Catalyst-Controlled [3 + 2] Annulation of Allenes with N-Monosubstituted Hydroxylamines for Regioselective Synthesis of Two Types of Isomeric Isoxazolidines

Catalyst-controlled regioselective [3 + 2] cascade annulation of allenes with N-monosubstituted hydroxylamines for precise construction of two types of isoxazolidine regiomers has been developed. The Ce(OTf)3 and MgCl2 can guide the nitrogen and oxygen atoms of N-hydroxyarylamides to both ends of the consecutive double bond of allenes, respectively, to afford two kinds of isomeric products. Notably and remarkably, the consecutive double bond of allenes served as a C3 synthon.