Environmentally Friendly One-Pot Synthesis of alpha-Alkylated Nitriles Using Hydrotalcite-Supported Metal Species as Multifunctional Solid Catalysts

摘要

A ruthenium-grafted hydro-talcite (Ru/HT) and hydrotalcite-sup-ported palladium nanoparticles (Pd_(nano)/ HT) are easily prepared by treating basic layered double hydroxide,hydro-talcite (HT,Mg_6Al_2(OH)_(16)CO_3) with aqueous RuCl_3 centre dot nH_2O and K_2[PdCl_4] 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 A is observed on the Pd_(nano)/HT surface by transmission electron microscopy analysis.These hydrotalcite-supported metal catalysts can effectively promote alpha-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.