A simple, metal- and ligand-free procedure for the Ullmann-type C–O coupling reactions has been achieved by allowing aryl bromides to react with a variety of phenols in the presence of t-BuOK. Moderate to excellent yields of O-arylation products are obtained under mild conditions in a short time. In addition, two examples of C–N coupling reactions are also reported. A benzyne mechanism is proposed
A New Biarylphosphine Ligand for the Pd-Catalyzed Synthesis of Diaryl Ethers under Mild Conditions
作者:Luca Salvi、Nicole R. Davis、Siraj Z. Ali、Stephen L. Buchwald
DOI:10.1021/ol202955h
日期:2012.1.6
A new bulky biarylphosphine ligand (L8) has been developed that allows the Pd-catalyzed C–O cross-coupling of a wide range of aryl halides and phenols undermilderconditions than previously possible. A direct correlation between the size of the ligand substituents in the 2′, 4′, and 6′ positions of the nonphosphine containing ring and the reactivity of the derived catalyst system was observed. Specifically