Stereoselective Desymmetrization of Cyclohexadienone-Tethered Enones: Efficient Access to Highly Strained Polycyclic Indoles

A highly regioselective
and stereoselective cascade annulation
of indoles with C2-symmetric enone tethered-cyclohexadienones provides
rapid access to complex indole alkaloid-like scaffolds in high yields.
Interestingly, a different reaction course was observed with 3-substituted
indoles giving C-2/N annulation products with similar complexity via
intramolecular aza-Michael addition. This desymmetrization approach
is highly practical and allows atom-economical synthesis of natural
product-like molecules containing several contiguous stereocenters
with broad range of substrate scope and high functional-group tolerance.
The synthetic utility of the products was demonstrated with various
chemoselective, regioselective, and diastereoselective transformations
on the highly strained polycyclic indoles to elaborate the value of
this tandem reaction.