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。聚集在一起的 温和、选择性和立体控制条件下的复杂分子 都是具有挑战性的目标。这些标准可以通过具有歧视性的 二价锗或锡的反应性和独特的结构特征。 这些元素有三个化学特征：小天使键，空心点 轨道和一对孤零零的电子。这些属性将用于 开发新的碳-碳键形成试剂和方法。我们是 为实现这些目标寻求三种合成方法；i)合成 一类新的化合物，将作为光学活性， 非对映选择性，α-烷氧基-阴离子合成子：锗(II)环氧化物。 在它们准备好之后，我们将检查它们的插入反应 使用不饱和有机底物。例如，添加一个 乙醛与锗(II)的环氧化物将立体选择性地形成邻位化合物 二醇，或添加亚胺将产生1，2-氨基醇。Ii) SnC12催化加成合成官能化有机酮 从重氮化合物到醛。这些产品含有非常多用途的 易于进一步合成的官能团 变形。例如，将重氮乙酸乙酯添加到一个 在非常温和的条件下，乙醛只能生成β-酮酯。 三)分子内插入反应的合成应用 导致立体控制的重排或烯烃反转。 溴代烃很容易从烯烃中获得(反式加成机理)。 用锗(II)试剂处理它们可能会导致SYN消除 从而导致烯烃几何构型的净反转。

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.