1. Introduction

1. 1. Introduction ily separable from thl.: re.lction products [3]. Among the various heterogeneous catalysts, particularly, silica gel Solid .lcids and especi..lly those based on micelle-tem- impregnated with sodium bisulfate has advantages of low plated silicas and other mesoporous high surf:'lce area su;,- cost, ease of preparation [3a], and catalyst recycling. port materials are beginning .0 play d signific.mt role in t:'~ The prevalence of imidazoles in natural products and greening of fine and spel.:'iality chemicals manufacturi::g pharmacologically acti\'e compounds has instituted a prl"\cl.'sses. A wide range of importint org.lnic re.lctil':1S di\'erse array of synthetic approaches to these heterocycles can be efficiently catalyzed by these materials, which c:!n [4]. However, despite intensive effort, only a handful of be Jesigned to provide different types of acidity as well as general methodologies exist for the construction of highly high degrees of reaction selectivity. The solid acids gene:-- substituted imid.lzoles. R~cently, several 4,5-diaryl-substi- ally have high turnover number$ and can be easily ser.1- tuted imidazoles have been identified .1$ potent inhibitl"\rs rated fI'om the organic component-. [1]. V$e of solid of p38 MAP kin.lse [5~ and thus have rekindled an supported rc.lgent$ [2] h:'lve rel.:'eivedconsid~rable impl"r- incre.lsed interest in 'btaining tri- and tetra-substituted tance in organic synthesi$ b~C.lU$-:of their eas~ of handli!:f. imid.lzoles via ab:.olute r~giocontro11ed processes. enh.mced reaction time$, gre.lte: selecti\ity. simrle In continuation of our previous \1;'ork on the applil.:':.l- workup. .md recoverabi1ity of c:.ltalysts. tions of solid supports tor development of new synth~tic Rer~l1tly, NaHSO4-SiOz, a$ an inexpen$ive and el.:'\.'- methodologies [61 and ~eterocyclic compounds cont.1ining friendly catalyst, has been effectively utilized in organic nitrogen [6], and due to the resultant pharmacological synthesis as an acid catalyst or an accelerator. which is e:.l$- interest in compound$ \\'hich belong to the imidazole family, in this paper, we wish to report the solve-llt-free synthesis of tetrasub$tituted imidazoles 4a-1 using ~ponding author. NH4OAc/NaHSO4 supported onto siliC.1 gel under micro- E.mailatltlre,-;s: ar_karimi55@yahoo.com K~rimi), (..\.R. wave irradiation or classic:.lI heating (Schemes 1 and 2). 1561'-;367/5 -sec front m~ttcr e 2006 Published by Els':\ler BY doi: 11J_1()16/j.:~tcom.2006.04.0~