Kinetic and Structure-Activity Studies of the Triazolium Ion- Catalyzed Intramolecular Stetter Reaction

Abstract

Mechanistic studies of the triazolium ion-catalyzed intramolecular Stetter reaction using initial rates analysis in NEt3/NEt3 ⋅ HCl buffered methanol showed the reaction to be first-order in catalyst and zero-order in aldehyde over a broad range of aldehyde concentrations. The observed reaction rate is higher for catalysts bearing N-aryl substituents with electron-withdrawing groups. A concurrent, NHC-independent substrate isomerization was also observed and found to demonstrate a first-order dependence on aldehyde concentration. The reported data are consistent with deprotonation to form the Breslow intermediate being turnover-limiting in this process.