Hydrochloric Acid → 4-(4-fluorophenyl)dihydro-2H-pyran-2,6(3H)-dione

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Reaction Steps

To a solution of commercial 4-fluorobenzaldehyde (12.4 g) in ethyl acetoacetate (25.3 ml) piperidine (2 ml) was added with stirring at rt. The cloudy solution solidifies within 3 h. The yellow solid was crushed, slurried with ethanol (20 ml), collected by suction filtration, and washed with ethanol. After drying in vacuo 27 g of a faint yellowish solid (the bis-adduct of acetoacetate to the benzaldehyde) was isolated. The powdered solid was added in portions to 40% NaOH (400 g) with stirring. The resulting yellow slurry was stirred at reflux for 2 h. After cooling in an ice bath the mixture was acidified by portionwise addition of conc. HCl (370 ml) to give a colourless precipitate. The solid was collected by suction filtration and washed with water. After drying in vacuo 3-(4-fluorophenyl)glutaric acid (12.3 g) was obtained. The suspension of finely divided 3-(4-fluorophenyl)glutaric acid in acetyl chloride (20 ml) was heated to reflux with stirring for 1 h. After cooling to rt precipitation of the product is completed by addition of petrol ether (150 ml). The precipitate is isolated by suction filtration, washed with petrol ether, and dried in vacuo to give 3-(4-fluorophenyl)glutaric anhydride (9.4 g) as colourless crystals.

Provenance & Evidence