Mechanistic Study Of Catalyzed Saturated C-C Bond Formation Reactions

The formation of carbon-carbon bonds is one of the most fundamental way to produce molecular complexity in organic synthesis.This field has attracted the attention of chemists from the outset,thus a variety of transformation methods have been developed to build carbon-carbon bonds.The saturated C-C bonds are widely found in industrial raw materials,pharmaceuticals and natural products.Therefore,the development of saturated C-C bond construction method is particularly important.The in-depth understanding of reaction mechanism is the important prerequisite for the reaction development.It is an important basis for continuously improving the efficiency of existing catalytic reactions,and designing new reactions and catalytic systems.With the continuous development of computer technology and quantum theory chemistry,the theoretical calculation method based on quantum chemical platform has become an important way to obtain mechanism information.Based on the theoretical calculation method,this paper systematically studies the mechanism of several saturated C-C bonds formation reactions.The first part of the paper summarizes the main methods of constructing saturated C-C bonds in the field of organic synthesis.The first category is the transition metal catalyzed coupling reaction,including cross coupling,oxidative coupling and reductive coupling.The second category is transition metal catalyzed C(sp3)-H bond activation/C(sp3)-C bond formation.The method of the C(sp3)-C(sp2),C(sp3)-C(sp3)and C(sp3)-C(sp)bond formation were introduced in detail.The third category is the transition metal catalyzed olefin difunctionalization,in which the Au catalyzed intramolecular and intermolecular difunctionalization were mainly described.The fourth category belongs to the field of nonmetallic catalysis,in which the NHC catalyzed homoenolation reaction was mainly described.Finally,the DFT method,basis set and solvation model were introduced.The second part of the paper introduces the mechanistic study of Palladium-catalyzed chemoselective C(sp3)-H activation of carbamoyl chloride.The results shows that the reaction undergoes oxidation addition/C-H activation/reductive elimination mechanism.It was found that the additive could increase the reaction rate,but could not determine the chemo-selectivity.The higher acidity of the benzylic C(sp3)-H than the C(sp2)-H is the main reason for the chemoselectivity.The third part of the paper introduces the mechanism of the visible light-mediated gold-catalyzed oxyarylation reaction of alkenes.The results show that the oxidative quenching of the photoredox catalyst is favorable.The favorable gold catalytic cycle is the radical addition/single electron transfer/coordination/cyclization/reductive elimination.The facility of the favorable mechanism is determined by two factors:First,both oxidation steps occur prior to the cyclization step to generate the feasible cyclization precursor of the Au(?)complex.Second,the radical addition formally increases the electron density on the gold center and thus favors the radical addition followed by SET sequence.The fourth part of the paper introduces the computational study of mechanism,chemoselectivity and stereoselectivity in the NHC-catalyzed homoenolate reaction of enals and nitroalkenes.Calculations show that the reaction undergoes the process of Breslow intermediate formation/nucleophilic attack of the Breslow intermediate on the nitroalkene/intramolecular proton transfer/HOAc involved protonation/concerted nucleophilic attack of OEt on the carbonyl/carbene dissociation.The highly exoergonic nucleophilic attack,the facile intramolecular proton transfer and attack of OEt on the carbonyl in the process result in its feasibility.The stereoselectivity determining step is the attack of the Breslow intermediate on the nitroalkene,in which the steric hindrance and hydrogen bonding determine the syn stereoselectivity.