%0 Journal Article
%T A Simple, Efficient Synthesis of 2-Aryl Benzimidazoles Using Silica Supported Periodic Acid Catalyst and Evaluation of Anticancer Activity
%A Vyankat A. Sontakke
%A Sougata Ghosh
%A Pravin P. Lawande
%A Balu A. Chopade
%A Vaishali S. Shinde
%J ISRN Organic Chemistry
%D 2013
%R 10.1155/2013/453682
%X A new, efficient method for the synthesis of 2-aryl substituted benzimidazole by using silica supported periodic acid (H5IO6-SiO2) as a catalyst has been developed. The salient feature of the present method includes mild reaction condition, short reaction time, high yield and easy workup procedure. The synthesized benzimidazoles exhibited potent anticancer activity against MCF7 and HL60 cell lines. 1. Introduction The benzimidazole nucleus is commonly present in a large number of natural products as well as pharmacologically active compounds [1]. It shows a wide spectrum of biological and pharmacological properties such as antifungal [2], antimicrobial [3], anthelmintic [4, 5], antiviral [6, 7], topoisomerase inhibition [8] and anticancer activities [9]. Some of their derivatives are marketed as antifungal drug (Carbendazim) [10], anthelmintic drug (Mebendazole and Thiabendazole) [11], antipsychotic drug (Pimozide) [12] and antiulcer agent (Omeprazole) [13]. Owing to their interesting pharmacological properties, great attention has been paid to the synthesis of benzimidazoles. Two main synthetic methods were well known in the literature. The most common method is direct condensation of 1,2-phenylenediamine and carboxylic acids [14, 15] or their derivatives [16], that require strong acidic conditions and sometimes need high temperature or the use of microwave [17]. The other synthetic route involves a two-step procedure that includes the cyclo-dehydrogenation of aniline Schiff¡¯s bases, which are often generated in situ from the condensation of 1,2-phenylenediamines and aldehydes [18], followed by oxidation with stoichiometric amount of oxidants, such as MnO2 [19], Oxone [20], NaHSO3 [21, 22], I2/KI/K2CO3/H2O [23] or catalytic use of CAN [24] and AIKIT-5 [25]. More recently, 2-alkyl substituted benzimidazoles are synthesized by using hexafluorophosphoric acid under microwave condition [26]. There is renewed interest in the silica supported catalyzed reactions [27]. These reactions have relatively shorter reaction time with high yield and cleaner chemistry. Moreover, the catalyst is easily separated from reaction mixture by simple filtration. There are very few reports involving solid supported catalyzed reaction for synthesis of benzimidazole derivatives. Jacob et al. [28] synthesized 1,2-disubstituted benzimidazoles by silica supported ZnCl2 catalyst that was found to be of poor yield. Patil et al. [29] developed a method for synthesis of 2-alkyl benzimidazoles using silica supported HBF4. Paul and Basu [30] described the synthesis of 1,2-disubstituted
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2013/453682/