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.