General procedure for the synthesis of 2-hydroxy-3,4-dimethoxybenzoic acid (3-B) from 2,3,4-trimethoxybenzoic acid (3-A):[04081]
1. 2,3,4-trimethoxybenzoic acid (3-A) (1.06 g, 5 mmol) was dissolved in dichloromethane (DCM) (30 mL) at -20 °C.
2. Boron tribromide (BBr3) (0.5 mL, 5.5 mmol) was slowly added to the above solution, keeping the reaction temperature at -20 °C.
3. The reaction mixture was stirred continuously for 30 minutes at -20°C. 4.
4. Upon completion of the reaction, sodium bicarbonate (NaHCO3) was added to quench the reaction.
5. 2N hydrochloric acid (HCl) (50mL) was added followed by extraction with dichloromethane (DCM).
6. The organic layer was separated and concentrated to give the target product 2-hydroxy-3,4-dimethoxybenzoic acid (3-B) (705 mg, 62.2% yield).
