Ir(III) Complex-Catalyzed Base-free Chemodivergent Transfer Hydrogenation of Enones Utilizing Methyl Formate under Aqueous Media: Modulating 1,4- vs 1,2- Insertion.

Abstract

Readily accessible enones are the building blocks for synthesizing three different classes of compounds viz, functionalized ketones, allylic alcohols, and saturated alcohols through selective hydrogenation. However, accessing all the three congeners under a single chemodivergent protocol remains challenging due to the inherent reactivity difference between C=C and C=O bonds. In general, the lower-energy 1,4-addition of a metal hydride preferentially reduces the C=C bond over the C=O bond. Thus, allylic alcohols remain inaccessible with current methodologies. The reactivity of a catalytic reaction can be enhanced under aqueous medium that involves water as a reactant. Additionally, the unique inherent H-bonding network in H2O medium can unlock new reactivity patterns with added sustainability. Herein, we demonstrated a proton-responsive Ir(III) complex catalyzed, base-free, chemodivergent CTH of enones utilizing methyl formate (MF) under aqueous media, enabling precise control over 1,4- vs 1,2- insertion into the Ir-H species. This strategy enabled the selective synthesis of all possible CTH products with high efficiency. Furthermore, a series of experimental studies provided deeper insights into the diversity of product formation, which were further supported by DFT calculations.