Unsymmetrical, oxazolinyl-containing achiral and chiral NCN pincer ligand precursors and their complexes with palladium(II)

The unsymmetrical, achiral and chiral NCN pincer ligand precursors (3a-3d) with oxazoline and pyrazole as N donors as well as (3e) which has oxazolinyl and amino group have been synthesized in a facile manner in four steps starting from commercially available isophthalaldehyde. Direct C2 metallation of the precursors (3a–3e) with Pd(OAc)2 in refluxing HOAc, followed by treatment with LiCl at room temperature provided convenient access to the corresponding pincer palladium(II) complexes (4a–4e). The molecular structure of complex 4e has been determined by X-ray single-crystal diffraction. The obtained Pd complexes exhibited good activities in the Suzuki reactions of aryl bromides and activated aryl chlorides with phenylboronic acid.

Graphical abstractA series of unsymmetrical, oxazolinyl-containing achiral and chiral NCN pincer ligand precursors (3a–3e) have been easily synthesized in four steps starting from commercially available isophthalaldehyde. The corresponding pincer Pd complexes (4a–4e) were prepared via direct C2 palladation of the precursors and used as efficient catalysts for Suzuki reactions.Figure optionsDownload full-size imageDownload as PowerPoint slide