Hydroxy-Assisted Regio- and Stereoselective Synthesis of Functionalized 4-Methylenepyrrolidine Derivatives via Phosphine-Catalyzed [3 + 2] Cycloaddition of Allenoates with o-Hydroxyaryl Azomethine Ylides.

In this work, we present a new strategy for the chemo-, regio-, and stereoselective synthesis of functionalized pyrrolidine derivatives via a hydroxy-assisted phosphine-catalyzed reaction of allenoates or substituted allenoates with o-hydroxyaryl azomethine ylides that offers a wide variety of 4-methylenepyrrolidine derivatives in synthetically useful yields with high stereoselctivities under mild conditions. Remarkably, it is the first example of highly regio- and stereoselective phosphine-catalyzed [3 + 2] cycloaddition of allenoates with o-hydroxyaryl azomethine ylides.