Ligand-free palladium catalyzed Ullmann biaryl synthesis: ‘household’ reagents and mild reaction conditions

Abstract

A palladium catalysed Ullmann biaryl synthesis has been developed using hydrazine hydrate as the reducing reagent at room temperature. The combination of Pd(OAc)₂ and hydrazine hydrate works smoothly for the coupling of both electron-rich and electron-deficient aryl iodides, as well as hetero-aryl iodides, leading to a wide range of biaryls in good to excellent yields. The reaction requires only 1 mol% Pd(OAc)₂ and the in situ generated palladium naoparticles are found to be active catalysts.