METAL MEDIATED ASYMMETRIC INTRAMOLECULAR HYDROSILATION

烯烃的水合作用和酮的还原作用 在综合战略建设中的重要作用 生物活性分子。当前的水合方法 例如，通过氢化硼化或氧化汞化烯烃，以及 酮的还原，例如通过氢化硼或氢化铝 大体上是化学计量转换。虽然很多人 在这些反应中，有对映体选择性地进行 生产对映体产品，化学选择性较差 在竞争中，酯基和酰胺基团通常会减少。 此外，不对称催化的例子很少。 分子内不对称催化硅氢化反应提供了一种 有吸引力的解决方案的化学选择性水合的烯烃和 酮的还原。这项建议是针对开发 用于不对称催化硅氢化反应的新型手性催化剂。一个 提供了机械论的合理化，这表明某些 容易获得的衬底将通过以下方式产生高光学产量 分子内过程。该战略采用了熟悉的概念。 通过优先的环状构象区分 对映体选择性转换位点。 硅氢化反应的产物很容易转化为光学的 活性1，4-，1，3和1，2-二醇。这些二元醇是关键的起点 合成大环内酯类和离子载体抗生素的材料。 该提案还针对一个重要的方法问题。 这涉及到选择正确的催化剂和 这将提供高光学产量的衬底。为此， 建议对该反应的机理进行研究。 以确定对映体选择的来源。是这样的 这些研究将为其他催化剂的设计提供依据 变形。

The hydration of olefins and the reduction of ketones play an important role in the synthetic strategies for the construction of biologically active molecules. The current methods of hydration of olefins by, for example, hydroboration or oxymercuration and reduction of ketones by, for example, boron or aluminum hydrides are, in the main, stoichiometric transformations. Although many of these reactions have been carried out enantioselectively to produce enantiomeric products, the chemoselectivity is poor in that ester and amide groups are generally reduced in competition. Moreover, there are few examples of asymmetric catalysis. Intramolecular asymmetric catalytic hydrosilation provides an attractive solution to the chemoselective hydration of olefins and the reduction of ketones. This proposal is directed at developing new chiral catlysts for asymmetric catalytic hydrosilation. A mechanistic rationalization is offered which suggests that certain readily available substrates will generate high optical yields by an intramolecular process. The strategy employs familiar concepts of discrimination by preferred cyclic conformations in the enantioseleetive transition sites. The products of hydrosilation are readily converted into optically active 1,4-, 1,3 and 1,2-diols. These diols are key starting materials in the synthesis of macrolide and ionophore antibioties. The proposal is also directed at an important methodological issue. This concerns the problem of selecting the correct catalyst and substrate which will give high optical yields. For this purpose, it is proposed to investigate the mechanism of the reaction in order to determine the origins of the enantioselection. Such studies will provide a basis for the design of catalysts for other transformations.