[Synthesis]
General procedure for the synthesis of ethyl 2-quinolinecarboxylate (6) from quinaldic acid (5) (2.0 g, 11.55 mmol) and ethyl iodide: quinaldic acid (5), dry K2CO3 (3.19 g, 23.10 mmol) and anhydrous DMF (24 mL) were mixed and stirred under argon protection until completely dissolved. Ethyl iodide (2.77 mL, 34.65 mmol) was then added and the reaction was stirred at 60 °C for 18 hours. After completion of the reaction, 30% cooled aqueous HCl solution (30 mL) was added for acidification. The reaction mixture was neutralized with saturated NaHCO3 solution until gas production stopped. The reaction mixture was extracted with ethyl acetate (3 x 60 mL). The organic phases were combined, washed with brine (30 mL), dried over anhydrous Na2SO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with hexane/ethyl acetate (8:2) as eluent to give ethyl 2-quinolinecarboxylate (6) as a translucent oil in quantitative yield. the TLC Rf value was 0.51 (hexane/ethyl acetate 7:3). νmax/cm-1 by IR (pure): 3061, 2982, 2938, 2904, 1714, 1463. 1368, 1312, 1133, 1103, 1016, 844, 774.1H NMR (400MHz, CDCl3) δ 7.96-7.94 (m, 1H), 7.85-7.81 (m, 1H), 7.76-7.73 (m, 1H), 7.42-7.36 (m, 2H), 7.22-7.18 (m, 1H), 4.22-7.18 (m, 1H). 1H), 4.22-4.17 (m, 2H), 1.14-1.10 (m, 3H).13C NMR (100 MHz, CDCl3) δ 164.9, 147.9, 147.2, 136.8, 130.3, 129.8, 128.9, 128.1, 127.2, 120.6, 61.7, 14.1. HRMS (ESI+) calculated value C12H11NO2 [M+H]+ 202.0868, measured value 202.0868. |