Environmentally friendly one-pot synthesis of α-alkylated nitriles using hydrotalcite-supported metal species as multifunctional solid catalysts

A ruthenium-grafted hydrotalcite (Ru/HT) and hydrotalcite-supported palladium nanoparticles (Pd-nano/ HT) are easily prepared by treating basic layered double hydroxide, hydrotalcite (HT, Mg6Al2(OH)(16)CO3) with aqueous RUCl3 center dot nH(2)O and K-2[PdCl4] solutions, respectively, using surface impregnation methods. Analysis by means of X-ray diffraction, and energy-dispersive X-ray, electron paramagnetic resonance, and X-ray absorption fine structure spectroscopies proves that a monomeric Ru-IV species is grafted onto the surface of the HT. Meanwhile, after reduction of a surface-isolated Pd-II species, highly dispersed Pd nanoclusters with a mean diameter of about 70 angstrom is observed on the Pd-nano/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote a-alkylation reactions of various nitriles with primary alcohols or carbonyl compounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the HT. In these catalytic alpha-alkylations, homogeneous bases are unnecessary and the only by-product is water. Additionally, these catalyst systems are applicable to one-pot syntheses of glutaronitrile derivatives.