5096-13-9Relevant academic research and scientific papers
Macrocyclic Enzyme Model System. Kinetic Activity of Paracyclophane Bearing 1,4-Dihydronicotinamide and 2-Pyridinecarboxylic Acid Moieties as Effected by Zinc Ion
Murakami, Yukito,Aoyama, Yasuhiro,Kikuchi, Jun-ichi
, p. 2898 - 2901 (1982)
As regards the effect of zinc(II) ion on the reduction of hexachloroacetone, the kinetic activity of a paracyclophane (PCP) bearing 1,4-dihydronicotinamide (HNA) and 2-pyridinecarboxylic acid (Py) moieties, HNA-PCP-Py, has been investigated as an alcohol dehydrogenase model in reference to that of PCP-HNA in the light of their metal-coordination behavior.The reduction ability of PCP-HNA was significantly lowered as it underwent complex formation with zinc.On the other hand, HNA-PCP-Py showed an apparent rate maximum in a relatively lower concentration range of ZnCl2.The kinetic behavior was analyzed on the basis of the formation of two kinds of zinc complexes of HNA-PCP-Py: the 1:1 complex , in which both Py and HNA moieties are simultaneously coordinated to the same zinc ion, showed a decreased reactivity relative to metal-free HNA-PCP-Py; while the 2:1 complex (HNA-PCP-Py-ZnII-Py-PCP-HNA), in which HNA is free from metal-coordination, exercised a much enhanced activity, 7 times as reactive as metal-free HNA-PCP-Py.A plausible reaction mechanism for the enhanced reactivity has been discussed.
MECHANISM AND TRANSITION-STATE STRUCTURE OF HYDRIDE-TRANSFER REACTIONS MEDIATED BY NAD(P)H - MODELS
Verhoeven, J. W.,Gerresheim, W. van,Martens, F. M.,Kerk, S. M. van der
, p. 975 - 992 (1986)
The energy to transfer one electron from NAD(P)H and related 1,4-dihydropyridines to a series of substrates is calculated and compared with the experimental activation energy for transfer of a hydride equivalent between these species.It is concluded that single electron-transfer (SET) cannot occur as a primary step in the overall hydride-transfer process except for substrates with very strong one-electron oxidizing properties.A simple valence-bond configuration mixing (VBCM) model is presented, that rationalizes the general occurrence of concerted hydride transfer as the lowest energy reaction-pathway and furthermore explains why the activtion energy of such a concerted pathway is often linearly related to that of a -hypothetical- SET process.For one intramolecular and two related, intermolecular hydride-transfer reactions the temperature dependence of the primary kinetic isotope effect (TDKIE) was studied.For the intramolecular reaction, where a face to face orientation of the reactants is enforced, the TDKIE parameters suggest the occurence of a bent hydride-transfer pathway.For both intermolecular reactions, however, a linear transition-state geometry is indicated.MNDO calculations of the reaction profile for hydride transfer from a 1,4-dihydropyridine to either a positively charged substrate (i.e. the pyridinium-ion) or to a neutral substrate (i.e. 1,1-dicyanoethylene) confirm, that a linear transition-state geometry is favoured, unless the system is geometrically restrained to prevent such a geometry.The MNDO calculations furthermore indicate that in a linear transition-state almost unimpeded rotation can occur about the C...H...C axis.This rotation interconverts the relative orientation of the reactants between parallel-exo and tilted-endo, which may have important consequences for the interpretation of the stereochemical outcome of reactions involving (pro)chiral reactants.
Sterically Stabilized End-On Superoxocopper(II) Complexes and Mechanistic Insights into Their Reactivity with O-H, N-H, and C-H Substrates
Debnath, Suman,England, Jason,Kr?mer, Tobias,Laxmi, Shoba,Quek, Sebastian Y.,Van Gastel, Maurice
supporting information, p. 19731 - 19747 (2021/11/30)
Instability of end-on superoxocopper(II) complexes, with respect to conversion to peroxo-bridged dicopper(II) complexes, has largely constrained their study to very low temperatures. This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of bulky ligands, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support copper(I) complexes that react with O2 to yield [CuII(?1-O2?-)(Ar3-TMPA)]+ species, which are stable against dimerization at all temperatures. Binding of O2 saturates at subambient temperatures and can be reversed by warming. The onset of oxygenation for the Ar = tpb and dpb systems is observed at 25 °C, and all three [CuII(?1-O2?-)(Ar3-TMPA)]+ complexes are stable against self-decay at temperatures of ≤-20 °C. This provides a wide temperature window for study of these complexes, which was exploited by performing extensive reaction kinetics measurements for [CuII(?1-O2?-)(tpb3-TMPA)]+ using a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2) versus oxidation potentials (Eox) for a range of phenols, construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicate that reaction with all substrates proceeds via H atom transfer (HAT), reaction with the phenols proceeds with significant charge transfer, and full tunneling of both H and D atoms occurs in the case of 1,2-diphenylhydrazine and 4-methoxy-2,6-di-tert-butylphenol. Oxidation of C-H bonds proved to be kinetically challenging, and whereas [CuII(?1-O2?-)(tpb3-TMPA)]+ can oxidize moderately strong O-H and N-H bonds, it is only able to oxidize very weak C-H bonds.
Photocatalytic reduction of artificial and natural nucleotide co-factors with a chlorophyll-like tin-dihydroporphyrin sensitizer
Oppelt, Kerstin T.,W??, Eva,Stiftinger, Martin,Sch?fberger, Wolfgang,Buchberger, Wolfgang,Kn?r, Günther
supporting information, p. 11910 - 11922 (2013/11/19)
An efficient photocatalytic two-electron reduction and protonation of nicotine amide adenine dinucleotide (NAD+), as well as the synthetic nucleotide co-factor analogue N-benzyl-3-carbamoyl-pyridinium (BNAD +), powered by photons in the long-wavelength region of visible light (λirr > 610 nm), is demonstrated for the first time. This functional artificial photosynthetic counterpart of the complete energy-trapping and solar-to-fuel conversion primary processes occurring in natural photosystem I (PS I) is achieved with a robust water-soluble tin(IV) complex of meso-tetrakis(N-methylpyridinium)-chlorin acting as the light-harvesting sensitizer (threshold wavelength of λthr = 660 nm). In buffered aqueous solution, this chlorophyll-like compound photocatalytically recycles a rhodium hydride complex of the type [Cp*Rh(bpy)H]+, which is able to mediate regioselective hydride transfer processes. Different one- and two-electron donors are tested for the reductive quenching of the irradiated tin complex to initiate the secondary dark reactions leading to nucleotide co-factor reduction. Very promising conversion efficiencies, quantum yields, and excellent photosensitizer stabilities are observed. As an example of a catalytic dark reaction utilizing the reduction equivalents of accumulated NADH, an enzymatic process for the selective transformation of aldehydes with alcohol dehydrogenase (ADH) coupled to the primary photoreactions of the system is also demonstrated. A tentative reaction mechanism for the transfer of two electrons and one proton from the reductively quenched tin chlorin sensitizer to the rhodium co-catalyst, acting as a reversible hydride carrier, is proposed.
Tandem synthesis of substituted 2,7-naphthyridin-1(7H)-ones via Reissert reaction/intramolecular nucleophilic addition/oxidation dehydrogenation
Tan, Hailiang,Wang, Jie,Zhang,Xing, Yongning,Sun, Qi,Li, Runtao
, p. 8299 - 8304 (2013/09/02)
A convenient method for the synthesis of substituted 2,7-naphthyridin-1(7H) -ones has been developed. This method was carried out starting from a simple nicotinamide salts via a tandem process including Reissert reaction, intramolecular nucleophilic addition and oxidation dehydrogenation. Using this method, a variety of substituted 2,7-naphthyridin-1(7H)-ones were obtained in good yields.
Conformations and Rotational Barriers in NADH and NAD+ Analogues. A Dynamic NMR and Molecular Mechanics Investigation
Berg, Ulf,Astroem, Nina
, p. 599 - 608 (2007/10/02)
The conformational preferences and rotational barriers about both the ring-amide bond and the C-N bond in NADH and NAD+ analogues have been investigated by dynamic NMR spectroscopy and molecular mechanics calculations with the intention to clarify the stereodynamic situation in these types of cross-conjugated amide.The results can be summarized as follows. (i) The primary amides an thioamides are planar or nearly planar and possess ring-amide barriers (ΔG ca. 4-7 kcal mol-1) over the 90 deg twisted state. (ii) The cis conformation is strongly preferred for NADH analogues, but in the indole analogue 6b the two conformations differ by only ca. 0.3 kcal mol-1. (iii) The tertiary amides are twisted in the ground state and have steric barriers (ΔG=6-10 kcal mol-1) over the planar state. (iv) The C-N barriers are considerably larger, (ΔG=11-17 kcal mol-1 for amides, and 12-21 kcal mol-1 for thioamides). (v) The barrier heights are governed by the efficiency of the cross-conjugation in the ground and transition states, and by the steric interactions in the planar conformations.The exchange process observed in NMR for NADH by Redfield et al. is due to C-N rotation and not to amide group rotation.
On the Electron-Proton-Electron Mechanism for 1-Benzyl-1,4-dihydronicotinamide Oxidations
Miller, Larry L.,Valentine, James R.
, p. 3982 - 3989 (2007/10/02)
The reaction of 1-benzyl-1,4-dihydronicotinamide (BNAH) with serveral ferrocenium (Fc+) salts in aqueous propanol was studied.The mechanism was shown to involve electron-proton-electron transfer with rate-limiting electron transfer from BNAH to Fc+.From the rate constants and E0(BNAH/BNAH.+) was estimated to be 0.89 V (SCE).The electrochemistry of BNAH was investigated in order to evaluate a previously determined E0(BNAH/BNAH.+).A reconsideration of the literature data for (non-DDQ) quinone oxidations of reduced nicotinamide adenine dinucleotide (NADH) in water and BNAH in CH3CN shows that the data are consistent with a hydride-transfer mechanism and inconsistent with an electron-proton-electron mechanism involving free NADH.+.A mechanismin which the hydride is transferred by electron-proton-electron transfer within one complex cannot be excluded.
NMR Properties and Synthesis of Ring-methylated 1,4-Dihydronicotinamides and the Corresponding Pyridinium Salts. Correlation of NMR with Ab Initio STO-3G Results
Bossaerts, Jan D.,Dommisse, Roger A.,Alderweireldt, Frank C.,Geerlings, Paul
, p. 2360 - 2384 (2007/10/02)
The synthesis of a series of ring-methylated 1-alkyl-1,4-dihydronicotinamides and the corresponding pyridinium salts is described.Their NMR properties involving aromatic-ring-shielding anisotropy, due to ring current effects, are discussed and compared with electron populations calculated from STO-3G results.
REDUCTION OF METHYL BENZOYLFORMATE BY REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE MODEL IN THE PRESENCE OF RHODIZONIC ACID
Endo, Takeshi,Takada, Tadayoshi,Okawara, Makoto
, p. 615 - 618 (2007/10/02)
The reduction of rhodizonic acid (RA) with 1-benzyl-1,4-dihydronicotinamide (BNAH; NADH model) was carried out at room temperature to obtain tetrahydroxy-p-quinone (THQ) and hexahydroxybenzene (HHB) by two-electron and four-electron reductions, respectively.The reduction of methyl benzoylformate with BNAH proceded smoothly in the presence of RA, although it could not be reduced at all without RA.
TEMPERATURE DEPENDENCE OF THE PRIMARY KINETIC ISOTOPE EFFECT FOR HYDRIDE TRANSFER MEDIATED BY A NAD(P)H-MODEL; DISCRIMINATION BETWEEN BENT AND LINEAR TRANSITION STATES
Gerresheim, W. van,Verhoeven, J. W.
, p. 339 - 340 (2007/10/02)
Temperature dependence of the primary kinetic isotope effect for hydride transfer from 1-benzyl-1,4-dihydronicotinamide (a NAD(P)H-model) to the 10-methyl-9-phenylacridinium ion conclusively shows the reaction to proceed through a linear transition state.
