The Synthesis Of Benzimidazoles And Their Derivative By Using Triphosgene

Under the normal situation, triphosgene is a kind of white solid chemical reagents. Compared with the phosgene, triphosgene is more convenient to transport and storage. During the operation, it is also more secure and easily to control. The reaction conditions are mild and the reaction equipments are simple. It does little harm to the environment and is very friendly to the humans. The heterocyclic compounds of benzimidazolones which have a variety of bio-chemical activities are widely used as Pharmaceuticals, pesticides and some important organic intermediates.In practice, there are many different ways to synthesize benzimidazolones. Traditionally, the synthetic methods of benzimidazolones include phosgene, urea and dimethyl carbonate, in which are involved unfriendly factors. For example, phosgene is highly toxic, it is very dangerous to humans and the environment. The method by urea requires high temperature and pressure, so the reaction equipments’ requirements are very high, and the reaction process can cause a great danger. The method of dimethyl carbonate need the protection of nitrogen and the reaction is under high pressure. The product yield by it is low and the post-processing is complex. In this paper, we hope to find a more safe and effective method to synthesize benzimidazolones. As one of the effective green chemical reagents, triphosgene becomes the main subject we will study.In this paper, synthesis of benzimidazolones using triphosgene was studied. Different factors affecting the product yield, such as reaction time, reaction temperature and the amount of triphosgene and so on were investigated. The preferred reaction conditions were as follows:with triethylamine as the catalyst, the dichloromethane as the solvent, maintaining the reaction temperature at20℃and the reaction time by22h, the highest yield of Benzimidazolone could get96%when n(o-PDA):n(BTC):n(Et3N)=1.00:0.35:1.05and the amount of the solvent was eighty times the quality of the o-phenylenediamine.In this paper, the method of one pot at room temperature and under atmospheric pressure was studied. With sodium borohydride as the reducing agent and Raney nickel as the catalyst, o-nitroaniline could be restored into o-phenylenediamine. Without the intermediate processing of the case, the benzimidazolone could be synthesized successfully by using triphosgene.