The C—H bond insertion reactions between benzyl methyl ether and CX 2(X=H, F, Cl) have been studied by using density functional theory at B3LYP/6 31G* level. The potential barriers for the C—H bond insertions in methyl group of benzyl methyl ether are 123.3 kJ/mol(X=Cl) and 240.4 kJ/mol(X=F), and those in benzyl group are 37.5 kJ/mol(X=Cl) and 112.2 kJ/mol(X=F) respectively. No potential barriers are present in both the insertion reactions with methylene group. The C—H bond insertion reactions between benzyl methyl ether and CX 2(X=H,F,Cl) take place primarily at α carbon of the benzyl group and the phenyl group promotes the C—H bond insertion by carbene at its neighboring α carbon more easily. [WT5HZ]
One-carbon unit transfer reaction of imidazolinium with 1,2-diaminobenzene has been studied with semi-empirical molecular orbital calculations, PM3. The result shows that there are two ways to complete this reaction because the imidazolinium ring has two different breaking patterns. These two ways both have seven steps, including two proton-migrating steps that limit the rate of the reaction. The structures and energies of the intermediates and transition states have been calculated.
One-carbon unit transfer reaction of folate cofactor model compound, 1-acetyl-2-methyl-imidazolinium, with 1,2-diaminobenzene has been studied theoretically with ONIOM method. The result shows that there are two pathways to complete this reaction because the imidazolinium ring has two breaking patterns. Both the two pathways have six steps. They are combination of two reactants, proton migration, break of five-membered ring, formation of benzimidazole derivate, another proton migration, and formation of final products. In each of the above pathways, the two proton migration steps have higher energy, which illuminate that the reaction is catalyzed by general acid-base. This fact agrees with the experimental results of enzymatic one-carbon unit transfer at oxidation level of formate.
Density Functional Theory (DFT) method was used in this paper to study one-carbon transfer from 1,10-tetrahydroquinoxaline, an analogue of tetrahydrofolic acid, to methylamine. This reaction can be completed via two paths. From the computation result we can conclude that a general-acid catalysis exists in this reaction. By computation we find DFT has its limitation in describing a newly incorporated structure with a unit charge.
Chuan Song QIDa Cheng FENGHua Yang WANGZheng Ting CAI
