[Synthesis]
GENERAL METHOD: Acetylpropionic acid (10 mmol) was dissolved in acetic acid (30 mL) and phenylhydrazine (15 mmol) was added to the solution under stirring conditions. The reaction mixture was heated to reflux for 4 hours. Upon completion of the reaction, it was cooled to room temperature and the mixture was poured into water (200 mL) and the pH was adjusted to 5-6 with 30% sodium hydroxide solution.The precipitated solid was collected by filtration, recrystallized from ethanol and dried under vacuum to give 2-methylindole-3-acetic acid (2a).
2-Methylindole-3-acetic acid (2a): yellow solid, 78% yield, melting point 200-203 °C (literature value 199-200 °C); 1H NMR (500 MHz, CDCl3) δ: 2.31 (3H, s, CH3), 3.65 (2H, s, CH2), 6.97 (1H, t, J = 7.5 Hz, ArH), 7.12 ( 1H, t, J = 7.5 Hz, ArH), 7.23 (1H, d, J = 6.0 Hz, ArH), 7.33 (1H, d, J = 6.0 Hz, ArH), 10.83 (1H, s, COOH), 12.15 (1H, s, NH); IR (νmax, cm-1): 1504, 1518, 1565, 1624, 1769, 2935, 3001, 3535; HRMS m/z: 190.0824 (calculated value C11H11NO2 [M + H]+: 190.0823). |