imidazole and benzimidazole synthesis pdf

Imidazole and benzimidazole synthesis pdf

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Synthesis of benzimidazoles has been developed by the o -phenylenediamine with aldehydes using boric acid an efficient catalyst under mild reaction conditions in aqueous media. The product is applicable to aryl and heteroaryl aldehydes.

Metrics details. Imidazole is a five-membered heterocyclic moiety that possesses three carbon, two nitrogen, four hydrogen atoms, and two double bonds. It is also known as 1, 3-diazole. It contains two nitrogen atoms, in which one nitrogen bear a hydrogen atom, and the other is called pyrrole type nitrogen. The imidazole name was reported by Arthur Rudolf Hantzsch — in

Background

An amidoxime containing 2-phenyl-1H-benzimidazole derivative, 4- 1H-Benzoimidazolyl -N-hydroxy-benzamidine, was synthesized by conversion of nitrile group of previously synthesized 2- 4-cyanophenyl -1H-benzimidazole by treatment with hydroxylamine under alkaline solution.

Its photophysical behavior was compared in methanol and DMSO under basic condition. Amidoxime group exhibited superior adsorption ability because it contains both amino and oxime groups that can form strong complexes with metal ions via the coordination reaction. On the other hand, a number of resin have been developed for selective adsorption of various metals such as resin containing amidoxime—guanidine 6 functional group for Ag I , silica gel based hybrid material 7 for Hg II , composite chelating particles poly amidoxime -silica 8 and polyacrylonitrile PAN grafted sago starch 9 for Cu II , silica gel-based sorbent 10 for Fe II , commercial amidoxine resin Duolite ES 11 for extraction of gallium, etc.

Amidoximes, for example, succinediamidoxime, 12 3. Meanwhile amidoximes are the valuable starting materials for the synthesis of various heterocyclic compounds and as well as useful building blocks for heteroarenes such as imidazoles, 16 benzimidazoles, 17 pyrimidines, 18 pyrazine, 19 quinazolines 20 etc. On the other hand benzimidazole rings are known to be very reactive because of the trivalent imidazole nitrogen offers a site for functionalization of the compound. Moreover benzimidazole have been reported to use as organic ligands 26 and fluorescent whitening agent dyes.

Till now, synthesis of 2-phenylbenzimidazole derivative containing amidoxime using sodium methoxide has not been reported before. Current approach is to reveal a route of synthesis of a 2-phenylbenzimidazole derivative compound 2 containing amidoxime and its characterization.

Moreover, the pH effect on amidoxime functional groups in aqueous media has been found highly important 28 to study the complexion of heavy metals especially uranium, 29 vanadium. Herein we report to photophysical behavior of compound 2 under basic condition in non-aqueous media like methanol and DMSO.

All of the chemicals used in this work were of analytical grade purchased from commercial suppliers and used without further purification. Organic compounds 4-cyanobenzaldehyde, phenyl-1, 2-diamine, sodium methoxide, hydroxylamine hydrochloride , organic solvents methanol, ethanol, ethyl acetate, dimethyl sulfoxide were used as obtained. The solution was refluxed for 4hrs. The solvent was then removed by distillation. The solid product was then purified by crystallization by ethanol.

General procedure of synthesis of 4- 1H-Benzoimidazolyl -N-hydroxy-benzamidine 2. The compound 1 0. The solution was refluxed for 24hrs. The reaction was monitored by TLC. The solvent was then removed by evaporation.

The crude product was dissolved in ethyl acetate and filtered off. The filtrate was then dried and water was added. The precipitate was then removed by filtration. Further purification was carried out by crystallization in ethanol. About 0. In order to characterize compound 1 and compound 2 FT-IR analysis was made.

FTIR spectra of these compounds were taken by mixing the compound about 0. UV-Vis absorption spectra were acquired using a UVseries spectrophotometer. UV-visible spectrophotometric investigations were performed at concentrations of 1. The stock solutions of the compounds 1. The stock solution of compound 2 and DMSO is prepared in similar manner. The base solutions of 1. The effect of pH upon absorption intensity was examined by the addition of 1.

Each time the pH was checked by the pH meter. In case of DMSO, same amount of sodium hydroxide was added. Mass spectra were obtained on a Bruker MHz spectrometer.

The compound 1 was prepared from 4-cyanobenzaldehyde and 1, 2-phenylenendiamine in ethanol using air as oxidant under reflux Scheme 1. The purification process involved the removal of solvent via rotary evaporator. The compound 2 was prepared from compound 1 that reacts with hydroxylamine hydrochloride in the presence of sodium methoxide in ethanol under reflux.

The crude product was dried and dissolved in ethyl acetate and filtered. The filtrate was dried to give crude product. The dried crude was washed with water to remove the excess starting materials and any byproduct that dissolve in water. Further purification was carried out by recrystallization from ethanol.

The completion of the reaction and the purity of the product were monitored by TLC. The compound remains at the top of the chromatogram in the hexane-ethylacetate solvent system. The reaction was carried out in acidic condition where in cyano group of compound 1 underwent protonation and then nucleophilic attack at C-atom of cyano group gave the final product Scheme 2.

Presence of amidoxime groups in the resin was confirmed by several methods of which vanadium ion test was employed in most case. The structures of the compounds were elucidated by spectral data analysis. The IR spectra of the compounds were consistent with the structures assigned to them. In the H 1 -NMR spectra for compound 2 , the peaks of aromatic protons of the phenyl ring attached at 2-position of benzimidazole ring were observed about 8.

The peaks of N-H protons of the imidazole ring were disappeared in the spectrum due to the exchange of proton at N with deuterium present in solvent. The electronic spectra of compound 2 in methanol and DMSO were recorded in basic conditions. The electronic absorption spectra of the studied compounds have been recorded in methanolic solutions of varying pH ranging from 7.

In methanolic solutions of pH ranging from 7 to 11, the visible spectra of the compounds comprise one main band with max of nm while its intensity decreases by increasing the pH value which represents the spectra of neutral form. This behavior can be attributed to ionization of O-H group of the benzene ring.

The recorded spectrum in the pH 11 represents the absorption of the deprotonated form of the compounds that takes place at the oxygen atom of the hydroxyl group of the benzene ring. Thus, a clear isosbestic point is observed in the pH range 11 - 13, which indicates the presence of anion-neutral equilibrium as represented below:. This behavior indicates that the excited state of compound 2 is more polar than their ground state and, thus, this red shift stabilizes the excited state more than the ground state as the polarity of the solvent increased.

In that case, the separation between the ground and excited state energies is decreased, i. The red shift by about 31 nm in case of DMSO is significantly higher than that in methanol by 14 nm that is almost double.

It can be concluded that the deprotonation in more polar solvent results in higher stability of the conjugation system than in less polar one. It is recent that synthesis of benzimidazole containing amidoxime functional group has been established.

Spectroscopical study of amidoximes in different pH and solvents is still an interesting scope of investigation and not reported in literature quite enough. We have found that amidoxime group of the compound 2 showed good pH sensing properties in methanol and DMSO.

Moreover, in higher basic conditions compound 2 shows a considerable red shift by about 31 nm in DMSO. Hence, our study reveals a means of further studies spectroscopically considering acidic and basic conditions as well as the choice of solvents. Goel, V. Gupta, J. Egawa, M. Nakayama, T. Nonaka, E. Sugihara, J. Egawa, T. Nonaka, S. Abe, M. Nakayama, J. Kabay, H. Egawa, J. Kabay, T. Hayashi, A. Jyo, H. Zhaoa, J. Lib, L. Zhaod, S. Zhanga, Y. Huanga, X. Wua, X. Wanga, Chem.

Egawa, N. Shuto, A. Jyo, J. Kubota and Y. Shigehisa, J. Nilchia, A. Babaloub, R. Rafieeb, H. Sid Kalala, React.

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Author s : S. Khabnadideh , Z. Rezaei , A. Khalafi-Nezhad , K. Pakshir , A. Roosta , Z.

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A series of benzimidazole derivatives 5a-c were synthesized by coupling 5-substituted 2-chloromethyl benzimidazole 3a-c with 2-mercapto-N-methyl imidazole. The synthesized compounds were characterized by infra-red IR , nuclear magnetic resonance NMR and elemental analyses. Further, the synthesized compounds were tested on plantlet production from protocorm like bodies PLBs sections of Oncidium. Key words: Benzimidazole derivatives, protocorm like bodies, plant growth regulators, 2-mercapto-N-methyl imidazole.

Information on the synthesis, properties, and chemical transformations of imidazole N-oxides that are aromatic in nature is correlated. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve. Khmel'nitskii, S. Novikov, and T.

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    Purchase Imidazole and Benzimidazole Synthesis - 1st Edition. Print Book & E-​Book. ISBN ,

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  • Helda L. 22.11.2020 at 04:29

    Imidazole and Benzimidazole Synthesis is a comprehensive survey of the known methods of syntheses and ring modification.

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  • Geppetto B. 26.11.2020 at 07:31

    Use of this Web site signifies your agreement to the terms and conditions.

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  • Menconochu 28.11.2020 at 18:26

    An amidoxime containing 2-phenyl-1H-benzimidazole derivative, 4- 1H-Benzoimidazolyl -N-hydroxy-benzamidine, was synthesized by conversion of nitrile group of previously synthesized 2- 4-cyanophenyl -1H-benzimidazole by treatment with hydroxylamine under alkaline solution.

    Reply

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