Synthesis
General procedure for the synthesis of 3-bromo-5-ethoxy-4-hydroxybenzaldehyde from the compound (CAS: 1567388-59-3): a mixture of substrate 1a (1 mmol), cobalt salt (n1 mol%), and NaOH (n2 equivalents) in ethylene glycol (EG, 5 mL) was stirred and reacted for 8 hr at 80 °C under oxygen (1 atm) atmosphere. Upon completion of the reaction, hydrochloric acid (10 mL, 2%) and methyl tert-butyl ether (MTBE, 10 mL) were sequentially added to the reaction mixture. The organic layer was separated and the aqueous phase was further extracted with MTBE (10 mL x 2). All organic phases were combined, dried with anhydrous sodium sulfate and concentrated to obtain the residue. The residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate, 10:1) to afford the target product 3-bromo-5-ethoxy-4-hydroxybenzaldehyde (2a).
References
[1] Tetrahedron Letters, 2014, vol. 55, # 8, p. 1406 - 1411
