Cu/Fe-catalyzed cyanation of aryl iodides using urea

Abstract

The fertilizer urea can be treated as a cheap and available raw material for chemical production. However, due to the high thermos-stability, its catalytic utilization involving C–N or C–O bond cleavage is highly challenging. The catalytic transformation of its C–N moiety into a nitrile group is attractive, albeit unknown for organic synthesis. Herein, a ligand-free copper-catalyzed cyanation of aryl iodides using urea is described for the first time, which has the potential to be applied as an alternative practical cyanation method. Being co-promoted by catalytic amounts of CuO and Fe(II) salts, various aryl iodides were transformed smoothly and the corresponding aryl nitriles including 13C/15N-labeled ones were obtained in moderate to excellent yields. Mechanistic studies support the formation of silyl isocyanates inserting into a copper-carbon bond and the subsequent 1,3-silyl N-to-O migration as the crucial driving force to form C–N triple bonds.