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

Abstract

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.

Keywords: [3 + 2] cycloaddition, pyrrolidine, diastereoselectivity, silver acetate