Calcium-Catalyzed Hydroboration of Alkenes

Earth-abundant group 2 metal complexes offer an inexpensive and sustainable alternative to precious transition metal catalysts in many synthetic scenarios. As such, calcium and magnesium catalysts have attracted ever increasing interest as viable replacements for traditional transition metal-based catalysts for alkene hydroboration. Herein, we report the alkaline-earth metal-catalyzed hydroboration of alkenes with HBpin using commercially available CaCl2, reusable MOF-Ca, and subvalent Mg(I) complexes as highly efficient catalysts. The simple air- and moisture-stable CaCl2 and MOF-Ca catalytic systems both show high reactivity in the hydroboration of various alkenes to afford the anti-Markovnikov products in high yield and high regioselectivity under low catalyst loading (1–3 mol %) and almost solvent-free conditions. To the best of our knowledge, this is the first example of a main-group Ca-catalyzed hydroboration of alkenes, and it represents a potential pathway for the further discovery and application of inexpensive alkaline-earth metal-based catalysis.