Flash Photolytic Generation of a Dithio Carbocation from 1,3-Dithiolane Derivatives and Its Reaction with Nucleophiles

Abstract 2-Phenyl-1,3-dithiolanylium ion is generated as a transient intermediate by flash photolysis of aqueous ethanol and acetonitrile solutions of 2-methoxy and other dithiolane derivatives with a xenon lamp. Decay of the absorption (342 nm) of the cation generated from the 2-methoxy derivative follows pseudo-first-order kinetics. Rate constants were measured for the reaction of the cation with various nucleophiles. Decay curves for the cations generated from 2-arylthio and 2-sulfonyl derivatives are steep and show second-order kinetic character owing to the recombination of the cation with the counter anions (thiolate and sulfinate).