1. Methyl (3E)-1-(2-chloroacetyl)-2,3-dihydro-3-(methoxyphenylmethylene)-2-oxo-1H-indole-6-carboxylate (390.0 g, 1.0109 mol) was suspended in methanol (1562 mL) and heated to reflux.
2. A solution of potassium hydroxide (23.35 g, 0.35 equiv) in methanol (196.8 mL) was added slowly and the reaction was stirred for 40 minutes at reflux.
3. After the reaction is complete, the reaction mixture is cooled to 5 °C and stirring is continued for 30 min to promote product precipitation.
4. The precipitated product was collected by filtration, washed with cold methanol and subsequently dried under vacuum to afford methyl (E)-3-(methoxy(phenyl)methylene)-2-oxo dihydroindole-6-carboxylate 292.2 g in 93.5% yield.
