Enantio‐ and Diastereoselective Synthesis of β<i>‐</i>Aryl<i>‐</i>β<i>‐</i>pyrazolyl α‐Amino Acid Esters via Copper‐Catalyzed Reaction of Azomethine Ylides with Benzylidenepyrazolones

Abstract

Abstract A fully stereoselective synthesis of unnatural chiral β‐aryl‐β ‐ pyrazolyl α‐amino acid esters via copper‐catalyzed addition reactions of azomethine ylides with benzylidenepyrazolones bearing two contiguous stereogenic centers was developed. A 1 H ‐pyrazol‐5‐ol was introduced by the aromatization of 3 H ‐pyrazol‐3‐one in the reaction. The transformation operated at room temperature and afforded β‐1 H ‐pyrazol‐5‐ol‐α‐amino esters in high yields with good to excellent levels of diastereo‐ and enantioselectivity. magnified image