Copper-Catalyzed Synthesis Of Benzimidazoquinazoline Derivatives

Nitrogen-containing heterocycles widely occur in nature, and they are commonconstituents in natural products, pharmaceuticals and biologically active molecules.With the rapid development of biology and pharmacology, variousnitrogen-containing heterocycles exhibit good biological activities, which lead to theirgood prospects for application in pharmaceutical industry, andbenzimidazoquinazoline derivatives are among one type of these compounds.Several approaches to benzimidazoquinazoline derivatives have been reported sofar, yet followed by many defects, such as narrow substrate generality, complicatedprocesses, the use of high toxic reagents like isocyanate and high reactiontemperatures, all of which restricted the extensive use of these approaches. Whilewith the application of benzimidazoquinazoline derivatives in biology and medicine,people are more committed to looking for a new and effective method to preparethese compounds systematically.In the field of organic synthesis, transition metal-catalyzed Ullmann reaction hasbeen an important means to construct C-N bond to prepare nitrogen-containingheterocycles. Among the numerous metal reagents, copper-cataylsts turn to be a newfocous of many organic chemistry researchers due to their advantages of low-cost,low toxicity, wide availablity and easy preservation. Recently, many improvementshave been made. For example, catalysts used in reactions have been into moreeconomical and green coppor catalyst from expensive and toxic noble metals such aspalladium; mild conditionds have been developed from high reaction temperatures;water has been reported as a reaction medium excluding using of toxic organicsolvents.In this paper, we have developed a simple and efficient copper-catalyed methodfor synthesis of benzimidazoquinazoline derivatives. The protocol uses amidines orguanidines hydrochloride, substituted2-（2-halophenyl）-1H-benzo[d]imidazoles as thestarting materials, CuI as the catalyst, K₃PO₄as the base, DMSO or the mixture ofDMSO and CH2Cl2as the solvent, and the reactions performed well at room temperature or80-100℃without addition of any ligand or additive. The advantagesof this method are shown as follows:（1） the used reagents and copper-catalyst arereadily available and lowly toxic;（2） the reaction conditions are mild, and reactionsproceed well at room temperature or80-100℃;（3） the catalyst system works wellwithout addition of any ligand or additive, and the purification is simple;（4） themethod is of good tolerance to various functional groups in substrates;（5） theprotocol can provide good yields （more than80%for most products, even up to90%）;（6） theproducts have good application prospects in organic chemistry and medicinalchemistry.