Hydrazine hydrate (1:1) → 4-Methoxy-2-indolinone

Participants

Reaction Conditions

Reaction Steps

Hydrazine monohydrate (265 mL, 5.46 mol) is added to a flask containing 4-methoxyisatin (484.26 g, 2.73 mol), sodium acetate (22.31 g, 0.27 mol) and dimethylformamide (2.4 L). The temperature rose from 19.2° C. to 31.9° C. within 5 minutes, and when the exotherm had ceased the solution is further heated to 110° C. over 40 minutes. Vigorous off-gassing is observed, and the temperature rose above the set point slowly. After 30 minutes the temperature stabilized at 110° C. and the gas evolution tapered off. The solution is kept at 110° C. for 40.5 hours at which point the heating mantle is removed and the solution is allowed to cool. At 40° C., the solution is seeded with 100 mg of 4-methoxyindole, and the contents are cooled to 17° C. with an ice bath. The resulting mixture is poured into water (6.2 L) which had been pre-cooled to 6° C. The flask is rinsed with water (600 mL), and the thick slurry is cooled to 4° C. before being filtered through polypropylene. The filter cake is rinsed with water (3×1.5 L) and the solid is dried in a 50° C. vacuum oven to provide 353 g of 4-methoxyindolin-2-one.

Provenance & Evidence