5-Formylsalicylic acid

89-56-5

616-76-2

General procedure for the synthesis of 5-formyl-2-hydroxybenzoic acid from 5-methylsalicylic acid: a mixture of the substrate 5-methylsalicylic acid (1 mmol), cobalt salt (n1 mol%), and NaOH (n2 eq.) in ethylene glycol (5 mL) was reacted with oxygen (1 atm) with stirring for 8 hours at 80 °C. Upon completion of the reaction, hydrochloric acid (10 mL, 2%) and methyl tert-butyl ether (MTBE, 10 mL) were added sequentially to the reaction mixture. The organic layer was separated and the aqueous phase was further extracted with MTBE (10 mL x 2). The organic phases were combined, dried with anhydrous sodium sulfate and concentrated to give the residue. The residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate, 10/1) to afford the target product 5-formyl-2-hydroxybenzoic acid.