Study of the ALDOL Reaction

碱金属（Li、Na、K和Cs）和非常少的另外的阳离子（B、Zn和Ti）稳定的试剂是有机合成中最广泛使用的有机金属试剂。然而，关于它们的溶液和固态结构及其反应的许多问题仍然没有答案。更好地理解的聚集状态，配位数，几何形状的连接的配体，和亲密的结构特征已经开始提供一个更彻底的模型，用于预测的立体选择性反应，利用这些试剂。Williard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负离子试剂的结构信息。具体到这个建议是一个重点的羟醛反应。长期目标是将获得的结构信息拟合成用于控制和预测机理和立体选择性的更连贯的模型模式。有机合成中立体选择性的控制对新试剂的设计尤为重要。重点将放在高活性和合成重要的碳负离子中间体的固态结构研究。该项目将针对特定的活性中间体，这是我们几乎所有合成机理模型的基础。一个众所周知的例子是经常引用的烯醇化物/羟醛反应的Zimmerman-Traxler过渡态模型。虽然这种特殊的结构模型是合理的成功应用于许多烯醇化反应的立体选择性的相关性，很少有实验证据存在，以建立这种模型的有效性。因此，该项目的一个主要目标是提供结构信息和具体的机制细节，可以直接与建立的模型，如流行的齐默尔曼-特拉克斯勒模型。布朗大学的Williard。Williard教授是一位领先的X射线晶体学家和有机化学家，他对使用羟醛化学将烯醇盐的结构与其反应性相关联感兴趣，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，其结果将是具有重大的实际意义的化学制造业。

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.