Copper-Catalyzed Asymmetric 1,3-Dipolar Cycloaddition of Imino Esters to Unsaturated Sultones.

The asymmetric 1,3-dipolar cycloaddition of glycine imino esters to 1-propene-1,3-sultone or sulfocoumarins is described. The reaction was efficiently catalyzed by Cu(MeCN)4BF4/DTBM-Segphos or Cu(MeCN)4BF4/tBu-FcPhox at room temperature to afford fused pyrrolidines as single regioisomers with excellent diastereoselectivity and enantioselectivity. The broad substrate scope of this reaction provides convenient access to structurally diverse multisubstituted pyrrolidines in an optically pure fashion.