Recyclable olefin metathesis catalysts are of considerable interest to the synthetic community.[1] Despite the stability of commercially available, well-defined Ru-catalysts,[2] 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, previous work in our group has involved the synthesis of a recyclable olefin metathesis catalyst bearing a resin-bound peptidic-benzylidene ligand.[3] The combination of organometallic catalysis with solid-phase peptide synthesis (SPPS) chemistry provides the potential for localized catalyst optimization induced by neighbouring 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 sequences[4] and are effective ligands on transition metal complexes for the catalysis of a number of reactions.[5] Thus, the modular design of such supported constructs could provide access to a multifunctional catalyst system and facilitate sequential catalytic transformations without isolation of intermediates.
[1] a) G. C. Vougioukalakis and R. H. Grubbs, Chemical Reviews 2010, 110, 1746-1787; b) E. L. Dias, S. T. Nguyen and R. H. Grubbs, Journal of the American Chemical Society 1997, 119, 3887-3897.
[2] G. C. Vougioukalakis, Chemistry – A European Journal 2012, 18, 8868-8880.
[3] E. C. Gleeson, Z. J. Wang, W. R. Jackson and A. J. Robinson, J. Org. Chem. 2015, 80, 7205-7211.
[4] a) G. Xu and S. R. Gilbertson, Organic Letters 2005, 7, 4605-4608; b) J. Lemke and N. Metzler-Nolte, European Journal of Inorganic Chemistry 2008, 2008, 3359-3366.
[5] M. N. Hopkinson, C. Richter, M. Schedler and F. Glorius, Nature 2014, 510, 485-496.