Design, Synthesis, Characterization and Biological Evaluation of Schiff Bases of 5-Amino -4-[2-(4-Nitro-1,3-Benzothiazol- 2yl) Hydrazinylidene]-2,4-Dihydro-3H -Pyrazol -3-One Derivatives.

Rajalakshmi, G (2012) Design, Synthesis, Characterization and Biological Evaluation of Schiff Bases of 5-Amino -4-[2-(4-Nitro-1,3-Benzothiazol- 2yl) Hydrazinylidene]-2,4-Dihydro-3H -Pyrazol -3-One Derivatives. Masters thesis, KMCH College of Pharmacy, Coimbatore.


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In the present work totally twelve 5-amino substituted -4-[2-(4-nitro-1, 3-benzothiazol-2 yl) hydrazinylidene]-2, 4-dihydro-3H -pyrazol -3-one (BTZP3a-l) compounds were synthesised. The compound 4-nitro-1, 3-benzothiazol-2-amine (BTZ) was synthesized from 2-nitroaniline, ammonium thiocyanate and glacial acetic acid with bromine. Ethyl cyano [2-(4-Nitro-1, 3- benzothiazol-2-yl)hyrazinylidene]acetate (BTZE) was prepared by coupling through diazonium salts of 4-nitro-1,3-benzothiazol-2-amine (BTZ) with ethylcyanoacetate. BTZE which was cyclised with hydrazine hydrate and the resulting product (BTZP) was subjected to schiff base reaction with 12 different aldehydes. The yield was found to be 70-95% in all the stage. The final compounds were found to be soluble in non polar solvents. Thin layer chromatography was used to find out the reaction time to completion the reaction and purity of the synthesized compounds. Melting points were taken in open glass capillary tubes and were uncorrected. The UV and IR spectra of synthesized compounds appeared in the exhibited regions. The structures of intermediates, the compound BTZ confirmed by the presence of characteristic peaks in the region 3132.79 cm-1associated for -NH2 stretching respectively. BTZE showed the disappearance of the characteristic bands of the -NH2 stretching and also shows the stretching for cyanide group, ester group in the region 2360.44 cm-1, 1786.44 cm-1 an respectively. The compound BTZP confirmed, the disappearance of the characteristic bands of the cyanide group and ester group and also showed the reappearance of the characteristic bands of the -NH2 stretching in the region 3343.05 cm-1 respectively. Compound BTZP3b containing – N (CH3)2 group showed absorption bands at 1321 cm-1. Compound BTZP3c, BTZP3e containing C-O-C group showed absorption bands at 1070.3 cm-1, 1081.62 cm-1. Compound BTZP3f containing NO2 group showed absorption bands at 1512.88 cm-1, for the N=O stretching. The peak at 830.20 cm-1, 821 cm-1, 837.19 cm-1 could be assigned to C-Cl stretching in the compound BTZP3d, BTZP3h, BTZP3l. Presence of hydroxyl group was confirmed by the appearance of broad peak at 3430-3161 cm-1 in the compound BTZP3e, BTZP3g, BTZP3i, BTZP3j. Compound BTZP3k containing C-F group showed absorption bands at 1416 cm-1. The structures of the newly synthesized compounds (BTZP, BTZP3a-l) were confirmed by 1HNMR spectra. The 1H-NMR spectra of all the synthesized compounds showed the absence of the peaks for the –NH2 proton signal at δ 8.32 ppm. All the synthesized compounds showed multiplets in the range δ 6.32-8.59 for the protons of aromatic ring and a singlet at δ 6.15, 3.57- 3.89,7.4-8.64ppm which may be assigned to –NH-N proton,-NH proton of pyrazolone,-N=CH proton of Schiff base. The spectrum of BTZP3b, BTZP3c, revealed a singlet at δ 3.04, 3.35 ppm which may be assigned to -N (CH3)2, OCH3 proton. The spectra of compound BTZP3g showed singlet at δ 9.87 ppm corresponding to OH group. The 2-aryl benzothiazole moieties are already known for different biological activities. In the present investigation an attempt has been made for the synthesis of some novel benzothiazole containing pyrazolone analogues combining with different substituted aldehydes by schiff base reaction to get a good antimicrobial, bactericidal, fungicidal, in vitro anti-tubercular, antioxidant and cytotoxic activity with high toxic effects. Biological screening results clearly indicated that the compounds of the scheme have shown good in vitro antimicrobial, anti-tubercular, antioxidant activity compared with the standard drugs and almost all the newly synthesized compounds are bactericidal and fungicidal in nature. Unfortunately, the overall results indicate that they were weekly active with a low selectivity index as indicate by the cytotoxic effect. Even though the synthesized compounds showed good antimicrobial activity with less safety index, due to compounds have high toxicity towards normal cell lines. The result obtained, taking into account the significant activities of the examined compounds, it is believed that further optimization of these identified chemical leads can probably lead to the development of more active molecules. Future studies are proposed reduced toxicity and to establish their in vivo efficacy and receptor interaction, after making suitable structural modifications.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Synthesis; Characterization; Biological Evaluation; Schiff Bases; 5-Amino -4-[2-(4-Nitro-1,3-Benzothiazol- 2yl; Hydrazinylidene; -2,4-Dihydro-3H -Pyrazol -3-One Derivatives
Subjects: PHARMACY > Pharmaceutical Chemistry
Depositing User: Ravindran C
Date Deposited: 17 Aug 2017 07:20
Last Modified: 12 Oct 2017 03:07

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