The synthesis of polysubstituted spirocyclopropyl oxindoles
using
a series of rare-earth metal (REM) salts is reported. REMs, in particular
Sc(OTf)3, allowed access to the target compounds by a multicomponent
reaction with high diastereoselectivity (≤94:6:0:0). Density
functional theory calculations on the model reaction are consistent
with the observed selectivity and revealed that the special coordinating
capabilities and the oxophilicity of the metal are key factors in
inducing the formation of one main diastereoisomer.