Theoretical Research Based On Au-catalyzed Coupling Reaction Of Diazonium Compounds With Phenyl Unsaturated Fatty Alcohols And Pd-catalyzed (E)-N-methoxycinnamamide Vinyl CH Functionalization Reaction

In this dissertation,the density functional theory?DFT?calculations have been conducted for the Au?I?-catalyzed diazo-based couplings with aryl unsaturated aliphatic alcohols as well as the Pd-catalyzed olefinic C-H functionalization of?E?-N-methoxy cinnamamide.Our aim is to rationalize the experimental phenomena and further reveal the intrinsic properties of these reactions.It is anticipated that the calculated results would provide theoretical guidance for developing new reactions and designing novel transition metal catalysts.?1?Density functional theory?DFT?calculations have been carried out to unravel the mechanisms and chemoselectivities of Au-catalyzed diazo-based couplings with phenyl unsaturated aliphatic alcohols:the propargyl alcohol Ba resulting in the[4+1]-cycloaddition product P_4a and the allyl alcohol Db giving the[2,3]-?rearrangement species P_5b.P_4a formation involves a catalyst interaction with phenyldiazoacetate,N₂ release,a hydroxyl O nucleophilic attack of Ba,a[1,4]-H shift,coordination isomerization,5-endo-dig cyclization,a[4,1]-H shift and a H₂O-assisted[1,3]-H shift.After the[4,1]-H shift,the slightl less favorable five-membered ring-opening possibly follows to afford trace P_5a?[2,3]-?rearrangement product?,which would be kept in solution due to subsequent irreversible evolution.In addition,the Ba-involved chemoselectivity was probed and explained as follows:?i?both large H?hydroxyl?…C?carbene?electrostatic repulsion and strong three-membered ring strain involved in the TS make the formation of the O-H insertion product P_1aa difficult and?ii?the nucleophilic attack from the C² atom of Ba brings about a structural twisting and thus increases the energy penalty forming the cyclopropenation product P_2a.On the other hand,compared with the sp-C² atom of Ba,the sp²-C² atom of Db greatly facilitates the five-membered ring-opening step because of the presence of an extra p?–p?orbital overlap and eventually provides P_5bb exclusively.?2?Density functional theory?DFT?calculations have been performed to study the Pd-catalyzed C-H functionalization of?E?-N-methoxy cinnamamide?^E1?,which selectively provides the?-C-H activation products?^EP as minor product and its C=C rotation isomer ^ZP?as major product?.Three crucial issues are solved:?i?The detailed mechanism leading to ^ZP?is one issue.The computational analyses of the mechanisms proposed in previously experimental and theoretical literature do not seem to be consistent with the experimental findings due to the high barriers involved.Alternatively,we present a novel oxidation/reduction-promoted mechanism featuring the Pd?0??Pd?II??Pd?0?transformation.The newly proposed mechanism involves the initial coordination of the active catalyst PdL₂?L=t-BuCN?with the C=C bond in ^EP,followed by the oxidative cyclization/reductive decyclization-assisted C=C double-bond rotation processes resulting in ^ZP?and regeneration of PdL₂.?ii?The origin of the product E/Z selectivity is the second issue.On the basis of the calculated results,it is found that,at the initial stage of the reaction,^EP is certainly completely generated,while no ^ZP?formation occurred.Once(^E1 is used up,^EP immediately acts as the partner of the new catalytic cycle and sluggishly evolves into ^ZP?.A small amount of generated ^ZP?would reversibly transform to ^EP due to the higher barrier involved.?iii?The intrinsic reasons for the regioselectivity are the third issue.The calculated results indicate that the regioselectivity for?-C-H activation is mainly attributed to the stronger electrostatic attraction between the?-C and the metal center.