Palladium-Catalyzed Arylation of Malonates and Cyanoesters Using Sterically Hindered Trialkyl- and Ferrocenyldialkylphosphine Ligands

Palladium-catalyzed reactions of aryl bromides and chlorides with two common stabilized carbanions-enolates of dialkyl malonates and alkyl cyanoesters-are reported. An exploration of the scope of these reactions was conducted, and the processes were shown to occur in a general fashion. Using P(t-Bu)(3) (1), the pentaphenylferrocenyl ligand (Ph(5)C(5))Fe(C(5)H(4))P(t-Bu)(2) (2), or the adamantyl ligand (1-Ad)P(t-Bu)(2) (3), reactions of electron-poor and electron-rich, sterically hindered and unhindered aryl bromides and chlorides were shown to react with diethyl malonate, di-tert-butyl malonate, diethyl fluoromalonate, ethyl cyanoacetate, and ethyl phenylcyanoacetate. Although alkyl malonates and ethyl alkylcyanoacetates did not react with aryl halides using these catalysts, the same products were formed conveniently in one pot from diethylmalonate by cross-coupling of an aryl halide in the presence of excess base and subsequent alkylation.