Basic hydrolysis of quinolinyl N,N‐dimethylcarbamates: a two‐step mechanism
Abstract
The reactivity of 6‐quinolinyl and 8‐quinolinyl N,N‐dimethylcarbamates was examined in several aqueous basic media. A quadratic dependence was observed for the constant rates upon hydroxide concentration for both compounds, which is a typical behaviour of a mechanism involving a base‐catalysed deprotonation of the tetrahedral intermediate with the formation of a dianion at high concentrations of hydroxide ion, while at lower concentrations a specific‐base catalysed addition–elimination mechanism seems to be predominant. The reactivity of 8‐quinolinyl N,N‐dimethylcarbamate was also studied in several amine buffers, showing specific base catalysis. The reactivity of 6‐quinolinyl N,N‐dimethylcarbamate was studied in H2O and in D2O and the solvent isotope effect supports the proposal of a mechanism involving a specific‐base hydrolysis. All results confirm the existence of a mechanism with a rate determining step involving the substrate anion and a second mole of hydroxide ion. This mechanism was so far unknown for carbamate reactivity, being only known to occur with amides. Copyright © 2011 John Wiley & Sons, Ltd.
