Trifluoroacetic acid → 2-[4-(5-Chloro-2-cyanophenyl)-5-methoxy-2-oxopyridin-1(2H)-yl]butanoic acid

Participants

Reaction Steps

Under argon and at RT, 7.8 ml (101.8 mmol, 10 eq.) of trifluoroacetic acid were added to a solution of 4.1 g (10.2 mmol) of tert-butyl 2-[4-(5-chloro-2-cyanophenyl)-5-methoxy-2-oxopyridin-1(2H)-yl]butanoate (racemate) in 40 ml of dichloromethane, the mixture was stirred at RT for 1 h, a further 7.8 ml (101.8 mmol, 10 eq.) of trifluoroacetic acid were added, the mixture was stirred at RT for 1 h, a further 7.8 ml (101.8 mmol, 10 eq.) of trifluoroacetic acid were added and the mixture was stirred at RT for 1 h. Once the reaction had gone to completion, the reaction mixture was concentrated under reduced pressure and the residue was co-evaporated in each case three times with dichloromethane and once with toluene and dried under reduced pressure. The residue was taken up in 100 ml of ethyl acetate and washed repeatedly with a strongly diluted aqueous sodium bicarbonate solution (where the pH of the washing water should not exceed pH 3-4 since otherwise the product is well soluble in water). The organic phase was subsequently dried (sodium sulphate), filtered and concentrated under reduced pressure. The residue was triturated with methyl tert-butyl ether, filtered, washed twice with methyl tert-butyl ether and dried under reduced pressure. Yield: 2.9 g (83% of theory)

Provenance & Evidence