Cobalt Mediated Reactions in Organic Synthesis

这项研究由有机合成计划资助。 克拉夫特博士将继续研究 羰基钴配合物作为反应试剂的潜力 五元环的受控构建。试剂如 这丰富了合成有机化学家的设备， 提供更强大的合成工具， 复杂分子 定向Pauson反应的工作已经进展到 现在人们可以计划与一些 信心 烯炔环加成反应具有高度的区域选择性 由于氮或硫配体的方向， 烯烃。 进一步的工作计划改进合成的 直接Pauson反应的效率 一些努力是 现在涉及到全合成硫代甲酰胺。 目前正在研究两种不同的办法。 非对称 Pauson环加成的改进也在 调查 使用炔-羰基钴的其他反应 正在进行中，即选择性氧化和亚砜 减少。 该项目的第二部分涉及审查 与酰基羰基钴络合物反应。 早期工作 证明了具有多种取代基的丁烯内酯 模式，可以通过以下反应以高产率合成： 炔与酰基羰基钴络合物。 一个主要问题 与反应相关的问题将通过使用 定向配体 在反应中形成的中间体是 π-烯丙基钴配合物。 碳碳键的形成 将研究pi-烯丙基配合物的反应。 酰基钴配合物在烯烃中的插入及反应机理 还将研究这些反应的不对称形式。

This research is being funded by the Organic Synthesis Program. Dr. Krafft will be continuing her studies of the synthetic potential of cobalt carbonyl complexes as reagents for the controlled construction of five-membered rings. Reagents like this enrich the armamentarium of synthetic organic chemists and provide more powerful synthetic tools for the synthesis of more complex molecules. The work on the directed Pauson reaction has progressed to the point where one can now plan total syntheses with some confidence. The ene-yne cycloaddition is highly regioselective due to the direction by nitrogen or sulfur ligands tethered to the alkene. Further work is planned to improve the synthetic efficiency of the directed Pauson reaction. Some efforts are now directed toward the total synthesis of asteriscanolide. Two different approaches are being examined. An asymmetric modification of the Pauson cycloaddition is also under investigation. Other reactions using alkyne-cobalt carbonyls are underway, i.e. selective oxidations and sulfoxide reductions. The second part of the project involves the examination of reactions with acylcobalt carbonyl complexes. Earlier work demonstrated that butenolides, with a variety of substitution patterns, can be synthesized in high yield by the reaction of alkynes with acylcobalt carbonyl complexes. One major problem associated with the reaction will be addressed by the use of a directing ligand. The intermediate formed in the reaction is a pi-allyl cobalt complex. The carbon-carbon bond forming reactions of the pi-allyl complex will be investigated. Insertion of acyl cobalt complexes into alkenes and the asymmetric versions of these reactions will also be studied.