A Probe into Hydrolysis of Nitrile Moiety in 2-Amino-1-methyl-4-oxo-1,4-dihydroquinoline-3-carbonitrile

2-Amino-1-methyl-4-oxo-1,4-dihydroquinoline-3-carbonitrile 2 was prepared by the reaction of N-methylisatoic anhydride 1 with malononitrile via the ring-opening/ring closure pathway. The treatment of this compound with concentrated sulfuric acid at 100 °C gave a mixture of 2-amino-1-methyl-4- oxo-1,4-dihydroquinoline-3-carboxamide 3 and 2-amino-1-methyl-4-oxo-1,4- dihydroquinoline-3-carboxylic acid 4. The NMR analysis showed that the ratio of compound 3 to 4 in the mixture was one to two (1:2). When the later reaction was performed in the presence of NaOH in refluxing H2O:EtOH, the compounds 3 and 4 were not formed, but instead, ring cleavage occurred to give compound 2-(methylamino) benzoic acid 5 in high yield. Density functional theory (DFT) calculations at the M06-2X/6-311+G(d,p) level of theory was also used to compute the 1H NMR chemical shifts of the compounds 3 and 4. Good agreement between the DFT-calculated 1H NMR chemical shifts and corresponding experimental values confirmed the suitability of the optimized geometries for these compounds. Characteristics of the bonding interactions were explored using the atoms in molecules (AIM) analysis.