DFT Investigations Of Mechanisms Of Two Addition Reactions: [Base-Pair + OH·] And Three-components Reaction Of [Aldehyde + Ketone + Indazole]

Addition reaction is one important organic chemical reaction that occurs in unsaturated compounds with double bonds or triple bonds. When the addition reaction happened, the unsaturated bonds containing double bonds or triple bonds were opened, two new groups or one new group would connect to the two ends or one end of the atom of the original unsaturated bonds to obtain a saturated or relative saturated addition products. The addition product can be the stable product or the unstable intermediate, which can further react to form a more stable product. According to the specific reaction mechanism, the addition reactions can be divided into the nucleophilic addition reaction, the electrophilic addition reaction, the free radical addition reaction and cycloaddition reaction. As a very hot topic of organic chemical reactions, this thesis focuses on two important addition reactions(i.e., [base-pair +OH?] reaction and the three-components reaction of [aldehyde + ketone + indazole]), and their reaction mechanisms were studied in detail. This thesis mainly includes the following parts:1. The addition reaction between the hydroxyl radical and base pair. To investigate the addition reactions of [A-T+OH?] and [G-C+OH?] at the M06-2X/6-311++G(2d,2p) level of DFT. Calculation result shows that in A-T base pair, the relative energy order of addition products is AC8-T>A-TC6>AC2-T>A-TC5>AC4-T>AC5-T; and the energy barrier order of hydroxyl addition reaction is A-TC6(1.71kcal/mol)<AC8-T(2.04kcal/mol)<A-TC5(2.47kcal/mol)<AC5-T(5.75kcal/mol) <AC4-T(9.32kcal/mol)<AC2-T(9.37kcal/mol). And about G-C base pair, the relative energy order of addition products is GC8-C>G-CC6>G-CC5>GC4-C>GC5-C; and the energy barrier order of hydroxyl addition reaction is G-CC5(2.30kcal/mol)<G-CC6(3.47kcal/mol)<GC8-C(3.86kcal/mol) <GC5-C(5.88kcal/mol)<GC4-C(7.71kcal/mol).2. The theoretical research of three-component addition reaction [aldehyde + ketone + indazole]. All the calculations in this work were performed at the M06-2X/6-31+G(d, p) level of DFT. In the first step, the reactants 5,5-dimethylcyclohexane 1,3-dione and benzaldehyde go through Knoevenagel condensation reaction to obtain the intermediate IM5 and product P1 via three possible pathways under the catalyst of piperidine in the alcohol solvent; when the solvent is isopropanol, the intermediate IM5 occurs a Michael addition reaction to get the final product P2, along with the addition of 5-aminoindazole. The calculation not only can reveal the reaction mechanism to produce P1 and P2, but also can provide theoretical insights into the design of new reactions.