584-87-2

100-97-0

99-96-7

584-87-2

GENERAL METHOD: To a solution of trifluoroacetic acid (5 mL) of the substrate (1a-1q, 0.15 mmol) was sequentially added hexamethylenetetramine (urotropine, 0.3 mmol) and cuprous oxide (0.15 mmol). The reaction mixture was heated to reflux for 5 h and subsequently cooled to room temperature. A 3 N hydrochloric acid solution (5 mL) was slowly added to the reaction system and stirring was continued for 1 hour. Upon completion of the reaction, the mixture was concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography (200-300 mesh) to afford the target product 3-formyl-4-hydroxybenzoic acid.