Studies On Selenium-Catalyzed Carbonylation To Unsymmetrical Ureas

Unsymmetrical urea is an important category of chemicals, most of which bear bio-activity. They attract people's attention as they are widely used as medicine, medical intermidiates, herdicide, pesticide, plant-regulators and germicide. The synthesis of ureas is also an important research topic in organic chemistry.There are many ways for synthesizing unsymmetrical ureas, among them, the most important ways are the methods concerning phosgene and phosgene deriviatives, intermidiate metal (such as palladium, ruthenium and rhodium, and their compounds) and nonmetalic elements such as surful, selenium and tellurium. The methods above are all effective, but the first method would generally use phosgene as material, which would cause evident pollution for the environment. Despite of their significant application(such as catalystic coupling-reaction), intermidiate metals, when used for the synthesis of ureas, are not suitalbe for industrical manufactory due to their high value and the difficulty to seprate catalyst from the reaction mixture. Some non-metalic elements, especially selenium, have excellent catalystic abilities that are used for research work. Under the catalystical system of carbon monoxide/selenium, nitro-containing and amino-containing compounds can be synthesized into unsymmetrical ureas through"one pot"method. This is an effective method with high atomic economicity and environmental friendness of synthesize ureas instead of using highly toxic phothgene and complicated cynantes.Selenium-catalyzed reaction is widely used for the oxi-red carbonylation of nitro compound and amines. No other reducing agent is needed, however, the usability of CO is reduced greatly (CO is the reducing agent for nitro compounds). CO is oxidated into CO2, which is waste that would cause great loss for industry. Aimming at resloving the problem, we investigated the oxi-carbonylation of 2-aminopyridine and aniline, using oxygen as oxidant, synthesized some unsymmetrical pyridyl ureas, and enriched the methods for preparing pyridylureas. We also investigated the factor for the reaction, such as the pressure of CO, reaction temperature, the content of selenium, the content of assistant catalyst and the influence of substituded group on aniline and the reusablities of the catalys, finding that the oxi-carbonylation reaction would slove the problem of the low usability of CO. The study is meanful for industrial manufactory. The former study about selenium-catalyzed reaction for the synthesis of ureas is focused on the study of nitrobenzene and its deriviatives. We think it would also be effective for other nitro compounds. Consequently, we synthesized some tri-substituted ureas in good selectivity and high yield, though the oxi-red carbonylation of 1-nitronaphthalene and several secondary amines, using selenium as catalyst, carbon monoxide as carbonylation reagent, and triethylamine as co-catalyst.Meanwhile we investigated the factor for the reaction, such as the reaction temperature, the pressure of CO, the content of selenium, the ratio of the materials and the content of assistant catalyst. Based on the result, we predicted the possible mechanism of the reaction. Then we took use of the reaction into the carbonylation of other nitro compounds with some secondary amines, synthesized some novel tri-substituted unsymmetrical ureas, and enriched the categories of unsymmetrical ureas.We investigated and enlarged the useness of selenium-catalyzed carbonylation, synthesized some novel ureas, and finished the conformation by 1H NMR and 13C NMR. We also investigated the factors affacting the reations. The research is meaningful for the study of the mechanism of Se/CO system. In sum, in the paper we synthesized some unsymmetrical ureas bearing potential bio-activity through selenium-catalyzed carbonylation reaction. The reasearch enriched the useness of CO/Se,which has is valuable for both industry and academic work.