Study On Transition-metal Catalyzed Synthetic Mtehods Of Indole Derivatives

Indole and its derivatives are the heterocyclic compounds distributing most broadly in the world. Given to its unique structure and properties, they play a critically important role in many areas, such as medicines, dyestuffs and agrochemicals. Development of simple and efficient methods for the synthesis of indole and its derivatives has been a hot research field of chemists. In this thesis, the research development and current progress of synthetic methods using transition-metal (TM) as the catalysts of indole and its derivatives are summarized and reviewed. Based on this and our going research, four new methods were developed for the TM-catalyzed synthesis of indole and its derivatives. The details are summarized as following:1. A concise Cu-catalyzed method for the preparation of tryptanthrins from indoles was developed. The cascade process is believed to involve copper-catalyzed aerobic oxidation of indole, hydrolysis of amide, the copper-catalyzed decarboxylative coupling, intramolecularly nucleophilic addition, and oxidative aromatization. The reactions could be carried out under mild reaction conditions with varying functional group tolerance. Moreover, the substituent diversity could be quickly expanded by the condensation between the substituted indoles and the substituted isatins via this strategy.2. A new Cu-mediated method for the synthesis of 3-cyanoindoles from 2-alkynylanilides and benzyl cyanide was developed. The cascade reaction proceeded via the cyclization of preformed 2-alkynylanilide can directly generated 3-cyanoindole using benzyl cyanide, which has lower toxicity, higher efficiency, and better solubility, as cyanating agents. The reactions could be carried out under mild reaction conditions with varying functional group tolerance.3. A rhodium-catalyzed synthesis of 9H-pyrido[2,3-b]indoles and tetrahydrofuro-[3’,2’:4,5]pyrolo[2,3-b]indoles by the reactions of 3-diazoindolin-2-imines with furans and dihydrofuran, respectively, has been developed. These transformations proceeded through an indole-embedded a-amidino rhodium carbene intermediate. The cascade mechanism for the formation of 9H-pyrido[2,3-b]indoles includes nucleophilic addition of furan to rhodium carbene, 6π-electronring closure, and elimination-aromatization.4. A facile Rh-catalyzed route toward 3-alkoxyindoles from 3-diazoindolin-2-imine and alcohol has been disclosed. The reaction involved a rhodium-catalyzed decomposition of 3-diazoindolin-2-imines and the formation of a-amidino rhodium carbene intermediate, which inserted into O-H bond of alcohol, subsequently. The reaction is suitable for a variety of secondary and tertiary alcohols.