The Mechanisms Of Cyclization Reactions Involving Alkyne Catalyzed By Iridium And Nickel Complexes

The cyclic compounds plays an important role in organic chemistry,as well as in medicinal chemistry,pharmaceutical and materials science.Constructing ring systems by organic reactions with transition metal catalysts is one of the most popular strategy in chemistry research.Inaddition,studies on catalytic cyclization by theoretical investigations have far-reaching guiding significance for the development of new catalyst systems.In this thesis,the mechanisms of the two kinds of reactions have been investigated by the density functional theory(DFT).The main contents of this reserch include the following two parts:1.Computational studies have been performed to elucidate the mechanism of iridium-catalyzed intermolecular cyclization of ring-fused benzocyclobutenols with alkynes by the density functional theory(DFT)calculations at the M06L/6?31IG(d,p)//B3LYP-D3/6-3IG(d)level of theory.Possible transition states with relatively low barriers have been achieved in the presence of the[{Ir(OMe)(COD)}2l.Noncovalent interaction(NCI)analyses show a favorable cooperative noncovalent interaction(C-H…? interactions)between cyclohexyl group of substrate and aromatic ring of alkyne.2.The mechanism of Ni-Al bimetallic catalyzed cycloaddition of cyclopropyl carboxamide with alkyne has been presented by the density functional theory(DFT)calculations at the level of B3LYP-D3/6-311G(d,p)//B3LYP/6-31G(d).Results showed that the ligand-metal-binding intermediate had a low Gibbs free energy by ligand dffects.The reactions would occour through oxidation addition,alkyne insertion and reduction elimination with relatively low barriers.Wherein,the reduction elimination step is the rate-determining step.The DFT results of the asymmetric alkyne reaction show that the energy barriers of TS2-a and TS3-a is smaller than TS2-b and TS3-b,and the Gibbs free energy of product a is smaller than that of product b,so the reaction shows a certain regional selectivity.