Palladium-Catalyzed Intermolecular B–H/C–H Oxidative Cross-Coupling of Carboranes with (Hetero)Arenes

Abstract

Transition-metal-catalyzed oxidative cross-dehydrogenative coupling (CDC) reactions represent an attractive strategy for the direct construction of C–C and C–X (X = heteroatom) bonds, owing to their inherent atom and step economy. This strategy has been recently extended to the B–H/C–H cross-dehydrogenative coupling of carboranes with arenes. However, such transformations typically either rely on the assistance of directing groups or are restricted to intramolecular processes. Herein, we report a palladium-catalyzed direct cross-dehydrogenative coupling between the B–H bond of carboranes and the C–H bond of (hetero)arenes, which affords B(9)-arylated products of o/m-carboranes in good to excellent yields with a broad substrate scope. Notably, this methodology is not limited to simple benzene rings but also delivers high yields with polycyclic aromatic hydrocarbons, five-membered heterocycles, and benzo-fused five-membered heterocycles. Control experiments reveal that B–H activation occurs preferentially over C–H activation. The high reactivity of carboranes toward Pd(II) and their steric hindrance are the keys to this successful transformation, suppressing the formation of (hetero)arene and carborane homo-coupling products, respectively.

Keywords

Boron / Cross-coupling / Carborane / B–H activation / Palladium-catalyzed / C–H activation

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