To a mixture of 217 g of 4-carboxybutyl-triphenylphosphonium bromide and 154 g of potassium tert.butoxide in 1.8 liters of tetrahydrofuran are added, at -25° C., 94 g of 3-acetylaminophenyl-3-pyridyl ketone. After 2 hours stirring at ambient temperature the reaction mixture is combined with 200 ml of water and then substantially evaporated down. The residue is taken up in 500 ml of water and washed with ethyl acetate. The aqueous phase is then neutralised by the addition of citric acid and extracted with ethyl acetate. The organic phase is evaporated down and the residue is recrystallised from ethyl acetate/acetone.
