Sulfuric Acid → 3-Methyl-2-(p-fluorophenyl)crotonic acid

Participants

Reaction Steps

A solution of 96.5 g of 2-(p-fluorophenyl)-3-hydroxy-3-methylbutyric acid in 200 ml of CH2Cl2 was cooled in an ice bath and then treated dropwise with 240 g of conc. sulphuric acid within 30 minutes, with the temperature being held at ≤20°. The CH2Cl2 was then removed to 20° on a rotary evaporator. The yellowish solution was stirred at 20° for a further 45 minutes and then poured into 1 kg of ice/water mixture while stirring well. The white precipitate was filtered off under suction, washed 3 times with 100 ml of water each time and twice with 100 ml of hexane each time and finally dried in a drying oven at 40° for 16 hours and at 100° for 2 hours. There were obtained 87.5 g of 2-(p-fluorophenyl)-3-methylcrotonic acid as a white powder of m.p. 124-126°; GC purity 99.9%; yield 95.6% based on p-fluorophenylacetic acid.

Provenance & Evidence