Copper(I)-N2S2-salen type complex covalently anchored onto MCM-41 silica: an efficient and reusable catalyst for the A3-coupling reaction toward propargylamines

The immobilization of copper complexes by covalent anchoring of the ligand on the surface of mesoporous MCM-41 has been described. Bis[2-(phenylthio)benzylidene]-1,2-ethylenediamine as a new N2S2 donor salen-type ligand was covalently anchored onto nanopores of MCM-41 coordinated with copper (I) halide. The organicinorganic hybrid material was achieved readily using 3-mercaptopropyltrimethoxysilane as a reactive surface modifier. 2-Nitrobenzaldehyde was reacted smoothly with the thiol moieties in order to form functionalized nanoporous silica with carbaldehyde groups. The resulting supported organic moieties were converted to thiosalen ligand and coordinated with CuX (X=CN, Cl, Br, I). Characterization of the heterogeneous catalyst by X-ray diffraction, N2 sorption, FT-IR, diffuse reflectance UV-visible and TGA techniques indicated successful grafting of the copper complex inside the nano-channels of MCM-41. The heterogenized catalyst was evaluated by the Mannich condensation reaction of aldehydes, amines and alkynes. In this reaction, the corresponding propargylamines were obtained as single products in good to excellent yields. Factors such as reaction temperature, solvent, catalyst loading, leaching and reusability of the catalyst also were discussed. The use of MCM-41 as support permits an easier separation and recycles with only a marginal decrease in reactivity. Copyright (c) 2013 John Wiley & Sons, Ltd.