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

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)CC-Ph}2 (Mg-2) was isolated and characterized via1H, 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.