Theoretical Study On The Mechanisms Of Two Organic Reactions Catalyzed By Lewis Base

Chemical reaction involved catalysts used to be known as catalytic reaction. To achieve the goal of the fracture of the old key, the formation of the new key, active energy is necessary. Organic systhesis always needs heeting, catalyst, light, pressure and other suitable conditions. To devise a new systhetic route, it is important to understand the reaction mechanisms of organic systhetic. These research will be helpful for the design of the more efficient catalysts and the route of systhesis.In this paper, we use the DFT, which is in short of Density Functional Theory to help understand these two organic reaction theories, including “the [4 + 2]cycloaddition of ketenes with 1-azadienes catalyzed by N-heterocyclic carbenes” and“the PPh3-catalyzed isomerization of 5-hydroxyl-2,3-dienoat”. The mechanism we put forward can reasonably explain the experimental phenomena, and will be the important theory basis for other similar research.1. The cycloaddition we used to call refers to two or more unsaturated compounds to form the cyclic adducts. Generally speaking this kind of reaction will have the characteristics of the system total key series reduce. Among them, the [4 + 2]cycloaddition reactions require very little energy. We study “the [4 + 2] cycloaddition of ketenes with 1-azadienes catalyzed by N-heterocyclic carbenes” at the M06-2X/6-31G(d) and M06-2X/6-311+G(d,p) level. We project two possible reaction routes according to the order of reactants combined with nitrogen heterocyclic. Our response to the two ways of energy calculation and comparison analysis, discovery channel B is the reaction path can reasonably explain the experimental phenomena, which including three elementary reaction: the adsorption of catalyst and reactant2, the cycloaddition of reaction intermediate and reactant1,the desorption of catalyst. Furthmore, the step of [4 + 2] cycloaddition is the rate and stereoselectivity-determining steps. In this step we get four configurations(SS/RR/SR/RS) of the two chiral centers. The product of our calculation results show that SS configuration as the main product, and the SS configuration can run only 6.5kcal/mol, which shows that the product at room temperature can be generated. This exploration can not only help us better understand ketene [4 + 2] cycloaddition reaction mechanism, but also provide important theoretical reference for latter design of this kind of reaction.2. Proton transfer reaction is a kind of fabulous reaction in organic reactions,which is in use of hydrogen donor for getting isomerization of the other one. We study “the PPh3-catalyzed isomerization of 5-hydroxyl-2,3-dienoat” at the M06-2X/6-31G(d,p) level. The differences between the two projects are the order of transfer hydrogen and geometric structure that hydrogen transfer via. We obtained the theory basis through to the reaction activation energy calculation, the global reaction index analysis.