Organocatalytic Arylation of 3‑Indolylmethanols via Chemo- and Regiospecific C6-Functionalization of Indoles

An
organocatalytic arylation of 3-indolylmethanols has been established
via chemo- and regiospecific C6-functionalization of 2,3-disubstituted
indoles, leading to the production of bisindolyloxindoles containing
an all-carbon quaternary stereocenter in high yields (up to 99% yield).
This reaction not only represents the first catalytic arylation of
3-indolylmethanols using 2,3-disubstituted indoles as aromatic nucleophiles
but also serves as a good example of direct catalytic C6-functionalization
of indoles, which have been scarcely investigated. Besides, this approach
also provides an efficient method to access a biologically important
3,3′-disubstituted oxindole framework and a 3′,6-linked
bisindole skeleton. Furthermore, the investigation of the activation
mode suggested that the dual activation of an ion pair and H-bond
between the substrates and the catalyst cooperatively contributed
to the success of the reaction.