A Phosphine-Free Manganese Catalyst Enables Stereoselective Synthesis of (1 + n)‑Membered Cycloalkanes from Methyl Ketones and 1,n‑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-二醇为原料，通过立体选择性合成（stereoselective synthesis）制备(1+n)元环烷烃（(1 + n)-membered cycloalkane）的方法。该反应采用搭载无膦配体（phosphine-free ligand）的锰(I)配合物（manganese(I) complex）作为催化剂，经由分子间与分子内借氢化反应的串联过程构建两条C–C键（C–C bonds）。反应仅生成2摩尔水作为唯一副产物，使得该过程兼具原子经济性与环境友好性。最终可获得良好至优异产率、极高选择性的多取代环烷烃产物。通过高精度密度泛函理论（DFT）计算开展的详尽机理分析，阐明了钳型配体（pincer）的选择依据，并证实了该配体的半配位性（hemilability）在该高效转化过程中的关键作用。