Photocatalyzed Homocoupling Of Phenylacetylene And Derivatives Using The Supported Copper Hydroxide Catalysts Under Visible Light

As a kind of widely utilized compounds, conjugate1,3-diynes have been used as key structural elements for super molecular chemistry, polymer chemistry, natural products, antibacterial medicaments and nanomaterials.’"Conjugate1,3-diynes were mainly synthesized through oxidative dimerization of terminal alkyne, so-called Glaser coupling reaction, which was a typical eaction for the formation of C-C bond. As the cheap and effective catalysts for Glaser coupling reaction, the copper catalysts have come through a series of improvements from Pd-Cuto Cu(Ⅰ) and Cu(Ⅱ) catalytic systems. Due to the ecycling properties, great attention has been paid to the supported eterogeneous catalytic systems, especially stable Cu(Ⅱ) catalysts. In recent years, the copper catalysts have been gradually used in the photocatalytic ynthesis field, especially oxidation reactions. However, the research on opper catalysts for Glaser coupling reaction has been not reported.In this study, the copper hydroxide supported on laponite catalysts Cu(OH)x/Lap) were prepared by the impregnation method and used as photocatalysts for synthesis of1,3-diynes by homocoupling of terminal alkynes under visible light. It was observed that the preparation condition of catalysts, the concentration of reactant, solvent, the kind and dosage of base, light intensity and light wavelength had the great effect on the Glaser homocoupling photocatalytic process. A tentative mechanism of this photocatalytic process was proposed.1. The supported copper catalysts were systematically characterized by transmission electron microscopy (TEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis spectrum (UV-Vis) and nitrogen physical adsorption-desorption to research the effect of different preparation conditions and copper loadings on the characteristics of catalysts. The results indicated that the catalyst Cu(OH)x/Lap which prepared in the condition of pH=10owned excellent photocatalytic activity and the activity center was Cu(Ⅱ).2. The initial experiments were carried out using5.0wt%Cu(OH)x/Lap as catalyst, phenylacetylene as a model substrate to optimize the reaction condition. The study revealed that polar solvent isopropanol was propitious to the reaction and the Cu(OH)x/Lap could work without base due to its surface alkalescence. The addition of trace base could effectively improve the yield and the opitimal amount of base changed along with the increasement of reaction temperature.3. The Xe light was used as simulation sunlight in the experiment. It was found that light irradiation had influence on the overall catalytic performance and the light in the wavelengths between600-800nm had the maximal influence. And the stronger the light intensity, the larger the contribution was found. These results further confirmed that this homocoupling reaction was driven by visible light. On the other hand, it was observed that the reaction was susceptible to temperature. High yield (99%) was obtained at the reaction temperature to50℃.