Theoretical Studies Of The Mechanisms For Transition Metal And Azacarbene Catalyzed Reactions

Heterocyclic compounds are very important characterized of class compounds in the pharmaceutical, organic and biochemical chemistry. Rencently, with the development of structural analysis and identifiable technology, more and more new heterocyclic compounds were found and investigated. Therefore, the synthesis and theoretical calculation about such compounds was a popular study. In this paper, based on the density functional theory(DFT), conceptual density functional theory, the natural bond orbital(NBO) and integral equation formalism polarizable continuum model(IEFPCM), we attempted to investigate the involving systems. The potential energy surfaces, the information of orbitals and the thermodynamic datum have been obtained, which can be used to analyze the reaction mechanism and supply the theoretical reference for relative experimental research.The whole paper consists of five chapters.Chapter 1 is mainly about the progress of the reaction of gold(I) and platinum(II)-catalyzed intramolecular hydroarylation and N-heterocylic carbene(NHC)-catalyzed annulations.Chapter 2 summarizes the theory of quantum chemistry and calculation methods of this paper.Chapter 3 reported the theoretical analysis of the mechanism and regioselectivity of gold(I)-catalyzed intramolecular hydroarylation to pyrrolopyridinones. Au PH3+ has been considered to account for some experimental observations. Our calculation results indicate that in the case of cationic gold, the nucleophilic attack of the pyrrole on the activated alkyne occurs in an exo-dig fashion generating six-membered intermediate, which upon deprotonation and protodeauration forms pyrrolopyridinone. In the exo-dig cyclization, a [1,2]-migration would not be needed.Chapter 4 reported the theoretical analysis of the mechanism and regioselectivity of platinum(II)-catalyzed catalyzed intramolecular hydroarylation to pyrroloazepinones. Pt Cl2 has been considered to account for some experimental observations. Our calculation results indicate that in the case of cationic platinum, an endo-dig fashion were located to which generate seven-membered intermediate. After deprotonation and protodeplatination pyrroloazepinone is formed. In the endo-dig cyclization, a [1,2]-migration would not be needed.Chapter 5 reported the reaction mechanisms of N-heterocylic carbene(NHC)-catalyzed annulation to 3-pyrancarbaldehydes or cyclopentene. Different from what has been reported for normal aldehydes or enals, our calculation results revealed the intermediate resulting from the conjugate addition to the central carbon atom of the allene moiety, instead of forming the Breslow intermediate. The next step of 1,4-addition with chalcone resulted in the formation of an enolate anion intermediate. Then, cyclic conjugate addition and elimination of the NHC catalyst afforded the final product. In addition, the computed results showed good agreement with the experimental evidence, suggesting that both the existence of an allene structure and charge distribution play a crucial role in the outcome of chemoselectivity and involvement of operative intermediates in the reaction pathway.