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 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 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.