caa a22 4500 445878460 CHVBK 20180317145534.0 cr unu---uuuuu 170323e20110201xx s 000 0 eng 10.1007/s11030-009-9213-1 doi (NATIONALLICENCE)springer-10.1007/s11030-009-9213-1 Supported heteropoly acids offering strong option for efficient and cleaner processing for the synthesis of imidazole derivatives under solvent-free condition [Elektronische Daten] [Ezzat Rafiee, Houri Mahdavi, Mohammad Joshaghani] A series of 12-phosphotungstic acid (PWA) supported on various porous carriers, such as silica, alumina, titania, clay, and carbon were prepared, and their catalytic performance evaluated in the synthesis of imidazoles in solvent-free condition. It was found that PWA supported on silica (PWA/SiO2) showed higher activity compared to other catalysts. The observed behavior has more or less correlated with the acidic characteristic found through the potentiometrically titrated acidic sites and proton availability. The catalyst was characterized by FTIR, XRD, TGA/DSC, BET, and SEM. The presence of the Keggin structure can be followed by the above techniques, eliminating any doubt about the collapse of the supported anion. It can be observed that the process tolerates both electron donating and electron withdrawing substituents on the aldehyde with both benzil and benzoin. The general applicability of the method is demonstrated by using both benzylic and aromatic amines. The yields obtained were excellent without forming any side products such as trisubstituted imidazoles, which are normally produced in the presence of strong acids. The protocol developed using PWA/SiO2 is superior in terms of process simplicity, reusable catalyst, high yields, short reaction time, and preclusion of toxic solvent. Springer Science+Business Media B.V., 2010 Imidazoles nationallicence Supported heteropoly acid nationallicence Solvent free nationallicence Benzil nationallicence Benzoin nationallicence Rafiee Ezzat Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut Mahdavi Houri Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut Joshaghani Mohammad Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut Molecular Diversity Springer Netherlands 15/1(2011-02-01), 125-134 1381-1991 15:1<125 2011 15 11030 https://doi.org/10.1007/s11030-009-9213-1 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11030-009-9213-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rafiee Ezzat Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut NATIONALLICENCE 700 1- Mahdavi Houri Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut NATIONALLICENCE 700 1- Joshaghani Mohammad Faculty of Chemistry, Razi University, 67149, Kermanshah, Iran aut NATIONALLICENCE 773 0- Molecular Diversity Springer Netherlands 15/1(2011-02-01), 125-134 1381-1991 15:1<125 2011 15 11030 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer