Stereospecific alkenylation of carboranes: copper-catalyzed access to pyridylcarboranyl alkenes

Abstract

The direct functionalization of carbon vertices in polyhedral carboranes has received considerable attention because of their wide applications in functional materials, catalysis, and pharmaceuticals. However, achieving direct C–H bond activation of o-carboranes remains a challenge, as it typically requires strong bases to facilitate the deprotonation of the C–H bonds. Herein, we report a copper-catalyzed stereospecific C–H alkenylation of o-carboranes using Na₂CO₃ as a mild base. Remarkably, the reaction exhibits stereospecificity, allowing for switchable syn- or anti-selectivity simply by employing the E- or Z-configuration of the alkenyl halide coupling partner. Structurally diverse E- and Z-alkenylcarboranes are accessible by this protocol, among which the latter are difficult to access by existing methods. The synthetic utility of this methodology was demonstrated by the late-stage modification of amino acids, sugars, and drug molecules. Furthermore, the synthesized carboranylethylene scaffolds exhibit aggregation-induced emission and bright solid-state luminescence, with quantum yields reaching 67%. Thus, this work unveils a Cu(I)/Cu(III) catalytic model for the C–H activation of carboranes and establishes pyridylcarborane–alkene hybrids as a new class of functional, bioisosteric architectures.