The Methodology Research Of Ullmann C-O Coupling And The Synthesis Of Simple Coumarins

Ullmann C-O coupling was studied by using heterogeneous reusable Cu2O-Cu/CNTs as catalyst, and new synthetic approach of coumarin derivatives was also explored tentatively. There are three chapters in this article. The research progress of Ullmann-type reaction was summarized in chapter1. The rest of two chapters are experimental sections.Chapter1the research progress of Ullmann-type reactionThe mechanism of Ullmann-type reaction, means to accelerate O-arylation, effects of metal catalyst and ligand on Ullmann coupling were discussed in chapter1, respectively. Palladium and copper catalysts have so far been the metals of choice for Ullmann coupling. Despite the high efficiency of the Pd-catalyzed methods, the use of expensive palladium and elaborate phosphorated ligands would limit its applications to large-or industrial-scale production. Cu-catalyzed Ullmann coupling is a viable alternative to Pd-catalyzed diarylether synthesis. However, traditional copper-mediated Ullmann-type coupling often needs harsh reaction conditions, such as high reaction temperature, stoichiometric amounts of copper. The development of new methods for Ullmann reaction under relatively mild conditions is demanded urgently. A large number of copper and palladium catalysts were prepared to increase the yield of Ullmann coupling. The catalysts could be reused for several times to reduce the Ullmann-type reaction cost. The addition of ligand which was more efficient, more applicable, and easily prepared was another progress for Ullmann coupling. Metal-free Ullmann coupling was demonstrated a mild and effective approach to prepare C-O, C-N, C-S compounds. Besides, microwave and ultrasound were also important means for Ullmann reaction.Chapter2experimental section of Ullmann C-O couplingVarious substituted diarylether derivatives were prepared by using heterogeneous reusable Cu2O-and Cu-coated carbon nanotubes (Cu2O/Cu-CNTs) as catalyst under ligand-free conditions, which provided good to excellent yields. The catalyst was characterized by TEM, XRD and AAS analysis. The effects of solvent, base and amount of catalyst for the O-arylation were investigated. The catalyst could be recovered by simple filtration from the reaction mixture without further treatment and reused several times with consistent catalytic activity. In addition. CNTs could also be recovered from the used Cu2O/Cu-CNTs by a simple acid treatment. Chapter3experimental section of the synthesis of simple coumarinsCoumarins have been widely used in many fields of our life, such as medicine and agricultural industry since it was discoverd. Many Coumarins exhibiting a broad pharmacological profile, including anticancer activity, anti-HIV activity, and anticoagulation activity. However, traditional synthetic methods of coumarins often need the promotion of base or corrosive acid. Herein, the development of traditional synthetic methods under relatively mild conditions or exploration of a new approach for the preparation of coumarins is demanded urgently. Two approaches were proposed according to literature for the synthesis of simple coumarins. A metal-free oxidative tandem coupling of phenylacrylate with carbonyl C(sp2)-H bonds and aryl C(sp2)-H bonds is established for the synthesis of simple coumarins. In addition, peroxides in combination with transition metal catalysts were applied to the oxidative coupling of aldehydes and coumarin to form simple coumarins. The synthesis of coumarins was studied by the reactions of phenylacrylate, coumarin and benzaldehyde, respectively. The effects of oxidant, solvent, reaction temperature and metal catalyst for the oxidative tandem coupling were investigated. It turned out that the reactions did not get the desired results, and an effective catalytic system was not found.