Towards environmentally friendlier Suzuki-Miyaura reactions with precursors of Pd-NHC (NHC = N-heterocyclic carbene) complexes

The preparation of [NHC center dot H][Pd(eta(3)-R-allyl)Cl-2] complexes is disclosed and represents a facile, atom-economical, environmentally friendly and rapid synthesis. These palladates are immediate synthetic precursors to the well-known [Pd(NHC)(eta(3)-R-allyl)Cl] complexes. Their activation leading to catalytically relevant species has been studied in the Suzuki-Miyaura reaction. The need for an activation step prior to the catalysis was examined. The reaction scope showcases its ease and breadth in terms of functional group tolerance. Electron-donating and electron-withdrawing aryl chlorides and bromides were coupled effectively as well as heteroatom-containing and sterically hindered aryl halides. The catalytic reaction was conducted in ethanol with a weak and inexpensive inorganic base.