A cascade deboronation/regioselective BÀ P coupling of closocarboranes is disclosed using a combination of palladium catalysts and nitrogen or phosphine-containing directing groups. Unsymmetric C-substituted closo-carboranes, including C-monosubstituted and unsymmetric 1,2-disubstituted closocarboranes, are tolerated. Select closo-carboranes bearing other directing groups, such as benzoxazole, and diphenylphosphine, are compatible substrates for this reaction. Phosphine and arsenic can be utilized as effective coupling partners. Furthermore, a catalytic amount of palladium salt mediates the regioselective BÀ H activation process. Readily available closocarboranes as the starting materials for direct one-pot synthesis of functionalized nido-carboranes and the in-situ formation of nido-carborane intermediates without purification are important features in terms of practical applications.
Efficient Pd-catalyzed regioselective B(6)−H phosphorization of nido-carboranes via cascade deboronation/B−H activation of readily available C-substituted o-carboranes with various phosphines using 3-methylpyridine or isoquinoline as a directing group in combination with pyridine ligands has been developed, affording unprecedented B(6)-phosphinated nidocarborane derivatives with high selectivity in a simple one-pot process.
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