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Page 2 of 8 Liu et al. Chem Synth 2023;3:11 https://dx.doi.org/10.20517/cs.2022.46

Scheme 1. The applications of representative molecules containing C3-arylindole framework and our designed strategy for their
asymmetric synthesis. (A) Bioactive molecules and chiral catalysts containing C3-arylindole scaffolds; (B) the asymmetric construction
of biaryl aminoalcohols using iminoquinones reported by our group; (C) our strategy for organocatalytic enantioselective synthesis of 3-
arylindole atropisomers with iminoquinones.

recently . Organocatalysis proved to be a useful synthetic tool and has unlocked strategies that range from
[10]
atroposelective functionalization of preformed arylindole scaffolds [11-13] to direct arylation of indoles [14-19] and
heteroarene formation [20-22] . The pioneering work in catalytic asymmetric construction of axially chiral
arylindoles came from Zhang et al. , who achieved atroposelective arylation of 2-naphthols or phenols
[19]
with C3-electrophilic 2-indolylmethanols in the presence of chiral phosphoric acid (CPA) catalyst. In 2019,
He et al. prepared axially chiral 3-pyrrolylindole skeletons with asymmetric Barton-Zard reaction,
[21]
following a sequence of pyrrole ring construction and central-to-axial chirality conversion. Differently, Lu
[22]
et al. successfully synthesized the axially chiral bridged C3-arylindoles through an ingenious cascade
reaction between propargylic alcohols and enals by employing chiral N-heterocyclic carbene catalyst.

Although these strategies represent significant advances in the asymmetric synthesis of axially chiral indole
compounds, more efficient synthetic methodologies are highly anticipated to enhance their availability and
further accelerate their development and applications . In particular, methods that could directly construct
[10]
and define the configuration of stereogenic axis would enable modular assembly of these useful scaffolds.
Our ongoing research on atroposelective organocatalytic arylation reactions has established the use of
iminoquinone and its derivatives as arene precursors, which could undergo addition with different arene
nucleophiles [23-25] . As an illustration, a CPA-catalyzed direct arylation of 2-naphthylamine with
iminoquinones as electrophiles could accomplish the asymmetric construction of axially chiral biaryl
aminoalcohols [Scheme 1B] . In light of these preceding studies and the verified use of iminoquinones in
[24]
the synthesis of axially chiral scaffolds, we envisioned the assembly of new axially chiral 3-arylindole
framework through the asymmetric coupling of indoles with iminoquinones, as shown in Scheme 1C.