Nucleophilic addition of hydrazines and thiosemicarbazide to the 2-(2-oxoindolin-3-ylidene) malononitrile derivatives
1, followed by elimination of malononitrile, lead to 3-(2-arylhydrazono)indolin-2-ones and 1-(2-oxoindolin-3-
ylidene)thiosemicarbzides respectively. Also the reaction of compounds 1 with 4-substituted thiosemicarbazides, followed
by elimination and cyclization, afforded spiro(indolone-3,2´-[1,3,4]thiadiazol)-2-ones. So all of these nucleophilic reactions
with isatin and substituted isatins released the same products.