2,4-Difluorophenylacetic acid

23915-07-3

81228-09-3

(a) 25.7 g of 2,4-difluorobenzyl bromide was dissolved in 100 mL of tetrahydrofuran and slowly added dropwise over 0.5 h to a stirred suspension containing 3.0 g of magnesium chips and 30 mL of tetrahydrofuran. After the dropwise addition was completed, stirring of the reaction mixture was continued for 10 minutes. Subsequently, a steady stream of carbon dioxide was continuously passed into the resulting Grignard reagent for 1 hour. After completion of the reaction, the mixture was evaporated to dryness and the residue was partitioned with ether and dilute hydrochloric acid. The ether phase was separated and extracted with 2 N sodium hydroxide solution. The basic extract was acidified with concentrated hydrochloric acid and extracted with ether to give 5.1 g (24% yield) of crude 2,4-difluorophenylacetic acid. The crude product was dissolved directly in 25 mL of tetrahydrofuran without further purification and added slowly dropwise to a stirred mixture of 2.0 g of lithium aluminum hydride suspended in 100 mL of tetrahydrofuran.