Department of Pharmaceutical Chemistry
JNTUA-OTRI, anantapur, India
The benzimidazole contains a phenyl ring fused to an imidazole ring, as indicated in the structure of benzimidazole. Recently in benzimidazole chemistry has been revived somewhat by the discovery that the 5, 6-dimethyl benzimidazole moiety is a part of the chemical structure of vitamin B12. Diversity of biological response profile has attracted considerable interest of several researchers across the globe to explore this skeleton for its assorted therapeutic significance. By using different synthetic methods new benzimidazole derivatives were synthesized and further Melting points were determined by using Precision melting point apparatus in open capillaries and are uncorrected. The purity of the compounds was checked by TLC on silica gel G plates using n-Hexane, ethyl acetate (1:3) and methanol: chloroform (1:9) solvent system. The synthesized benzimidazole derivatives were characterized by IR spectral analysis. Benzimidazole is a lead nucleus for future developments to get effective compounds.
Key words: Benzimidazole, Imidazole, n-Hexane, Ethyl acetate, Chloroform, Methanol
Many important biochemical compounds and drugs of natural origin contain heterocyclic ring structures. Among these e.g. Carbohydrates, essential amino acids, vitamins, alkaloids, glycosides etc. the presence of heterocyclic structures in such diverse types of compounds is strongly indicative of the diverse types of the pharmacological activity and recognition of this is reflected in efforts to find useful synthetic drugs.
An important feature of modern pharmaceutical chemistry is the introduction of more refined and sensitive methods of physicochemical analysis such as Spectroscopy and chromatography that enable one to assay the quality and quantity of the drugs more accurately with the smallest consumption of the analyze, reagent and time.
The benzimidazole contains a phenyl ring fused to an imidazole ring, as indicated in the structure of benzimidazole. The important group of substances has found practical application in a number of fields. Recently in benzimidazole chemistry has been revived somewhat by the discovery that the 5, 6-dimethyl benzimidazole moiety is a part of the chemical structure of vitamin B12.
1. Synthesis of 2-mercapto benzimidazole
A mixture of 10.8gm (0.1mole) of o-phenylenediamine, 5.65 gm (0.1mole) of potassium hydroxide and 7.67 gm (0.1mole, 6.19ml) of carbon disulfide, 100ml of 95% ethanol and 15 ml of water was taken in a 500ml round bottom flask heated under reflux for three hours. Then 1-1.5 gm of charcoal was added cautiously and the mixture is further heated at the reflux for 10 minutes, the charcoal is removed by filtration. The filtrate is heated to 60-70oC, 100ml of warm water is added, and acidified with dilute acetic acid with good stirring. The product separated as glistening white crystals, and the mixture is placed in a refrigerator for three hours to complete the crystallization. The product is collected on a Buckner funnel and dried over night at 40oc. The dried product is recrystallised by ethanol.
2. Synthesis of ethyl (1H-benzimidazol-2-yl-sulfanyl) acetate
A stirred mixture containing 4.5gm of (0.03mole) of 2-mercaptobenzimidazole, 60ml of ethanol and 1.68gm of (0.03mole) potassium hydroxide was added and heated at 78-80oC for 10-minutes. Then ethyl chloro acetate (3.66ml, 0.03mol) was added in one portion, an exothermic reaction set in causing a temperature rise from 30-40oC. After stirring at 25-300c for 18-hours, the reaction mixture was added to 100gm of ice-water and stirred for 30-minutes at 0-100C. The precipitate was collected by filtration washed with water until free of chloride and air dried at 500c and recrystallised by water the yield is 6 gm (62.25%). melting point is 1050C.
Results & Discussion
The present study explains the synthesis and characterization of benzimidazol derivative i.e., ethyl (1H-benzimidazol-2-yl-sulfanyl) acetate. The synthesized new benzimidazol derivative characterized by IR spectral studies. By this studies find the structural activity relationship (SAR) and to optimize the structure. The purity of the synthesized benzimidazol derivative was checked by thin layer chromatography (TLC) and Rf value was recorded.
I R Spectral Data:
The IR spectrum of the compound IV was recorded on FTIR spectrometer by KBr method. The FTIR spectra from the figure.1 and the table.3 shows bands at 3023 cm-1,687 cm-1,1723 cm-1, 1223 cm-1 and 1022 cm-1, 1614 cm-1, 721 cm-1 corresponds to aromatic ring, (C-S), (>C=O of ester), C-O-C, (-C=N-) respectively.