Study of the ALDOL Reaction

碱金属（Li, Na， K和Cs）和极少数附加的阳离子（B， Zn和Ti）稳定试剂是有机合成中应用最广泛的有机金属试剂。然而，关于它们的溶液和固态结构及其反应，仍有许多问题没有得到解答。对这些试剂的聚集状态、配位数、附着配体的几何形状和密切的结构特征的更好理解，已经开始为利用这些试剂预测反应的立体选择性提供一个更全面的模型。willard教授提出了一项研究计划，旨在通过衍射分析获得许多常用碳离子试剂的结构信息。这个提议的重点是醛醇反应。长期目标是将获得的结构信息拟合到用于控制和预测机制和立体选择性的更连贯的模型模式中。在有机合成中控制立体选择性对新试剂的设计尤为重要。重点将放在固态结构研究的高活性和合成重要的碳离子中间体。该项目将针对特定的反应中间体，这是我们几乎所有合成机制模型的基础。一个著名的例子是经常被引用的齐默尔曼-特拉克斯勒过渡态模型。虽然这种特殊的结构模型在许多烯酸酯反应的立体选择性的相关性上应用得相当成功，但很少有实验证据证明该模型的有效性。因此，该项目的主要目标是提供结构信息和具体的机械细节，这些信息可以直接与已建立的模型（如流行的Zimmerman-Traxler模型）相关。通过这个奖项，有机和大分子化学项目支持了布朗大学Paul G. willard教授的研究。willard教授是一位领先的x射线晶体学家和有机化学家，他对利用醛醇化学将烯酸盐的结构与它们的反应性联系起来感兴趣，这是有机合成中碳-碳键形成的关键。他的工作将涉及本科生作为研究人员，其结果将对化学制造业具有重要的实际意义。

Alkali metal (Li, Na, K and Cs) and a very few additional cationic (B, Zn, and Ti) stabilized reagents are among the most widely utilized organometallic reagents in organic synthesis. However, many questions remain unanswered concerning their solution and solid-state structures and their reactions. A better understanding of the aggregation state, the coordination number, the geometry of the attached ligands, and the intimate structural features have begun to provide a more thorough model for use in predicting the stereoselectivity in reactions utilizing these reagents. Professor Williard proposes a research program designed to obtain structural information by diffraction analyses for many commonly utilized carbanionic reagents. Specific to this proposal is a focus on the Aldol reaction. The long-range goal is to fit the structural information that is obtained into a more coherent pattern of models utilized to control and to predict mechanism and stereoselectivity. Controlling stereoselectivity in organic synthesis is especially important to the design of new reagents. An emphasis will be placed on the solid-state structural studies of highly reactive and synthetically important carbanionic intermediates. This project will target specific reactive intermediates, which are the basis of almost all of our synthetic mechanistic models. A well-known example is the often-cited Zimmerman-Traxler transition state model for enolate/aldol reactions. Although this particular structural model is applied with reasonable success to the correlation of stereoselectivity of many enolate reactions, very little experimental evidence exists to establish the validity of this model. Hence, a major goal of this project is to provide structural information and specific mechanistic details that can be directly related to established models such as the popular Zimmerman-Traxler model.With this Award, the Organic and Macromolecular Chemistry Program supports the research of Professor Paul G. Williard of Brown University. Professor Williard is a leading x-ray crystallographer and an organic chemist who is interested in correlating the structure of enolate salts with their reactivity using aldol chemistry, which is the key to carbon-carbon bond formation in organic synthesis. His work will involve undergraduate students as researchers and the results will be of significant practical importance to the chemical manufacturing industry.