Example 1 Synthesis of tert-butyl 4-formylbenzoate: To a 250 mL round bottom flask were sequentially added tert-butyl para-formylbenzoate (5.0 g, 33 mmol), di-tert-butyl dicarbonate (14.54 g, 66.6 mmol), 4-dimethylaminopyridine (0.814 g, 6.66 mmol) and tetrahydrofuran (100 mL). The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure to give the crude product. Ethyl acetate (150 mL) was added to the residue and washed with saturated sodium bicarbonate solution (25 mL) and water (25 mL). After partitioning, the aqueous phase was back-extracted with ethyl acetate (2 x 100 mL). The organic phases were combined, washed with saturated saline (50 mL), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. Finally, it was purified by fast column chromatography (eluent: petroleum ether to 10% ethyl acetate-petroleum ether gradient elution) to give tert-butyl 4-formylbenzoate (1.90 g, 28% yield) as a white solid. The product was characterized by 1H NMR (CDCl3, 400 MHz): δ 10.10 (s, 1H), 8.14 (d, J = 8.3 Hz, 2H), 7.93 (d, J = 8.5 Hz, 2H), 1.61 (s, 9H).
