Organo-Cation Catalyzed Asymmetric Homo/Heterodialkylation of Bisoxindoles: Construction of Vicinal All-Carbon Quaternary Stereocenters and Total Synthesis of (−)-Chimonanthidine

A novel chiral spirocyclic
amide (SPA)-derived triazolium organocatalyst
has been designed and demonstrated to effect asymmetric homo- and
heterodialkylations of various bisoxindoles, enabling enantioselective
construction of vicinal all-carbon quaternary stereocenters. These
reactions feature excellent enantio- and diastereoselectivities (up
to 99% ee and >20:1 dr) as well as good to high yields (up to 89%
over two steps). As an application of this methodology, the first
asymmetric total synthesis of (−)-chimonanthidine has been
achieved.