Cu–N‐heterocyclic carbene‐catalysed synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from one‐pot tandem coupling of o‐phenylenediamines and terminal alkynes

A series of new benzimidazolium chlorides bearing N,N′‐benzyl, 2,4,6‐trimethylbenzyl and 2,4,6‐triisopropylbenzyl substituents have been designed and synthesized from various o‐phenylenediamines. Subsequently, corresponding Cu‐based N‐heterocyclic carbenes (NHCs) were generated in situ in the reaction medium which represents a new application of NHCs exploiting distinct catalytic property towards intermolecular cyclization reaction cascade for the synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from o‐phenylenediamines and terminal alkynes. The outcome of the cyclization reaction product depends upon the N,N′‐substituents present on the benzimidazolium chlorides.     

Synthesis of novel Ag(I)-N-heterocyclic carbene complexes soluble in both water and dichloromethane and their antimicrobial studies

Abstract

The interaction of the benzimidazolium salt with Ag₂O in dichloromethane to prepare novel Ag(I)-N-heterocyclic carbene complexes has been carried out at room temperature for 48?h in the absence of light. The obtained complexes were identified and characterized by ¹H and ¹³C NMR, FT-IR and elemental analysis techniques. In addition, it has been found that some of the complexes are antimicrobially active and show higher activity than the free ligand. Probably metal chelation affects significantly the antimicrobial behavior of the ligands. The minimum inhibitory concentration of the complexes was determined. The results indicated that these complexes exhibit antimicrobial activity.     

2-单核和双核茂铁基-1,3-二烷基苯并咪唑盐的合成、结构及性质研究

以2-二茂铁基苯并咪唑(2)为原料,合成了1-甲基-2-二茂铁基-3-乙基苯并咪唑碘盐(4)和六氟磷酸盐(5);甲酰化的2,2-双二茂铁基丙烷(6)与邻苯二胺在甲醇作溶剂,回流,碘催化下反应,得到2-[1’-(2-二茂铁基丙烷-2-基)二茂铁-1-基]苯并咪唑(7),以7为原料合成了1-甲基-2-[1’-(2-二茂铁基丙烷-2-基)二茂铁-1-基]-3-乙基苯并咪唑碘盐(9)和六氟磷酸盐(10).电化学分析表明所得的盐化合物中,与苯并咪唑阳离子直接相连的二茂铁的氧化电位相对2和7均产生了较大正移.对化合物4的单晶结构进行了解析,晶体结构中存在π-π堆积.UV-Vis吸收光谱表明所得盐化合物具有光致电荷迁移现象.DSC-TG(差示扫描量热-热重)测试表明碘盐4对高氯酸铵(AP)热分解有较好催化效果.     

A stable dimeric mono‐coordinated NHC–Pd(II) complex: synthesis,characterization, and reactivity in Suzuki–Miyaura cross‐coupling reaction

A stable dimeric mono‐coordinated NHC–Pd(II) complex with bridging iodine atoms was synthesized and characterized by single‐crystal X‐ray diffraction. It has been successfully applied to the Suzuki–Miyaura cross‐coupling reaction under aerobic conditions. Good to excellent yields were obtained in most cases with the addition of H₂O. Copyright © 2005 John Wiley & Sons, Ltd.     

基于萘酰亚胺-苯并咪唑鎓的荧光传感器对H2PO-4的高选择性识别

设计合成了基于萘酰亚胺-咪唑鎓的受体分子1和2,通过荧光发射光谱研究了受体分子1和2对阴离子F^-、Cl^-、Br^-、I^-、AcO^-、HSO^-₄、H₂PO^-₄、NO^-₃、ClO^-₄的识别性能。 研究发现,在受体分子1和2的乙腈溶液(5.0×10^-6 mol/L)中加入10倍化学计量的H₂PO^-₄时,受体分子1的荧光猝灭率高达98%,受体分子2的荧光猝灭率仅为24%。 表明具有多重识别位点的受体分子1在构型上与H₂PO^-₄更匹配,可作为H₂PO^-₄的荧光关闭型(turn-off)探针。 受体分子1与H₂PO^-₄的结合比为1∶1,结合常数为(1.25±0.11)×10⁵ L/mol,检出限为6.90×10^-6 mol/L。     

碲氢化钠与苯并咪唑盐的反应和醛的合成新方法

自1975年Barton首次制备了碲氢化钠以来,由于它是一种温和的选择性还原剂和良好的亲核试剂,并具有试剂易得、后处理方便等优点,在有机合成中的应用得到了迅速发展[1-5].例如,Barton等[1]用碲氢化钠对吡啶盐和异喹啉盐的季铵化的碳氮双键在碱性乙醇溶液中还原脱卤能生成加氢衍生物.本文则首次报道碲氢化钠对苯并咪唑盐还原脱卤生成苯并咪唑烷的反应.其合成路线如图示1所示:     

Discovery of Amide-Functionalized Benzimidazolium Salts as Potent α-Glucosidase Inhibitors

α-Glucosidase inhibitors (AGIs) are used as medicines for the treatment of diabetes mellitus. The α-Glucosidase enzyme is present in the small intestine and is responsible for the breakdown of carbohydrates into sugars. The process results in an increase in blood sugar levels. AGIs slow down the digestion of carbohydrates that is helpful in controlling the sugar levels in the blood after meals. Among heterocyclic compounds, benzimidazole moiety is recognized as a potent bioactive scaffold for its wide range of biologically active derivatives. The aim of this study is to explore the α-glucosidase inhibition ability of benzimidazolium salts. In this study, two novel series of benzimidazolium salts, i.e., 1-benzyl-3-{2-(substituted) amino-2-oxoethyl}-1H-benzo[d]imidazol-3-ium bromide 9a–m and 1-benzyl-3-{2-substituted) amino-2-oxoethyl}-2-methyl-1H-benzo[d] imidazol-3-ium bromide 10a–m were screened for their in vitro α-glucosidase inhibitory potential. These compounds were synthesized through a multistep procedure and were characterized by ¹H-NMR, ¹³C-NMR, and EI-MS techniques. Compound 10d was identified as the potent α-glucosidase inhibitor among the series with an IC₅₀ value of 14 ± 0.013 μM, which is 4-fold higher than the standard drug, acarbose. In addition, compounds 10a, 10e, 10h, 10g, 10k, 10l, and 10m also exhibited pronounced potential for α-glucosidase inhibition with IC₅₀ value ranging from 15 ± 0.037 to 32.27 ± 0.050 µM when compared with the reference drug acarbose (IC₅₀ = 58.8 ± 0.12 μM). A molecular docking study was performed to rationalize the binding interactions of potent inhibitors with the active site of the α-glucosidase enzyme.     

Antiproliferative activities of 2-hydroxyethyl substituted benzimidazolium salts and their palladium complexes against human cancerous cell lines

Abstract

Benzimidazolium salts (1a and 1b) and respective palladium complexes (2a and 2b) were prepared and characterized with ¹H and ¹³C NMR, IR, elemental analysis as well as HRMS (for 2a). All target compounds were screened as potential anticancer agents against human cell lines for assessing their cytotoxicity. Heterocyclic organic compounds (1a and 1b) showed more cytotoxic activity than their complexes (2a and 2b) in the tested two cell lines. Particularly, a benzimidazolium salt including a 4-methylbenzyl group had a high cytotoxic potency towards MDA-MB-231 and DLD-1 cell lines with IC₅₀ values comparable to a well-known anticancer drug cisplatin, which is generally used in clinical studies. Furthermore, a compound namely 1-(2-hydroxyethyl)-3-(2,3,4,5,6-pentamethylbenzyl)-1H-benzo[d]imidazol-3-ium bromide was found to be more cytotoxic activity in MDA-MB-231 cell line compared to cisplatin with following IC₅₀ value of 7.59?±?0.68?μM.     

Synthesis and antimicrobial activity of bulky 3,5‐di‐tert‐butyl substituent‐containing silver–N‐heterocyclic carbene complexes

A series of novel benzimidazolium bromides containing bulky 3,5‐di‐tert ‐butyl group were synthesized in high yields as N‐heterocyclic carbene (NHC) ligands. These NHC ligands were metallated with Ag₂O under moderate conditions to give novel silver–NHC complexes. The structures of all compounds were characterized using ¹H NMR, ¹³CNMR, infrared and elemental analysis techniques, which supported the proposed structures. The silver–NHC complexes were screened for their in vitro antimicrobial activities against the standard bacterial strains Enterococcus faecalis , Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa and the fungal strains Candida albicans and C. tropicalis . The results showed that most of the silver–NHC complexes inhibited the growth of all bacterial strains and fungal strains and were found to display effective antimicrobial activity against different microorganisms.