Synthesis and Mechanistic Study of Cyclic Oxoguanidines via Zn(OTf)2‐Catalyzed Guanylation/Amidation from Readily Available Amino Acid Esters and Carbodiimides

The Zn(OTf)2-catalyzed guanylation/amidation from readily available amino acid esters and carbodiimides is achieved to provide efficiently various cyclic oxoguanidines, including 2-amino-1H-imidazol-5(4H)-ones and 2-aminoquinazolin-4(3H)-ones in medium-to-high yields. It is the first time that an ammonium salt has been used in a guanylation reaction. The application of cyclic oxoguanidines to provide the conjugated heterocyclic compounds via oxidative CN formation or aldol reaction is explored. The reaction mechanism is well elucidated by the isolation and characterization of three important intermediates.