Alkyl Aluminum-Catalyzed Addition of Amines to Carbodiimides: A Highly Efficient Route to Substituted Guanidines

The commercially readily available alkyl aluminums, such as AlMe3, AlEt3, and AlEt2Cl, can serve as excellent catalyst precursors for the catalytic addition of amines to carbodiimides, yielding quantitatively their corresponding trisubstituted guanidines. Aromatic C-X (X = F, Cl, Br, and I) bonds, nitro NO2, and terminal alkyne units can survive the reaction conditions. An aluminum guanidinate species has been characterized by single-crystal X-ray structural analysis and has been confirmed to be a true catalyst species.