At room temperature, 6-methylbenzofuran-2-carboxylic acid (11 g, 62.4 mmol) was dissolved in a solvent mixture of toluene (468 mL) and methanol (156 mL). 2N trimethylsilyl diazomethane (TMS-CHN2, 46.8 mL, 94 mmol) was slowly added dropwise to the above solution. The reaction mixture was stirred continuously for 6 hours at room temperature. Upon completion of the reaction, the reaction was quenched by dropwise addition of acetic acid at 0 °C until the yellow color of the solution disappeared and no gas escaped. Subsequently, the reaction mixture was concentrated under reduced pressure to remove the solvent and the residue was purified by rapid chromatography on silica gel with a gradient of 100% heptane to 10% ethyl acetate/90% heptane as eluent to yield methyl 6-methylbenzofuran-2-carboxylate (7.96 g). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 2.46 (s, 3H), 3.88 (s, 3H), 7.20 (dd, J=8.3,1.0 Hz, 1H), 7.53 (s, 1H), 7.67 (d, J=8.1 Hz, 1H), 7.71 (d, J=1.0 Hz, 1H).
