Efficient microwave synthesis of novel aromatic esters catalyzed by zirconia and its modified forms: a kinetic study

Abstract

A series of solid acids such as ZrO 2 , 5% Mo(VI)/ZrO 2 , 10% Mo(VI)/ZrO 2 , 20% Mo(VI)/ZrO 2 and SO 4 2-/ZrO 2 were prepared. These solid acids were characterized by BET, NH 3 -TPD / nbutylamine back titration, powder-XRD, FT-IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ICP-OES techniques. The catalytic performance of these solid acids was evaluated in the synthesis of novel aromatic esters by the assistance of microwave irradiation and the catalytic activity of these solid acids was compared with pTsOH. The results clearly indicated that the zirconia based solid acids are efficient green catalysts for esterification reactions, which gave maximum yield of ester in shorter reaction time and comparable to the catalytic activity of pTsOH Brönsted acid. Kinetic studies were carried out to calculate the temperature coefficients (1.66 and 1.56) and energy of activation (66.

Copper borate (CuB4O7)-promoted multi-component green synthesis of 2,4,5-triarylimidazole derivatives and evidence of in situ conversion of copper borate (CuB4O7) into Cu(OAc)2 in the presence of NH4OAc

“…Off white solid, yield = 93%, melting point (°C) = 290–293, IR (KBr, cm −1 ) υ max = 3451 (NH), 3062, 3027 (aromatic C–H), 1694 (C C), 1601 (C N), 1 H NMR (400 MHz, DMSO-d 6 ): δ 12.83 (s, 1H, NH), 8.30 (s, Ar H, 1H), 7.24–8.10 (m, Ar H, 13H) ppm; 13 C NMR (100 MHz, DMSO d 6 ): δ 144.4, 138.8, 135.4, 134.9, 133.5, 131.3, 130.2, 129.6, 129.4, 128.7, 127.7, 127.5, 126.3, 119.7, 110.8 ppm [lit. 97 ].…”

Magnetic polyborate nanoparticles as a green and efficient catalyst for one-pot four-component synthesis of highly substituted imidazole derivatives

“…Furthermore, they have been proved as efficient anti-cancer and anti-inflammation as well as anti-tuberculosis, antimicrobial and anti-anaphylaxis compounds. 58–66 Moreover, highly-substituted 1,3-dialkylimidazoles have demonstrated their high potential in the form of ionic liquids, as green solvents, or precursors of N-heterocyclic carbenes (NHCs) as efficient organocatalysts or ligands in coordination chemistry in the recent decades. 67–71 Indeed, the potency and vast application of imidazole derivatives can be attributed to their hydrogen bond donor–acceptor capability as well as high affinity for metals, such as the zinc, iron and magnesium present in many receptor active sites of the biological systems along with anti-corrosion property.…”

A sustainable route toward the synthesis of highly substituted imidazole and quinoxaline derivatives using CuO@g‐C3N4 as an efficient and reusable heterogeneous catalyst

“…Furthermore, quinoxaline applies its significance in biological activities, efficient electron luminescent materials, material chemistry, etc 30–33 . A few reports that are available via condensation of diketones and diamines for the synthesis of quinoxalines are the use of molecular iodine, montmorillonite, oxalic acid, ZrO 2 ‐AlO 3 , VB 1 @g‐C 3 N 4 , etc 34–38 . Table 1 shows some of the reported works for the synthesis of quinoxalines.…”