Palladium-Catalyzed Carbonylative Annulation of 1-Hydroxy-o-Carborane and Internal Alkynes via Regioselective B-H Activation.

A Pd-catalyzed three-component carbonylative-annulation of 1-hydroxy-o-carborane, internal alkyne and carbon monoxide has been achieved via direct and regioselective cage B-H activation. A class of C,B-substituted carborano-coumarin derivatives with potential applications in pharmaceuticals were facilely prepared in moderate to high yields with excellent chemoselectivity and regioselectivity. A plausible reaction mechanism including CO insertion, electrophilic B-H metalation, alkyne insertion and reductive elimination was proposed.