Theoretical Study On Gold-catalyzed Functionalization Of Alkyne Derivative

Alkenes and alkynes with unsaturated bonds are popular substrates in the field of homogeneous gold catalysis,and alkynes have been studied more frequently because of their high reactivity.At the same time,the excellent properties of gold catalysts,such as high catalytic activity and good functional group tolerance,have attracted much attention.The production of gold carbene by gold catalyzed alkynes is undoubtedly the most important aspect of homogeneous gold catalysis.In an effort to deeply comprehend its nature and the nature of chemical reaction,this dissertation will use density functional theory（DFT）calculations to carry out detailed theoretical calculations for the following two works,aiming to reveal the nature of chemical reaction and provide some theoretical guidance for experimental research.1.The mechanism analyses and origins of chemoselectivity for four gold（III）-catalyzed annulations of sulfilimines with ynamides have been investigated in details using DFT calculations.The calculated results reveal that the reaction of2-acylphenylsulfilimine A1b with ynamides A2b（System a）,the five-membered ring intermediate obtained by nucleophilic attack carries on the subsequent reaction to produce the product.This is quite different from the proposed reaction mechanism involvingα-imide gold carbene compounds.The key five-membered cyclized intermediate is the chemoselectivity-determining intermediate,and the chemoselectivity-determining step is the synergistic H-transfer and C-O bond breaking process.This is the fact that a-system did not produce products byα-imide gold carbene compound as previously reported.But the other four systems have a similar mechanism for the formation ofα-imino gold carbene compounds.The chemical selectivity of the three systems is due to the different structural characteristics of the gold compounds.In this work,experimental observations were made at the molecular level,which provided a basis for exploring the efficient synthesis of aza-heterocycles.2.Through the calculation of density functional theory（DFT）,the mechanism of skeleton rearrangement reactions between N-（o-alkynylphenyl）iminesand vinyldiazoketones by Au（I）-catalyzed was performed to gain an in-depthunderstanding.The calculated results show that the potential barrier of the proposed reaction path is as high as 54.3kcal/mol,which is not consistent with the experimental reaction condition（70℃）.In this process,it is mainly due to the high barrier required to break C¹-N¹bond,which prompted us to find a reasonable reaction path to reduce the barrier required to break C¹-N¹bond.That is,after gold-catalyzed coordination with N-（o-Alkynylphenyl）imines,cyclization to get indole skeleton,nucleophilic attack of vinyldiazone,H migration,dissociation of vinyldiazone and release of N₂,nucleophilic cyclization,OTf^--assisted[1,3]-H migration,1,3 functional group migration,and H₂O-assisted[1,3]-H migration.The final product contains indole-containing skeleton compound（3a）and regeneration catalyst.