Diastereoselective Stereo-Divergent Synthesis of Spiroindolines via Ligand-Controlled Silver(I)-Catalyzed Asymmetric [3 + 2] cycloadditions

A series of spirocyclic pyrrolidine derivatives with quaternary stereocenters was constructed via asymmetric [3 + 2] cycloaddition reactions between imino esters and 2-oxindole. By ingenious use of ligands on the silver catalyst allows stereoselectivity to either endo-isomers (ee up to 98 %, yields up to 96 %) with (R, Rp)-Ph-Phosferrox or exo-isomers (ee up to 99 %, yields up to 87 %) with (R)-BINAP. This work is notable for its high yields, broad substrate adaptability and excellent enantioselectivity.