Guanidine derivatives are an important class of nitrogen-containing organic compounds, which are widely used in various pharmaceuticals, agrochemicals, sweeteners, explosives, and so on. Although classical methods for the synthesis of guanidines are established, there are still many fatal shortcomings which need to be resolved. In recent years, it has been gradually turned to the direct catalytic guanylation reaction of amines with carbodiimides. In this paper, the recent progress in transition-metal-cataly...