Building inherently chiral icosahedral-carborane-fused boron heterocycles

<h2>Summary</h2> In this article, we present an asymmetric synthesis of inherently chiral carborane-fused boraphenanthrenes. The introduction of axially chiral biaryl moieties can facilitate stereoselective oxidative cyclization to generate carborane-fused boraphenanthrene moieties. In this transformation, aryl groups were first installed on the carborane's vicinal boron vertices. Following regioselective bromination at the sterically hindered aryl C–H bond, the asymmetric cross-coupling reactions produced the axially chiral biaryls adjacent to the carborane. The final intramolecular oxidative-cyclization-induced chiral transfer involving two vicinal aryl groups resulted in the generation of non-coplanar carborane-fused boraphenanthrene analogs. The stereochemistry of axial biaryls is crucial for determining the configuration of twisted carborane-fused boraphenanthrenes. Notably, during the oxidative cyclization, a formal 1,2-carboranyl transposition was observed. These results represent the first example, to our knowledge, of a 1,2-B–C(sp²) bond migration reaction. Initial photophysical studies reveal a significant redshift in the photoluminescence spectra of the products compared to the uncyclized substrates.