General procedure for the synthesis of methyl 3-fluoro-2-hydroxy-benzoate from methyl 3-fluorobenzoate: Ru(MesCO2)(L) (p-cymene) [L is 2,2'-pyridine or 4,4'-dibromo bipyridine] (2.5 mol%), oxidizing agent (2.0 eq.) and methyl 3-fluorobenzoate (1.0 eq.) were added to a sealed tube. Subsequently, a solvent mixture of trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) in the ratio of 0.6 mL:0.4 was added. The reaction mixture was placed in an oil bath preheated to 110 °C with continuous stirring until the reaction was completed, and the reaction process was monitored by thin layer chromatography (TLC). After completion of the reaction, the reaction mixture was quenched by addition of ice water and extracted with dichloromethane. The organic layer was dried with anhydrous sodium sulfate (Na2SO4) and subsequently concentrated by rotary evaporation. Finally, the residue was purified by silica gel column chromatography to afford the target product methyl 3-fluoro-2-hydroxy-benzoate.
