Application Of Chiral Double - Tooth NHC - Pd Catalyst In Asymmetric Suzuki - Miyaura Coupling Reaction

The neutral and cationic diaqua palladium complexes, namely{Pd[(1R,2R)-(LOMe)]X2}(X=Br,2a; Cl,2f; OAc,2b; OC(O)CF3,2c),{Pd[(1R,2R)-(LOMe)](OH2)2}X2(X=OTf,2d; SbF6,2e) and{Pd[(1R,2R)-(LBn)]Br2}(4A),{Pd[(1R,2R)-(Lp-OMe-Bn)]Br2)(4b),{Pd[(1R,2R)-(Lp-NO2-Bn)]Br2)(4c),{Pd[(1R,2R)-(LP-COOC2H5-Bn)]Br2}(4d),{Pd[(1R,2R)-(L2-NaP)]Br2}(4e) bearing chiral bis-N-heterocyclic carbene ligands1a-b and3a-e derived from chiral1,2-cyclohexanediamine have been prepared in moderate to good yields. These chiral palladium complexes were fully characterized by elemental analysis, high-resolution mass spectra,1H&13C NMR, optical rotation determinations. The crystal structure of the chiral complex2a and2d was further confirmed to adopt a distorted square planar coordination geometry around palladium centre. The obtained chiral NHC-Pd compounds were able to catalyze the asymmetric Suzuki-Miyaura couplings of aryl bromides with arylboronic acids in good yields and moderate enantioselectivities...