Organocatalytic Tandem Synthesis of Chiral Hexacyclic Bisindoles from Propargylic 3-Methyleneindoles with 2-Indolylmethanols

A novel chiral phosphoric acid-catalyzed tandem regioselective 1,6-addition/double intramolecular nucleophilic addition annulation of the propargylic 3-methyleneindoles in situ generated from α-indolyl propargylic alcohols with 2-indolylmethanols has been developed. The methodology afforded the new chiral trifluoromethyl pentalenobisindoles bearing an all-carbon quaternary stereogenic center in generally good yields with excellent enantioselectivities.