Evidence for a trigonal bipyramidal intermediate during nucleophilic substitution at a sulfonyl centre and for a sulfonylium cation in the acid catalysed reaction

Abstract

The rate of alkaline hydrolysis of a substituted β-sultam shows a dominant term second-order in hydroxide ion, clearly indicating the reversible formation of a monoanionic trigonal bipyramidal intermediate; substituent effects and kinetic parameters for the acid catalysed hydrolysis are indicative of the formation of a sulfonylium ion intermediate.