Asymmetric Nucleophilic Catalysis with an Octahedral Chiral-at-Metal Iridium(III) Complex

Herein,
we report about the design, synthesis, and application
of a nucleophilic octahedral chiral-only-at-metal iridium­(III) complex.
We demonstrate that the enantiopure form of this complex serves as
an efficient catalyst for the asymmetric Steglich rearrangement of O-acylated azlactones (up to 96% ee and 99% yield) and the
related asymmetric Black rearrangement of O-acylated
benzofuranones (up to 94% ee and 99% yield). We provide insight into
the mechanisms of these two acyl migration reactions and the catalyst’s
manner of chiral recognition with crystal structures of the active
catalyst and a catalysis intermediate analog, as well as with quantum
chemical calculations based on them. Furthermore, we demonstrate that
the presented catalyst also efficiently catalyzes the asymmetric reaction
between aryl alkyl ketenes and 2-cyanopyrrole to give the corresponding
α-chiral N-acyl pyrroles (up to 95% ee and
99% yield).