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

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.