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 metalbased catalysts for alkene hydroboration. Herein, we report the alkaline-earth metal-catalyzed hydroboration of alkenes with HBpin using commercially available CaCl 2 , reusable MOF-Ca, and subvalent Mg(I) complexes as highly efficient catalysts. The simple air-and moisture-stable CaCl 2 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.

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A catalyst-free and solvent hydroboration of alkynes and alkenes with catecholborane was reported. Various alkynes and alkenes including aromatic and aliphatic groups were smoothly converted into the corresponding anti-Markovnikov alkenyl and alkyl boronate esters in high yields and high regio/stereoselectivity at room temperature and 50 ℃, respectively. The gram-scale hydroboration and further versatile conversions demonstrated great potential in the practical application. A plausible reaction mechanism was proposed based on the corresponding density function theory (DFT) calculations.