As in transition metal complexes, CN–R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of CN–R, primary amines (R′NH 2 ) and O 2 to give carbodiimides (R′–NCN–R). An analogous reaction of CO, RNH 2 , and O 2 gives isocyanates (R–NCO), which react with additional amine to give urea (RNH) 2 CO products. The gold-catalyzed reaction of CN–R with secondary amines (HNR′ 2 ) and O 2 gives mixed ureas RNH(CO)NR′ 2 . In another type of gold-catalyzed reaction, secondary amines HN(CH 2 R) 2 react with O 2 to undergo dehydrogenation to the imine product, RCHN(CH 2 R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.