Computational Study Of Mechanisms Of Transition Metal-Mediated Key Bond-Formation/Cleavage Reactions

Due to the superiority of transition metals in catalyzing organic chemical reactions,this has been a hot trend in recent years.Numerous researchers are committed to developing novel organic reactions and exploring the mechanisms behind the reaction phenomena.But there are still many important chemical reactions,and even the mechanisms of the primitive process have only limited researchs.Therefore,the first part of this paper selected a transition metal catalyzed organic reaction system,and the second part focused on the elementary reaction:reductive elimination.Respectively,we have detailed discussed.The conclusion is divided into the following two parts:1.Mechanisms of Pd(?)Catalyzed Sselective Five-fold Cascade ArylationThe mechanisms and regioselectivities of Pd(?)catalyzed selective five-fold cascade arylation were detailed investigated with density functional theory(DFT)calculations.We found that the catalystic mechanism involves two parts:arylation and decarboxylation.Arylation process includes sequential carboxylate-directed C-H activation,oxidative addition and reductive elimination,and penta-arylation proceeds through a very specific manner,either clockwise or anticlockwise in a merry-go-round fashion.Decarboxylation peocess goes through by five-arylated carborane dianion without the help of other transition metals.2.Stepwise versus Concerted Reductive Elimination MechanismsThe mechanisms of reductive elimination in reaction of generating MeI by(DPEphos)RhMeI2 were comprehensive investigated with density functional theory(DFT)calculations.The C-I bond formation proceeds via two competing pathways,the anionic and zwitterionic stepwise pathways.The strong directionality of the methyl group in the reductive formation step controls the preference for the stepwise pathway.We also analyzed and compared stepwise pathway and classic concerted pathway.