Study On The Mechanism Of The CC Coupling Reaction Catalyzed By The Transition Metal Rh(?)/Ni(?) Complex

Transition metal-catalyzed C-C coupling reaction is a powerful method to construct carbon-carbon(C-C)bonds.It has wide application value in environmental protection,chemical,biological,pharmaceutical synthesis and material research,etc.,and has been one of the hot spots in the field of chemical synthesis.Transition metal-catalyzed C-C couplings have attracted more and more attention because of their advantages of atomic economy,short reaction time and high reaction selectivity.However,due to the limitation of experimental technique,it is still difficult to capture the reaction intermediates and understand the details of the reaction,which need theoretical explorationa.In this paper,we explored the catalytic reaction mechanism of metal Rh/Ni-catalyzed aldehyde-alkyne coupling and amine-ester coupling by using density functional theory(DFT)calculation.The results would provide the detail understanding of the reaction mechanism for future experimental studies and rational design of catalyst.The main research work is as follows:(1)The mechanism of the stereodivergent coupling reactions of aldehydes and alkynes catalyzed by rhodium and amine.We explored the mechanism of coupling reaction between ?-branched aldehydes and alkynes,and how the catalysts acted to produce the stereocentric center.Reaction pathways included Rh catalyzed C-H activation of alkyne and ?-amination of ?-branched aldehydes,the activated intermediates process the coulping reaction to produce ?,?-unsaturated aldehyde with vicinal quaternary and tertiary carbon stereocenters.Through the combination of two catalysts,the origin of stereoselectivity was found from the transition state of C-C bond forming.The C-C bond was formed by controlling the outer-sphere mechanism of the catalyst to generate all possible stereoisomers.The noncovalent interaction analysis of stereocontrolled transition states reveals how to achieve stereoselectivity.This study explored the important role of phosphoric acid additives in multiple steps,such as the formation of active catalysts,promoting the formation of C-N bonds,and affecting C-C bonds through hydrogen bonding.In addition,we have simply proved that Rh and amine synergistic catalyzed alkynes and aldehydes is superior to metal Rh and organic amine catalyzed separately.(2)The mechanistic study on nickel catalyzed cross-coupling of dimethyl aryl amines and arylboronic esters.We study the detail theoretical mechanism of Ni-catalyzed Suzuki-Miyaura coupling of dimethyl aryl amines and arylboronic esters.The reaction pathways include the ligand exchange,oxidation addition,transmetalation and reductive elimination.It was found by calculation that the reaction was carried out through Ni(I)/Ni(III)catalytic cycle instead of the Ni(0)/Ni(II)catalytic cycle.In addition,we also studied the role of the Mg in the reaction:(i)it acted as a sufficient reductant to reduce Ni(II)to Ni(I)species,(ii)played a pivotal role in some elementary of the catalytic cycle.The results on the mechanism of transition metal catalyzed alkyne-aldehyde coupling and amine-ester coupling forming C-C bond has deepened understanding of the coupling reaction mechanism of transition metal catalysis,and has the theoretical guidance for related synthesis methods,design of new reaction mechanism and exploration of new catalytic system.