Base-free Knoevenagel condensation catalyzed by copper metal surfacesElectronic supplementary information (ESI) available: Experimental procedures, supplementary kinetic figures, SEM micrographs, X-ray crystallographic analysis and 1H and 13C NMR spectra. See DOI: 10.1039/c5cc02541a

For the first time Knoevenagel condensation has been catalyzed by elemental copper with unexpected activity and excellent isolated yields. Inexpensive, widely available copper powder was used to catalyze the condensation of cyanoacetate and benzaldehyde under mild conditions. To ensure general applicability, a wide variety of different substrates was successfully reacted. Commercially available dendritic copper powder catalyses Knoevenagel condensation under mild conditions with high isolated yields obtained by filtration of Cu and subsequent recrystallization.