AbstractA nuclearity‐dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)TiIII complex and its self‐assembled oxygen‐bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy‐controlled enantio‐differentiation mode in mononuclear catalysis, whereas an entropy‐controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity‐distinct transition‐metal complexes.
摘要 研究人员开发了一种核性依赖的对映异构环氧化物开环反应,在该反应中,手性醇产物的两个对映异构体均可在同一立体配体支架内通过单核(沙伦)TiIII 复合物及其自组装的氧桥双核对应物选择性地获得。基于艾林方程的动力学研究表明,在单核催化过程中,对映体分离模式是由焓控制的,而在双核催化过程中,对映体分离模式是由熵控制的。DFT 计算概述了单核催化中对映体控制的起源,并指出了双核催化体系中的实际催化剂种类。这些机理上的见解可能会为利用核性不同的过渡金属复合物进行立体不对称催化的策略提供启示。