Nickel-Catalyzed Regioselective Hydroboration of Unactivated Alkenes and Allenes with HBEpin at Room Temperature

Earth-abundant metal-catalyzed alkene hydroboration reactions are an atom-economical process with a low environmental impact and cost. Herein, we report the application of an air-stable nickel precatalyst Ni(IPr)[P(Oi-Pr)3](o-tol)Cl, for the hydroboration of alkyl-substituted olefins and allenes. The hydroboration process occurs at room temperature with low catalytic loading, using either HBpin or HBEpin. In the case of terminal alkenes, the hydroboration occurs with good to excellent regioselectivity, while, in the case of allenes, borylation occurs selectively at the central carbon. Overall, the BEpin-derived boronates proved to be more hydrolytically stable and could be isolated by using standard silica chromatography. The Ni(NHC)[P(OR)3](Ar)Cl complex was shown to be activated by KOt-Bu and HBEpin with the loss of toluene.