2-(4'-Fluorophenylthio)-4-carboxyphenylacetic acid → 10-Oxo-8-fluoro-dibenzo[b,f]thiepin-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Heat to 120° C. with stirring 450 gm of commercial polyphosphoric acid and add 35.9 gm of crude diacid from Step A. Stir under a nitrogen atmosphere at 120° C. for 90 minutes. Cool and slowly add 1.5 liters of ice and water. Separate the solids by filtration. Stir the residue in 500 ml of refluxing ethyl acetate for 90 minutes and filter while hot to obtain a first crop. Concentrate the filtrate until solids appear, allow to stand overnight and filter to obtain a second crop. Combine the crops (18.26 gm-54% crude) which may be used in the next step as such. Purify by boiling in ethyl acetate for 15 minutes, hold at room temperature overnight and filter (m.p. 289°-291° C.)

Provenance & Evidence