Water → 5-Methoxyoxindole

A mixture of 5-methoxyisatin (5.0 g) and 30 ml of hydrazine hydrate was refluxed for 15 minutes. The reaction mixture was cooled to room temperature and 50 ml of water was added. The mixture was extracted 3 times with 25 ml of ethyl acetate, the organic layers combined, dried over anhydrous sodium sulfate and concentrated to give a yellow solid. The solid was stirred in ethyl acetate and 1.1 g of insoluble material removed by vacuum filtration and saved. This material proved to be 2-hydrazinocarbonylmethyl-4-anisidine. The filtrate was concentrated and chromatographed on silica gel eluting with ethyl acetate:hexane 1:1 to give 0.7 g of 5-methoxy-2-oxindole as a dirty yellow solid. The 1.1 g of 2-hydrazinocarbonylmethyl-4-anisidine was refluxed for 1 hour in 20 ml of 1 N sodium hydroxide. The mixture was cooled, acidified to pH 2 with concentrated hydrochloric acid and extracted 3 times with 25 ml of ethyl acetate. The organic extracts were combined, washed with brine, dried over anhydrous sodium sulfate and concentrated to give 0.8 g of 5-methoxy-2-oxindole as a dirty yellow solid. The combined yield was 1.5 g or 33%.