Synthesis of Benzimadazoles in presence of nanocatalyst Fe2O3

 

G. Venkateswararao1, G.SatyaSree2, B. SathishMohan3*, K. Ravi4

1Dept of Organic Chemistry, Mrs. A.V.N. College, Visakhapatnam-530001, India.

2Dept of Organic Chemistry, AdikaviNannayaUniversity, Rajamahendravaram-533296, India.

3Dept of Inorganic and Analytical Chemistry, Andhra University, Visakhapatnam-530003, India.

4Dept of Organic Chemistry and FDW, Andhra University, Visakhapatnam-530003, India.

*Corresponding Author E-mail: bsathish401@gmail.com

 

ABSTRACT:

We have an attempt to the synthesis of benzimidazoles by treatment of phenylenediamine with boric acid in water at 120°C in the presence of nanocatalyst, Fe2O3 (5 mol%). Initially, we studied the structure and morphology of as prepared nanocatalyst using XRD, FTIR and SEM. Further, the synthesis of benzimidazoles and their derivatives using Fe2O3.

 

KEYWORDS:Fe2O3, hydrothermal, nanoflakes and benzimidazoles.

 

 

 

INTRODUCTION:

Nowadays, catalysis is a vital utensil of green chemistry because of it offers new synthetic pathways to desired yield by less polluting chemical processes [1, 2]. The superior property of catalyst is ability to be recovered and use in large scale applications at industrial level [3]. The metal oxides homogenous catalysts like rhodium, palladium and iron[4-7] have been reported earlier owing to their possessive properties in view of activity and selectivity; the majority of industrial catalysts remain heterogeneous because of the simplicity of the latter in terms of recovery[3]. The NPs are robust, stable in air, amenable to functionalization, suspendable in many solvents including water or other protic benign solvents; their size, shape and crystallinity can be finely tuned[8].

 

Due to high activity, selectivity, recyclability and tunability, the metal containing nanoparticles (NPs) are most attractive catalyst. During the past decade, the concept of magnetic NPs (MNPs) has quickly evolved to further simplify the recovery process in catalysis, biology and medicine [9-11].

 

Based on substituents present at different positions, benzimidazole structure is found in many classes of drugs[12]. Benzimidazole and its derivatives have been widely used in various applications like antimicrobial agents[13], antiviral agent against several viruses such as HIV, influenza and herpes (HSV-1), antitumor, anti-inflammatory, anthelmintic agents and antiprotozoal agents [14-19]. Benzimidazole derivatives are being explored in pharmaceutical industries and substituted benzimidazole derivatives have also been found in the diverse therapeutic applications such as in anti-ulcers, antihypertensive, anti-viral, anti-fungal, anti-cancers and anti-histaminics[20].

 

Boric acid, a water soluble catalyst and has been found to be effective in various organic transformations such as esterification of hydroxycarboxylic acids [21], aza Michael [22], thia Michael [23], addition, and bromination[24]. Herein, we report a method for the synthesis of benzimidazole and their derivatives by using phenyldiamine and boric acid in presence of nanocatalyst to obtain product with high yield in moderate reaction time and easy work-up.

 

2. EXPERIMENTAL:

Materials and method:

Potassium ferrocyanide (K3[Fe(CN)6]), boric acid were purchased from Merck. DMSO𝑑6was used as solvent for NMR analysis. Milli Q water is used throughout the synthesis of magnetite NPs.

 

Characterization:

As prepared magnetite NPs were characterized by XRD, FTIR (prestige IR 21), FESEM, NMR (Brucker DRX500), 1H and 13C NMR DMSO𝑑6 as solvent. All the reactions were monitored by TLC using 0.25 mm silica gel plates (Merck 60F254) UV indicator.

 

Synthesis of Magnetite NPs:

In a simple synthesis, 0.1 mol/L of K3[Fe(CN)6] was dissolved in aqueous water to form a clear solution in a hydrothermal bomb and placed in a Teflon-sealed hydrothermal bomb and was kept in autoclave to maintained at a temperature of 180oC for 20 h. The red precipitate was formed and washed with Milli Q water followed by ethanol. Finally, the yield was dried at overnight [27].

 

3. RESULTS AND DISCUSSION:

The phase formation of magnetic NPs was confirmed by XRD was shown in Fig 1.The corresponding peaks at 2θ = 24.3°, 33°, 35.5°, 54°, 57.4°, 62.6°, 63.9°, and 75.3° which are attributed to their respective planes (012), (104), (110), (116), (122), (214), (300), and (220) and well in agreement with standard JCPDS(File No. 33-0664)[25]. There was no any other substance peaks observed, which indicates the formation of pure magnetite NPs by hydrothermal approach.

 

 

Fig 1: XRD patterns of prepared Fe2O3 NPs

 

Fig 2 indicates the FTIR spectrum of as-synthesized magnetic NPs by hydrothermal method. Themajor absorption peak at 530 cm−1 corresponding to the Fe–O vibration, which confirmed the formation of NPs are related to magnetite phase [26].

 

 

Fig 2: FTIR spectrum of Fe2O3NPs

 

The morphology of prepared magnetic NPs was studied using FESEM (Fig 3 (a, b)).The images clearly showed the prepared magnetic NPs exhibited flake like shape with uniform size. The EDX analysis was stated that the presence of iron (Fe) and oxygen (O) in prepared magnetic NPs.

 

 

Fig 3: (a, b) SEM images and (c) EDX spectra of prepared Fe2O3 NPs

 

Synthesis of benzimidazoles:

Phenylenediamine (0.2 mol), requisite boric acid (0.3 mol), 20 mL of H2O and (0.5 mol) Fe2O3 NPs were boiled for 30-40 min under reflux. On neutralization of filtered solution with ammonia, the corresponding benzimidazole is separated.

 

Scheme 1: Synthesis of Benzimadazoles

 

 

Spectral data: UV- Ethanol, λmax (logε) m μ, 280 (3.89); 272 (3.91); 243 (3.80), IR- 1410–1630 cm-1 for –C=N– stretching, 3330-3120 cm-1 for C–H stretching vibrations and 3320–2810 cm-1 broad –NH stretching frequencies. 1H NMR- δ 7.69 (C2–H), 7.68 (C4–H), 7.16 (C5–H), 7.22 (C6–H) and 7.30 ppm (C7–H) respectively. 13C NMR- 2 (150.45), 4, 7 (116.41) 5, 6 (120.10) and 8,9 (143.88). Mass- m/z 91 (C6H5N).

 

Table 1:Optimization Study for the amount of catalyst [a]

Entry

Catalyst

(mol %)

Temperature

(°C)

Reaction Time (h)

Yield

(%)

1

01

120

2.0

80

2

02

100

2.0

70

3

05

80

2.0

50

4

10

50

2.0

30

 

Initially, we have focused on model reaction by refluxing the desirable amount of phenyenediamine and boric acid in the presence of Fe2O3 under the temperature of 50oC which results in the formation of desired compound with low yield (Table 1, entry 4). This experimental result declared further investigation of effect of temperature. Finally, the temperature was increased from 50 to 120oC. The temperature optimization clearly suggested that 120oC is the best for the desired product due to fast reaction rate and high yield (Table1, entry 1).

 

4. CONCLUSION:

In conclusion, we have demonstrated a simple, efficient protocol for the synthesis of benzimidazoles with boric acid as catalyst in aqueous media under simple and convenient conditions. This method is a simple, cost effective and environmentally benign.

 

5. REFERENCES:

1.        E. Serrano-Torregrosa, The chemical element: Chemistry’s contribution to our global future, Wiley.com, 2011.

2.        R. S. Varma, Green Chem., 2014, 16, 2027–2041.

3.        D. J. Cole-Hamilton and R. P. Tooze, Catalyst separation, recovery and recycling: chemistry and process design, Springer, 2006.

4.        C. Sui-Seng, F. Freutel, A. J. Lough and R. H. Morris, Angew. Chem., Int. Ed, 2008, 47, 940–943.

5.        H. Rao and C.-J. Li, Angew. Chem., Int. Ed., 2011, 50, 8936– 8939.

6.        L.C. Campeau, D. J. Schipper and K. Fagnou, J. Am. Chem. Soc., 2008, 130, 3266–3267.

7.        M. B. Gawande, P. S. Branco and R. S. Varma, Chem. Soc. Rev., 2013, 42, 3371–3393.

8.        J. Park, E. Lee, N.-M. Hwang, M. Kang, S. C. Kim, Y. Hwang, J.G. Park, H.J. Noh, J.Y. Kim, J.H. Park and T. Hyeon, Angew. Chem., Int. Ed., 2005, 117, 2932–2937.

9.        V. Polshettiwar and R. S. Varma, Green Chem., 2010, 12, 743–754.

10.     R. S. Varma, Pure Appl. Chem., 2013, 85, 1703–1710.

11.     A. H. Latham and M. E. Williams, Acc. Chem. Res., 2008, 41, 411–420.

12.     J. Vel´ık, V. Baliharova, J. Fink-Gremmels, S. Bull, J. Lamka and L. Skalov a, Research in Veterinary Science, 76, 2, 95–108, 2004.

13.     T. Fonseca, B. Gigante, and T. L. Gilchrist, Tetrahedron, 57, 9, 1793–1799, 2001.

14.     T. Roth, M. L. Morningstar, P. L. Boyer, S. H. Hughes, R. W. Buckheit Jr., and C. J. Michejda, Journal of Medicinal Chemistry, 40, 26, 4199–4207, 1997.

15.     M. T. Migawa, J.-L. Girardet, J. A. Walker II, Journal of Medicinal Chemistry, 41, 8, 1242–1251, 1998.

16.     W. A. Denny, G. W. Rewcastle, and B. C. Baguley, Journal of Medicinal Chemistry, 33, 814–819, 1990.

17.     S. M. Sondhi, N. Singh, A. Kumar, O. Lozach, and L. Meijer, Bioorganic and Medicinal Chemistry, 14, 11, 3758–3765, 2006.

18.     D. Yang, D. Fokas, J. Li, L. Yu, and C. M. Baldino, Synthesis, 1, 47–56, 2005.

19.     D. Valdez-Padilla, S. Rodr´ıguez-Morales, A. Hernandez-Cam-pos, Bioorganic and Medicinal Chemistry, 17, 1724–1730, 2009.

20.     A.A. Spasov, I.N. Yozhitsa, L.I. Bugaeva and V.A.Anisimova, Pharm Chem J., 1999, 33, 232.

21.     T. A. Houston, B. L. Wilkinson, and J. T. Blanchfield, Organic Letters, 6, 5, 679–681, 2004.

22.     M. K. Chaudhuri, S. Hussain, M. L. Kantam, and B. Neelima, Tetrahedron Letters, 46, 48, 8329–8331, 2005.

23.     M. K. Chaudhuri and S. J. Hussain, Journal of Molecular Catalysis A, 269, 214–217, 2007.

24.     J. Nath and M. K. Chaudhuri, Green Chemistry Letters and Reviews, 1, 4, 223–230, 2008.

25.     S.B. Wang, W. Wang, P. Zhan, S.Q. Jiao, ChemElectroChem.,1, 1636–1639, 2014.

26.     Mahdavi, M.; Ahmad, M.B.; Haron, M.J.; Gharayebi, Y.; Shameli, K.; Nadi, B, J. Inorg. Organomet. Polym. 2013, 23, 599–607.

27.    B.A.Rachuri, G.P. Naidu, R. Muralikrishna and B.S. Mohan, preparation, characterization and photocatalytic activity of leaf like a-iron oxide-reduced graphene oxide composite, IJEAST, 1(10), 103-109, 2016.

 

 

 

 

 

 

 

Received on 12.03.2018         Modified on 28.03.2018

Accepted on 07.04.2018         © AJRC All right reserved

Asian J. Research Chem. 2018; 11(3):521-523.

DOI:10.5958/0974-4150.2018.00093.7