Oxidative coupling of carboxylic acids or benzaldehydes with DMF using hydrotalicite-derived oxide catalysts

Hydrotalcite-derived (HT-derived) oxide catalysts were synthesised from hydrotalcite-like (HT-like) materials prepared by co-precipitation method (Cu-Al, Cu-Fe, Mg-Al, Mg-Fe, Ni-Fe and Ni-Al) followed by calcination and their catalytic activity was studied for oxidative amidation of carboxylic acids and substituted benzaldehydes with N,N-dimethylformamide (DMF). Catalyst screening was done using benzoic acid and DMF as a model reaction. Subsequently, we have optimised the reaction with different reaction parameters, catalyst loading, temperatures and oxidants. Cu-Fe HT-derived oxide catalyst showed excellent activity towards oxidative amidation using TBHP as an oxidant at 80 degrees C in 10 h. The fresh and spent catalysts were thoroughly characterised by different analytical techniques; XRD, SEM, HRTEM, TPD, N-2 adsorption-desorption isotherm and XPS. Moreover, the catalyst was easily separated by simple filtration and reused up to four cycles without significant loss in catalytic activity.