Phosgene → N-[2-(2,3-dihydro-1H-indol-1-yl)-5-fluorophenyl]-4-methyl-1-piperazine carboxamide maleate

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To a stirred solution under nitrogen, of 50.2 g (0.22 mole) of 1-(3-amino-4-fluorophenyl)indoline of Example 2b, and 66.7 g (0.66 mole) of triethylamine in 900 ml of chloroform was added 65.7 g (0.33 mole) of 4-methyl-1-piperazine carbonyl chloride hydrochloride in portions over 5 minutes. The reaction was refluxed for 6 hours when an additional 22.2 g (0.22 mole) of triethylamine and 43.8 g (0.22 mole) of the carbonyl chloride reagent were added. After refluxing overnight (about 16 hours) the reaction was cooled, treated with 1 liter of water and stirred vigorously for 15 minutes. The layers were separated, and the organic phase was washed twice with water, dried over Na2SO4, and concentrated in vacuo to leave 50 g. This material was dissolved in 150 ml of toluene and absorbed on a tall chromatography column containing 1.5 kg of silica gel made up in toluene. Elution first with toluene, then with increasing percentages (25% per step) of dichloromethane (CH2Cl2) in toluene, followed by 100% CH2Cl2, and finally by increasing percentages of methanol (1% per step) in CH2Cl2 brought forth 27.3 g (35% overall yield) of pure urea. 12.7 g (0.036 mole) was converted to the maleate salt in the following manner. The urea was dissolved in 30 ml of ethanol and treated with a solution of 4.64 g (0.04 mole) of maleic acid in 20 ml of warm ethanol. The salt crystals were collected, and found to weigh 13.2 g (78%). Two recrystallizations from ethanol furnished N-[2-(2,3-dihydro-1H-indol-1-yl)-5-fluorophenyl]-4-methyl-1-piperazine carboxamide maleate, m.p. 117°-120° C.

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