Research Journal of Chemical Sciences Vol. 1 (1) April (2011) Res.J.Chem.Sci. 18 A Simple and Efficient Procedure for Synthesis of Biologically Active 1,2,4-Triazolo-[3,4-b]-1,3,4-thiadiazole -2-aryl-thiazolidine-4-one Derivatives Parmar Kokila *, Prajapati Sarju, Patel Rinku, Patel Rekha, Department of Chemistry, Hemchandracharya North Gujarat University, Patan-384265, INDIA Available online at: www.isca.in (Received 21st March 2011, revised 25th March 2011, accepted 30th March 2011) Abstract Some new and biologically active [1,2,4] triazolo [3,4-b][1,3,4] thiadiazole-2-aryl-thiazolidinone-4-ones were synthesized by reaction of Schiff bases with mercapto acetic acid in presence of THF with adding anhydrous ZnCl. The structure of the synthesized compounds have been estabilished on the bases of IR, PMR, CMR and elemental analysis. The compounds have been evaluated for antibacterial activity againstB. subtilis,S. aureus, P. aeruginosa and E. coli.Key words: Synthesis, Biological activity,Triazolo, Thiadiazole, thiazolidinonesIntroduction In the last few decades, the chemistry of heterocycles bearing a triazole or 1,3,4-thiadiazole moiety are reported to show a wide spectrum of biological activity1-8 such as antibacterial, anti aggregatory agent10, antiviral11 and anti-inflammatory12 activities. In addition, the N-bridged heterocycles derived from 1,2,4-triazoles have applications in field of medicine, agriculture and industry.13 1,3,4-Thiadiazoles exhibit broad spectrum of biological activites possibly due to the presence of toxophoric N-C-S moiety14. They found applications as antibacterial, antitumor, anti inflammatory agents, pesticides, herbicides, dyes, lubricants and analytical reagents.15 The [1,2,4]-triazolo-[3,4-b]-[1,3,4]-thiadiazole derivatives obtained by fusing the biolibale [1,2,4]-triazole and [1,3,4]-thiadiazole ring together, are reported to possess anti bacterial, antifungal, CNS depressant, anti viral, analgesic and plant growth regulatory effects.16 In literature revealed, some derivatives of [1,2,4]-triazolo-[3,4-b]-[1,3,4]-thiadiazoles have been show as optically active with L-Amino acid.17The 4-carbonyl derivative of thiazolidine is known as 4-thiazolidinone. 4-thiazolidinones have been well studied and a variety of biological activities have been reported for a large number of their derivatives. Suchasantibacterial18antimicrobial19anti fungal20, anti anthelmintic21anti infiammatory22, anti tubercular 23 and diuretic agents24, anti thyroid 25 and as a local anaesthetic . We report here in the reaction of Schiff bases with mercapto acetic acid in presence of THF with adding anhydrous ZnCl to give biologically active [1,2,4] triazolo [3,4-b][1,3,4] thiadiazole-2-aryl-thiazolidinone-4-ones with the hope of to obtained compounds with good yield. Material and Methods Melting points were determined using an electro thermal digital apparatus and are uncorrected. Purity of the compound was checked by thin layer chromatography (TLC). IR spectra were prepared on a FT-IR spectrophotometer using KBr discs. H PMR spectra were recorded on Bruker spectrophotometer (300 MHz) in DMSO-d or CDCl using TMS as an internal standard. Synthesis of methyl benzoate (1): Benzoic acid (0.01 mole) in 20 ml of methanol and 0.5 ml conc. Sulfuric acid was refluxed for 12 hrs. and poured into ice. The product was isolated and treated with standard sodium bicarbonate solution to give desired compounds. Research Journal of Chemical Sciences Vol. 1 (1) April (2011) Res.J.Chem.Sci. 19 Synthesis of benzoic acid hydrazide (2): A mixture methyl benzoate (0.01 mole) and hydrazine hydrate (0.5 g, 0.01 mole) was heated for 9 hrs. and poured into ice. The product was isolated and crystallized from ethanol. Synthesis of potassium-benzoic acid hydrazide dithiocarbamate(3): A mixture of benzoic acid hydrazide (0.01 mole), KOH (0.84 g, 0.015 mole) and 1.5 ml CS in absolute alcohol was stirred for 21 hrs. and product was isolated from diethyl ether. Synthesis of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol (4): Potassium salt (0.01 mole) was taken in hydrazine hydrate and heated up to the evolution of S gas cussed nearly 5 hrs. in oil bath. The reaction mixture was poured into crushed ice and treated with glacial Acetic acid .The product was filtered and purified by KOH treatment and crystallized from ethanol. Synthesis of 3-(phenyl)-6-(4-N-acetylamino phenyl) [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (5): A mixture of n-acetyl-p-amino benzoic acid (0.01 mole) and 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol (0.01 mole) in POCl (25 ml) was refluxed for 10 hrs. The reaction mixture was poured into crushed ice and thus solid separated out was filtered, washed with water and crystallized from ethanol. Synthesis of 3-(phenyl)-6-(4-amino phenyl) [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (ATT)(6): 3-(phenyl)-6-(4-N-acetylamino phenyl) [1,2,4] triazolo[3,4-b][1,3,4]thiadiazole was hydrolysed by refluxing with 75 ml of ethanol containing 15 ml of concentrated HCl for 4-5 hrs. it was then poured into ice-cold water and finally made just alkaline with liquid ammonia. The resultant product 3-(phenyl)-6-(4-amino phenyl) [1,2,4] triazolo [3,4-b] [1,3,4] thiadiazole (ATT) is filtered off and washed with water and air dried. It was then recrystallised from ethanol. Synthesis of Arylidine-[3,6-(diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole] (7a-h): A mixture of equimolar amount of 3-(phenyl)-6-(4-amino phenyl) [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (0.01 mole) and various aromatic aldehydes (0.01mole) in 50 ml acetic acid and refluxed for about 10-12 hrs. on oil bath. The reaction mixture was cooled and it was poured in to ice water and extracted with ethyl acetate and water and finally dried over anhydrous sodium sulfate. The solvent was evaporated to give the solid product. It was crystallized from ethyl acetate hexane using decolorizing charcoal to give various anils Synthesis of 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-aryl-thiazolidine-4-ones (8a-h): A mixture of Schiff bases (7a-h) (0.01 mole ) in THF (30 ml) and mercapto acetic acid (thioglycolic acid) (0.01 mole) with a pinch of anhydrous ZnClwas refluxed for 12 hours. The solvent was then removed to get a residue, which was dissolved in benzene and passed through column of silica gel using benzene : chloroform (8:2;v/v) mixture as eluent. The eluate was concentrated and the product crystallized from alcohol to give 4-thiazolidinones(8a-h). Spectral Analysis of Synthesized compounds (8a-h) (1) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-phenyl-thiazolidin-4-one (8a): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600, 1680 (C=O of thiazolidinone). PMR ( ppm): 6.12-7.8 (m, aromatic), 3.1 (2H of CH for thiazolidinone), 5.35 (H of CH for thiazolidinone). 13CMR ( ppm): 113-130 (benzene),136-145 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH). (2) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-(4-methoxyphenyl)-thiazolidin-4-one (8b): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600, 1690 (pyridine ring, C=O of thiazolidinone), 1200 (Ar-O-CH). PMR ( ppm): 6.12-7.8 (m, aromatic), 3.2 (2H of CH for thiazolidinone), 5.35 (H of CH for thiazolidinone), 3.35 (3H of CH of thiazolidinone). 13CMR ( ppm): 113-131 (benzene),135-145 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH), 56 (CH).(3) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazole]-2-(4-hydroxyphenyl)-thiazolidin-4-one (8c): I.R. (KBr, cm-1): 3030, Research Journal of Chemical Sciences Vol. 1 (1) April (2011) Res.J.Chem.Sci. 20 1500 (aromatic C-H), 1600, 1690 (C=O of thiazolidinone), 3200-2600 (broad, OH stretching), 2880, 2920 (CH stretching). PMR ( ppm): 6.12-7.8 (m, aromatic), 3.2 (2H of CH for thiazolidinone), 5.35 (H of CH for thiazolidinone), 3.9 (H of OH). 13CMR ( ppm): 113-132 (benzene),135-145 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH).(4) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazole]-2-(2-hydroxyphenyl)-thiazolidin-4-one (8d): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600, 1690 (C=O of thiazolidinone), 3200-2600 (broad, OH stretching), 2880, 2920 (CH stretching). PMR ( ppm): 6.12-7.8 (m, aromatic), 3.1 (2H of CH for thiazolidinone), 5.35 (H of CH for thiazolidinone), 3.9 (H of OH). 13CMR ( ppm): 113-133 (benzene),135-147 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH). (5) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-(2-methylphenyl)-thiazolidin-4-one (8e): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600, 1690 (C=O of thiazolidinone), 2950,1370 (CH stretching), 2880, 2920 (CH stretching). PMR ppm): 6.2-7.9 (m, aromatic), 3.2 (2H of CH for thiazolidinone), 2.1 (3H of CH), 5.35 (H of CH for thiazolidinone) . 13CMR ( ppm): 113-134 (benzene),135-148 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH), 25 (CH). (6) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-(methylenedioxyphenyl)-thiazolidin-4-one (8f): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600 (thiazole ring), 1690 (C=O of thiazolidinone), 1200 (Aryl-alkyl ether), 2880, 2920 (CH stretching). PMR ( ppm): 6.15-7.8 (m, aromatic), 5.35 (H of CH for thiazolidinone), 5.35 (2H for CH of -O-CH-O-), 3.2 (2H for CH). 13CMR ( ppm): 114-130(benzene),135-149 (triazolo-thiadiazole), 169 (C=O), 36 (CH), 46 (CH), 95 (O-CH-O). (7) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazole]-2-(3-methylenedioxyphenyl)-thiazolidin-4-one (8g): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600,1680 (C=O of thiazolidinone), 3200-2600 (OH), 1200 (Aryl-alkyl ether), 2880, 2920 (CH stretching). PMR ( ppm): 6.12-7.9 (m, aromatic), 3.2 (2H for CH), 5.35 (H of H for thiazolidinone), 3.35 (3H for –OCH), 3.9 (H for OH). 13CMR ( ppm): 113-135 (benzene),135-150 (triazolothiadiazole), 169 (C=O), 36 (CH), 46 (CH), 56 (CH).(8) 3-[(3,6-diphenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole]-2-(3,4-diethoxyphenyl)-thiazolidin-4-one (8h): I.R. (KBr, cm-1): 3030, 1500 (aromatic C-H), 1600,1680 (C=O of thiazolidinone), 1200 (Aryl-alkyl ether), 2880, 2920 (CH stretching). PMR ( ppm): 7.2-8.1 (m, aromatic), 3.25 (2H for CH), 3.35 (H for CH), 2.1-2.5 (6H for 2CH), 2.89-3.18 (4H for 2 CH). 13CMR ( ppm): 113-136 (benzene),135-151 (triazolo thiadiazole), 169 (C=O), 36 (CH), 14 (CH), 58 (OCH).Results and Discussion All the new derivatives of 1,2,4-triazolo[3,4-b][1,3,4] thiadiazoles-2-aryl-thiazolidinone-4-ones were synthesized and the structures were established by means of IR, H NMR spectral data as well as elemental analysis. All the thiazolidinone-4-ones were evaluated for anti-microbial activity. The newley synthesized compounds (8a-h) were obtained by the treatment of Schiff bases in THF and mercapto acetic acid (thio-glycolic acid) with a pinch of anhydrous ZnCl was refluxed for 12 hours. All the synthesized structures showed satisfactory result. The IR data of the compounds clearly showed a strong C=O stretching band around 1600 cm-1 and aromatic C-H in thiazolidinone of absorption band around 3030, 1500 cm-1. The PMR also confirms the presence of shift value at 3.1 for CH in thiazolidinone and 5.35 for H also in thiazolidinone groups respectively. Antibacterial screening of newly synthesized compounds was carried out against B. subtilis,S. aureus, P. aeruginosa and E. coli in DMF solventusing cup-plate method. From the results obtained in the biological activity, it was observed that, the compound 8b, 8c, 8d and 8h were shown significant Research Journal of Chemical Sciences Vol. 1 (1) April (2011) Res.J.Chem.Sci. 21 activities and compound 8a, 8e, 8f and 8g have shown moderate activity. Biological evaluation: Cup-plate agar diffusion method12,13 was employed for in vitro study of antibacterial. Efficacy of the target compounds against B. subtilis, S. aureus, Ps. aeruginosa and E. coli in DMF solvent. The study has been conducted according to the method adopted by Nutrient agar broth was melted in a water bath and cooked to 45C with gentle shaking to bring about uniform cooling. It was inoculated with 0.5-0.6 ml of 24 hour old culture especially and mixed well by gentle shaking before pouring on the sterilized Petri dish (25 ml each). The poured material was allowed to set (1.5 hour) and there after the “cups” were made by punching into the agar surface with a sterile cork borer and sooping out the punched part of agar. Into this “cups” 0.1 ml of test solution (prepared by dissolving 10gm of sample in 10ml DMF) was added by sterile micropipette. The plates were noted. Ampicillin, Tetracycline, Gentamycin, and Chloramphenicol were used as standard drugs. The biological activity test data are presented in Table 2. The compound 8b, 8c, 8d and 8h were shown significant activities and compound 8a, 8e, 8g and 8h have shown moderate activity. Acknowledgement The authors are thankful to Director, C.D.R.I, Lucknow (U.P.) and R.S.I.C,Chandigrah and National Chemical Laboratory, Pune for providing spectral and analytical data of the compounds. They are also thankful to the Microcare Laboratory, Surat (Gujarat) for the biological activity. References 1. Kumar S., Rajendraprasad G.V., Mallikarjuna Y., Chandrashekar B.P., Kistayya S.M., Eur. J. Med. Chem.,45, 2063, (2010) 2. Mallikarjuna B.P., Sastry B. S., Kumar G.V., Rajendraprasad Y., Chandrashekar S.M., Sathisha K. Eur . J. Med. Chem.,44, 4739, (2009) 3. Onkol T., Cakir B., Sahin M. F. Turk. J. Chem.,28, 461, (2004) 4. Schenone S., Bruno O., Ranise A., Bondavalli F., Filippeli W., Falcone G., Giordano L., Vitelli M. R. Bioorg. Med. Chem., 9, 2149, (2001) 5. Holla B. S., Gonsalves R., Shenoy, Eur. J. Med. Chem.,35,267, (2000) 6. Gokce M., Cakir B., Erol K., Sahin M. F., Arch. Pharm.,334, 279, (2001) 7. Laddi U. V., Desai S. R., Bennur R. S., Bennur S. C., Ind. J. Heterocycl. 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