First Application of Secondary Phosphines as Supporting Ligands for the Palladium-Catalyzed Heck Reaction: Efficient Activation of Aryl Chlorides

Abstract

Secondary dialkylphosphines were successfully used for the first time as efficient supporting ligands for the palladium-catalyzed Heck reaction of electron-rich and electron-poor aryl chlorides with olefins such as acrylate, ethylene, styrene, and n-butyl vinyl ether. The yields with HP(t-butyl)2 and HP(adamantyl)2 were comparable or better than those obtained with known systems of tertiary phosphines such as P(cyclohexyl)3 and P(t-butyl)3, especially at a catalyst loading of <1 mol %. In comparison with tertiary phosphines, the secondary phosphines have the advantage of being readily available at low cost on a technical scale, and are comparable with respect to handling and oxygen sensitivity.