The reduction of the carbonyls to alcohol via hydride transfer is an important process, leading to molecules with hydroxyl functionalities. Enantioselective reduction of prochiral ketones is one of the processes for preparing enantioenriched secondary alcohols, which are important precursors to several enantiopure compounds and natural products. The helical chirality of DNA has been exploited in various asymmetric catalytic reactions. These hybrid catalysts are self-assembled from DNA and a metal complex, affording an asymmetric reaction environment. In our approach to DNA-based asymmetric hydrogenation of ketones, here we report the isolation and characterization of a series of newly synthesized tridentate copper(II) <i>N</i>-heterocyclic carbene (NHC) complexes with different azole rings including imidazoles benzimidazoles, 5,6-dimethylbenzimidazoles. The hybrid catalyst is generated by the noncovalent binding of these Cu-NHCs to DNA, allowing the effective transfer of chirality of the DNA double helix to the catalyzed hydrogenation reaction. These complexes and the hybrid catalysts have been optimized for their application in the ketone reduction reactions using a variety of different target ketones and phenylsilane as the reducing agent in various solvent media. The relationship between product formation and temperature, time, and catalyst loading is described, for the ketone hydrogenation reactions. The new copper(II) NCN-pincer complexes are comprehensively characterized by X-ray crystallography, elemental analysis, HR-MS, cyclic voltammetry, UV-Vis, and EPR spectral studies. The binding modes and efficiencies of the Cu-NHCs to the DNA have been studied using ITC, UV-Vis titration, and CD experiments.

Enantioselective ketone reduction with silanes catalyzed by DNA- copper(II) <i>N</i>- heterocyclic carbene-based hybrid catalysts via copper hydride formation

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Enantioselective ketone reduction with silanes catalyzed by DNA- copper(II) N- heterocyclic carbene-based hybrid catalysts via copper hydride formation