Catalytic guanylation of aliphatic, aromatic, heterocyclic primary and secondary amines using nanocrystalline zinc(II) oxide

Nanocrystalline ZnO was found to be a highly efficient heterogeneous catalyst for the guanylation of amines with various carbodiimides to afford N,N′,N″-trisubstituted guanidines in excellent yields. Structurally divergent aliphatic, aromatic, heterocyclic primary and secondary amines were converted to the corresponding N,N′,N″-trisubstituted guanidines using optimal conditions. The catalyst was easy to handle even under atmospheric conditions and can be easily recovered by centrifugation and reused for five cycles with consistent activity.