Over the past few decades a range of catalysts have been heterogenized onto solid supports (eg. SiO2, Al2O3, mol sieves, etc) and activated carbon is one of the most commonly employed. The Lipshutz group, has pioneered the use of metal based catalysts on carbon supports, for example, Ni/C, Ni/Cg, Cu/C, and mixed metal systems for a variety of reactions. In particular they have used copper nanoparticles supported within the pores of activated carbon to act as a source of copper(I) or (II) for a range of heterogeneously catalysed reactions.1 Our multi-disciplinary team are interested in the use of heterogeneous catalysts for a variety of applications and we have previously investigated the role of copper(II) compounds as pre-catalysts in copper alkyne azide cycloaddition (CuAAC) reactions.2 In those reactions the copper(II) species act as a catalyst in Glaser coupling reactions and is thereby reduced to copper(I) with concomitant formation a copper(I) acetylide which can subsequently catalyse the CuAAC reaction. Here we will show that the copper species responsible in “Cu/C” for reactions such as the CuAAC process has been identified as Gerhardite (Cu2(OH)3NO3) which is reduced under the reaction conditions to a copper(I) acetylide in order to carry out the triazole forming step. Additionally we have also observed an impurity phase in the materials prepared using the Darco-KB® activated carbon (also present in commercial “Cu/C"). This impurity was identified as Libethenite (Cu2(OH)PO4), and was shown to be inactive in the CuAAC reaction. Knowledge of the active catalyst should enable greater catalyst design for future applications in organic synthesis. References: 1. a) Lipshutz, B. H.; Taft, B. R. Angew. Chem. 2006, 118, 8415-8418; b) Lee, C.-T.; Huang, S.; Lipshutz, B. H. Adv. Syn. Catal. 2009, 351, 3139-3142. 2. a) Buckley, B. R.; Heaney H., in Topics in Heterocyclic Chemistry, Springer Berlin Heidelberg, Berlin, Heidelberg, 2012, pp. 1–29; b) Buckley, B. R.; Dann, S. E.; Heaney, H.; Stubbs, E. C. Eur. J. Org. Chem. 2010, 2011, 770–776; c) Buckley, B. R.; Dann, S. E.; Heaney, H. Chem. Eur. J. 2010, 16, 6278–6284; d) Buckley, B. R.; Dann, S. E.; Harris, D. P.; Heaney, H.; Stubbs, E. C. Chem. Commun. 2010, 46, 2274–2276.

Copper(I) ladder complexes and their use in organic synthesis

249th National Meeting (2015)

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