Silver Supported Nanoparticles on [Mg4Al-LDH] as an Efficient Catalyst for the Alkylation of Nitriles, Oxindoles and Other Carboxylic Acid Derivatives with Alcohols

Abstract

[EN] An efficient heterogeneous silver-catalyzed ¿-alkylation of nitriles and oxindoles using alcohols via borrowing hydrogen strategy has been developed for the first time. The active nanostructured material, namely [Ag/Mg4Al-LDH], composed by silver nanoparticles (3-4-nm average particle size) homogeneously stabilized onto a [Mg4Al-LDH] support with suitable Brønsted basic properties, constitutes a stable catalyst for the sustainable building of novel C¿C bonds from alcohols and C-nucleophiles. By applying this catalyst, a broad range of ¿-functionalized nitriles and oxindoles has been accessed with good to excellent isolated yields and without the addition of external bases. Moreover, the novel silver nanocatalyst has also demonstrated its successful application to the cyclization of N-[2-(hydroxymethyl)phenyl]-2-phenylacetamides to afford 3-arylquinolin-2(1H)-ones, through a one-pot dehydrogenation and intramolecular ¿-alkylation. Control experiments, kinetic studies, and characterization data of a variety of [Ag/LDH]-type materials confirmed the silver role in the dehydrogenation and hydrogenation steps, while [Mg4Al-LDH] matrix is able to catalyze condensation. Interestingly, these studies suggest as key point for the successful activity of [Ag/Mg4Al-LDH], in comparison with other [Ag/LDH]-type nanocatalysts, the suitable acid-base properties of this material.