Regio- and Diastereoselective Construction of Spirocyclopenteneoxindoles through Phosphine-Catalyzed [3 + 2] Annulation of Methyleneindolinone with Alkynoate Derivatives

A phosphine-catalyzed [3 + 2] annulation of isatin-derived α,β-unsaturated ketones with alkynoates for the synthesis of cyclopentene spiro-oxindole skeletons has been developed. This reaction afforded the desired products in high to excellent yields (up to 99%) with high regioselectivity and moderate to high diastereoselectivities (up to 20:1). This strategy allows facile diastereoselective preparation of biologically important spiro-(cyclopentene) oxindoles containing three contiguous stereocenters, including the quaternary stereogenic center joining the two rings.