The Study On The Catalytic Performance Of Pd/γ-Al₂O₃ In The Coupling Reaction Of 1,4-Naphthoquinone With 4-Iodoanisole

Naphthoquinones compounds widely exist in the nature and have been widely applied in medicine, pesticide, dye and other fields due to their various biological activites. Aryl-naphthoquinone of naphthoquinone compounds plays an important role in our life. The synthesis of aryl-naphthoquinone is generally accomplished by C-C coupling reaction. Synthetic methods reported have some problem such as harsh reaction conditions, low yield, liquid is difficult to separate and so on. Therefore it is very meaningful that finding a heterogenous catalytic synthetic method of aryl-naphthoquinone in green and mild conditions. In this study, we studied the preparation conditions of Pd/γ-Al2O3, optimized them and used the catalyst to catalyze the coupling reaction of 1,4-naphthoquinone with 4-iodoanisole. The influence of reaction conditions on the catalytic behavior of the catalysts was also investigated.1. The different kinds of impregnation-reduction method were used in the preparation of Pd/γ-Al2O3. The catalysts were characterized by X-ray diffraction, Transmission electron microscopy, Atomic absorption spectroscopy, X-ray photoelectron spectroscopy, Low temperature N2 adsorption and so on. The results showed that the particle size and particle dispersion degree of Pd are the main factors which influence catalytic performance of Pd catalyst in the coupling reaction of 1,4-naphthoquinone with 4-iodoanisole. The small and well dispersed Pd nanoparticles which were prepared by the impregnation-reduction method with L-Lysine protected,and properly adjusting pH of the solution is conductive to increase the catalytic performance of Pd catalyst.2. The Pd/γ-Al2O3 catalyst was used for catalyzed coupling reaction of1,4-naphthoquinone with 4-iodoanisole and had a good performance with the conversion of 4-iodoanisole was 94.6% and the selectivity of2-(4-Methoxy-Phenyl)-1,4-Naphthoquinone was 93.4% in mild conditions(The reaction with 0.15 mmol of K2CO3 as additive and 2 ml of acetonitrile as the solvent was conducted at 70℃ for 24 h). The effects of solvent, supports, Pd loading, base, reaction temperature and reaction time on catalytic performance of Pd catalyst for this reaction were studied. A tentative mechanism was proposed based on the experimental and relevant literatures.We found the catalyst was difficult to reuse.