Practical Synthesis of 2‐Arylacetic Acid Esters via Palladium‐ Catalyzed Dealkoxycarbonylative Coupling of Malonates with Aryl Halides

Abstract A new palladium‐based system was developed that catalyzes the coupling of aryl halides with diethyl malonates in the presence of mild bases. In the course of the reaction, the intermediately formed diethyl arylmalonate is directly converted into the arylacetic acid ester via liberation of carbon dioxide and an alkanol. This cross‐coupling/dealkoxycarbonylation process provides an efficient and high‐yielding synthetic entry to diversely functionalized arylacetic acid esters. Two complementary protocols were developed, one of which is optimal for electron‐rich, the other for electron‐poor aryl halides. Both make use of low loadings of palladium(0) bis(dibenzylideneacetone) (0.5 mol%)/tri‐ tert ‐butylphosphonium tetrafluoroborate (1.1 mol%) as the catalyst and diethyl malonate as the reaction solvent. The new procedures are particularly effective for sterically hindered substrates.