Silver trifluoroacetate (1.5 g) was added, over a period of 1 hour, to a stirred solution of 3-amino-4-chlorophenol (0.67 g) and 3-oxo-2-(4-pyrazol-1-ylbenzyl)thiobutyric acid S-tert-butyl ester (1.7 g) in 1,2-dimethoxyethane (10 mL) at room temperature, and the resulting mixture was stirred at room temperature for 4 hours. The mixture was concentrated under reduced pressure and the residue purified by column chromatography on silica gel, eluting with a mixture of dichloromethane and ethyl acetate (1:0 to 3:1 by volume) to afford title compound as a brown solid (1.1 g).
