Catalytic hydroboration of α,β-unsaturated ketones using β-diketiminate magnesium hydride and mechanistic insights

Abstract

We report the selective hydroboration of ynones and enones catalyzed by ^DepNacnac-stabilized magnesium hydride Mg-1 [{LMgH}₂; L = ^DepNacnac = (DepNCMe)₂CH; Dep = 2,6-Et₂-C₆H₃] under mild conditions. A wide range of ynones and enones, including testosterone propionate, have been quantitatively converted into the corresponding boronate esters. This magnesium-catalyzed method offers an efficient, eco-friendly alternative to traditional reductions of carbonyl compounds. The active catalyst {LMg–OCH(CH₃)CC–Ph}₂ (Mg-2) was isolated and characterized via ¹H, ¹³C{¹H} NMR and single-crystal X-ray diffraction analyses. Based on the isolation of Mg-2 and stoichiometric reactions, a plausible catalytic cycle was established. The results highlight magnesium's potential in sustainable and selective organic transformations.