Heteroallyl and alpha-Heterosubstituted Allyllithium Reagents

这笔有机化学和高分子化学方面的拨款为宾夕法尼亚州斯塔塔大学的劳埃德·杰克曼博士提供了支持。这项工作的重点是各种有机盐的化学和机理，特别是那些涉及锂的有机盐。这些物种是合成化学中使用的最重要的试剂之一，了解它们的基本方面具有重要的现实意义。最重要的一类合成有用的有机反应是基于C=C-X(-)类型的两亲阴离子的反应。这一群体的代表人数正在迅速增加。对这些阴离子与亲电性的反应没有一个正确的机理理解，部分原因是两亲阴离子盐在溶液中的结构通常是未知的。在锂盐情况下解决这种结构问题的方法，这项研究将通过比较已知晶体结构的13C，6Li和7Li在溶液中和固体中的核磁共振谱特征来扩展我们的知识。所有上述技术都将应用于锂的烯醇酸盐、酯的烯醇酸盐和烯胺类化合物，以及杂取代的烯丙基锂试剂。很明显，碳负离子锂盐和锂盐之间的混合聚集体(二聚体、四聚体)是弱极性溶剂中的重要实体，因为它们控制着速度和区域化学。将对混合集料形成的热力学进行研究，以确定控制其稳定性的因素。结构信息将与反应动力学结合起来，以确定酚酸锂的酯交换反应、羟醛反应以及酚酸盐、烯醇酸盐和烯胺的烷基化反应机理。将特别强调界定主要反应物物种，并了解混合聚集体作为中间物种的作用。还将探讨当亲电试剂具有可与聚集体中的锂相互作用的碱性中心时，配位诱导的邻近效应的参与。要研究的反应包括一些在合成有机化学中广泛使用的反应。这些研究的结果应该允许合成化学家更有效地执行它们，并设计新的方法来实现高的区域和立体选择性。

This grant in Organic and Macromolecular Chemistry provides support for Dr. Lloyd Jackman, Pennsylvania Stata University. The work focuses on the chemistry and mechanisms of various organic salts, particularly those involving lithium. These species are among the most important reagents used in synthetic chemistry and an understanding of their fundamental aspects has important practical significance. The most important single group of synthetically useful organic reactions is that based on ambident anions of the type C=C-X(-). The number of representatives of this group is rapidly increasing. A proper mechanistic understanding of the reactions of these anions with electrophiles does not exist, in part because the structures of the ambident anion salts in solution are usually unknown. With methodologies for solving such structural problems in the case of lithium salts, this study will extend our knowledge by effecting a comparison between the 13C, 6Li, and 7Li nmr spectral characteristics in solution with those in the solid state for known crystal structures. All the above techniques will be applied to lithium enolates, ester enolates and enamides and to heterosubstituted allyllithium reagents. It is becoming clear that mixed aggregates (dimers, tetramers) between lithium carbanion salts and lithium salts which are strong electrolytes are important entities in weakly polar solvents in that they control rates and regiochemistry. The thermodynamics of mixed aggregate formation will be studied in order to determine the factors controlling their stabilities. The structural information will be used in conjunction with reaction kinetics to establish the reaction mechanisms of the transesterification of lithium phenolates, the aldol reaction, and the alkylation of phenolates, enolates, and enamides. Particular emphasis will be placed on defining the primary reactant species and understanding the role of mixed aggregates as intermediate species. The involvement of coordination induced proximity effects arising when the electrophilic reagents possess basic centers which can interact with lithium in aggregates will also be probed. The reactions to be studied include some that are widely used in synthetic organic chemistry. The results of these studies should allow synthetic chemists to perform them more efficiently and to design new ones for achieving high regio- and stereo-selectivities.