N-Heterocyclic carbenes (NHC) are useful both as ligands and organocatalysts. A variety of strategies to recycle NHC-ligated catalysts have been developed both by our group and others.  However, problems remain in recycling NHCs not complexed to transition metals because of their air and moisture sensitivity. This report will describe work in our group that uses polyisobutylene (PIB) as a phase anchor to recycle NHCs.  Two approaches will be discussed.  The first emphasizes using PIB-modified aryl groups of N-substituents on the NHCs.  The second strategy uses PIB on ancillary groups of known aryl isothiocyanate-NHC adducts whose use as latent NHC catalysts was recently reported. In either case, PIB was used as a heptane-phase selective support to insure hydrocarbon phase selective solubility of the NHC catalysts after a reaction.  The activity of PIB-bound NHCs in both cyclization and polymerization reactions will be discussed using phenyl isocyanate trimerization and lactide polymerization as examples.

Polyisobutylene-supported <i>N</i>-heterocyclic carbenes as recyclable and reusable catalysts

243rd National Meeting (2012)

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Polyisobutylene-supported N-heterocyclic carbenes as recyclable and reusable catalysts