The Shvo catalyst represents a class of complexes that display ligand-metal bifunctional catalysis, providing a unique reactivity manifold. Recent reports have provided detailed mechanistic insight into the catalytic cycle of these reductions displaying the unique nature of the electronically coupled acidic and hydridic hydrogens. Presently, ligand-metal bifunctional catalysis with unsaturated substrates is limited to hydrogenation. This proposal outlines the development of analogous ruthenium complexes for the delivery of heteroatoms. Generation of ruthenium bound electropositive heteroatom complexes containing the acidic hydroxy hydrogen would provide ruthenium catalysts that have unprecedented reactivity. This proposal focuses on ruthenium-boryl complexes of the Shvo catalyst which are expected to provide the equivalent of a boryl anion in the hydroboration of polar unsaturated substrates. This postulated reactivity would have widespread applications in synthetic organic chemistry. The goal of this project is to develop asymmetric reductive coupling reactions of boranes and diboranes with unsaturated substrates. Ultimately, this methodology would be expanded to include additional heteroatoms. In conjunction with well-established methods in organic synthesis, the expansion of the Shvo catalyst to include ruthenium-boryl complexes would be useful in the preparation of natural products and pharmaceutical targets. Notably, ?-heteroatom-substituted boronate esters have been used in the synthesis of several natural products. The ability to achieve asymmetric reductive coupling reactions of boranes to advanced synthetic intermediates (such as a complex aldehyde) would greatly reduce the number of steps of a given synthesis. Relevance: The incorporation of main group substituents into organic substrates have received increasing attention over the past several decades due to the ability to transform the carbon-main group bond into functional groups that are common in natural products and pharmaceutical targets. This project will allow for the introduction of boron substituents into complex organic molecules with selectivities that are not possible with the current technology. This method could have numerous applications in synthesis. ? ? ?
| Koren-Selfridge, Liza; Query, Ian P; Hanson, Joel A et al. (2010) Synthesis of Ruthenium Boryl Analogues of the Shvo Metal-Ligand Bifunctional Catalyst. Organometallics 29:3896-3900 |
| Casey, Charles P; Clark, Timothy B; Guzei, Ilia A (2007) Intramolecular trapping of an intermediate in the reduction of imines by a hydroxycyclopentadienyl ruthenium hydride: support for a concerted outer sphere mechanism. J Am Chem Soc 129:11821-7 |
