solution of 5-chloro-4-iodo-2-nitroaniline (15 g, 50.26 mmol) in dioxane (200 ml) and water (20 ml) was added (4-chlorophenyl)boronic acid (15.7 g, 100.40 mmol), K3PO4 (21.2 g, 99.87 mmol) and Pd(PPh3)4 (3 g, 2.60 mmol) with stirring for 6 h at 95° C. maintained with an inert atmosphere of nitrogen. Then the resulting mixture was concentrated under vacuum to give a residue, which was purified by a silica gel column with 5%˜10% ethyl acetate in petroleum ether to afford 5-chloro-4-(4-chlorophenyl)-2-nitroaniline as a yellow solid (9 g, 63%). To a solution of 5-chloro-4-(4-chlorophenyl)-2-nitroaniline (12 g, 42.39 mmol) in ethanol (150 ml) was added hydrogen chloride (conc, 10 ml) to this was followed by the addition of Zn powder (16.6 g, 253.34 mmol) in portions at room temperature. The resulting solution was stirred for 4 h at 85° C. Then the resulting mixture was concentrated under vacuum, dissolved in water (200 ml) and extracted with ethyl acetate (3×200 ml). The combined organic layers was dried and concentrated under vacuum to give a residue, which was purified by a silica gel column with 10%˜20% ethyl acetate in petroleum ether to produce 4-chloro-5-(4-chlorophenyl)benzene-1,2-diamine as an off-white solid (8.7 g, 81%). Finally, a solution of 4-chloro-5-(4-chlorophenyl)benzene-1,2-diamine (7 g, 27.65 mmol) in heptafluorobutanoic acid (70 ml) was stirred for 1.5 h at 120° C. Then the mixture was poured into water (200 ml), adjusted pH value of the solution to 7 with aqueous sodium bicarbonate and extracted with ethyl acetate (3×200 ml). The combined organic layers was dried over anhydrous magnesium sulfate and concentrated under vacuum to give a residue, which was purified by a silica gel column with 5% ethyl acetate in petroleum ether to afford 5-chloro-6-(4-chlorophenyl)-2-(heptafluoropropyl)-1H-1,3-benzodiazole as an off-white solid (7.3977 g, 62%).

Provenance & Evidence