Zhang Min, Huang Guoling, Zhang Xuefang, Lin Zhenyuan, Li Yibiao, Li Bin, Chen Lu
School of Chemical & Environmental Engineering, Wuyi University, Jiangmen 529020, China.
Comb Chem High Throughput Screen. 2018;21(8):567-570. doi: 10.2174/1386207321666181018163940.
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.
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.
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.
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.
通过减肥辅助剂（L-肉碱）作为廉价催化剂获得苯并咪唑衍生物。多种芳香醛在温和条件下易于与取代的邻苯二胺发生缩合反应，以优异的产率得到目标分子。
熔点在Electrothemal X6显微镜数字熔点仪上测定。1H NMR和13C NMR光谱在Bruker AVANCE 400（400 MHz）仪器上于DMSO-d6中记录，以d 0.00 ppm处的TMS作为内标。C、H和N分析由Perkin-Elmer 2400 CHN元素分析仪进行。所用化学品为商业级，无需进一步纯化。将邻苯二胺1、芳香醛2和L-肉碱（10 mol%）的等摩尔（1.0 mmol）混合物在60°C下于乙醇（3 mL）中剧烈搅拌特定时间，该时间由TLC（石油醚：乙酸乙酯 = 4:1）指示。反应完成后，通过加入水（20 mL）淬灭混合物，用乙酸乙酯（3×10 mL）萃取，合并的萃取液用无水硫酸镁干燥。滤液蒸发后，得到相应的苯并咪唑作为唯一产物。产物3a - 3r的产率为82 - 95%。产物3的结构通过其红外光谱、1H NMR、13C NMR和元素分析光谱鉴定。
产物在30 - 80分钟内以82 - 95%的产率获得。该方法具有几个优点，如简单、清洁且环保、产率优异以及避免使用不便制备的催化剂。同时，催化剂L-肉碱是一种减肥辅助剂，可应用于广泛的绿色催化体系。
提供了一种简便的苯并咪唑合成方法，该方法包括使用L-肉碱作为有效催化剂，使各种醛与取代的邻苯二胺反应，产率良好至优异。该方案克服了早期的缺点，如反应条件苛刻、后处理繁琐、成本高、产生废物以及使用金属氧化物等，可应用于苯并咪唑类药物的合成以满足环境友好的要求。
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