3-Methyl-2-furoic acid

6141-57-7

4412-96-8

The general procedure for the synthesis of 3-methyl-2-furoic acid from 3-methyl-2-furan methyl ester was as follows: 3-methyl-2-furoic acid methyl ester (2.0 g, 14.3 mmol) was mixed with 30% aqueous sodium hydroxide solution (3.8 mL, 28.5 mmol) and methanol (3.6 mL, 88.8 mmol) and the reaction was carried out under refluxing conditions for 3.5 hours. After completion of the reaction, the solvent was removed by rotary evaporation. The crude product was dissolved in water (10 mL) and the pH was adjusted with concentrated hydrochloric acid to 1. Subsequently, extraction was carried out with ether (4 x 3 mL), the organic phases were combined and dried with anhydrous magnesium sulfate. After filtration, the filtrate was concentrated to dryness to give 3-methyl-2-furoic acid (1.7 g, 13.6 mmol, 95% yield). The melting point of the product was 135 °C (ether). 1H NMR (400 MHz, CDCl3, δ, ppm): 2.40 (3H, s, CH3), 6.41 (1H, d, J4,5 = 1.6 Hz, H4), 7.52 (1H, d, J5,4 = 1.6 Hz, H5). 13C NMR (100 MHz, CDCl3, δ, ppm): 170.2 (COO), 150.1 (C5), 139.9 (C2), 125.3 (C3), 112.0 (C4), 13.3 (Me). IR (membrane, ν, cm-1): 1102 (st.CO), 1136 (st.CO), 1189 (st.CO), 1488 (def.CH), 1599 (st.C=C Ar.), 1670 (st.C=O), 2200-3200 (st.OH). MS (EI, m/z, %): 126.03 (M+, 100); 127.03 (7); 109.03 (M+-OH, 20); 81.03 (40, M+-CHO2). Elemental Analysis (EA). Calculated value C6H6O3: C (57.14), H (4.80). Measured value: C (57.11), H (4.83).