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Studies on Cu-Catalyzed Synthesis of Pyrazoles

Posted by Ellis
TAGS: heterocyclespyrazolescopper_catalysis
bases
This thesis aims at the studies on the new method for synthesis of pyrazoles with phenylhydrazones and dialkyl ethylenedicarboxylates by copper catalyzed in the presence of bases. Which is divided three parts as follows:PartⅠ:The applications of pyrazolesPyrazoles are a well known class of nitrogencontaining heterocycles that find extensive use in the pharmaceutical and agrochemical substances. For instance, pyrazoles constitute the core structures of some well known drugs such as Celebrex, Viagra and Acomplia, as well as a number of compounds containing the pyrazole core have been used in therapeutic area such as antiinflammatory, analgesic and anti-cancer.PartⅡ:Developments of the synthesis of pyrazolesDue to the attractive medicinal properties of the pyrazole skeleton, easy and efficient methods for the preparation of such compounds are of considerable interest in synthetic organic chemistry. By far classical methods for synthesis of these heterocycles are the reactions between 1,3-diketones with hydrazines. However, such procedures suffer a major drawback is that the lack of rgioselectivity in many cases depending on the nature of the 1,3-diketones. Other methods of obtaining pyrazoles that do not require 1,3-diketones have been reported, but often have serious drawbacks such as being step-intensive.PartⅢ:Cu-Catalyzed Synthesis of Pyrazoles from Phenylhydrazones and Dialkyl EthylenedicarboxylatesAs a part of our continuing study on the utilization of copper catalysis in organic synthesis, herein we described an easy and efficient copper-catalyzed reaction for the synthesis of ploysubstituted pyrazoles from phenylhydrazones and dialkyl ethylenedicarboxylates in the presence of bases in this paper, which reaction proceeded smoothly and the corresponding adducts were achieved in moderate to good yields. All the products mentioned in this paper have been unequivocally identified through NMR、MS and IR studies.
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