Palladium-Catalyzed α-Arylation of Esters

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Abstract
A new and simple one-pot procedure for the palladium-catalyzed intermolecular α-arylation of esters is described. A number of esters can be functionalized with a wide range of aryl bromides using Pd(OAc)2 or Pd2(dba)3 and bulky electron-rich o-biphenyl phosphines 1−3. Under the reaction conditions, using LiHMDS as base, α-arylation proceeds at room temperature or at 80 °C with very good yields and high selectivities for monoarylation. Important nonsteroidal antiinflammatory drug derivatives such as (±)-naproxen tert-butyl ester and (±)-flurbiprofen tert-butyl ester can be prepared in 79% and 86% yield, respectively. The catalyst system based on the di-tert-butylphosphine (2) is also active for the α-arylation of esters using aryl chlorides. Furthermore, using (3) the α-arylation of trisubstituted ester enolates can be accomplished to provide compounds that have quaternary centers.