DIVALENT GERMANIUM AND TIN IN ORGANIC SYNTHESIS

我们的具体目标是构建功能化的有机分子， 生物相关化合物的亚结构。 的装配 在温和、选择性和立体控制条件下的复杂分子 是具有挑战性的目标。 这些标准可以通过区分 反应性和二价锗或锡的独特结构特征。 这些元素有三个化学特征：小的键角，空的p 轨道和孤对电子。 这些属性将用于 开发新的碳-碳键形成试剂和程序。 我们 为实现这些目标，采用三种综合方法; 一类新的化合物， 非对映选择性的α-烷氧基-阴离子配体：锗（II）环氧化物。 准备好后，我们将检查它们的插入反应 与不饱和有机基质。 例如，添加一个 醛转化为环氧化锗（II）将立体选择性地形成邻位 二醇，或亚胺的加成将产生1，2-氨基醇。 （二） SnCl_2催化加成合成功能化有机酮 重氮化合物转化为醛。 这些产品含有高度通用的 容易使其自身进一步合成的官能团 转变 例如，将重氮基乙酸乙酯加入到 醛在非常温和的条件下仅产生β-酮酯。 iii）分子内插入反应的合成应用 导致立体控制的重排或烯烃转化。 溴代醇很容易从烯烃中获得（反式加成机理）。 用锗（II）试剂处理它们可以诱导顺式消除， 因此导致烯烃几何结构的净反转。

Our specific aim is to construct functionalized organic molecules which are substructures of biologically relevant compounds. The assemblage of complex molecules under mild, selective, and stereocontrolled conditions are challenging goals. These criteria can be met by the discriminating reactivity and unique structural features of divalent germanium or tin. These elements hare three chemical features; small bond angels, an empty p orbital, and a lone pair of electrons. These properties will be used to develop new carbon-carbon bond forming reagents and procedures. We are pursuing three synthetic methods towards these goals; i) The synthesis of a new class of compounds that would serve as optically active, diastereoselective, alpha-alkoxy-anion synthons: germanium (II) epoxides. After they have been prepared, we will examine their insertion reactions with unsaturated organic substrates. For example, the addition of an aldehyde to a germanium (II) epoxide would stereoselectively form a vicinal diol, or the addition of an imine would yield a 1,2-amino alcohol. ii) The synthesis of functionalized organoketones via the SnC12 catalyzed addition of diazo compounds to aldehydes. These products contain highly versatile functional groupings that readily lend themselves to further synthetic transformations. For example, the addition of ethyl diazoacetate to an aldehyde exclusively yields a beta-keto ester, under very mild conditions. iii) The synthetic application of intramolecular insertion reactions leading to stereocontrolled rearrangements or olefin inversions. Bromohydrins are readily obtained form olefins (trans addition mechanism). Treating them with a germanium (II) reagent may induce a syn elimination to take place thus resulting in a net inversion of olefin geometry.