Cobalt-Catalyzed Asymmetric Sequential Hydroboration/Hydrogenation of Internal Alkynes

A highly regio- and enantioselective cobalt-catalyzed hydroboration/hydrogenation of internal alkynes with HBpin and a hydrogen balloon in one pot was developed. A new type of chiral imidazoline iminopyridine (IIP) ligand was introduced for the first time in this novel and efficient strategy. This protocol used relatively simple and available starting materials with good functional group tolerance to construct more valuable chiral secondary organoboronates. The primary mechanistic studies illustrated that the cobalt-catalyzed regioselective hydroboration of alkynes did initially occur followed by HBpin-promoted and cobalt-catalyzed enantioselective hydrogenation of alkenylboronates.本研究开发了一种兼具高度区域选择性与对映选择性的钴催化内炔烃一锅法硼氢化/氢化反应，反应以频哪醇硼烷（HBpin）与氢气球为试剂。该新颖高效的合成策略首次引入了一类新型手性咪唑啉亚胺吡啶（IIP）配体。此方法采用相对简单易得的起始原料，且具备良好的官能团兼容性，可用于构建更具应用价值的手性二级有机硼酸酯。初步机理研究表明，反应首先发生钴催化的炔烃区域选择性硼氢化过程，随后经由HBpin促进、钴催化的烯基硼酸酯对映选择性氢化反应完成整体转化。