Silver-Catalyzed [3+2] Cyclization of α-Imino Esters with Isocyanoacetate
Highly Diastereo- and Enantioselective Silver-Catalyzed Double [3+2] Cyclization of α-Imino Esters with Isocyanoacetate.
Angew. Chem. Int. Ed. 2014;
18 July 2014 (online)
The authors present a double [3+2] cyclization of α-amino esters with isocyanates to produce highly functionalized oxazole-imidazoles. Therefore, a silver oxide quinine derived amino phosphine ligand was used. For the pioneering work regarding isocyanates using a gold catalyst, see: Y. Ito, M. Sawamura, T. Hayashi J. Am. Chem. Soc. 1986, 108, 6405–6406.
Kinetic studies identified two cyclization processes to be step-wise. The intermediates, mono-[3+2] cyclization products, were isolated. The products can be hydrolyzed to yield functionalized α,β-diamino esters.