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Cascade CuH-Catalyzed Conversion of Alkynes to Enantioenriched 1,1-Disubstituted Products
preprintsubmitted on 09.04.2019, 09:31 and posted on 09.04.2019, 14:00 by De-Wei Gao, Yang Gao, Huiling Shao, Tian-Zhang Qiao, Xin Wang, Brittany Sanchez, Jason Chen, Peng Liu, Keary Engle
Enantioenriched α-aminoboronic acids play a unique role in medicinal chemistry and have emerged as privileged pharmacophores in proteasome inhibitors. Additionally, they represent synthetically useful chiral building blocks in organic synthesis. Recently, CuH-catalyzed asymmetric alkene hydrofunctionalization has become a powerful tool to construct stereogenic carbon centers. In contrast, applying CuH cascade catalysis to achieve reductive 1,1-difunctionalization of alkynes remains an important, but largely unaddressed, synthetic challenge. Herein, we report an efficient strategy to synthesize α-aminoboronates via CuH-catalyzed hydroboration/hydroamination cascade of readily available alkynes. Notably, this transformation selectively delivers the desired 1,1-heterodifunctionalized product in favor of alternative homodifunctionalized, 1,2-heterodifunctionalized, or reductively monofunctionalized byproducts, thereby offering rapid access to these privileged scaffolds with high chemo-, regio- and enantioselectivity.