1,2-Bis(diphenylphosphino)carborane As a Dual Mode Ligand for Both the Sonogashira Coupling and Hydride-Transfer Steps in Palladium-Catalyzed One-Pot Synthesis of Allenes from Aryl Iodides

One-pot allene synthesis from aryl iodides 1 and propargyldicyclohexylamine 2 proceeded in the presence of Pd2(dba)3·CHCl3 catalyst (2.5 mol %), 1,2-bis(diphenylphosphino)carborane 5 (10 mol %), CuI (15 mol %), and Et3N (150 mol %) to give the corresponding allenes 4 in good to high yields. Electron-deficient bidentate phosphines, such as 1,2-bis(diphenylphosphino)carborane 5 and (C6F5)2PC2H4P(C6F5)2, play the role of a dual mode ligand for both the Sonogashira coupling and hydride-transfer reactions.