A Study On Microwave Assisted Synthesis And Properties Of Functional Substituted Benzimidazoles

Benzimidazole is a compound containing both a benzene ring and a five membered heterocyclic structure with two nitrogen atoms,and multiple substituents can be introduced at multiple positions,which can be designed to synthesize variety of new compounds.The molecules possess rigid planar and conjugated structures.The introduction of strong electron donating or withdrawing groups may help electron transfer in imidazole ring.Therefore,benzimidazole compounds have excellent luminescent properties.At the same time,benzimidazole as a structural unit of Vitamin B12 own a similar stucture with purine.It can be used as a competitive inhibitor to inhibit the biosynthesis of key components in bacteria and other pathogens,so benzimidazole compounds are of certain antibacterial properties.In view of triphenylamine possess conjugated structure and unique hole transport ability as well as its exellent performance in the field of organic luminescence.Herein,triphenylamine?s monoaldehyde,dialdehyde and trialdehyde were synthesized by Vilsmeier-Haack reaction.Sequentially,both solid phase and liquid phase mcrowave assisted methods for synthesizing triphenylamine substituted benzimidazoles were respectively explored using triphenylamine aldehyde as raw material.The results showed liquid phase mcrowave assisted method was a more appropriate method for synthesizing triphenylamine substituted benzimidazoles.Finally,ten triphenylamine substituted benzimidazoles were synthesized starting from triphenylamine monoaldehyde or dialdehyde and five different o-phenylenediamines,using sodium bisulfite as catalyst and N,N-dimethylformamide as solvent under liquid phase microwave radiation.The synthesized ten compounds were characterized by mass spectrometry,IR and NMR.Their structures were determined.Also,their UV and fluorescence spectra were tested.The quantum yield of fluorescence was calculated based on quinine sulfate and their luminescent properties were studied.Besides,because hydrogen bonds play a important role in the effect of the drug molecules in human body,and hydroxyl helps the formation of hydrogen bonds.Therefore,phenolic hydroxyl substituted benzimidazole was attempted to synthesize to get good germicidal efficacy.In this paper,4-chlorobenzene-1,2-diamine and 4-hydroxy-3,5-dimethoxybenzaldehyde were used as raw materials under liquid phase microwave radiation condition to ensure the optimum reaction conditions.The effect of catalyst,catalyst loading,reactant ratio,reaction temperature and solvent on the yield of target product were explored.twelve phenolic hydroxyl substituted benzimidazole were prepared from a variety of phenolic hydroxyl aromatic aldehydes and five o-phenylenediamines.The structures of the synthesized twelve compounds were characterized by mass spectrometry,IR and NMR.Additionally,antimicrobial activities of the synthesized compounds on five bacteria and a fungi were assessed using 96 hole plate dilution method,and ciprofloxacin and itraconazole were used as positive control.One of the synthesized compounds containing naphthalene ring showed inhibition activity towards both bacterial and fungal,the compounds can be regard as a research direction in broad-spectrum antibiotic.