Enantioselective metallaphotoredox
catalysis, which combines
photoredox
catalysis and asymmetric transition-metal catalysis, has become an
effective approach to achieve stereoconvergence under mild conditions.
Although many impressive synthetic approaches have been developed
to access central chirality, the construction of axial chirality by
metallaphotoredox catalysis still remains underexplored. Herein, we
report two visible light-induced cobalt-catalyzed asymmetric reductive
couplings of biaryl dialdehydes to synthesize axially chiral aldehydes
(60 examples, up to 98% yield, >19:1 dr, and >99% ee). This
protocol
shows good functional group tolerance, broad substrate scope, and
excellent diastereo- and enantioselectivity.