Isatin → Oxindole diamine

In a most preferred embodiment of the process of this invention, a solution of 0.05 equivalents of the isatin derivative, 0.06 mole equivalents of the carbanilide, and 0.30 moles of aluminum chloride in 200 ml. of nitrobenzene are maintained at 100° C for about 12 hours. The cooled solution is poured into one liter of ice water and 600 ml. of hexane to precipitate the product. After filtering, the product is suspended in 200 ml. of acetic acid, 5 ml. of water, and 20 ml. of sulfuric acid. This solution is refluxed for approximately 24 hours, cooled and filtered. This refluxing hydrolyzes the reacted anilide and yields the desired oxindole diamine derivative. The filtrate containing the oxindole diamine derivative is neutralized with sodium carbonate and the solution concentrated in vacuo and taken in about 300 ml. of boiling 1N hydrochloric acid. This solution is diluted in about 300 ml. of water, cooled to about 5° C, filtered, and made basic with ammonia to precipitate the product. The product is collected and may be recrystallized from a dioxane hexane solution to yield the pure oxindole diamine derivative.