Studies On Reaction Mechanism Of Coenzyme NADH Models And Application To Organic Synthesis

This Thesis consists of the following five pacts: Following a brief Introduction on the mechanism of reactions of coenzyme NADH models with activated ethylenic compounds is discussed. Pross-Shaik treatment is employed to analyze the results. Catalytic oxidation of primary and secondary benzyl alcohols and reduction ofα,β-epoxy ketones with coenzyme NAD~+/NADH models.In the mechanistic study, oxygen is used as spin trapping agent to study the structure of transition state in the reaction between 1-benzyl-1,4-dihydronicotinamide (BNAH) and 1,1-diaryI-2,2-dinitroethylenes (DArDN), as an extension of the work published previously from this laboratory. The results show that both reduction product and oxidation product of DArDN are obtained. This indicates that a spectrum of intermediate mechanism between electron transfer mechanism and hydride transfer mechanism (polar mechanism) exists in the reaction.It was reported that benzylidenemalononitrile did not react with 1-benzyl-1,4-dihydronicotinamide (BNAH). However, similar reaction easily takes place under the same condition when the phenyl group is replaced by the pyridyl group. It is rationalized by the electron-withdrawing property of the pyridyl group due to the presence of N atom. The results lent support to the concerted electron-hydrogen atom transfer mechanism for the formal hydride transfer in BNAH mediated reductions of activated ethylenic compounds.There are many reports and controversy in the literature on the reaction mechanism of coenzyme NADH model. Most research workers have focused their attention on the distinction between the polar mechanism and electron transfer mechanism and paid less attention to the relationship between them. In this thesis, the relationship between the two mechanisms in the reactions of four coenzyme NADH models with two olefinic substrates is discussed in terms of Pross-Shaik treatment.It is realized that a catalytic amount of NADH/NAD~+ model can bring about the hydrogenation ofα,β-epoxyketones toβ-hydroxyketones. Also, primary or secondary benzyl alcohol can be oxidized with catalytic amount AcrR~+ (R= H or Ph) to the corresponding aldehyde or ketone. The results may have important use in synthetic organic chemisty.