In this thesis, initially, the complex formation of Cu(II) with polyvinyl alcohol (PVA) and the synthesis of PVA-stabilized Cu2O particles was examined. This PVA-Cu2O composite has been prepared via chemical reduction method using PVA-Cu(II) complex as precursor. Firstly, Cu(II) ions were stabilized in PVA matrix via complex formation with OH grou subsequently, this PVA-Cu(II) macromolecular complex as precursor reacted with ascorbic acid as reducing agent at pH = 12 to prepare PVA-Cu2O composite. The products were characterized by FTIR, XRD, FE-SEM, TEM, Visible Spectroscopy and Atomic Absorption. The antibacterial properties of the prepared composites were examined against Gram-positive (Bacillus thuringiensis) and Gram-negative bacteria (Escherichia coli), and the results showed excellent antibacterial activity of these materials. The PVA–Cu2O composite was applied as an effective and recyclable heterogeneous catalyst for 1,3-dipolar cycloaddition reactions between terminal alkynes and azides to prepare 1,2,3-triazoles under an environmentally friendly reaction conditions. The substituted triazoles were produced employing various aryl and benzyl azides using a catalytic amount of this composite as efficient, stable and air- and moisture-tolerant catalyst in excellent yields in water at room temperature. These PVA–stabilized Cu2O particles could be recovered in a facile manner from the reaction mixture and reused several times without any loss of catalytic activity. Various silica-supported nano-palladium catalysts was successfully prepared via a ‘‘click’’ route. The catalysts were well characterized and evaluated in Suzuki–Miyaura coupling. It was found to be highly efficient for the coupling reactions of various aryl halides with phenylboronic acid under phosphine-free and low Pd loading conditions. The reuseability of the click-catalysts was also investigated and interesting results were obtained A new and effective catalytic system using [N-Benzyl DABCO]+[Cu4Cl5]? was developed for the palladium-free Sonogashira cross coupling reactions of phenylacetylene with a variety of aryl halides. In this homogeneous catalytic system, 1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride as a quaternary ammonium salt containing a coordinating centre plays an important role and increases the efficiency of Cu(I) species during the reaction. A number of internal alkynes were produced in moderate to excellent yields in short reaction times in DMF at 135 ?C. In the presence of amino acides as the ligand, CuI-catalyzed sonogashira cross-coupling of aryl halides with phenylacetylene was conducted smoothly to afford the corresponding internal alkynes. L-methionine and L-proline were found to be useful for this palladium-free and amine-free coupling reaction. Also this found that the solvent system plays an important role in this reaction, and significantly affect the product formation and reaction rate. Sonogashira coupling of aryl iodides and aryl bromides in DMSO or DMF at 140 °C gave the corresponding internal alkynes in good to excellent yields. An efficient approach to aryl azides has been developed via coupling reaction of aryl halides with sodium azide under catalysis of Cu2O/tetraethylammonium prolinate in short reaction times and good to excellent yields.
