| Since the importance of aryl nitriles, this dissertation mainly focuses on the researches of metal-catalyzed cyanation reactions towards aryl nitriles using benzyl cyanide as novel cyanating agents.Firstly, previous researches on the synthesis of aryl nitriles based on different kinds of cyanating agents are summarized. Recent advances in cyanating agents used in cyanation reactions are discussed, including metal cyanide and non-metal cyanide.Secondly, a palladium-catalyzed cyanation of aryl halides using benzyl cyanide as cyanating agents is described in this dissertation. Compared to previous commonly used cyanating agents, benzyl cyanide has lower toxicity, higher efficiency, and better solubility. And this reaction also owns several advantages on ligand-free, mild conditions, easy handling, and high efficiency. The possible mechanism seems to be the initial coordination of benzyl cyanide to palladium catalyst, followed by nucleophilic attacking to produce "CN" unit. Owing to the slow releasing of cyano anions, the poisoning of palladium catalyst is avoided efficiently.Thirdly, a copper catalyzed systhesis of aryl nitriles by cyanation of aryl halides is demonstrated, also employing benzyl cyanide as cyanating agents. The reaction is proceeded with the C-H bond activation and oxidation of benzyl cyanide to release cyano anions, and the subsequent copper catalyzed cyanation reaction. This method affords aryl nitriles in good to excellent yields with wide substrate scope. Moreover, low-cost copper catalyst makes it more practical for application.Finally, a copper-catalyzed three component reaction of pyridin-2-amines, aryl methyl ketones, and benzyl cyanide is disclosed, approaching to 3-cyano-imidazo[1,2-a]pyridine derivatives. Imidazo[1,2-a]pyridine compound is firstly formed, followed by copper-catalyed cyanation reaction with aryl acetonitrile. Several products obtained by this method can be converted to important commercially available drugs by several simple steps. |
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