Electronic Effect-Guided, Palladium-Catalyzed Regioselective B–H Activation and Multistep Diarylation of o-Carboranes with Aryl Iodides

Density functional theory calculations at IDSCRF-B3LYP/DZVP computational level were conducted on palladium-catalyzed regioselective B-H activation and diarylation of o -carboranes with aryl iodides in solution. Computational results indicate that this reaction follows a multistep mechanism and needs to get over several transition states before the final B(4,5)-diarylated o -carborane derivatives are formed. B-H activation, oxidation addition, and successive reduction of the Pd(II) catalyst involving a Pd(II)-Pd(IV)-Pd(II) catalytic cycle has been confirmed, in which AgOAc plays a crucial role. Electron-donating group on the cage carbon of o -carboranes is verified to be beneficial for its B-H activation and diarylation, while steric hindrance between the aryl and o -carboranyl groups retards it. Natural population analysis and Gibbs free energetic results predict consistent regioselectivities with experiments and manifest the pivotal role of electronic effect in controlling regioselective B-H activation of o -carboranes. These results are expected to shed some light on further improvement of experimental conditions and better controlling of regioselectivities.