Synthesis Of1,3-bisamide Palladium (Ⅱ) Pincer Complexes And Their Catalysis In α-arylation Coupling Reaction

Pincer complex are widely used in many fields, they contain the characteristicsof both the C-M (M=metal) bond and donor-metal coordination. Recent years,pincer complexes have attracted much attention. And most researches have beenfocused on the type of NCN pincer compounds, in addition, the PCP and SCS pincercompounds have also been documented. However, the type of OCO pincercompounds is rare. So we have synthesized one type of OCO ligand bearing amidogroups.Six novel OCO pincer ligands, i.e.4,6-dimethyl-1,3-bisamides (R=acetyl,cyclopropanylformyl, tert-butylformyl, benzoyl, tolylformyl, p-chlorobenzoyl) wereobtained after a series of transformations including nitration, hydrogenation andacylation starting from m-xylene. Treatment of these ligands with palladium acetate(II) in the presence of TsOH in1,4-dioxoane or dichloromethane resulted in thecorresponding PdII-OCO pincer complexes.α-Arylation reactions of acetophenone with aryl halides catalyzed by PdII-OCOpincer complexes as mentioned above were studied. The coupling ofm-nitrobromobenzene and acetophenone was chosen as an example reaction, the bestreaction condition was optimized. And their catalytic activities were also compared.In addition, the α-arylation of acetophenone with a series aryl halides (halo=I, Br, Cl)were assessed. All these results show that our PdII-OCO pincer complexes are highlyactive to the α-arylation.