Synthesis of Benzimidazole using waste Magnesium oxide

 

Charansingh H Gill¹, Gurumeet C. Wadhawa², Laxman Gavali², Vitthal S. Shivankar², Komal Pawar²

¹Professor, Department of Chemistry, Babasaheb Ambedkar Marathwada University, Aurangabad.

²Post Graduate, Department of Chemistry, Karmaveer Bhaurao Patil College, Vashi, Navi Mumbai, 400703, Maharashtra, India.

 

ABSTRACT:

Waste magnesium oxide is used for the synthesis of Benzimidazole derivatives. Orthophenyl diamines and Aromatic Aldehydes are fused in presence of catalyst in pristle and mortar .this reaction gives very good yield with good purity.

 

 

 

INTRODUCTION:

Most important drug in drug discovery is benzimidazole nucleus. Wide spectrum of bioactivity benzimidazole have 2-4. Benzimidazole nucleus exhibit wide spread occurrence and exhibit various properties like Anti HIV, Protecting RNA, Against influenza, also they have Bis benzimidazoles derivatives as mirror groove binding agent for DNA for antitumor activity [1-6] many times they are used for biological modelling of biological systems [7-8]. Benzimidazole are also important in organic synthesis for various reactions [9-10]

 

Therefore the benzimidazole is centre of attraction now days. Preparation of benzimidazoles has gained considerable attention in recent years [11-12]. Despite their importance from pharmacological, industrial and synthetic points of view, comparatively few methods for the preparation of benzimidazoles have been reported. The most popular synthetic approaches generally involve the condensation ofan arylenediamine with a carbonyl equivalent [13-14].

 

These includes the condensation of o-aryldiaminesand aldehyde using air as the oxidant [17] the condensation of oaryldiamineswith carboxylic acids or their derivatives recently by PS-PPh3/CCl3CN [18], thermal or acid promoted cyclization reactions [19] or the use of microwave irradiation [20]. In all these approaches, condensation of arylenediamines with aldehyde involves atwo-step procedure that includes the oxidative cyclodehydration of aniline Schiff’sbases, which often generated in situ. Various recent oxidative reagents, such as (bromodimethyl) sulphonium bromide [21], Sulphamic acid [22].

 

EXPERIMENTAL:

Melting points were determined on an electro thermal digital melting point apparatus of Buchi and also using paraffin tube method. The IR spectra were recorded on shimadzu ftir affinity 1spectrometer. NMR spectra were recorded on a Bruker Advance (300 MHz) spectrometer.  Chemical shifts (ppm) were referenced to the internal standards tetramethylsilane (TMS).

 

Reactions were monitored by thin layer chromatography using silica gel s.d.fine aluminium sheets .Almost all synthesized compounds are known and identified using IR and NMR spectroscopy and also by comparison with their authentic samples and literature.

 

Experimental procedure:

Experimental procedure for synthesis of 2 substituted benzimidazole derivative using Mgo To a mixture of substituted aromatic aldehyde 10 mmole and orthophenyldiamine 10 mmole along with magnesium oxide (waste ) 0.6 gm grind in pristle and mortar for specified  time ,then after TLC complies extract the product using etylacetate  ,purify product over column using hexane and etylacetate.

 

Observation Table 1

Sr. No	Aromatic group	Time (min)	(%)Yield	MP (0C)
1.	C6H5	20	73	292
2.	2-ClC6H4	18	84	133
3.	3- ClC6H4	18	86	231
4.	4- MeOC6H4	25	68	219
5.	2-NO2C6H4	16	85	257
6.	3- NO 2C6H4	16	86	304
7.	4- NO2C6H4	17	87	305
8.	4-MeC6H5	25	45	268
9.	2-Furanyl	20	48	283

 

Spectral Analysis:

2-Phenyl-1H-benzimidazole:

IR (KBr): ν= 3245 (NH), 3047 (CHaromatic), 1455 (C=C) cm-1.

 

Proton NMR (300MHz, DMSO): δ ppm = 7.10-7.85 (m 7H, CHaromatic), 8.06-8.40 (m, 2H, CHaromatic), 12.53 (BS, 1H, NH).

 

2-(4-Methylphenyl)-1H-benzimidazole:

IR (KBr): ν = 3223 (NH), 3159 (CHaromatic) 1438 (C=C), 1632 (C=N) cm-1.

Proton NMR (300 MHz, DMSO): δ (ppm) = 2.28 (s, 3H, CH3), 7.27-8.18 (m, 8H, CHaromatic), 12.73(bs, 1H, NH).

 

2-(2-Nitrophenyl)-1H-benzimidazole:

IR (KBr): ν= 3364 (NH), 3024 (CH aromatic), 1446 (C=C), 1518 (N=O) cm-1.

Proton NMR (300 MHz, acetone-d6): δ (ppm) = 7.15-8.15 (m, 8H, aromatic), 12.06

(bs, 1H, NH).

 

2-(3-Nitrophenyl)-1H-benzimidazole:

IR (KBr): ν= 3358 (NH), 3086 (CH aromatic), 1431 (C=C), 1516 (N=O) cm-1.

Proton NMR (300 MHz, acetone-d6): δ (ppm) = 7.28-9.05 (m, 8H, aromatic), 12.21 (bs, 1H, NH).

 

CONCLUSION:

Reactions were carried out by taking a 1:1 mol ratio mixture of o-phenylenediamine with aromatic aldehydes 2 in the presence of Magnesium oxide to form 2-arylbenzimidazoles. However, aliphatic aldehydes such as formaldehyde or acetaldehyde were also tested under the same conditions, but the corresponding products were isolated in trace amounts. Most of the reactions gives 70-90 % yield. For solid aldehydes small amount of ethanol is used.

 

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Received on 09.03.2018        Modified on 13.04.2018

Accepted on 14.05.2018       ©A&V Publications All right reserved