Nitric Acid → 2-Chloro-4-fluoro-5-nitrobenzoic Acid

Participants

Reaction Conditions

Reaction Steps

First, 50 g (0.29 mol) of 2-chloro-4-fluorobenzoic acid was dissolved in 150 ml of hydrochloric acid at room temperature, to which a mixed acid of 28 ml (0.31 mol) of fuming nitric acid and 56 ml of concentrated sulfuric acid was added dropwise at 35° to 45° C. Then, the solution was stirred at 40° C. for 1 hour and poured into 250 ml of ice-water. The precipitated crystals were collected by filtration and recrystallized from a mixed solution of hexane and ethyl acetate, which afforded 55 g (0.25 mol) of 2-chloro-4-fluoro-5-nitrobenzoic acid. Then, 55 g (0.25 mol) of 2-chloro-4-fluoro-5-nitrobenzoic acid was dissolved in 50 ml of ethyl acetate, to which 33 g (0.28 mol) of thionyl chloride was added, and the mixture was heated under reflux for 3 hours and then allowed to stand for cooling to room temperature. Then, 20 ml of ethanol and 30 g of triethylamine were added under ice cooling, and the mixture was stirred at room temperature for 2 hours. The solvent was distilled out, and the residue was purified by silica gel chromatography, which afforded 57 g (0.23 mol) of ethyl 2-chloro-4-fluoro-5-nitrobenzoate.

Provenance & Evidence