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The formation of a novel ring system, furo[2,3‐h][1,6]naphthyridine via the Smiles rearrangement and intramolecular cyclization is described. Cyclization of 5‐(ω‐hydroxyalkylamino)‐8‐methyl‐1,2‐dihydrofuro[2,3‐h][1,6]naphthyridines provided novel spiro compound with rearrangement.

Objective: This study was conducted to synthesise some 2-substituted-5-nitro benzimidazole derivatives to evaluate their antioxidant activity. Methods:The titled compounds were synthesised by sodium metabisulfite mediated reaction of 4-nitro-1, 2-phenylenediamine with a number of para-substituted benzaldehydes. The antioxidant activity was evaluated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Results: All the compounds exhibited good antioxidant activity having IC50Conclusion: Among the synthesised compounds, compounds 3a-c have been found to possess the most prominent antioxidant activity which might be attributed due to the presence of chloro, bromo and fluoro substituents in the molecule. The compounds may act as the future lead(s) for the development of potential antioxidant compounds.values in the range of 3.17 to 7.59 µg/ml while that of standard butylated hydroxytoluene (BHT) was 18.42 µg/ml. [10] activity. A Recent report shows that two groups of substituted benzimidazoles, namely 5, 6-dinitro and 2-trifluoromethylderivatives are the promising candidates for antimicrobial drugs [11,12]. Besides 2-mercapto-benzimdiazole compounds have been reported to have significant antimicrobial properties [13]. KeywordsTherefore benzimidazole has drawn considerable interest as an important scaffold in drug discovery [14]. However, many of the activities of benzimidazole derivatives have not been extensively investigated like antioxidant activity. But the compounds having antioxidant and free radical scavenging properties are considered to be used for the prevention or treatment of human diseases like neurodegenerative disorders, atherosclerosis, rheumatoid arthritis and carcinogenesis, because oxygen-derived free radicals such as superoxide (O2 The major reagents for synthesis were purchased from SigmaAldrich Chemical Corporation and were used after being purified by standard procedures. The other chemicals used were of reagent/analytical grade. Melting points were determined by open capillary method with the help of WRS-1B (Germany) digital melting point apparatus and are uncorrected. All the reactions were monitored by TLC on silica gel thin layer plates. UV data were taken using Shimadzu UV-166V spectrophotometer. IR spectra were recorded by using the KBr disk on Shimadzu IR-470 spectrophotometer..-), nitric oxide (NO.), hydroxyl (OH.) and peroxy (ROO.) play an important role in causing these diseases [15]. Nsubstituted benzimidazole derivatives and 2-aryl substituted benzimidazole and benzothiazole derivatives have recently been reported to show significant antioxidant activity [16,17]. Taking in mind all these recent observations regarding biological activities of benzimidazole derivatives we became interested in synthesising 2-substituted benzimidazole derivatives in order to investigate their anti-oxidant activity. In the present study, we had studied the antioxidant activity of 2-substituted-5-nitro benzimidazole derivatives 3 (scheme 1) and we herein report the results of...