Presidential Young Investigator Award: Application of Group Transfer from Metals to Olefins

9318794 Jacobsen Eric N.雅各布森是由有机合成计划资助的总统青年研究员。 他将研究用于有机合成的对映选择性催化剂的发展。 非官能化烯烃的氧化将是他将探索的第一个反应。 基团转移到前手性烯烃的表面选择性可以通过纯粹的非键合相互作用或通过底物预配位限制非对映过渡态的自由度来控制。 目前正在根据这两种原理开发催化系统。 设计了一系列手性锰配合物，它们催化碘代芳烃环氧化未官能化的烯烃，对映体过量可达33%。 这些配合物的配体很容易通过手性二胺与水杨醛衍生物的缩合来制备，从而允许它们的空间和电子性质的系统变化。 目前的努力是针对调整周围的反应位点的空间环境，以增加对映体选择性合成有用的水平，并使用观察到的立体化学的偏好，绘制出的轨迹烯烃的方法的中间体金属含氧物种。 迄今为止制备的六种催化剂的结果和对最有效系统的晶体结构的检查已经允许开发从锰到烯烃的氧原子转移的详细过渡结构。 这个模型现在正在完善的系统变化的金属，配体和基板;阐明一个过渡结构，具有预测价值的立体化学方面也将提供机械洞察氧原子转移从金属到烯烃的一般问题，在广泛的实验室，工业和生物过程中的一个重要步骤。

9318794 Jacobsen Dr. Eric N. Jacobsen is being funded by the Organic Synthesis Program as a Presidential Young Investigator. He will be studying the development of enantioselective catalysts for organic synthesis. The oxidation of unfunctionalized olefins will be the first reaction that he will explore. %%% Facial selectivity in group transfer to a prochiral olefin can be controlled by purely non-bonded interactions or by constraining the degrees of freedom in diastereometric transition states through substrate pre-coordination. Catalytic systems are being developed based on both principles. A series of chiral manganese complexes have been designed which catalyze epoxidation of isolated and unfunctionalized olefins by iodosoarenes with up to 33% enantiomeric excess. The ligands for these complexes are readily prepared by condensation of chiral diamines with salicylaldehyde derivatives, permitting systematic variation of their steric and electronic properties. Current efforts are directed toward tuning the steric environment surrounding the reactive site in order to increase enantioselectivity to synthetically useful levels and to use observed stereochemical preferences to map out the trajectory of olefin approach to the intermediate metal oxo species. The results with six catalysts prepared to date and examination of a crystal structure of the most effective system have allowed a detailed transition structure for oxygen-atom-transfer from manganese to olefin to be developed. This model is now being refined by systematic variation of metal, ligand, and substrate; the elucidation of a transition structure which holds predictive value with regard to stereochemistry will also provide mechanistic insight into the general question of oxygen-atom transfer from metals to olefins, an important step in a wide range of laboratory, industrial, and biological processes.