Nano-cuprous Oxide Catalyze Carbon-nitrogen And Carbon-oxygen Bond Coupling Reactions

So far,Ullmann coupling reaction was found more than100years, the reactionproducts are widely used in synthesis of important medical intermediates and materialchemistry fields, such as N-aryl imidazole,N-aryl benzimidazole and so on. Althoughthese kinds of compounds can be gotten by traditional Ullmann preparationmethods,regretfully, being limited too harsh reaction conditions in Ullmann, like hightemperature, excess copper joined, the reaction time is too long and so on. Therefore,how to improve the experiment conditions to make Ullmann reaction having a moreextensive application attracts attentions of scientists. In the course of studying,Ma,D.W and Buchwald professors find that joining a particular ligand can makespecific reaction yield greatly improved, then, a large number of ligands such asN,N’two teeth ligands, O,O’ two teeth ligands, N,O’two teeth ligands are successivelyfound and being applyed. Although ligands joined can greatly promote the reaction,with a large number of ligands joined,making it difficult to deal with reacted complex,influencing the purification of products. Some scholars also put attentions to noligands copper catalytic reaction, Sreedhar in India reported nano CuI catalyzing C-N,C-O coupling reaction, as the concept of nano copper catalysts introducted, manyscholars follow this with interests.First, a new type of copper catalysts Cu₂O/TiO₂NTs without ligands will beresearched, first of all, Cu crystals were electroplated on nano TiO₂in a solutioncontaining5mM CuSO4, the Cu loaded TiO₂NTs were then anodized to Cu₂O,obtaining nano Cu₂O growing on TiO₂NTs, determining the content of Cu₂O On aunit mass with iodine method, the consequence is0.5mmol/g.Second,Using this catalyst for C-N, C-O coupling reactions, previous reports inthe literature, coupling of chlorinated aromatic were less mentioned, but here,chlorinated aromatic can get good reactions.By optimizing experiment condition, theoptimum reaction conditions were attempering to110℃,in DMF solvent, reacting24h with K2CO3.taking3-nitro-chlorobenzene reacting with imidazole for example, itachieving93%yield. In the studying of C-N coupling, we choosed imidazole,benzimidazole and aniline as nucleophilic substrates respectively react with4-methyl-chlorobenzene, chlorobenzene and4-nitro-chlorobenzene,without ligands,generating the corresponding aryl products, the results showed that the yields wasdirectly affected by the substituents in difference of electrical,4-nitro-chlorobenzene was higher than the yield of the4-methyl-chlorobenzene, products were measuredthrough the HRMS,1H NMR,13C NMR and melting point. In order to furtherexpanding the application range of the catalyst,choosing more substrates to makesuitable development,choose the phenol compounds as nucleophilic reagent to reactwith chlorobenzene and4-nitro-chlorobenzene, getting a series of aryl-oxygen-arylaether products. Diaryl ether structures are prevalent in natural products, drugs andother chemical products, even some simple diaryl ether natural compound also has aspecial physiological activity, but the synthesis of diaryl ether structure is not an easyexperiment. Therefore, we expect a mild reaction conditions, the synthesis with acommon substrate and higher yield.In the end, using chlorobenzene,4-nitro-chlorobenzene as the electrophilicreagent, imposing4-nitro-phenol,4-methyl-phenol and phenol as nucleophiles.Weobtained the C-O conjugates. The results proved electron donor group on nucleophileis more conducive to the reaction.Because of Cu₂O nanowires growing on TiO₂slice,equivalently providing a fixed bed reaction, Cu₂O will not have a heavy loss in thecourse of reaction, catalyst can be repeated used through proper treatment,by doingcycle experiments, it proved that this catalyst can be recycled, increasing theeconomic benefit.