Phosphorus tribromide → 4-Chloroisatoic anhydride

Participants

Reaction Steps

A mixture of 2-benzyloxycarbonylamino-4-chlorobenzoic acid (564 g) and phosphorus tribromide (1.5 kg) in diethyl ether (9 l) was refluxed for 40 hours and allowed to stand at room temperature for 5 days. The resulting precipitates were collected by filtration and washed in turn with diethyl ether (5 l) and ethanol (3 l) to give 7-chloro-2H-3,1-benzoxazine-2,4(1H)-dione (335 g).

Provenance & Evidence