PREPARATION OF 4-FLUOROPHENOL AND 4-FLUOROBENZOIC ACID BY THE BAEYER-VILLIGER REACTION

The possibility of preparing 4-fluorophenol or 4-fluorobenzoic acid vi a the Baeyer-Villiger reaction starting from unsymmetrical fluoroaryl ketones is discussed. Several unsymmetrical 4-fluorobenzophenones havi ng different substituents in the fluorine-free aryl group were prepare d and converted to esters by treatment with peracetic acid. The electr ophilicity of the substituents influenced the molecular structure of t he ester formed as a result of a carbon-to-oxygen migration, and hence 4-fluorophenol or 4-fluorobenzoic acid formation. Electron-withdrawin g substituents favoured the formation of 4-fluorophenol in good yield, while electron-donating substituents formed 4-fluorobenzoic acid pref erentially.