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A series of novel 2-(1H-benzimidazol-2-ylsulfanyl)-N-(4-oxo-2-phenyl-thiazolidin-3yl)-acetamide 5a-j have been synthesized from various aldehydes and 2-(5-phenyl-[1,3,4]-oxadiazol-2-ylmethylsulfanyl)-1H-benzimidazole 6a-j from various benzoic acids. These compounds were screened for their in-vitro anti-bacterial activity against Staphylococcus aureus and Enterococcus faecalis as Gram positive, Klebsiella pneumoniae and Escherichia coli as Gram negative bacterial strains and for in-vitro anti-fungal activity against Asperigillus fumigatus and Candida albicans. The in vitro cytotoxic properties were studied using brine shrimp bioassay. Results revealed that, compounds 5b, 5d, 5g, 5i, 6b, 6e, 6f, and 6i showed excellent activity against a panel of microorganisms. The cytotoxic activities of 5b, 5g, 5i, 6b, 6f, 6h, and 6i were found to be good. All the newly synthesized compounds were characterized by elemental analysis, IR, (1)H-NMR, (13)C-NMR and MS.

An eco-friendly catalytic amount (0.3 g) of tungstate-promoted zirconia (WO x /ZrO2) solid acid catalyst has been explored in the synthesis of 2-aryl benzimidazoles using aryl aldehydes and o-phenylenediamine. This is one of the fundamental aspects in green chemistry for simple experimental and product isolation protocol combined with easy recovery and reusability of the catalyst. It is expected to contribute in the development of clean and environment friendly strategy for synthetic protocols. The incorporated promoter showed strong influence on the surface and bulk properties of zirconia. The catalytic activity results suggest that the methodology adopted offers significant improvements for the synthesis of benzimidazole derivatives with respect to yields, simplicity and green aspects by avoiding toxic conventional catalysts and solvents. Henceforth, a good substrate conversion and excellent product selectivity were obtained over tungstate promoted zirconia solid acid catalyst. A straightforward and general method has been developed for the synthesis of 2-aryl benzimidazoles using aryl aldehydes and o-phenylene diamine in the presence of eco-friendly tungstate-promoted zirconia (WO x /ZrO2) solid acid catalyst.

A new series of novel 5-(nitro/bromo)-styryl-2-benzimidazoles (1-12) has been synthesized by simple, mild and efficient synthetic protocol by attempted condensation of 5-(nitro/bromo)-o-phenylenediamine with trans-cinnamic acids in ethylene glycol. Screening for in vitro anti-tubercular activity against Mycobacterium tuberculosis H(37) Rv, anti-bacterial activity against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae bacterial strains and anti-fungal activity against Candida albicans and Asperigillus fumigatus fungal strains were carried out. Compounds 5, 7, 8, 9, 11 showed higher anti-tubercular activity and compounds 7, 8, 10, 11, 12 have proved to be effective with MIC (microg/ml) and emerged as lead molecules showing excellent activities against a panel of microorganisms. All synthesized compounds were characterized using IR, (1)H, (13)C NMR, GC-MS and elemental analysis.

In this research work, we report an efficient and easy method for preparation of 2-arylbenzimidazoles from o-phenylenediamines and phenoxyacetic acids under microwave condition using a Wells–Dawson heteropolyacid (H6P2W18O62 · 24H2O) as catalyst. The heterogeneous reaction conditions provided a very simple, environmentally friendly, clean, economical and selective protocol, for the preparation of benzimidazole derivatives. The catalyst is easily recycled and reused without loss of the catalytic activity. In this research work, we report an efficient and easy method for preparation of 2- arylbenzimidazoles from o-phenylenediamines and phenoxyacetic acids under microwave condition using a Wells-Dawson heteropolyacid (H6P2W18O62 · 24H2O) as catalyst. The heterogeneous reaction conditions provided a very simple, environmentally friendly, clean, economical and selective protocol, for the preparation of benzimidazole derivatives.

Some of the newly synthesized compounds, e.g. (Va), show significant anti-pyretic activities comparable with standard drug aspirine.

A group of 1,3,4-oxadiazoles and 4-thiazolidinones containing a 2-mercapto-benzimidazole moiety is synthesized and screened for new lead structures.

A variety of new azetidinone derivatives bearing chromene moiety is synthesized via reaction of azomethines (I) with chloroacetyl chloride.

Developing novel antimicrobial drugs is increasingly important in the modern pharmaceutical industry. A series of novel 3-chloro-4-[4-(2-oxo-2H-chromen-4-ylmethoxy)phenyl]-1-phenylazetidin-2-ones 5a-o have been synthesized from 4-bromomethylcoumarins 1a-e and 4-aryliminomethyl-phenols 3a-c. These compounds were screened for their in-vitro antibacterial activity against two Gram-positive (Staphylococcus aureus and Vancomycin resistant enteroccoccus) and two Gram-negative (Escherichia coli and Shigella dysentery) bacterial strains and antifungal activity against Aspergillus fumigatus, Candida albicans, and Penicillium. Results revealed that compounds 5c, 5f, 5h, 5j, and 5m showed excellent activity against a panel of microorganisms. The brine-shrimp bioassay was also carried out to study their in-vitro cytotoxic properties and two compounds, 5h and 5m, possessing LD(50) = 7.154x10(-4 )M and 5.782x10(-4) M, respectively, displayed potent cytotoxic activity against Artemia salina. The presence of a chlorine group in the coumarin moiety, its effect on their antibacterial, antifungal, and cytotoxic activities is discussed. All newly synthesized compounds were characterized by elemental analysis, IR, (1)H-NMR,( 13)C-NMR, and MS.

A novel series of 4-[4-(6-phenyl-pyrimidin-4-yl)-phenoxymethyl]-chromen-2-ones [5-7(a-e)] were synthesized from various 4-bromomethyl coumarins 1(a-e). The synthesized compounds were screened for in-vivo analgesic and anti-pyretic activities at a dose of 25 and 100 mg/kg body weight (b.w), respectively. Among them, compounds 5(d), 6(c) and 7(d) exhibited significant analgesic activity comparable with standard drug analgin using Tail-flick model. Compounds 5(a) and 7(a-d) showed significant anti-pyretic activities comparable with standard drug aspirin using yeast-induced pyrexia model. DNA cleavage study by agarose gel electrophoresis method was also studied. Qualitative SAR studies indicate that, compounds with amino group at 2-position of pyrimidine ring enhances analgesic and anti-pyretic activities and compounds with hydroxyl and thio group at 2-position of pyrimidine ring increase DNA cleavage activities.

In seeking broad spectrum pharmacological activities of benzimidazole derivatives, a group of 4-thiazolidinones 5(a-j) and 1,3,4-oxadiazoles 6(a-j) containing 2-mercapto benzimidazole moiety were synthesized and screened for in vivo anticonvulsant activity by Maximal Electroshock (MES) model and antidiabetic activity using Oral Glucose Tolerance Test (OGTT). Compounds (5c), (5d), (5g) and (5i) exhibited potent anticonvulsant results and (6c), (6d), (6h) and (6i) showed excellent antidiabetic activities and also pharmacophore derived from active molecules suggested that presence of -OH group was a common feature in all active compounds. In DNA cleavage studies, compound (5d) cleaved DNA completely as no trace of DNA was found. On the other hand, a sharp streak was found for compounds (5c), (6a) and (6d).

A novel series of 3-chloro-4-[4-(2-oxo-2H-chromen-4-ylmethoxy)-phenyl]-1-phenyl-azetidin-2-one derivatives (5a-j) have been synthesized from 4-aryloxymethylcoumarins (1a-e) and 4-aryliminomethyl-phenols (3a-b). The title compounds were screened for their in vitro anti-bacterial and anti-fungal activities. Results revealed that, compounds (5c), (5f), (5h) and (5j) showed excellent anti-microbial activity against a panel of microorganisms. Brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties among which (5h) and (5j) displayed potent cytotoxic activity against Artemia salina. The DNA cleavage activity of some compounds was studied by agarose gel electrophoresis method. All synthesized compounds were characterized using IR, (1)H NMR, (13)C NMR, MS and elemental analysis.