On the basis of a novel umpolung
strategy, an efficient l-amino acid ester-mediated in situ
reduction of 2-(2-oxoindolin-3-ylidene)malononitrile
and sequential nucleophilic addition/cyclization cascade reaction
is reported. Various densely substituted cyclopentene bispirooxindoles
and dihydrofuran bispirooxindoles with two quaternary spirocenters
were constructed in high yields (≤93%) with excellent diastereoselectivities
(>20:1 dr). The method has advantages of readily available starting
materials, mild reaction conditions, a one-pot process, a metal-free
biomimetic reducing agent, a wide substrate scope, and operational
simplicity (single filtration without column chromatography).