ION PAIR CARBON ACIDITY

碳负离子通常以离子对或聚集体的形式存在， 许多有机合成中的重要中间体 生物活性天然产物、药物、药品等。 一种常见的合成方法是将底物 与烷基锂或氨基锂在醚中反应，然后 与合适的亲电试剂反应。 我们建议把这个 在定量科学基础上， 继续我们的平衡常数的测定， 反应，R-M+ + R 'H = R'-M+ + RH，用于指示烃 (e.g.,芴、芳基甲烷等）在四氢呋喃（THF）中， 铯和锂作为正离子。 这些指标体系将 用于测定碳酸与各种 在合成中重要的官能团。 重点将 被放置在用于控制区域和 生物活性化合物合成中的立体化学， 天然产物，如肟醚和二甲基腙 羰基化合物的衍生物。 该研究将包括其他 羰基化合物和衍生物如酰胺和恶唑啉 以及硫、硒和硅的衍生物，乙烯基，烯丙基， 苄基和芳基化合物、杂环化合物及相关化合物 二价阴离子如肟二价阴离子。 作为下列因素的函数的确定 浓度将提供定量估计的程度， 聚合来 对于那些表现为以单体形式存在的体系， 二聚体离子对，烷基化和缩合的动力学研究将 作为集中的函数来完成， 在这种反应中，两种物质。 平衡测量作为 温度函数将提供热力学量 和铯平衡的比较，这是已知的， 涉及接触离子对，与相应的锂 平衡，其中各种类型的离子对是可能的， 将有助于理解更复杂的锂情况。 电导率研究将离子对与解离离子联系起来。 结果将借助相关动力学解释 酸度测量，聚集体系的研究，理论 量子化学计算和计算机图形分析 电子密度分布 理论研究包括ab 结构和反应路径的初始计算。

Carbanions, generally involved as ion pairs or aggregates, are important intermediates in the organic synthesis of many biologically active natural products, pharmaceuticals, drugs, etc. A common synthetic procedure is the metallation of a substrate with an alkyllithium or lithium amide in an ether followed by reaction with a suitable electrophile. We propose to put this largely empirical technique on a quantitative scientific basis by continuing our determination of equilibrium constants for the reactions, R-M+ + R'H = R'-M+ + RH, for indicator hydrocarbons (e.g., fluorenes, arylmethanes, etc.) in tetrahydrofuran (THF) with cesium and lithium as gegenions. These indicator systems will be used to determine equilibria for carbon acids with various functional groups important in synthesis. Important emphasis will be placed on functional groups used to control regio- and stereochemistry in synthesis of biologically active compounds and natural products, such as oxime ethers and dimethylhydrazone derivatives of carbonyl compounds. The study will include other carbonyl compounds and derivatives such as amides and oxazolines as well as sulfur, selenium and silicon derivatives, vinyl, allyl, benzyl and aryl compounds heterocyclic compounds, and related dianions such as oxime dianions. Determinations as a function of concentration will provide quantitative estimates of the degree of aggregation. For those systems shown to exist as monomer and dimer ion pairs, kinetic studies of alkylation and condensation will be accomplished as a function of concentration to show the role of both species in such reactions. Equilibrium measurements as a function of temperature will provide thermodynamic quantities and comparison of the cesium equilibria, which are known to involve contact ion pairs, with the corresponding lithium equilibria, in which a variety of types of ion pairs are possible, will facilitate understanding of the more complex lithium cases. Conductivity studies will relate the ion pairs to dissociated ions. The results will be interpreted with the help of related kinetic acidity measurements, studies of aggregated systems, theoretical quantum chemical calculations and computer graphics analysis of electron density distributions. The theoretical studies include ab initio computations of structure and reaction paths.