Preparation of Pd-NHC Catalyst Immobilized on γ-Alumina for Suzuki-Miyaura Cross-Coupling Reaction

Abstract

ABSTRACT

Preparation of Pd-NHC Catalyst Immobilized on γ-Alumina for Suzuki-Miyaura Cross-Coupling Reaction

Min-Ki Kang School of Chemical and Biological Engineering The Graduate School Seoul National University

γ-Alumina (γ-aluminium oxide) supported palladium(II)-N-heterocyclic carbene (Pd-NHC) complex is one of the effective Suzuki-Miyaura cross-coupling catalysts in water dominant environment. NHCs are stable ligands in aqueous conditions, and they have been used for spectator ligands of Suzuki-Miyaura cross-coupling catalyst. γ-Alumina is one of the suitable solid supports due to its hydrophilicity and large surface area but has not been fully studied for Suzuki-Miyaura reaction. In this research, two kinds of 1-substituted imidazoles were synthesized as precursors of NHCs, and Pd-NHC complexes were prepared by using Pd(OAc)2 and these precursors. Finally, the catalysts were prepared by immobilizing the Pd-NHC complexes on γ-alumina. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron mictrscope (SEM), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The catalytic activity was investigated under various solvents and basic conditions via conventional heating or microwave heating methods. As a result, up to 99% yields were obtained from the reactions of aryl bromides with phenylboronic acid at 50℃ for 2 h.