Substrate-Controlled Diastereo- and Enantiodivergent Synthesis of Bis-Spirocyclopropyloxindoles from Available Isatin as a Single Starting Material

The first diastereo- and enantiodivergent asymmetric
synthesis
of new bis-spirocyclopropyloxindole scaffolds has been accomplished
from the readily available isatin as a single starting material. Four rel-(1R,2R,3R), rel-(1S,2S,3R), rel-(1R,2R,3S), and rel-(1S,2S,3S) configurations of desired products
were constructed in excellent enantiopurity via a simple switch in
substrates using the chiral auxiliary-controlled method. The absolute
configuration of cycloadducts with three contiguous quaternary/tertiary
stereogenic centers was confirmed through X-ray diffraction analysis.
A facile synthesis of versatile precursor 3-chlorooxindoles was also
introduced.