To a stirred suspension of 4.13 g of 5-fluoroisatin in 40 ml of water was added a solution of 5.62 g of sodium hydroxide in 20 ml of water. This mixture was heated to 85°-90° C. and a warm solution of 9.3 g of 2-amino-1 (2'-fluoro[1,1'-biphenyl]-4-yl)ethanone, hydrochloride in 140 ml of ethanol:water (1:1) and 30 ml of tetrahydrofuran was added dropwise over 2 hours. This mixture was stirred at reflux for 2 hours, then the ethanol was distilled off. The reaction was filtered and the filtrate acidified to pH 4-5 with acetic acid. The resulting solid was collected, washed with water and crystallized from 400 ml of hot ethanol, giving 7.45 g of the desired product as a yellow solid, mp 248°-250° C.
