Nucleophilic Substitution Reactions of Aryl Dithiocyclohexanecarboxylates with Anilines in Acetonitrile

摘要

The mechanisms of the aminolysis of aryl esters and carbonates have been well established. These reactions are known to proceed stepwise through a zwitterionic tetrahedral intermediate, T~(±). The existence of the intermediate has been deduced from curved Bronsted-type plots. A biphasic dependence of the rate on the amine basicity showing a change of slope from a large (β_(nuc)≥ 0.8 ) to a small (β_(nuc) ≈ 0.1 - 0.3) value at pK_a~o, where the amine and leaving group have the same expulsion rates from T~(±), has been attributed to a change in the rate-limiting step from breakdown to formation of a tetrahedral intermediate as the basicity of the amine increases.