27383-86-4

273-53-0

124-38-9

74-88-4

27383-86-4

Catalyst (9.9 mg, 0.025 mmol, 5 mol%), potassium tert-butoxide (0.0672 g, 0.6 mmol) and DMF (3.0 mL) were added to the reaction flask under argon protection. Benzoxazole (50.7 μL, 0.5 mmol) was then added and carbon dioxide gas was passed under atmospheric pressure. The reaction mixture was stirred at 80 °C for 18 hours. After completion of the reaction, the temperature was lowered to 65 °C, iodomethane (93 μL, 1.5 mmol) was added, and stirring was continued at 65 °C for 1 h. The reaction was carried out with the aid of deionized water. At the end of the reaction, the reaction was quenched with deionized water and the reaction product was extracted with ethyl acetate. The yield of the product, methyl benzo[d]oxazole-2-carboxylate, was measured to be 95% by gas chromatography analysis. Further purification by column chromatography using ethyl acetate/petroleum ether (1:10, v/v) as the unfolding solvent gave 90% yield of the purified product.