Inexpensive Weight-Reducing Aid (L-Carnitine) as An Efficient Catalyst for Synthesis of Benzimidazoles

Author(s): Min Zhang, Guoling Huang, Xuefang Zhang, Zhenyuan Lin, Yibiao Li, Bin Li , Lu Chen*.

Journal Name: Combinatorial Chemistry & High Throughput Screening

Volume 21 , Issue 8 , 2018

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Abstract:

Aim and Objective: The benzimidazole derivatives have been obtained via weightreducing aid (L-Carnitine) as a cheap catalyst. A wide range of aromatic aldehydes easily undergo condensations with substituted o-phenylendiamine under mild condition to afford the target molecular in excellent yields.

Materials and Methods: Melting points were measured on an Electrothemal X6 microscopy digital melting point apparatus. 1H NMR and 13C NMR spectra were recorded in DMSO-d6 on a Bruker AVANCE 400 (400 MHz) instrument with the TMS at d 0.00 ppm as an internal standard. C, H and N analysis were performed by a Perkin-Elmer 2400 CHN elemental analyzer. Chemicals used were of commercial grade without further purification.

An equimloar (1.0 mmol) mixture of o-phenylenediamine 1, aromatic aldehyde 2, and L-Carnitine (10 mol%) was vigorously stirred at 60°C in EtOH (3 mL) for the specific time indicated by TLC (petroleum: ethyl acetate ether = 4:1). After completion of the reaction, the mixture was quenched by adding H2O (20 mL), extracted with EtOAc (3 x 10 mL), and the combined extracts were dried by anhydrous MgSO4. The filtrate was evaporated and the corresponding benzimidazole was obtained as the only product. The products 3a–3r were obtained in 82–95% yields. The structures of the products 3 were identified by their IR, 1H NMR, 13C NMR and elemental analysis spectra.

Results: The products were obtained in 82–95% yields in 30–80 min. The method has several advantages such as simple, clean and environmentally process, excellent yield and avoiding use of inconvenient preparation of catalyst. Meanwhile, the catalyst L-Carnitine is a kind of weightreducing aid, which might be applied to broad green catalyzed system.

Conclusion: A facile synthesis of benzimidazoles comprising the reaction of various aldehydes with substituted o-phenylendiamine in good to excellent yield is provided using L-Carnitine as an efficient catalyst. The protocol overcomes the earlier disadvantages like harsh reaction conditions, tedious work-up, expensive process, wastes generation and the use of metallic oxide, which might be applied to the synthesis of benzimidazoles pharmaceticals in order to meet friendly environmental demands.

Keywords: Green protocol, benzimidazole, L-Carnitine, heterocycles, catalysis, 2-arylbenzimidazoles.

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Article Details

VOLUME: 21
ISSUE: 8
Year: 2018
Page: [567 - 570]
Pages: 4
DOI: 10.2174/1386207321666181018163940
Price: $58

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