The influence of ultrasonic irradiation on catalytic performance of ZnO nanoparticles toward the synthesis of chiral 1‐substituted‐1H‐tetrazolederivatives from α‐amino acid ethyl esters

• Published in: Applied organometallic chemistry 2020-09, Vol.34 (9), p.n/a
• Main Authors: Mohamed, Yasser Mahmoud A., Attia, Yasser A.
• Format: Article
• Language: English
• Subjects: Amino acids; Chemistry; Ethyl esters; Irradiation; nanocatalysts; Nanoparticles; Reaction time; Solvents; Substitutes; Tetrazoles; ultrasonic‐assisted; Zinc oxide; Zinc oxides; Zinc salts; ZnO NPs; α ‐amino acid ethyl esters
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.5758

In this work, a simple and greener protocol for the synthesis of 1‐substituted 1H‐tetrazole derived from α‐amino acid ethyl esters was demonstrated in the presence of zinc oxide nanoparticles (ZnO NPs) under conventional conditions, with heating (at 60 and 80°C and under reflux) compared with ultrasonic. The effect of solvent was investigated to reveal that the solvent system CH3CN/H2O was optimum to obtain 1‐substituted 1H‐tetrazole in high yield. In addition, the effect of irradiation power was studied, which showed that the yield of the reaction was improved at 200 W and the reaction time was shortened to be 30 min. Also, an improvement in the rate of the reaction and the yield of the products was observed when reactions were carried out under sonication conditions in the presence of ZnO NPs compared with conventional methods using various zinc salts as catalysts. The yields of tetrazole compounds 2a–i under sonication were determined (88–96%). Furthermore, the investigated heterogeneous catalytic system was recycled and reused for five runs with significant production of tetrazole 2a as a model target compound in excellent yields at each reaction cycle. In general, the investigated synthetic strategy for the heterocyclization of α‐amino acid ethyl ester derivatives to 1‐substituted 1H‐tetrazoles was in agreement with the green chemistry point of view. • Greener approach for the synthesis of 1‐subtituted‐1H‐tetrazoles derived α‐amino acids catalyzed by ZnO nanoparticles using sonication conditions was developed. • ZnO NPs showed higher catalytic activity than different Zinc salts in the terms of the reaction time and the yields of the formed tetrazoles under sonication • The investigated procedure presented could be considered efficient, simple, and eco‐friendly approach for the synthesis of new tetrazole derivatives.