A Phosphine-Free Manganese Catalyst Enables Stereoselective Synthesis of (1 + <i>n</i>)‑Membered Cycloalkanes from Methyl Ketones and 1,<i>n</i>‑Diols

Herein, we report the stereoselective synthesis of (1 + n)-membered cycloalkane from methyl ketone and 1,n-diol. A manganese­(I) complex bearing a phosphine-free ligand catalyzed the reaction, which involved the formation of two C–C bonds via a sequence of intermolecular- and intramolecular-borrowing hydrogenation reactions. It produces 2 mol of water as the sole byproduct, making the process atom economical and environmentally benign. Multisubstituted cycloalkanes were obtained in good to excellent yields with very high selectivities. A thorough mechanistic analysis by high-level DFT computation rationalizes the choice of the pincer and establishes the role of hemilability of the ligand for this efficient transformation.本文报道了以甲基酮与1,n-二醇为底物，立体选择性合成(1+n)元环烷烃的方法。该反应由一种配位有无膦配体的锰(I)配合物催化，通过依次发生分子间与分子内借氢氢化反应构建两条C-C键，仅以2摩尔水作为唯一副产物，使得该工艺具备原子经济性与环境友好性。所得到的多取代环烷烃产物可获得中等到优异的产率与极高的选择性。通过高水平密度泛函理论（DFT）计算开展的详尽机理分析，阐明了钳形配体的选择依据，并明确了配体半解离性在该高效转化过程中的关键作用。