Reduction products of 3(2H)-cinnolinones

Reduction of 3(2H)-cinnolinone with zinc and ammonium hydroxide forms 1,4-dihydro-3(2H)-cinnolinone which rapidly rearranges to 1-amino-2-indolinone (1-aminooxindole) in acid solution. 1,4-Dihydro-2-methyl-3(2H)-cinnolinone is formed from 2-methyl-3(2H)-cinnolinone under the same conditions, but its rearrangement to 1-(N-methylamino)-2-indolinone (1-(N-methylamino)oxindole) in acid solution is much slower.