Copper-in-charcoal

Also, copper in charcoal (Cu/C) is found to be an active catalyst for effecting click reactions between organic azides and terminal aUcynes [84]. Rates of cycloaddition are dramatically increased when carried out in the presence of triethylamine or using microwave assistance. There is no sensitivity to air or moisture and the catalyst can be recycled several times without loss of activity or selectivity for the 1,4-adduct. 

Another approach to heterogeneous Cu-catalyzed diaryl ethers calls for use of copper-in-charcoal (Cu/C), preferably with a 10-15 wt% loading of the metal into the support. All diaryl ether formations using Cu/C (5 mol% vs. substrate) have been run at high temperatures (180-200 °C) using either conventional heating in a Teflon... 

Lipshutz, B. H. and Taft, B. R. 2006. Heterogeneous copper-in-charcoal-catalyzed click chemistry. Angew. Chem. Int. Ed. 45(48) 8235-8238. 

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