Efficient Cu-Based Mixed Oxides Catalyst for α-Alkylation of Ketones with Alcohols

A series of Cu-based mixed oxides were prepared by calcinations of corresponding CuMgAl-layered double hydroxides precursors at different temperatures with nominal Cu/Mg/Al ratios of 1 : 1 : 2(Cu-LDH-1), 1 : 2 : 1(Cu-LDH-2),1 : 1 : 1(Cu-LDH-3), and 2 : 1 : 1(Cu-LDH-4). The synthesized catalysts were characterized using X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and N₂ physisorption analysis techniques. All as-obtained catalysts showed adequate catalytic performance for the α-alkylation of ketones with alcohols through a hydrogen autotransfer mechanism. The catalyst CuMgAl-I-650 (obtained by calcining Cu-LDH-1 at 650 °C) displayed the highest activity and selectivity. Using this catalyst system, a wide range of branched ketones were synthesized in good to excellent isolated yields. Moreover, the catalyst CuMgAl-I-650 could be recycled and reutilized for four cycles without any significant loss of activity and selectivity. This study provides a very simple and inexpensive catalysis based on transition metals, which are in abundance on earth.