Palladium with spindle-like nitrogen ligand supported on mesoporous silica SBA-15: A tailored catalyst for homocoupling of alkynes and Suzuki coupling

A mesoporous silica SBA-15-supported palladium with spindle-like nitrogen donor groups, 1,4-diaza-bicyclo[2.2.2]octane, has been successfully prepared and applied for homocoupling of terminal alkynes. The catalyst exhibited very high activity for terminal alkynes carrying various substitution groups, yields ranging from 70% to 94%, with a significant advantage that air acted as the oxidant. It also showed good reusability, could be easily recovered through filtration and washing, and reused at least five times with virtually no evident loss of catalytic performance. Furthermore, it was also proved to be an effective and air-stable heterogeneous catalyst for Suzuki coupling of aryl halides (X = I, Br) with arylboronic acids. The catalyst was systematically characterized by elemental analysis, X-ray photoelectron spectroscopy, high-resolution transmission electron microscope, nitrogen physical adsorption, Brunauer–Emmett–Teller method and X-ray powder diffraction. The analyses indicated that the mesoporous structure of the materials was retained during the immobilization process.

Graphical abstractA mesoporous SBA-15 supported palladium catalyst with a spindle-like nitrogen containing ligand was proved to be effective for homocoupling of terminal alkynes and Suzuki cross-coupling reactions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mesoporous SBA-15-supported palladium with spindle-like DABCO was synthesized. ► High activity for homocoupling of terminal alkynes and Suzuki coupling was proved. ► The catalyst was reusable and air was used as the oxidant for the homocoupling.