Palladium-Catalyzed (Asymmetric) B(9)-Alkylation of o / m -Carboranes with α-Aryl-α-diazoesters

Although Pd(II)-catalyzed selective B(9)–H activation of o/m-carboranes via an electrophilic palladation process has been well explored, other pathways in directly Pd(II)-catalyzed B(9)–H functionalization have not been reported. Herein, we report an efficient Pd(II)-catalyzed selective B(9)–H alkylation of o/m-carboranes via a carbene B–H insertion process, in which α-aryl-α-diazoesters serve as carbene precursors. The reaction features good B(9) selectivity, mild reaction conditions without any additives, and a broad substrate scope. Furthermore, an asymmetric version was explored by adding a chiral phosphoric acid to the reaction system, and up to 88% ee was obtained.