Research news, Jul. 8th, 2015
Synthesis and Mechanistic Study of Cyclic Oxoguanidines via Zn(OTf)2-Catalyzed Guanylation/Amidation from Readily Available Amino Acid Esters and Carbodiimides
Chi, Yue; Xu, Ling; Du, Shanshan; Yan, Haihan; Zhang, Wen-Xiong*; Xi, Zhenfeng
Chem. Eur. J. 2015, 21, 10369-10378. (Cover Paper)
Recent years have witnessed a rapid growth in the area of catalytic guanylation reaction of amines with carbodiimides (CGAC reaction). This is because CGAC reaction will provide a straightforward and atom-economical method to prepare substituted guanidines, which have unique value in pharmacy, organometallic and coordination chemistry, and organic synthesis. In this work, we will report a tandem Zn(OTf)2-catalyzed guanylation/amidation process from readily available amino acid ester hydrochlorides and carbodiimides to efficiently construct 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 to use the ammonium salt in guanylation reaction. Application of cyclic oxoguanidines is also explored to provide the conjugated heterocyclic compounds via oxidative C–N formation or aldol reaction. The reaction mechanism is well elucidated by the isolation and characterization of three important intermediates.