Methyl 3-isocyanatobenzoate → 3-[3-(2,2-Diethoxyethyl)-3-(4-isopropylphenyl)ureido]benzoic acid methyl ester

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Reaction Steps

A solution of N-(4-isopropylphenyl)-2,2-diethoxyethylamine (0.50 g, 2.0 mmol) prepared above and 3-carbomethoxyphenyl isocyanate (0.36 g, 2.05 mmol) in dry dichloromethane (10 mL) was stirred at room temperature overnight. The solution was then chromatographed (silica gel, hexanes:ethyl acetate, 8:2) to give the pure urea, 3-[3-(2,2-diethoxyethyl)-3-(4-isopropylphenyl)ureido]benzoic acid methyl ester as a colorless oil (0.73 g, 85.3%). MS (ES−) m/z: 427. This was then stirred with HCl (0.5 M, 50 mL) at 80° C. for 4 h. After cooling to room temperature, the white precipitate formed was collected and purified by chromatography (silica gel, dichloromethane:ethyl acetate, 9:1) to give pure methyl 3-[3-(4-isopropylphenyl)-2-oxo-2,3-dihydroimidazol-1-yl]benzoate as white solid [0.42 g, 73.7%, MS (ES+) m/z: 337]. The solid was then treated with boron tribromide in dichloromethane (1.0 M, 4.0 mL) at room temperature overnight. The volatiles were removed in vacuum and the residue was suspended in water and stirred for 30 min. The solid was collected by filtration and washed with water to furnish 3-[3-(4-isopropylphenyl)-2-oxo-2,3-dihydroimidazol-1-yl]benzoic acid (0.40 g, 100%). m.p. 283-285° C. 1H NMR (CDCl3, 300 MHz) δ (ppm) 1.24 (d, 6H), 2.84-3.00 (m, 1H), 6.69 (d, 1H), 6.74 (d, 1H), 7.26 (d, 2H), 7.45-7.54 (m, 3H), 7.91 (d, 1H), 8.02 (d, 1H), 8.12 (s, 1H). MS (ES−) m/z: 321.

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