Formaldehyde → 4-Fluoro-2-hydroxybenzaldehyde

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Magnesium methoxide (13 g, 150 mmol, 6% in methanol) in methanol (50 mL) was treated with 3-fluorophenol (22.4 g, 200 mmol). The solution was heated to reflux and approximately half the methanol distilled off. Toluene (300 mL) was added and the reaction mixture was heated with azeotropic removal of solvent until the temperature of the distillate reached 95° C. A slurry of paraformaldehyde powder (22 g, 720 mmol) in toluene (20 mL) was added in small portions over 1 hour to the reaction with concurrent removal of volatile materials by distillation. The mixture was stirred was at 95° C. for 1 hour, cooled to 25° C., quenched by slow addition to 10% sulfuric acid and stirred at 30-40° C. for 2 hours. The layers were separated and the aqueous portion extracted with toluene (2×50 mL). The organic layers were combined, washed with 10% sulfuric acid, washed with water, dried with sodium sulfate, filtered and the solvent was evaporated. The resulting yellow oil was purified by flash chromatography over silica gel eluting with hexane:ethyl acetate (5:1) to provide 9.7 g of the title compound as a white solid.

Herkunft & Nachweise