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Catalyst (9.9 mg, 0.025 mmol, 5 mol%), potassium tert-butoxide (0.0672 g, 0.6 mmol), DMF (3.0 mL), and 5-chlorobenzoxazole (76.79 mg, 0.5 mmol) were added to the reaction flask under argon protection. The reaction mixture was stirred at 80 °C for 18 h under carbon dioxide atmosphere at atmospheric pressure. Upon completion of the reaction, the system was cooled to 65 °C, followed by the addition of iodomethane (93 μL, 1.5 mmol) and continued stirring at 65 °C for 1 hour. At the end of the reaction, the system was cooled to room temperature and the reaction was quenched with deionized water. The reaction mixture was extracted with ethyl acetate, and the organic phases were combined and purified by column chromatography (Expanding agent: ethyl acetate/petroleum ether, 1:10, v/v). The target product methyl 5-chlorobenzoxazole-2-carboxylate was finally obtained in 82% yield.

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