Solventless amide synthesis catalyzed by biogenic CaCO3 materials

Abstract

Biogenic carbonates were studied as catalysts in this work for the direct synthesis of amides under solvent-free conditions. Solids were synthesized by microbial coprecipitation of CaCl2 and Ni salts and Cu and Fe salts. The catalysts were characterized by thermogravimetric analysis, nitrogen physisorption measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The polymorphism, hydrophilicity, and textural properties depended on the metal oxides type incorporated on CaCO3. N-Arylsuccinimides synthesis was employed as test reaction, obtaining remarkable selectivity and conversion in the reaction of succinic acid with p-toluidine and aniline, respectively. Optimized conditions were subsequently extended to the solvent-free synthesis of diverse amides in good yields using CuO-CaCO3 as the catalyst in air. The direct amidation protocol was amenable to the use of different primary amines and nonactivated carboxylic acids.