Intramolecular hydrogen migration

The theory of stereoselectivity found in intramolecular hydrogen migration in polyenes was disclosed by Woodward and Hoffmann 51>. The HO—LU interaction criterion is very conveniently applied to this problem 64>. The LU of the C—H sigma part participates in interaction with the HO of the polyene n part. The mode of explanation is clear-cut... 

Yates, B.F. Radom, L. Intramolecular Hydrogen Migration in Ionized Amines a Theoretical Study of the Gas-Phase Analogues of the Hofmann-Loffler and Related Rearrangements. J. Am. Chem. Soc. 1987,109,2910-2915. 

An intramolecular hydrogen migration observed in the hydroxylation of aromatic rings in certain enzyme-catalyzed reactions as well as some chemical reactions. The rearrangement was first observed at the National Institutes of Health (hence the name NIH ) in studies of the synthesis of L-tyrosine from L-phenylalanine via phenylalanine hydroxylase. Observation of this shift requires appropriate deuteration of the aromatic reactant. 

Subsequent one-electron transfer and intramolecular hydrogen migration lead to radical 102 followed by reaction with 02 to yield hydroperoxide radical 103. Radical 103 is further oxidized to a dihydroperoxide (104), which decomposes to anthra-quinone. Alternatively, 103 may be transformed to a diradical that eventually gives anthracene as a byproduct. The ratio of the two products strongly depends on the solvent used. The highest yield of anthraquinone (85% at 100% conversion) was achieved in 95% aqueous pyridine. 

Experimental data are also consistent with a dissociative oxygen insertion pathway initiated by the dissociation of the anion PhCOO-, followed by coordination of 02, intramolecular hydrogen migration, and recoordination of PhCOO-. This mechanism has been ruled out on the basis of density functional calculations that placed the free energy of the intermediate for O2 insertion at about 120 kJ/mol above the energy of the corresponding intermediate in the reductive elimination mechanism. 

Bis(phenylethynyl)naphthaIene (356), with parallel triple bonds, undergoes [2-t-2-i-2] cycloaddition with intramolecular hydrogen migration to give 357 , and similar behaviour is found for the analogue with crossed triple bonds (358),... 

The photocatalytic isomerization is explained by intramolecular hydrogen migration. The reactive state is an n-n triplet and the products arise from a common biradical intermediate. The cis isomer does not react. Irradiation of oxiranes not containing the phenyl group gives rise to cyclobutanol epimers (Eq. 350). ... 

Bouchoux, G., Choret, N. Intramolecular hydrogen migrations in ionized aliphatic alcohols. Barton type and related rearrangements. Int. J. Mass Spectrom. 2000, 201, 161-177. 

The relative rates for intramolecular hydrogen migration and competing ethylene elimination allow just one exchange process. The decision whether the exchange processes are concerted reactions (proceeding via bicyclic transition states) or whether reactive intermediates come into existence (multistep reaction) is open to question. 

NIH shift The INTRAMOLECULAR hydrogen MIGRATION that can be observed in enzymatic and chemical hydroxylations of aromatic rings. It is evidenced by appropriate deuterium labeling, for example ... 

Analogous intramolecular hydrogen migration has been reported in methylenetrimethylphosphorane at 100 °C by Schmidbaur and Tronich 127,128,129) using nmr spectroscopy. A similar migration is also reported for trimethylsulfonium methylide. Since the methylenetriphenylphos-... 

The Chalk and Harrod mechanism is consistent with the known stereochemical data and most steps now have known precedents. Cis addition is easily explained, since intramolecular hydrogen migration in complex 129 (eq. [44]) lead to a cis o-vinyl complex 130. Upon reductive elimination the cis addition product 131 is then obtained. 

Zelenko O, Gallagher J, Sigman DS. Scission of DNA with bis(l, 10-phenanthroline) copper without intramolecular hydrogen migration. Angew Chem Int Ed. 1997 36 2776-2778. 

The above researches show that intramolecular hydrogen migration in the decomposition routes of pyridine plays an important role to make the reaction go easily and adjust different distribution of products in pyrolysis reaction. 

The above researches show that the conformational tautomerism of 1-indene imine intermediate plays an important role in the kinetic mechanisms of pyrolysis of quinoUne and isoquionUne. 1-indene imine intermediate determines the composition of the pyrolysis products to be the same, and also determines the total disappearance rates of the reactants to be the same whether the original reactant is quinoline or isoquinoUne. The intramolecular hydrogen migration is an important reaction step, which appears widely in the paths of the pyrolysis mechanism. 

The intramolecular hydrogen migration appears often in the pyrolysis mechanism of oxygen-, nitrogen-, and sulfur-containing model compounds, and plays an important role, which can be summarized as follows (a) it offers more reasonable reaction paths for the formation of products (b) it allows for reasonable interpretation of experimental results (c) it needs less activation energy (d) it explains the distribution of products. 

Intramolecular hydrogen migration between carbon and metal atoms is, of course, important to various catalytic reactions and may be sufficiently fast to give nmr coalescence. Treatment of compound 29 with D2O in CD3NO3 at... 

B.F. Yates and L. Radom, Intramolecular hydrogen migration in ionized amines A theoretical study of the gas-phase analogues of the Hofmann-Loffler and related rearrangements, J. Am. Chem. Soc., 109 (1987) 2910. 

The appearance of the complex (XXXIV) is interesting in that its formation must involve hydrogen transfer from the free diene or its complexed form. Although intramolecular hydrogen migration reactions are frequently encountered, such intermolecular hydrogen transfer reactions are most uncommon. 

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