Enantioselective Construction of Tetrahydroquinolin-5-one-Based Spirooxindole Scaffold via an Organocatalytic Asymmetric Multicomponent [3 + 3] Cyclization

The first catalytic enantioselective
construction of biologically
important tetrahydroquinolin-5-one-based spirooxindole has been developed
via a chiral cinchona alkaloid catalyzed asymmetric three-component
[3 + 3] cyclization of cyclic enaminone, isatin, and malononitrile,
which afforded a series of tetrahydroquinolin-5-one-based spirooxindoles
in high yields and with excellent enantioselectivities (up to 99%
yield, 97:3 er). This reaction could be applicable to large-scale
synthesis of enantioenriched tetrahydroquinolin-5-one-based spirooxindoles.
This synthetic methodology will not only provide a unique approach
for the construction of chiral tetrahydroquinolin-5-one-based spirooxindole
scaffolds but also increase our understanding of catalytic enantioselective
multicomponent reactions.