Study On Selenium-catalyzed The Carbonylation Of Nitrobenzene To Synthesize Symmetrical Diphenylureas Under Atmospheric Pressure Conditions

Urea compounds have important applications in many fields,especially in the fields of pesticides and medicines.It is widely used in medical research because it is an important intermediate and raw material for the synthesis of many drugs.In the pesticide industry,it is widely used in the production of pesticides due to its efficacy in sterilization and weeding.Therefore,it is necessary to further explore the synthesis methods of urea compounds.This paper is further exploration based on the Se/CO system.The nitrobenzene compounds are used as substrates to react with water and CO under the normal pressure conditions.Se was used as a phase transfer catalyst in the reaction to synthesize diphenylurea compound in one step.Different from the high pressure reaction,the side reaction is obviously reduced due to its higher selectivity from the reaction itself;From the perspective of green chemistry,the atmospheric pressure reaction is relatively less demanding on the reaction equipment,and it also reduces the risk of operation and increases productivity.The increased selectivity of the reaction can effectively reduce the type of by-products,which means that the post-treatment step is simplified.Thereby,it is effectively reducing the cost of the synthesis and saving energy.This paper mainly uses nitrobenzene as a substrate.The solvent and cocatalyst have been selected through a large number of experiments.The optimum amount of solvent,cocatalyst,selenium powder,substrate,water,etc.,as well as the appropriate temperature and duration are also explored.And determined the best conditions:nitrobenzene 5 mmol,Se 0.2 mmol,sodium acetate 3 mmol,water 2 mL,DMF 20 mL,temperature 95?,time 3 h,CO continuous bubbling.The experiment was carried out under the above reaction conditions to obtain a yield of diphenylurea of about 97%.The above feed ratio is applied to a nitrobenzene compound with other substituents to obtain a series of diphenylureas.The product is purified by column chromatography,recrystallization,etc.The melting point of the pure product was determined by melting point instrument.Finally the structure was determined by ~1H NMR and IR.The aim of this thesis is to optimize the reaction of selenium-catalyzed carbonylation of nitrobenzene compounds to synthesize diphenylurea under normal pressure conditions.Based on the experimental results,a reaction mechanism was proposed to explain the formation of diphenylurea and the important role of by-product aniline in the reaction process.