Ni<sup>II</sup>-Catalyzed Enantioselective <i>Anti</i>-Markovnikov Hydrophosphination of Unactivated Alkynes
Wei-Han Wang, Yue Wu, Peng-Jia Qi, Qing‐Wei Zhang
Abstract
A mechanism-inspired, reaction mode-controlled enantio- and regioselective anti -Markovnikov hydrophosphination of unactivated alkynes was accomplished by Ni II catalysis. Alkenyl phosphine products could be obtained with high regio- and enantioselectivity and easily derivatized to structurally diverse chiral phosphine compounds. Mechanistic studies on both Ni 0 -catalyzed Markovnikov addition and Ni II -catalyzed anti -Markovnikov addition have been carried out by combining experimental and computational methods. In the Ni 0 system, an allyl nickel complex was obtained as the catalyst resting state whose structure was unambiguously determined by single-crystal XRD analysis. A sequential hydrometallation, ligand exchange, and reductive elimination mechanism was elucidated corroboratively by DFT calculations. In the Ni II system, the cationic secondary phosphine nickel complex serves as the active catalyst. A migratory insertion and protonation sequence was operative to accomplish anti -Markovnikov hydrophosphination.