Methyl Formate Meets Water: Phosphine-Free Mn(I) Catalysis for Chemoselective Olefin & Carbonyl Hydrogenation.

Employing 3d-metal hydrides in hydrogen-transfer catalysis with water as a supplementary reagent remains in its infancy. Herein, we report a phosphine-free Mn(I)-bisNHC system that mediates methyl formate dehydrogenation in water, enabling chemoselective transfer hydrogenation of olefinic bonds in diverse aryl acrylonitriles and phenyl enones and carbonyl groups in α,β-epoxy ketones. Combined experimental and DFT studies reveal base-assisted Mn-H formation from MF/H2O and substrate-driven electronic effects governing selectivity, establishing a robust platform for aqueous hydrogen-transfer transformations.