41489-76-3

5-Formyl-2-hydroxybenzoic acid (500 g, 30 mmol, Sigma-Aldrich) was used as a raw material, mixed with concentrated H2SO4 (200 mL) and methanol (50 mL), and the reaction was stirred under reflux conditions for 24 hours. After completion of the reaction, the mixture was concentrated under reduced pressure to give 536 g of methyl 5-formyl-2-hydroxybenzoate (compound of formula FO) as a colorless oil in 99% yield.

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