1-alkyl-1,4-dihydro-4-imino-3-quinolinecarboxylates. Part 2.1 Hydrolysis and rearrangement products

The title compounds, while relatively stable in acid solution, undergo basic hydrolysis to afford the corresponding 1-alkyl-4-oxo-3-quinolinecarboxylic acids. Preferential removal of the 4-imino function may be achieved in dilute alkali. Neutral (H₂O) hydrolysis yields a 4-oxo-3-quinolinecarboxylic ester together with an unusual water-soluble, dipolar 4-imino-3- quinolinecarboxylic acid. Some properties and reactions of the latter are described. Certain of the title imino esters, specifically those bearing electron-withdrawing substituents in the carbocyclic framework, undergo a novel rearrangement in basic medium to afford 2(1H)-quinolone derivatives; in other instances the outcome is a 2-acetimidoyl-N-alkylaniline derivative. A tentative pathway for the D₂O-exchange, undergone at room temperature by the 2-methyl protons of the title imino esters and related compounds, is presented.