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

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posted on 23.06.2017, 00:00 by Thomas Cruchter, Michael G. Medvedev, Xiaodong Shen, Thomas Mietke, Klaus Harms, Michael Marsch, Eric Meggers
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).