Catalytic Asymmetric Hydroboration: Uncapping the Potential with Two-Point Bindin

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DESCRIPTION (provided by applicant): Developing efficient methods for the reliable, stereocontrolled synthesis of small molecules via asymmetric catalysis is central to providing the means to prepare potential mechanistic probes and pharmaceuticals. These are essential tools that enable the better understanding and control of biological processes relevant to human health. The development of new catalytic asymmetric reactions is therefore of both practical and fundamental importance to the NIH mission. Chiral organoboranes are finding increasing use as synthetic intermediates en route to other useful functionality via stereospecific functional group interconversion, reagents for asymmetric synthesis, and synthetic targets for pharmaceutical applications. The stereochemistry of carbon-boron bond is retained upon transmetallation or conversion to other useful functional groups. Organoboranes are therefore seen as important intermediates for incorporating a variety of functional groups with defined stereochemistry in natural product, pharmaceutical intermediate, and drug synthesis. Recent breakthroughs in the development of methods for the stereospecific conversion of carbon-boron to carbon-carbon bonds increase the demand for efficient methods to synthesize chiral organoboronates. While stoichiometric asymmetric hydroboration is useful for asymmetric synthesis, its ultimate replacement, the greener direct catalytic asymmetric hydroboration (CAHB), remains as one of the unsolved problems in asymmetric catalysis. Notwithstanding a series of impressive recent advances using pinacol diborane as a (mono)borane surrogate, the lack of a versatile direct method for catalytic asymmetric hydroboration remains a critical barrier to the use of chiral organoboranes. The proposed studies build on recent breakthroughs in the catalytic asymmetric hydroboration of two-point binding substrates. Accomplishing the specific aims of the proposal will develop and expand the generality of that methodology and better define the mechanism through computational studies supported by experimental data. The computational studies will be carried out in collaboration with faculty and undergraduate students from the Department of Chemistry and Physics at Purdue University Calumet.