Studies on N-heterocyclic carbene-catalysed reactions

Abstract

We have explored both the carbon-carbon bond forming and carbon-carbon bond breaking processes promoted by Ν-heterocyclic carbenes. It has been shown for the first time that triazolium ion based-precatalysts promote the highly chemoselective crossed acyloin condensation reactions between aliphatic and ortho-substituted aromatic aldehydes. An o-bromine atom can serve as a temporary directing group to ensure high chemoselectivity (regardless of the nature of the other substituents on the aromatic ring) which then can be conveniently removed. Preliminary data indicates that highly enantioselective variants of the reaction are feasible using chiral triazolium ion based- precatalysts.