American Journal of Organic Chemistry 2012, 2(2): 1-6 DOI: 10.5923/j.ajoc.20120202.01 SBSA as a New and Efficient Catalyst for the One-Pot Green Synthesis of Benzimidazole Derivatives at Room Temperature Sami Sajjadifar * , Seyed Ahmad Mirshokraie, Nematollah Javaherneshan, Omid Louie Department of Chemistry, Payame Noor University, P. O. BOX 19395-4697, Tehran, Iran Abstract silica boron sulfonic acid (SBSA) was easily prepared and used as a new and efficient solid acid catalyst for the synthesis of benzimidazole derivatives with high isolated yields. Various substituted benzimidazoles were synthesized by a combination of o-phenylenediamines and aldehydes in the presence of boron sulfonic acid in with good yields in water and under a mild reaction conditions. This method is also applicable for precursors such as: aromatic and unsaturated alde- hydes and o-phenylenediamines. Keywords Silica Boron Sulfonic Acid, SBSA, Solid Acid, Benzimidazole Synthesis, Drugs, Green Synthesis 1. Introduction Benzimidazole moieties are classified under several classes of drugs[1], based on the possible substitution at different positions of the benzimidazole nucleus. Benzimi- dazole derivatives exhibit significant activity against several viruses such as HIV, human cytomegalovirus (HCMV)[2], herpes (HSV-1)[3], RNA[4] and influenza[4]. Furthermore they have been also used to act as topoisomerase inhibi- tors[6], selective neuropeptide YY1 receptor antagonists[7], angiotensin II inhibitors[8], potential antitumor agents[9] and smooth muscle cell proliferation inhibitors[10]. In addi- tion benzimidazoles are very important precursors in or- ganic synthesis. Vitamin B 12 constitutes a milestone in the chemistry of benzimidazoles. Bisbenzimidazole is DNA- minor grove binding agents possessing anti-tumour activ- ity[11]. A number of methods have been reported for the synthe- sis of benzimidazoles such as the condensation of o-aryldiamines and aldehyde in refluxing nitrobenzene[12]. The coupling of phenylenediamines and carboxylic acids [13] or their derivatives (nitriles, imidates, or orthoest- ers)[14], which often requires strong acidic conditions[15], and sometimes combines with very high temperatures or microwave irradiation[16]. The other route involves a two-step procedure that includes the oxidative cyclo- dehy- drogenation of Schiff bases, which are often generated from the condensation of o - phenylenediamines and * Corresponding author: ss_sajjadifar@yahoo.com (Sami Sajjadifar) Published online at http://journal.sapub.org/ajoc Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved aldehydes. Dir - condensation of o-aryldiamines and alde- hydes is not a good synthetic reaction, as it is well known to yield a complex mixture, being 1,2-disubstituted benzimi- dazoles, the bis anil and dihydrobenzimidazoles as the main side products[17]. However, the addition of transition metal, namely copper (II) acetate[18], mercury oxide[19] or lead tetracetate[20] allows a partial selective synthesis of ben- zimidazoles. In recent years, solvent-free synthesis of ben- zimidazoles under microwave irradiation using Yb(OTf) 3 [21], KSF clay[22], PPA[23], Na 2 SO 4 [24], K-10 clay[25], metal halide supported alumina[26] and solid support[27] have been reported. Various oxidative and catalytic reagents such as sulfamic acid[28], I 2 [29], DDQ[30], Air[31], Oxone[32], FeCl 3 ·6H 2 O[33], In(OTf) 3 [34], Yb(OTf) 3 [35], Sc(OTf) 3 [36], KHSO 4 [37], IL[38], Ni- trobenzene[39] , 1,4 – benzo quinine [40], tetracyano eth- ylene [41], benzofuroxan [42], MnO 2 [43], Pb(OAc) 4 [44], NaHSO 3 [45], Na 2 S 2 O 5 [46], DMP[47], NH 4 VO 3 [48], have been employed. Benzimidazole derivatives can be synth- sised by another catalysts such as CAN [49], p-TsOH[50], BE 3 .OEt 2 [51], KHSO 4 [52], CuPy 2 Cl 2 [53], polyphosphoric acid[54], mineral acids[55], boric acid [56], p-TSA [57], Dowex 50W [58], SSA [59], solid acid scolecite [60], YCl 3 [61], Zn(OAc) 2 [62], N- halosuccinamide (X = Cl, Br, I) [63], Yb(OTf) 3 [64], PEG-100 [65], (NH 4 )H 2 PW 12 O 40 [66], bismuth chloride[67], mercury chloride[68], Ionic liq- uids[69], AMA[70], TBAF[71], H 2 O 2 / SiO 2 -FeCl 3 [72], HBF 4 -SiO 2 [73] and MoO 3 /CeO 2 -ZrO 2 [74]. Unfortunately, many of these processes suffer some limitations, such as drastic reaction conditions, low yields, tedious work up procedures and co-occurrence of several side reactions. In this article, we report a simple and efficient method for the synthesis of benzimidazole derivatives using SBSA as a