Umpolung Strategy for the Synthesis of Chiral Dispiro[2-amino-4,5-dihydrofuran-3-carbonitrile]bisoxindoles

Based
on a novel umpolung strategy, an efficient and highly enantioselective
cascade aldol/cyclization/tautomerization of the 2-(2-oxoindolin-3-yl)­malononitrile
to active carbonyl compounds with excellent diastereo- and enantioselectivity
has been developed. Also, various enantio-enriched multifunctional
dispiro­[2-amino-4,5-dihydrofuran-3-carbonitrile]­bisoxindoles with
adjacent spiro-stereocenters were conveniently obtained by this novel
methodology. Also, the dispiro­[2-amino-4,5-dihydrofuran-3-carbonitrile]­bisoxindoles
were easily transformed into structurally complex molecules without
any effect on the diastereo- and enantioselectivity.