We are engaged in the first systematic efforts to exploit hydrogenation in C-C couplings beyond hydroformylation. Using cationic rhodium and iridium catalysts, we have found that diverse ?-unsaturated reactants reductively couple to carbonyl compounds and imines under hydrogenation conditions, offering a byproduct-free alternative to stoichiometric organometallics in a range of classical C=X (X = O, NR) addition processes. This concept is extended further via """"""""C-C bond forming transfer hydrogenation"""""""". Here, using ruthenium or iridium catalysts, alcohols serve dually as hydrogen donors and aldehyde precursors, enabling carbonyl addition directly from the alcohol oxidation level in the absence of stoichiometric byproducts. In the proposed funding period, byproduct-free C-C couplings of alcohol and amines with abundant, renewable feedstocks will be developed, including the first hydrogen-mediated Grignard additions of organic halides. Other areas of investigation include redox neutral couplings of ?-olefins to carbonyl partners, and initial explorations into the use of iron-based catalysts for transfer hydrogenative coupling.
Over 50% of the world's top-selling drugs are single enantiomers and it is estimated that 80% of all drugs currently entering development are chiral and will be marketed as single-enantiomer entities. In 1994, the chiral drug market grossed over 45.2 billion US dollars worldwide, which corresponds to an increase of 27% in a single year! In 1999, the chiral drug market topped 100 billion US dollars in sales. In 2002, world-wide sales of single enantiomer drugs reached more than 159 billion US dollars. Notably, enantioselective hydrogenation accounts for over half the chiral drugs produced industrially, withstanding physical or enzymatic resolution. The enormous impact of hydrogenation portends an equally powerful approach to reductive C-C bond formations mediated by hydrogen. However, since the discovery of alkene hydroformylation and the parent Fischer-Tropsch reaction, processes restricted to the use of carbon monoxide, the field of hydrogen-mediated C-C coupling has lain fallow. We are engaged in the first systematic efforts to exploit hydrogenation in C-C couplings beyond hydroformylation. Using cationic rhodium and iridium catalysts, we have found that diverse ?-unsaturated reactants reductively couple to carbonyl compounds and imines under hydrogenation conditions, offering a byproduct-free alternative to stoichiometric organometallics in a range of classical C=X (X = O, NR) addition processes. This concept is extended further via C-C bond forming transfer hydrogenation. Here, using ruthenium or iridium catalysts, alcohols serve dually as hydrogen donors and aldehyde precursors, enabling carbonyl addition directly from the alcohol oxidation level in the absence of stoichiometric byproducts.
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