Ethyl isocyanate → 3-Ethyl-5,6-dimethoxyquinazolin-2,4(1H, 3H)-dione

Participants

Reaction Conditions

Reaction Steps

To ethyl isocyanate (1.65 ml, 1.48 g, 20.8 mM) in pyridine (9.2 ml) at 0° C. was added a cold solution of 2-amino-5,6-dimethoxybenzoic acid ethyl ester (3.0 g, 20.8 mM) in pyridine (16.7 ml). The solution was stirred at 0° C. for thirty minutes, then kept at room temperature for one hour. During this time, a precipitate formed. The mixture was concentrated to dryness to give an off-white solid. This was dissolved in 69.9 ml of 1N NaOH (4:1 MeOH-H2O) and heated at reflux for two hours. The solvent was removed in vacuo and the residue dissolved in H2O (150 ml). The mixture was taken to pH 6 with acetic acid and the resulting white solid filtered, washed with H2O (50 ml), and dried to give crude product as a white solid; 3.12 g; mp 208°-211° C. Recrystallization from isopropanol (100 ml) and drying afforded the title compound as a white solid; 2.09 g; mp 212°-214° C., total yield 80.5%, CF3COOH(TMS), 7.60 (d, 1H, J7,8 =9.0 Hz, 7-H), 7.13 (d, 1H, J8,7 =9.0 Hz, 8-H), 4.20 (9, 2H, J=6.0 Hz, 9-H), 4.19 (s, 3H, 5 or 6-OCH3), 4.05 (s, 3H, 5 or 6-OCH3), 1.40 (t, 3H, J=6.0 Hz, 10-H). M+ 250.

Provenance & Evidence