Diaryldiacyloxyspirosulfuranes. Part 4. A kinetic study on the mechanism of hydrolysis

Abstract

Kinetics of the hydrolysis of diaryldiacyloxyspirosulfuranes leading to sulfoxides have been studied under pseudo-first-order conditions in dioxane–water mixtures. It has been found that high solvent polarities and ionic strengths increase the reaction rate. The reaction is also promoted by electron-donating substituents (ρ–0.52). Strong acids have a catalytic effect on the reaction in which case the substituent effect is more pronounced (ρ–1.55). In neutral medium the deuterium solvent isotope effect is k_H2O/k_D2O 1.66, while in acidic medium the ratio of catalytic constants is found to be 0.56. The rate of the reaction is greatly increased with the increasing size of the spiroring (from 5 to 7) in the sulfurane. Kinetic data suggest a dissociative reaction mechanism.