Theoretical Study of the Mechanism for the Markovnikov Addition of Imidazole to Vinyl Acetate Catalyzed by the Ionic Liquid bmImOH.

By performing density functional theory calculations, we have studied the Markovnikov addition of imidazole to vinyl acetate catalyzed by 1-butyl-3-methylimidazolium hydroxide, bmImOH, a novel basic ionic liquid. The purpose is to show the detailed reaction mechanism, to rationalize the experimental observations, and in particular to better understand the role of bmImOH played in the reaction as a catalyst. Two different reaction pathways (stepwise and concerted) have been charactered and analyzed in detail. It was found that both the cation and anion of bmImOH play important roles in the Markovnikov addition, which decrease the barrier and increase the selectivity of Markovnikov addition. The present results rationalize the early experimental findings well and provide a prototype for theoretically understanding the Markovnikov addition catalyzed by room-temperature ionic liquids. [ABSTRACT FROM AUTHOR]