Stereoelectronic Effects in the Activation of Oxygens by Lewis Acids

这个项目，在有机动力学计划，是由一个年轻的 调查员罗伯特·C·科科伦大学 内华达州里诺，谁将研究增加化学方法， 某些含氧有机化合物的反应性。 的 由此产生的信息预计将有助于设计 允许更快速和/或立体选择性反应的催化剂 在这些功能组中。 刘易斯酸活化的立体电子效应 研究缩醛和羰基化合物中的氧。在 刘易斯酸介导的缩醛的裂解，酸可以络合 与氧孤对是反周面的 相邻的C-O键，或与一个是笨拙的;动力学 反周面孤对电子激活的优先性 应该是可观察的。 刘易斯酸活化的两种模式 羰基氧是可能的;在羰基的平面中，或 垂直于这个平面。 虽然面内络合是 通常假定为激活的主导模式， 垂直络合作用也可能起作用。 激活中存在立体电子偏好 这些系统中的氧将通过检查 包含刘易斯碱的构象刚性体系 可以与所讨论的氧气以一种 螯合环 螯合定向络合将允许 刘易斯酸相对于 目标氧气 其他方面相似的比率差异 底物的差异激活，在几何 sense将是立体电子偏好的指示。 这种立体电子偏好的确定将有助于 缩醛和羰基反应的非对映选择性 化合物.

This project, within the Organic Dynamics Program,is by a young investigator, Robert C. Corcoran of the University of Nevada-Reno, who will study methods for increasing the chemical reactivity of certain oxygen containing organic compounds. The resulting information is expected to aid in the design of catalysts to allow more rapid and/or stereoselective reactions at these functional groups. Stereoelectronic effects in the Lewis acid activation of the oxygen in acetals and carbonyls are to be investigated. In the Lewis acid mediated cleavage of acetals the acid may complex with an oxygen lone pair which is antiperiplanar to the adjacent C-O bond, or to one which is gauche; a kinetic preference for activation of the antiperiplanar lone pair should be observable. Two modes of Lewis acid activation of carbonyl oxygens are possible; in the plane of the carbonyl, or perpendicular to that plane. Though in-plane complexation is generally assumed to be the dominant mode of activation, perpendicular complexation may also play a role. The existence of stereoelectronic preferences in the activation of oxygens in these systems will be investigated by examining conformationally rigid systems which incorporate a Lewis base appendage that can cooperate with the oxygen in question in a chelate ring. The chelation-directed complexation will allow the selective positioning of a Lewis acid with respect to the target oxygen. Rate differences between otherwise similar substrates which are differentially activated in a geometric sense will be an indication of steroelectronic preferences. The determination of such stereoelectronic preferences will aid diastereoselectivity in the reactions of acetals and carbonyl compounds.