untitled European Journal of Chemistry 6 (3) (2015) 270‐274 European Journal of Chemistry ISSN 2153‐2249 (Print) / ISSN 2153‐2257 (Online)  2015 Atlanta Publishing House LLC ‐ All rights reserved ‐ Printed in the USA http://dx.doi.org/10.5155/eurjchem.6.3.270‐274.1242 European Journal of Chemistry Journal webpage: www.eurjchem.com Synthesis of some novel benzimidazole derivatives and their biological evaluation Dnyandev Radhu Gund 1, Balivada Venkata Satyasai Varaprasad Rao 2, Pandurang Narayanrao Mandhare 3 and Sanjay Dashrath Vaidya 1,* 1 Department of Chemistry, Jagdishprasad Jhabarmal Tibrewala University, Jhunjhunu, Rajasthan, 333001, India 2 Department of Chemistry, Pacific University, Udaipur, Rajasthan, 313024, India 3 Department of Chemistry, Shreemati Nathibai Damodar Thackersey Women’s University, Mumbai, 400049, India * Corresponding author at: Department of Chemistry, Jagdishprasad Jhabarmal Tibrewala University, Jhunjhunu, Rajasthan, 333001, India. Tel.: +91.0810.4883369. Fax: +91.01595. 265114. E‐mail address: sanjayjjtu@gmail.com (S.D. Vaidya). ARTICLE INFORMATION ABSTRACT DOI: 10.5155/eurjchem.6.3.270‐274.1242 Received: 11 January 2015 Received in revised form: 05 April 2015 Accepted: 05 April 2015 Published online: 30 September 2015 Printed: 30 September 2015 A series of novel benzimidazole derivatives have been synthesized by the condensation of o‐ phenylenediamine with 4‐bromophenoxy acetic acid and product obtained was alkylated at the benzimidazole ‐NH with different electrophilic reagents. Subsequent reactions of the products by the Suzuki Coupling between benzimidazole derivatives and phenylboronic acid derivatives were accomplished. All these compounds were characterized by FT‐IR, 1H NMR, MS and elemental analysis. These compounds were screened for their potential antibacterial and antifungal activities. This exhibited some promising results towards testing organism in‐ vitro. KEYWORDS Alkylation Benzimidazole Suzuki coupling Antifungal activity Phenyl boronic acid Antibacterial activity Cite this: Eur. J. Chem. 2015, 6(3), 270‐274 1. Introduction The benzimidazole nucleus is a useful structure for research and development of new pharmaceutical molecules. Benzimidazole are among the important heterocyclic compounds found in several natural and non‐natural products such as Vitamin B12 [1], marine alkaloid kealiiquinone [2], benzimidazole nucleosides [3,4] etc. Some of their derivatives are marketed as anti‐fungal [5], anti‐helmintic [6,7] and anti‐ psychotic [8,9] drugs and other derivatives have been found to possess some interesting bioactivities such as anti‐tubercular [10], anti‐cancer [11,12], HIV‐inhibitors [13], anti‐hyperten‐ sive agent [14], anti‐inflammatory activity [15], anti‐allergic activity [16], anti‐diabetic activity [17], anticonvulsant activity [18], DNA inhibitory activity [19] etc. We have also published some series of biologically active benzimidazoles [20]. Owing to the immense biological importance of benzimidazole derivatives, we now synthesized some novel class of benzimi‐ dazole derivatives and their biological activity screening studies. 2. Experimental 2.1. Chemicals Phenylboronic acid, 4‐ethyl phenylboronic acid, palladium acetate, potassium fluoride and 18‐crown‐6 ether obtained from Aldrich. o‐Phenylenediamine, 4‐bromophenoxy acetic acid, alkylating agents and sodium hydride were obtained from commercial suppliers. All the solvents used were of commercial grade only. 2.2. Instrumentations Melting points recorded on a MRVIS Series, Lab. India Instrument. TLC analysis was done using pre‐coated silica gel plates and visualization was done using iodine/UV lamp. Infrared spectra were recorded on Perkin Elmer model FT‐IR using the KBr disc. 1H NMR spectra of the compounds were recorded on BRUKER Avance II 400 MHz NMR spectrometer with CDCl3 as solvent unless otherwise mentioned. Elemental analysis was carried out on a Perkin Elmer Series II Elemental Analyzer 2400. Gund et al. / European Journal of Chemistry 6 (3) (2015) 270‐274 271 BrO NH2 NH2 N H N O Br Reflux, 6 h (1) (2) (3) HOOC + N H N O Br Base (3) N N O Br R1 (4a-g) 4a, R1=CH3 4b, R1=CH2-CH3 4c, R1=CH2-CH2-CH3 4d, R1=CH2-CH2-CH2-CH3 4e, R1=CH2-CH-(CH3)2 4f, R1=CH2-C6H5 4g, R1=SO2-CF3 4 N HCl R1-X Scheme 1 2.3. Synthesis 2.3.1. Synthesis of 2‐(4‐bromo‐phenoxymethyl)‐1H‐ benzimidaziole by condensation of o‐phenylenediamine (1) (OPDA) with 4‐bromophenoxy acetic acid (2) under Philip’s condition [21] To a solution of 4‐bromophenoxy acetic acid (2) (10.8 g, 50 mmol) and 4 N HCl (50 mL), o‐phenylenediamine (1) (5.40 g, 50 mmol) was added. The reaction mixture was heated slowly to reflux temperature for 6 hours (TLC monitoring). The reaction mixture was then cooled to room temperature and neutralized with 10% aq. NaHCO3 till the neutral pH. The reaction mixture was stirred for 30 min resulted free flowing suspension. The solid separated out was filtered, washed with water (3 × 30 mL) and dried under vacuum to afford an off‐ white solid. The crude product was recrystallized from hot aq. ethanol to obtain the pure white crystalline compound 3 (Scheme 1). Yield: 13.5 g, 89 %. M.p.: 260‐262 °C (Lit. [22]: 260 °C). 2.3.2. Synthesis of compound 3 via microwave irradiation To a solution of 4‐bromophenoxy acetic acid (2) (10.8 g, 50 mmol) and 4 N HCl (50 mL), o‐phenylenediamine (1) (5.40 g, 50 mmol) was added. The reaction mixture was irradiated in a microwave oven at 100 W for 3 min at 100 °C. The reaction mixture was then cooled to room temperature and neutralized with aq. NaHCO3 (10%) till the neutral pH. The reaction mixture was stirred for 30 min resulted free flowing suspension. The solid separated out was filtered, washed with water (3 × 30 mL) and dried under vacuum to afford an off‐ white solid. The crude product was recrystallized from hot aq. ethanol to obtain the pure white crystalline compound 3. Yield: 13.0 g, 87%. M.p.: 260‐262 °C (Lit. [22]: 260 °C). 2.3.3. General procedure for the synthesis of N‐alkylated derivatives of 2‐(4‐bromo‐phenoxymethyl)‐1H‐ benzimidaziole (4a‐g) [23] To a solution of 2‐(4‐bromo‐phenoxymethyl)‐1H‐ benzimidazole (2 mmol) (3) in dimethylformamide (10 mL) was added sodium hydride (60 %, 2.4 mmol) lot wise at 0 °C. After completion of addition, the temperature of the reaction mixture was slowly raised to room temperature and stirred at this temperature for 1 h. The reaction mixture was again cooled to 0 °C and the respective alkyl halide (2.4 mmol) was added at 0 °C. The temperature of the reaction mixture was then allowed to warm to room temperature and stirred for 2 h. After completion of the reaction, (TLC monitoring) water (50 mL) was slowly added to reaction mixture and extracted with ethyl acetate (2 × 25 mL). The organic layer was washed with water (2 × 25 mL), brine and dried over anhydrous sodium sulfate and concentrated under vacuum to yield the corresponding N‐substituted derivatives (4a‐g) the crude compounds were recrystallized from hot aq. ethanol to obtain pure products. Scheme 1. 2.3.4. General procedure for the synthesis of Suzuki coupling [24‐26] compounds 5a‐n To a solution of N‐alkylated benzimidazole compounds 4a‐ g (2.5 mmol) in toluene (50 mL) was added phenylboronic acid and 4‐ethylphenylboronic acid (3 mmol), presence of potassium fluoride (5 mmol), 18‐crown‐6 ether (1.25 mmol) and palladium acetate (0.125 mmol). The reaction mixture was then refluxed and maintained for 3 h (TLC monitored). Upon completion, reaction mixture was allowed to cool to room temperature and filtered through hyflo. The toluene filtrate was washed with 5% NaHCO3 (25 mL), brine (25 mL) and water (25 L and dried over anhydrous sodium sulphate. Evaporation of the solvent yielded crude products, which were subjected to column chromatography to isolate the pure products 5a‐n, Scheme 2. 2.3.5. Synthesis of Suzuki coupling compounds 5a‐n via microwave irradiation To a solution of N‐alkylated benzimidazole compounds 4a‐ g (2.5 mmol) in toluene (50 mL) was added phenylboronic acid and 4‐ethylphenylboronic acid (3 mmol), presence of potassium fluoride (5 mmol), 18‐crown‐6 ether (1.25 mmol) and palladium acetate (0.125 mmol) was heated under microwave conditions at 150 °C and 200 Watt for 2 minutes. It was allowed to cool to room temperature and filtered through hyflo. The toluene filtrate was washed with 5% NaHCO3 (25 mL), brine (25 mL) and water (25 mL) and dried over anhydrous sodium sulphate. Evaporation of the solvent yielded crude products, which were subjected to column chromatography to isolate the pure products 5a‐n, Scheme 2. 2‐(Biphenyl‐4‐yloxymethyl)‐1‐methyl‐1H‐benzoimidazole (5a): Colour: White. Yield: 60%. M.p.: 83‐85 °C. FT‐IR (KBr, , cm‐1): 2961 (C‐H), 1683 (C=N), 1011 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 3.80 (s, 3H, CH3‐N‐), 5.29 (s, 2H, CH2‐O‐), 6.86‐ 6.90 (d, 2H, J = 8.1 Hz, Ar‐H), 7.18‐7.34 (m, 8H, Ar‐H), 7.43‐ 7.45 (d, 1H, J = 8 Hz, Ar‐H), 7.71‐7.75 (dd, 2H, J = 8.7 Hz, Ar‐H). MS (EI, m/z (%)): 315.2 (M+1). Anal. calcd. for C21H18N2O: C, 80.23; H, 5.77; N, 8.91. Found: C, 80.10; H, 5.90; N, 9.04%. 272 Gund et al. / European Journal of Chemistry 6 (3) (2015) 270‐274 Scheme 2 2‐(Biphenyl‐4‐yloxymethyl)‐1‐ethyl‐1H‐benzoimidazole (5b): Colour: White. Yield: 70.27%. M.p.: 88‐90 °C. FT‐IR (KBr, , cm‐1): 2902 (C‐H), 1674 (C=N), 1045 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.46‐1.50 (t, J = 7.24 Hz, 3H, CH3‐CH2), 4.33‐4.38 (q, J = 7.24 Hz, 2H, CH2‐N), 5.41 (s, 2H, CH2‐O‐), 7.14‐ 7.17 (m, 2H, Ar‐H), 7.25‐7.33 (m, 3H, Ar‐H), 7.38‐7.42 (m, 3H, Ar‐H), 7.51‐7.53 (d, J = 8.84 Hz, 4H, Ar‐H), 7.79‐7.81 (dd, J = 6.92 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 329.2 (M+1). Anal. calcd. for C22H20N2O: C, 80.46; H, 6.14; N, 8.53. Found: C, 80.56; H, 6.20; N, 8.65. MS (m/z): (M+1) 329.2%. 2‐(Biphenyl‐4‐yloxymethyl)‐1‐propyl‐1H‐benzoimidazole (5c): Colour: White. Yield: 64.86%. M.p.: 95‐98 °C. FT‐IR (KBr, , cm‐1): 2947 (C‐H), 1672 (C=N), 1045 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.02‐1.05 (t, J = 7.40 Hz, 3H, CH3‐CH2), 1.90‐2.00 (m, 2H, CH2‐CH3), 4.27‐4.31 (t, J = 7.30 Hz, 2H, CH2‐ N), 5.44 (s, 2H, CH2‐O‐), 7.17‐7.19 (d, J = 8.64 Hz, 2H, Ar‐H), 7.28‐7.34 (m, 3H, Ar‐H), 7.40‐7.45 (m, 3H, Ar‐H), 7.54‐7.56 (d, J = 8.32 Hz, 4H, Ar‐H), 7.80‐7.84 (dd, J = 8.28 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 343.2 (M+1). Anal. calcd. for C23H22N2O: C, 80.67; H, 6.48; N, 8.18. Found: C, 80.60; H, 6.60; N, 8.12%. 2‐(Biphenyl‐4‐yloxymethyl)‐1‐butyl‐1H‐benzoimidazole (5d): Colour: White. Yield: 68.91%. M.p.: 100‐103 °C. FT‐IR (KBr, , cm‐1): 2961 (C‐H), 1683 (C=N), 1011 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 0.94‐0.98 (t, J = 7.40 Hz, 3H, CH3‐ CH2) , 1.38‐1.46 (m, 2H, CH2‐CH3), 1.82‐1.89 (m, 2H, CH2‐CH2‐ CH3 ), 4.27‐4.31 (t, J = 7.64 Hz, 2H, CH2‐N ), 5.42 (s, 2H, CH2‐O), 7.13‐7.17 (m, 2H, Ar‐H), 7.25‐7.33 (m, 3H, ArH), 7.37‐7.42 (m, 3H, Ar‐H), 7.50‐7.53 (m, 4H, Ar‐H), 7.79‐7.84 (dd, J = 6.8 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 357.2 (M+1). Anal. calcd. for C24H24N2O: C, 80.87; H, 6.79; N, 7.86. Found: C, 80.70; H, 6.85; N, 7.81%. 2‐(Biphenyl‐4‐yloxymethyl)‐1‐isobutyl‐1H‐benzoimidazole (5e): Colour: White. Yield: 66.21%. M.p.: 99‐102 °C. FT‐IR (KBr, , cm‐1): 2937 (C‐H), 1676 (C=N), 1037 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 0.97‐0.99 (d, J = 6.68 Hz, 6H, (CH3)2‐ CH), 2.33‐2.38 (m, 1H, CH‐CH2), 4.11‐4.13 (d, J = 7.64 Hz, 2H, CH2‐N), 5.42 (s, 2H, CH2‐O), 7.14‐7.16 (d, J = 8.72 Hz 2H, Ar‐H), 7.25‐7.32 (m, 3H, Ar‐H), 7.36‐7.42 (m, 3H, Ar‐H), 7.51‐7.54 (d, J = 8.4 Hz, 4H, Ar‐H), 7.79‐7.81 (dd, J = 6.52 1H, Ar‐H). MS (EI, m/z (%)): 357.2 (M+1). Anal. calcd. for C24H24N2O: C, 80.87; H, 6.79; N, 7.86. Found: C, 80.70; H, 6.90; N, 7.80%. 1‐Benzyl‐2‐(Biphenyl‐4‐yloxymethyl)‐1H‐benzoimidazole (5f): Colour: White. Yield: 70.27%. M.p.: 158‐161 °C. FT‐IR (KBr, , cm‐1): 2961 (C‐H), 1677 (C=N), 1011 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 5.39 (s, 2H, CH2‐O), 5.56 (s, 2H, CH2‐ N), 7.05‐7.08 (m, 2H, Ar‐H), 7.10‐7.13 (m, 2H, Ar‐H), 7.28‐7.31 (m, 7H, Ar‐H), 7.41‐7.44 (m, 2H, Ar‐H), 7.49‐7.55 (m, 4H, Ar‐ H), 7.85‐7.87 (dd, J = 7.40, 1H, Ar‐H). MS (EI, m/z (%)): 391.2 (M+1). Anal. calcd. for C27H22N2O: C, 80.05; H, 5.68; N, 7.17. Found: C, 79.85; H, 5.80; N, 7.12%. 2‐(Biphenyl‐4‐yloxymethyl)‐1‐trifluoromethanesulfonyl‐1H‐ benzoimidazole (5g): Colour: Yellow. Yield: 80%. M.p.: 85‐88 °C. FT‐IR (KBr, , cm‐1): 2825 (C‐H), 1621 (C=N), 1352 (S=O), 1069 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 5.41 (s, 2H, CH2‐ O), 7.14‐7.17 (m, 2H, Ar‐H), 7.25‐7.33 (m, 3H, Ar‐H), 7.38‐7.42 (m, 3H, Ar‐H), 7.51‐7.53 (d, J = 8.84 Hz, 4H, Ar‐H), 7.79‐7.81 (dd, J = 6.92 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 433.2 (M+1). Anal. calcd. for C21H15F3N2O3S: C, 58.33; H, 3.50; N, 6.48. Found: C, 58.25; H, 3.60; N, 6.42%. 2‐(4’‐Ethyl‐biphenyl‐4‐yloxymethyl)‐1‐methyl‐1H‐benzoimi dazole (5h): Colour: White. Yield: 61.04%. M.p.: 84‐87 °C. FT‐ IR (KBr, , cm‐1): 2948 (C‐H), 1623 (C=N), 1024 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.17‐1.21 (t, J = 7.64 Hz, 3H, CH3‐ CH2), 2.57‐2.63 (q, J = 7.64 Hz, 2H, CH2‐CH3), 3.83(s, 3H, CH3‐ N), 5.35 (s, 2H, CH2‐O), 7.04‐7.08 (m, 2H, Ar‐H), 7.15‐7.19 (m, 2H, Ar‐H), 7.21‐7.31 (m, 3H, Ar‐H), 7.36‐7.38 (m, 2H, Ar‐H), 7.41‐7.45 (m, 2H, Ar‐H), 7.69‐7.72 (dd, J = 7.12 Hz ,1H, Ar‐H). MS (EI, m/z (%)): 343.2 (M+1). Anal. calcd. for C23H22N2O: C, 80.67; H, 6.48; N, 8.18. Found: C, 80.52; H, 6.60; N, 8.10%. 2‐(4’‐Ethyl‐biphenyl‐4‐yloxymethyl)‐1‐ethyl‐1H‐benzoimi dazole (5i): Colour: White. Yield: 71.20%. M.p.: 90‐93 °C. FT‐IR (KBr, , cm‐1): 2902 (C‐H), 1639 (C=N), 1043 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.24‐1.28 (t, J = 7.60 Hz, CH3‐CH2), 1.47‐1.51 (t, J = 7.2 Hz, 3H, CH3‐CH2‐N), 2.64‐2.70 (q, J = 7.60 Hz, 2H, CH2‐CH3), 4.34‐4.39(q, J = 7.2 Hz, 2H, N‐CH2‐CH3), 5.41 (s, 2H, CH2‐O), 7.13‐7.16 (m, 2H, Ar‐H), 7.23‐7.27 (m, 2H, Ar‐ H), 7.28‐7.34 (m, 2H, Ar‐H), 7.37‐7.41 (m, 1H, Ar‐H), 7.44‐7.46 (d, J = 8.16 Hz, 2H, Ar‐H), 7.49‐7.53 (m, 2H, Ar‐H), 7.79‐7.81 (dd, J = 6.96, 1H, Ar‐H). MS (EI, m/z (%)): 357.2 (M+1). Anal. calcd. for C24H24N2O: C, 80.87; H, 6.79; N, 7.86. Found: C, 80.90; H, 6.90; N, 7.82%. 2‐(4’‐Ethyl‐biphenyl‐4‐yloxymethyl)‐1‐propyl‐1H‐benzoimi dazole (5j): Colour: White. Yield: 60.13%. M.p.: 85‐89 °C. FT‐IR (KBr, , cm‐1): 2960 (C‐H), 1675 (C=N), 1010 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 0.89‐0.93 (t, J = 7.64 Hz, 3H, CH3‐ CH2), 1.17‐1.21 (t, J = 7.6 Hz, 3H, CH3‐CH2), 1.78‐1.86 (m, 2H, CH2‐CH3), 2.57‐2.63 (q, J = 7.64 Hz, 2H, CH2‐CH3), 4.13‐4.17 (t, J= 7.64 Hz, 2H, CH2‐CH2‐CH3), 5.30 (s, 2H, CH2‐O), 6.87‐6.90 (m, 2H, Ar H), 7.16‐7.26 (m, 5H, Ar H), 7.29‐7.33 (m, 4H, Ar H) 7.75‐7.77 (dd, J = 6.64 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 371.2 (M+1). Anal. calcd. for C25H26N2O: C, 81.05; H, 7.25; N, 7.56. Found: C, 80.92; H, 7.25; N, 7.45%. 2‐(4’‐Ethyl‐biphenyl‐4‐yloxymethyl)‐1‐butyl‐1H‐benzoimida zole (5k): Colour: White. Yield: 63.22%. M.p.: 101‐104 °C. FT‐ IR (KBr, , cm‐1): 2947 (C‐H), 1660 (C=N), 1031 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 0.87‐0.89 (t, J = 7.64 Hz, 3H, CH3‐ CH2), 1.18‐1.20 (t, J = 7.64 Hz, 3H, CH3‐(CH2)3), 1.32‐1.34 (m, 2H, CH2‐CH3), 1.78‐1.84 (m, 2H, CH2‐CH3), 2.57‐2.63 (q, J = 7.64 Hz, 2H, CH2‐CH2‐CH3), 4.13‐4.17 (t, J = 7.64 Hz, 2H, CH2‐ CH2‐ CH2‐CH3), 5.30 (s, 2H, CH2‐O), 6.87‐6.90 (m, 2H, Ar H), 7.16‐ 7.26 (m, 5H, Ar H), 7.29‐7.33 (m, 4H, Ar H), 7.75‐7.77 (dd, J = 6.64 Hz, 1H, Ar H). Gund et al. / European Journal of Chemistry 6 (3) (2015) 270‐274 273 Table 1. Antibacterial activity of compound 5a‐n (Minimal inhibition concentration, MIC). Compound Antibacterial activity (MIC, µg/mL) E. coli P. Aeruginosa S. Aureus S. Pyogenus 5a 100 62.5 200 100 5b 125 100 62.5 200 5c 100 100 200 250 5d 62.5 100 125 250 5e 125 200 125 100 5f 250 100 250 125 5g 100 200 100 125 5h 100 100 250 250 5i 250 200 250 250 5j 250 125 100 250 5k 100 125 125 200 5l 200 250 250 500 5m 150 200 250 250 5n 125 250 250 100 Gentamycin 0.05 1 0.25 0.5 Ampicillin 100 ‐ 250 100 Chloramphenicol 50 50 50 50 Ciprofloxacin 25 25 50 50 Norfloxacin 10 10 10 10 Table 2. Antifungal activity of compound 5a‐n (Minimal inhibition concentration, MIC). Compound Antifungal activity (MIC, µg/mL) C. Albicans A. Niger A. Clavatus 5a 250 >1000 >1000 5b >1000 500 500 5c 500 500 500 5d >1000 >1000 >1000 5e 1000 250 500 5f 500 >1000 >1000 5g 1000 1000 1000 5h 250 500 500 5i 1000 250 250 5j 500 500 500 5k 1000 500 1000 5l >1000 >1000 >1000 5m >1000 >1000 >1000 5n 500 500 500 Nystatin 100 100 100 Greseofulvin 500 100 100 MS (EI, m/z (%)): 385.2 (M+1). Anal. calcd. for C26H28N2O: C, 81.25; H, 7.34; N, 7.29. Found: C, 81.35; H, 7.50; N, 7.25%. 2‐(4’‐Ethyl‐biphenyl‐4‐yloxymethyl)‐1‐isobutyl‐1H‐benzoimi dazole (5l): Colour: White. Yield: 61.77%. M.p.: 103‐105 °C. FT‐ IR (KBr, , cm‐1): 2960 (C‐H), 1683 (C=N), 1011 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 0.95‐0.99 (d, J = 6.68 Hz, 6H, (CH3)2‐ CH2), 1.24‐1.28 (t, J = 7.64 Hz, 3H, CH3‐CH2) 2.33‐2.40 (m, 1H, CH‐(CH3)2, 2.65‐2.70 (q, J = 7.6 Hz, 2H, CH2‐CH3), 4.11‐4.13 (d, J = 7.6 Hz, 2H, ‐N‐CH2), 5.41 (s, 2H, ‐O‐CH2), 7.12‐7.15 (m, 2H, Ar‐H), 7.23‐7.32 (m, 4H, Ar‐H), 7.36‐7.39 (m, 1H, Ar‐H), 7.44‐ 7.44 (d, J = 8.16 Hz, 2H, Ar‐H), 7.49‐7.53 (m, 2H, Ar‐H), 7.78‐ 7.80 (dd, J = 6.64 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 385.3 (M +1). Anal. calcd. for C26H28N2O: C, 81.25; H, 7.34; N, 7.29. Found: C, 81.15; H, 7.50; N, 7.24%. 1‐Benzyl‐2‐(4’‐ethyl‐biphenyl‐4‐yloxymethyl)‐1H‐benzoimi dazole (5m): Colour: White. Yield: 62.50%. M.p.: 160‐164 °C. FT‐IR (KBr, , cm‐1): 2963 (C‐H), 1693 (C=N), 1008 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.17‐1.20 (t, J = 7.6 Hz, 3H, CH3‐CH2), 2.57‐2.63 (q, J = 7.52 Hz, 2H, ‐CH2‐CH3), 5.46 (s, 2H, ‐ O‐CH2), 5.56 (s, 2H, ‐N‐CH2), 6.93‐6.96 (m, 2H, Ar‐H), 7.00‐7.02 (m, 2H, Ar‐H), 7.17‐7.24 (m, 8H, Ar‐H), 7.35‐7.41 (m, 4H, Ar‐ H), 7.74‐7.76 (dd, J = 7.12 Hz, 2H, Ar‐H). MS (EI, m/z (%)): 319.3 (M +1). Anal. calcd. for C29H26N2O: C, 83.22; H, 6.26; N, 6.69. Found: C, 83.32; H, 7.41; N, 6.60%. 2‐(4’‐ethyl‐biphenyl‐4‐yloxymethyl)‐1‐trifluoromethane sulfonyl‐1H‐benzoimidazole (5n): Colour: Yellow. Yield: 75.63%. M.p.: 80‐83 °C. FT‐IR (KBr, , cm‐1): 2945 (C‐H), 1656 (C=N), 1348 (S=O), 1026 (C‐O). 1H NMR (400 MHz, CDCl3, δ, ppm): 1.24‐1.28 (t, J = 7.60 Hz, 3H, CH3‐CH2), 2.64‐2.70 (q, J = 7.60 Hz, 2H, CH2‐CH3), 5.41 (s, 2H, ‐O‐CH2), 7.13‐7.16 (m, 2H, Ar‐H), 7.23‐7.27 (m, 2H, Ar‐H), 7.28‐7.34 (m, 2H, Ar‐H), 7.37‐ 7.41 (m, 1H, Ar‐H), 7.44‐7.46 (d, J = 8.16 Hz, 2H, Ar‐H), 7.49‐ 7.53 (m, 2H, Ar‐H), 7.79‐7.81 (dd, J = 6.96 Hz, 1H, Ar‐H). MS (EI, m/z (%)): 461.07 (M +1). Anal. calcd. for C23H19F3N2O3S: C, 59.99; H, 4.16; N, 6.08. Found: C, 60.05; H, 4.25; N, 6.02%. 2.4. Biological evaluation‐antibacterial and antifungal activity studies The microbial activity was undertaken to evaluate the effect of the synthesized compounds on different bacteria and fungal strains. The compounds 5a‐n were screened for their antibacterial activity [27,28] against human pathogenic Gram negative bacteria such as Escherichia coli MTCC442, Pseudomonas aeruginosa MTCC441 and Gram positive bacteria Staphylococcus aureus MTCC96, and Streptococcus pyogenes MTCC443. DMSO was used as diluents and Gentamycin, Ampicillin, Chloramphenicol, Ciprofloxacin and Norfloxacin as standard. The compounds 5a‐n were also screened for their antifungal activity [29] against Candida albicans MTCC227, Aspergillus Niger MTCC282 and Aspergillus clavatus MTCC1323. Broth dilution method was used to evaluate the antibacterial activity. It is carried out in tubes. Mueller Hinton Broth [30] was used as nutrient medium. Serial dilutions were prepared in primary and secondary screening. Each synthesized drug was diluted obtaining 2000 μg/mL concentration, as a stock solution. In primary screening 1000, 500 and 250 μg/mL concentrations of the synthesized drugs were taken. The drugs found active in primary screening were similarly diluted to obtain 200, 100, 50, 25, 12.5, and 6.250 μg/mL, and concentrations. The highest dilution showing at least 99% inhibition zone was taken as MIC. 274 Gund et al. / European Journal of Chemistry 6 (3) (2015) 270‐274 3. Results and discussion We have synthesized a series of novel benzimidazoles; initially we have carried out the condensation of o‐phenylene diamine (OPDA) (1) with 4‐bromophenoxy acetic acid (2) in 4 N HCl at reflux temperature for 6 h. After simple workup gives 2‐(4‐bromo‐phenoxymethyl)‐1H‐benzimidaziole (3) [22] (Scheme 1). Having obtained compound 3, we have carried out N‐ alkylation to get compounds 4a‐g (Scheme 1). Compounds 4a‐ g were then reacted phenyl boronic acid and 4‐ethylphenyl boronic acid in presence of potassium fluoride, palladium acetate and 18‐crown‐6 under suzuki coupling condition to get compounds N‐substituted 2‐(biphenyl‐4‐yloxymethyl)‐1H‐ benzimidazole, 2‐(4’‐ethyl‐biphenyl‐4‐yloxymethyl)‐1H‐benzi‐ midazole derivatives (5a‐n) (Scheme 2). It is noteworthy to mention here that we have synthesized compound 3 and 5a‐n alternatively by microwave irradiation in comparable yield, which give the scope of alternative route to synthesis benzimidazoles at low temperature and in less reaction time. The structures of all the synthesized compounds were characterized by spectroscopic data, and allowed these molecules for study of antibacterial and antifungal activities. The examination of the data reveals that compounds 5a, 5c, 5d, 5g, 5h and 5k possess high activity against Escherichia coli whereas compounds 5a‐n were highly active against Staphylococcus aureus and compound 5a, 5e, and 5n have also exerted very good activity against Streptococcus pyogenes employed for screening, the results are presented in Table 1. The compounds 5a and 5h show excellent activity against Candida albicans. But rests of other compounds are not displayed significant anti‐fungal activity when compared to the standard Nystatin and Greseofulvin; the results are presented in Table 2. 4. Conclusion Newly synthesized N‐substituted 2‐(biphenyl‐4‐yloxy methyl)‐1H‐benzimidazole, 2‐(4’‐ethyl‐biphenyl‐4‐yloxymeth yl)‐1H‐benzimidazole derivatives by using Suzuki coupling conditions were thoroughly characterized and some of them exhibited antibacterial activity. The compounds 5a and 5h exhibited antifungal activity. 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