Assembly of Indolenines, 3‑Amino Oxindoles, and Aldehydes into Indolenine-Substituted Spiro[pyrrolidin-2,3′-oxindoles] via 1,3-Dipolar Cycloaddition with Divergent Diastereoselectivities

A novel
one-pot 1,3-dipolar cycloaddition of indolenines, 3-aminooxindoles,
and aldehydes is reported. The reaction provides indolenine-substituted
spiro­[pyrrolidin-2,3′-oxindoles] containing four contiguous
stereogenic centers in high yields (up to 99%) and excellent diastereoselectivities
(up to >20:1 dr) under mild conditions. Remarkably, the inversion
of diastereoselectivity could be readily achieved through slightly
modifying the reaction conditions.