Copper(I)-Catalyzed Synthesis of Unsymmetrical All-Carbon Bis-Quaternary Centers at the Opposing α‑Carbons of Cyclohexanones

We describe a new
synthetic reaction that generates all-carbon
bis-quaternary centers at the opposing side of α-carbons in
cyclohexanone with four different substituents in a controlled manner.
Catalyzed by Cu­(MeCN)4BF4 salt, this chemistry
is proposed to proceed via an intermediacy of unsymmetrical O-allyl oxyallyl cations, which undergo a sequence of regioselective
nucleophilic addition with substituted indoles and diastereoselective
Claisen rearrangement in a single synthetic operation. The stereochemical
outcome of the products features the cis diastereorelationship
between the two aryl groups at the α,α′-positions.