Study On The Reaction Mechanism Of Platinum And Rhodium Catalyzed Synthesis Of Indole Compounds

In this dissertation,we used the methods of computational chemistry to study the synthesis of two types of indole derivatives catalyzed by the transition metals platinum and rhodium with the M06 and B3LYP level of density functional theory?DFT?.Our theoretical and computational studies aim to provide a reasonable reaction mechanism,to reasonably explain the experimental phenomena,and to provide theoretical guidance for the experimental study of transition-metal-catalyzed indole synthesis.Serving as the important component of nitrogen-containing aromatic heterocyclic compounds,indole derivatives are not only one of the most widely distributed heterocyclic compounds in nature,but also important organic materials and fine chemical products.They have important value in chemical engineering and agriculture.Indole derivatives are synthesized by the following two paths in the present:One is related to the introduction of a functional group on the phenyl ring of the indole ring,and the other involves the introduction of a functional group on the pyrrole ring of the indole.In the previous theoretical studies,the most studied types are functionalization of the pyrrole ring of indole.However,few theoretical studies focus on the on the benzene ring of indole skeletons.The first part of this dissertation describes the mechanistic study of the first type functionalization of indole with Pt?II?as the catalyst.The second part of this dissertation investigates the mechanistic study of the second type functionalization of indole with Rh?III?as the catalyst.In the first part of the dissertation,the mechanism of Pt?II?-catalyzed cyclization/alkynylation of benziodoxole with pyrrole homopropargylic ethers to generate C5-alkenylated indole derivatives has been studied with the aid of density functional theory?DFT?calculations.We found that five-membered ring cyclization/six-membered ring cyclization was competitive in the formation of indole skeleton.The following aromatization stage prefers the reaction sequence:bicarbonate-assisted deprotonation at C3a position,H₂CO₃-promoted methoxy elimination at C7 position and bicarbonate-assisted deprotonation at C6 position.In the last alkynylation stage,the oxidative substitution mechanism assisted by H₂CO₃,was found to be favored over the previously proposed 1,2-iodo shift and oxidative addition.The overall rate-determining step was oxidative substitution.Additionally,an interesting substituent effect on chemoselectivity was investigated.The electronic and steric effects caused by methyl result in reverse chemoselectivity.In the second part of the dissertation,we studied the reaction mechanism of Rh-catalyzed reaction of tertiary amines with alkynes through the oxidation coupling reaction to produce alkyl indole.This reaction proceeds with the following sequence:C-H activation,oxygen atom transfer,and C-N cleavage.We found that the insertion of the alkyne into the Rh-C bond was more favorable than into the Rh-O bond.We found that in the protonation stage,the additive MesCO₂H played an important role as proton source.As for the role of silver salt played in the reaction process,we will carry out further study in the later work.