Synthesis Of N-heterocyclic Carbene- Palladium(Ⅱ) Complexes And Their Chemoselective Coupling Toward Dichlorobenzenes

In this paper,a series of novel N-heterocyclic carbene-palladium(Ⅱ)complexes were successfully synthesized in a one-step process,and successfully used in the chemoselective coupling of dichlorobenzenes:(1)First,a novel type of N-heterocyclic carbene-palladium(Ⅱ)-2-methyl-4,5-dihydrooxazole complexe was successfully prepared and it was found that complex 3a showed very high chemoselective mono-Suzuki-Miyaura coupling of dichlorobenzenes.Compared to some easily available NHC-Pd(Ⅱ)complexes having different N-containing ancillary ligands,NHC-Pd(Ⅱ)complex 3a showed the most efficient catalytic activity.Under the optimal reaction conditions,it was an efficient catalyst in the selective Suzuki-Miyaura coupling of dichlorobenzenes with arylboronic acids to give the mono-arylated products in excellent yields.(2)Second,this type of N-heterocyclic carbene-palladium(Ⅱ)complexes was successfully used in the selective C-N coupling reaction of dichlorobenzene with primary and secondary amines.Under the optimal reaction conditions,such transformation took place smoothly to give the desired aminated products in moderate to good yields.