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5-Nitrobenzoxazole is a useful reactant for copper-catalyzed direct carboxylation of C-H bonds in benzoxazoles and related compounds with carbon dioxide.

To a 50 mL single-necked round-bottomed flask equipped with a magnetic stirrer was added 2-amino-4-nitrophenol (5.0 mmol, 1.0 eq.) and triethyl orthoformate (60.0 mmol, 12.0 eq.). The reaction mixture was slowly heated to 150 °C and the reaction was stirred at this temperature for 6 hours. Upon completion of the reaction, the mixture was cooled to room temperature, followed by distillation under reduced pressure to remove the excess triethyl orthoformate and the resulting ethanol by-product. The crude product was purified by silica gel column chromatography to give the final target compound 5-nitrobenzoxazole (see Table S-2).

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