1-Isopropyl-2-oxo-1,2-dihydro-quinoline-3-carboxylic acid

2033-24-1

103718-15-6

158577-01-6

The general procedure for the synthesis of 1-isopropyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid from cyclic (sub)isopropyl malonate and 2-isopropylaminobenzaldehyde (CAS:103718-15-6) was as follows: Meldrum acid (2,2-dimethyl-[1,3]dioxane-4,6-dione, 166.9 g, 1.16 mol) was added to a stirring in a solution of 2-isopropylaminobenzaldehyde (105 g, 0.64 mol) in acetic acid. A mixed solution of ethylenediamine (43.0 mL, 0.64 mol) and acetic acid (73.6 mL, 1.29 mol) dissolved in methanol (1 L) was slowly added to the reaction system at 0°C. The reaction was continued at 0°C for a few minutes. The reaction mixture was continued to be stirred at 0 °C for 1 h, then brought to room temperature and stirred overnight. Upon completion of the reaction, the suspension was filtered and the resulting solid was washed with methanol and collected to afford the target product 1-isopropyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid (146 g, 98% yield) as an off-white solid. The structure of the product was confirmed by 1H NMR (CDCl3; 300 MHz): δ 1.72 (d, 6H, CH(CH3)2), 5.50 (bs, 1H, CH(CH3)2), 7.44 (t, 1H, ArH), 7.75-7.77 (m, 2H, ArH), 7.82 (d, 1H, ArH), 8.89 (s, 1H, CH).