[3 + 2]-Cycloadditions of Azomethine Imines and Ynolates.

A novel [3 + 2]-cycloaddition between azomethine imines and lithium ynolates is described to synthesize bicyclic pyrazolidinones. These bicyclic pyrazolidinones are versatile intermediates to form β-amino acids and monocyclic pyrazolidinones. High diastereoselectivity and stereospecificity allow access to optically active products.