Synthesis, structure, and catalytic activity of palladium complexes with new chiral cyclohexane-1,2-based di-NHC-ligands

A pair of novel palladium complexes {[(1S,2S)-L]PdBr2} and {[(1R,2R)-L]PdBr2} of chiral di-N-heterocyclic carbene ligands derived from chiral 1,2-cyclohexanediamine have been prepared in moderate to good yields and characterized by NMR, HRMS and X-ray single crystal diffraction studies. The obtained chiral NHC–Pd compound was able to catalyze the asymmetric Suzuki–Miyaura couplings of aryl bromides with arylboronic acids in good yields and moderate enantioselectivities (up to 61% ee).

Graphical abstractA pair of novel palladium complexes {[(1S,2S)-L]PdBr2} and {[(1R,2R)-L]PdBr2} of chiral di-N-heterocyclic carbene ligands derived from chiral cyclohexane-1,2-diamine have been proved to catalyze the asymmetric Suzuki–Miyaura couplings of aryl bromides with arylboronic acids in good yields and moderate enantioselectivities (up to 61% ee).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New chiral cyclohexane-1,2-based di-N-heterocyclic carbenes were used as auxiliary ligands. ► A pair of mononuclear chiral organopalladium complexes have been characterized by X-ray crystallography. ► The chiral bis-NHC palladium complexes are moderately effective catalysts for the asymmetric Suzuki–Miyaura couplings.