Study On The Formation Of Gold-catalyzed Nitrogen-containing Heterocyclic Compounds

In recent years,gold-catalyzed tandem reactions have attracted a lot of attention for chemists to construct natural product and bioactive molecular containing complex skeletons,since these reactions have the unique characteristics such as convenient operation,insensitivity to water and air,and the products formed via multi-step reactions can be obtained without separation of the intermediates,which not only enhance the efficiency of the synthesis,but also friendly to the environment.This thesis mainly studied the formation of nitrogen-containing heterocyclic compounds via tandem cyclization of alkyne-based substrates.The thesis consists of the following two parts:In the first part,we have developed a gold-catalyzed cascade cyclization of alkynones with external nucleophiles,which provided an effective access to highly functionalized pyrroles.The reaction may proceed via a cascade sequence involving nucleophilic addition/double bond isomerization/condensation reactions.We carried out a series of investigations into mechanism:in this process,the unique cis-addition product of indole to alkynones was obtained;in the presence of a stoichiometric of gold catalyst,however,the corresponding alkenyl-gold intermediate was not isolated,but the di-gold complex was obtained,which indicated that the rate of 1,3-carbonyl migration of alkynones was faster than that of nucleophilic addition.We also carried out the derivatization of the obtained pyrrole products,and the polyheterocyclic compounds linked by single bonds was synthetized through the coupling reaction catalyzed by palladium and copper.In the second part,we have developed a gold-catalyzed intramolecular cascade reaction of N-propargylaniline,which provided polysubstituted quinolines.The reaction may proceed via 6-endo-dig-type cyclization via nucleophilic attack of the benzene ring to the tethered alkyne,followed by oxidation.In this reaction,various substituted quinolines,especially quinolines with a substituent at C-8 position,can be easily obtained by this one-pot method by employment of alkynes bearing an ortho-substituted N-aryl ring.