Recyclable olefin metathesis catalysts are of considerable interest to the synthetic community.1-2 Despite the stability of commercially available, well-defined Ru-catalysts,3 their retrieval from reaction mixtures remains challenging. Catalyst immobilization on heterogeneous solid support structures facilitates recyclability via simple filtration methods and is therefore a highly attractive solution. Towards this end, we have designed and synthesized a recyclable olefin metathesis catalyst bearing a resin-bound peptidic-benzylidene ligand.4 The combination of organometallic catalysis with solid-phase peptide synthesis (SPPS) chemistry provides the potential for localized catalyst optimization induced by neighboring amino acids. As an extension to this finding, the presented study utilizes a similar strategy for efficient catalyst recyclability, albeit with immobilization via the non-labile NHC ligand. Latent NHC precursors can be readily incorporated into peptide sequences5-6 and are effective ligands on transition metal complexes for the catalysis of a number of reactions.7 Thus, the modular design of such supported constructs provides access to a multifunctional catalyst system and facilitate sequential catalytic transformations without isolation of intermediates.
1 Vougioukalakis, G. C.; Grubbs, R. H., Chem. Rev. 2010, 110, 1746.
2 Dias, E. L.; Nguyen, S. T.; Grubbs, R. H., J. Am. Chem. Soc. 1997, 119, 3887.
3 Vougioukalakis, G. C., Chemistry – A European Journal 2012, 18, 8868.
4 Gleeson, E. C.; Wang, Z. J.; Jackson, W. R.; Robinson, A. J., J. Org. Chem. 2015, 80, 7205.
5 Xu, G.; Gilbertson, S. R., Org. Lett. 2005, 7, 4605.
6 Lemke, J.; Metzler-Nolte, N., Eur. J. Inorg. Chem. 2008, 2008, 3359.
7 Hopkinson, M. N.; Richter, C.; Schedler, M.; Glorius, F., Nature 2014, 510, 485.