- Solvent effects on hydride transfer from Cp?(P-P)FeH to BNA+ cation
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Examining of the hydride transfer reaction between Cp?(Ph2PNtBuPPh2)-FeH (Ph2PNtBuPPh2 = N,N-bis(diphenylphosphanyl)tert-butylamine, 1-H) and 1-benzyl-3-carbamoylpyridinium cation (BNA+) in different solvents, we found that the solvents exert considerable influence on the hydride transfer processes. A coordinating solvent molecule such as MeCN is not only a ligand which stabilizes the organo-iron fragment producing [Cp?(Ph2PNtBuPPh2)Fe(NCMe)]+ ([1(NCMe)]+), but also assists the hydride transfer. In THF, reaction of 1-H with BNA+ under high pressure of nitrogen (60 psi) giving the iron(II)-nitrogen complex [Cp?(Ph2PNtBuPPh2)Fe(N2)]+ ([1-N2]+) and BNAH. In CH2Cl2, [1-N2]+ catalyzes the conversion of 1-H to Cp?(Ph2PNtBuPPh2)- FeCl (1-Cl), which hampers the expected hydride transfer reaction. In the presence of MeCN, the hydride transfer process in THF, CH2Cl2, or benzene was achieved affording the reduced BNAH and [1(NCMe)]+. New iron complexes in the [Cp?(Ph2PNtBuPPh2)-FeX]n+ series (where n = 0, X = H or Cl; n = 1, X = MeCN, N2, or Cl-) were obtained and well characterized.
- Zhang, Fanjun,Xu, Xin,Zhao, Yingjie,Jia, Jiong,Tung, Chen-Ho,Wang, Wenguang
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- A model for catalytically active zinc(II) ion in liver alcohol dehydrogenase: A novel "hydride transfer" reaction catalyzed by zinc(II)-macrocyclic polyamine complexes
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The role of ZnII ion at the active center of liver alcohol dehydrogenase has been well-defined for the first time by the comparative studies of ZnII[12]aneN3, 1 ([12]aneN3 = 1,5,9-triazacyclododecane, L1), ZnII[12]aneN4, 2 ([12]aneN4 = 1,4,7,10-tetraazacyclododecane, L2), ZnII[14]aneN4, 3 ([14]aneN4 = 1,4,8,11-tetraazacyclotetradecane, L3), and free ZnII salts, 4. Variations in ZnII acidity and coordination environment in these complexes result in varying degrees of catalytic activity in the reduction of p-nitrobenzaldehyde (9) and an NAD+ model compound (18) with alcohols as the "hydride" sources (e.g., 2-PrOH) to p-nitrobenzyl alcohol (10) and the corresponding NADH model compounds (19 and 20), respectively. Among ZnII species tested, the ZnII complex of macrocyclic triamine [12]aneN3, 5 (L1ZnII-OH)3·(TfO) 3·TfOH (TfO = CF3SO3-), was by far the most effective catalyst: 10 was obtained from 9 in 7820% yield (based on the concentration of ZnII) in the presence of 5 (0.8 mol %) in refluxing 2-PrOH for 24 h. The ZnII complex 5, also promotes the "hydride transfer" from 2-PrOH to an NAD+ model compound, N-benzylnicotinamide chloride (18), to yield the 1,4-adduct, N-benzyl-1,4-dihydronicotinamide (19), almost exclusively. It is concluded, from the comparison of 5 with other ZnII complexes of [12]aneN4 and [14]aneN4, that the most acidic and coordinatively least saturated ZnII in L1 catalytically generates zinc(II)-alkoxide complex to facilitate the hydride transfer to the hydride acceptor on the ZnII coordination sphere. The present study provides the first chemical model illustrating the significance of the ZnII acidity and the steric requirement around ZnII coordination sphere in the hydride transfer reaction (from alcohol) catalyzed by ZnII-containing alcohol dehydrogenases (ADH).
- Kimura, Eiichi,Shionoya, Mitsuhiko,Hoshino, Ayumi,Ikeda, Takuya,Yamada, Yuko
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- A Novel Type of Hydride-transfer Photocatalysis by RuII-Pyridine Complexes: Regiocontrolled Reduction of an NAD(P) Model Compound by Triethylamine
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2+ (trpy = 2,2':6',2''-terpyridine, bpy = 2,2'-bipyridine, py = pyridine) and 2+ (LL = abidendate ligand) photocatalysed the regiocontrolled reduction of 1-benzyl-4-carbamoyle-pyridinium cation to the
- Ishitani, Osamu,Inoue, Nobuyo,Koike, Kazuhide,Ibusuki, Takashi
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- Dithionite adducts of pyridinium salts: Regioselectivity of formation and mechanisms of decomposition
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1H and 13C NMR spectroscopy has been used to detect and to characterize the adducts formed, in alkaline solutions, by the attack of dithionite anion on 3-carbamoyl or 3-cyano substituted pyridinium salts. In all studied cases, only 1,4-dihydropyridine-4-sulfinates, formed by attack of dithionite oxyanion on the carbon 4 of pyridinium ring, were found. This absolute regioselectivity seems to suggest a very specific interaction between the pyridinium cation and the dithionite through the formation of a rigidly oriented ion pair, determining the position of attack. In weak alkaline solution, the adducts decompose according to two mechanisms SNi and SNi′: the SNi path is operative in all studied cases and preserves the 1,4-dihydro structure yielding the corresponding 1,4-dihydropyridines, whereas the SNi′ path involves the shift of 2,3 or 5,6 double bonds yielding 1,2- or 1,6-dihydropyridines, respectively. The formation of 1,2- or 1,6-dihydropyridines, in addition to 1,4-dihydro isomers, depends on their respective thermodynamic stabilities.
- Carelli, Vincenzo,Liberatore, Felice,Scipione, Luigi,Di Rienzo, Barbara,Tortorella, Silvano
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p. 10331 - 10337
(2007/10/03)
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- NAD(P)+-NAD(P)H Model.47. Mechanism of the Formation of 1,4-Dihydronicotinamide in the Reaction of Pyridinium Salt and Amine
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An amine reduces 1-benzyl-3-carbamoylpyridinium ion (BNA)+ into 1-benzyl-1,4-dihydronicotinamide (BNAH) in aqueous solution.The mechanism of reduction has been elucidated.The covalently bound adduct of the amine and BNA+ at the 6-pos
- Ohno, Atsuyoshi,Ushida, Satoshi,Oka, Shinzaburo
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p. 506 - 509
(2007/10/02)
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- Regioselectivity of Hydride Transfer to and between NAD+ Analogues
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The reaction of 1-methyl- or 1-benzylquinolinium compounds, also bearing an electron-withdrawing substituent in the 3-position, with NaBH4, gives mixtures of the corresponding 1,2-dihydroquinolines and 1,4-dihydroquinolines in which the 1,2-dihydro derivatives usually predominate.The 1,2-derivatives can be isolated.The 1,2-isomers react with the quinolinium salts, giving the 1,4-isomers and regenerating quinolinium salts.This bimolecular isomerization can be used to convert a mixture of isomers to the 1,4-isomer on a preparative scale. 3-Cyano-1,2-dihydro-1-methylquinoline also isomerizes to the 1,2-isomer in the crystalline solid.The major first product of NaBH4 reduction of 3-(aminocarbonyl)-1-benzylpyridinium ion is the 1,6-dihydro derivative.This also isomerizes to the 1,4-dihydro compound in the presence of the pyridinium ion.Reduction of quinolinium derivatives with Na2S2O4 or a dihydropyridine directly produces the 1,4-isomer predominantly.Reduction of 3-(aminocarbonyl)-1-benzylpyridinium ion with Na2S2O4 in D2O gives the 1,4-dihydro derivative, but 8percent of the deuterium is in the 2-position; presumably by reversible isomerization.This deuterium redistribution may have important consequences for the interpretation of isotope effects.
- Roberts, R. M. G.,Ostovic, D.,Kreevoy, M. M.
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p. 2053 - 2056
(2007/10/02)
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