Acid-Catalyzed Addition of Water to 1,4-Dihydronicotinamide Derivatives<sup>*</sup>

Johnston, Clare C.; Gardner, J. L.; Suelter, Clarence H.; Metzler, David E.

doi:10.1021/bi00904a012

Cited by 79 publications

(39 citation statements)

References 12 publications

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“…We also note that acidcatalyzed hydration of both 1,2-dihydropyridine and 1,4-dihydropyridine may generate undesirable side products. 118,119 We have thus far described likely steps that transform Py into PyH2, a species which we now show to be competent in performing catalytic direct HT to carbonyls.…”

Section: Scheme 2 Formation Of Pyridinium Radical (Pyh 0 )mentioning

confidence: 80%

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Lim¹,

Holder²,

et al. 2014

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ABSTRACT:We use quantum chemical calculations to elucidate a viable homogeneous mechanism for pyridine-catalyzed reduction of CO2 to methanol. In the first component of the catalytic cycle, pyridine (Py) undergoes a H + transfer (PT) to form pyridinium (PyH + ) followed by an e -transfer (ET) to produce pyridinium radical (PyH 0 ). Examples of systems to effect this ET to populate PyH + 's LUMO (E 0 calc ~ -1.3V vs. SCE) to form the solution phase PyH 0 via highly reducing electrons include the photo-electrochemical p-GaP system (ECBM ~ -1.5V vs. SCE at pH= 5) and the photochemical [Ru(phen)3] 2+ /ascorbate system. We predict that PyH 0 undergoes further PT-ET steps to form the key closed-shell, dearomatized 1,2-dihydropyridine (PyH2) species. Our proposed sequential PT-ET-PT-ET mechanism transforming Py into PyH2 is consistent with the mechanism described in the formation of related dihydropyridines. Because it is driven by its proclivity to regain aromaticity, PyH2 is a potent recyclable organo-hydride donor that mimics the role of NADPH in the formation of C-H bonds in the photosynthetic CO2 reduction process. In particular, in the second component of the catalytic cycle, we predict that the PyH2/Py redox couple is kinetically and thermodynamically competent in catalytically effecting hydride and proton transfers (the latter often mediated by a proton relay chain) to CO2 and its two succeeding intermediates, namely formic acid and formaldehyde, to ultimately form CH3OH. The hydride and proton transfers for the first reduction step, i.e. reduction of CO2, are sequential in nature; by contrast, they are coupled in each of the two subsequent hydride and proton transfers to reduce formic acid and formaldehyde.

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Section: Scheme 2 Formation Of Pyridinium Radical (Pyh 0 )mentioning

confidence: 80%

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Lim¹,

Holder²,

et al. 2014

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“…of added HCl (to make an acidic environment), a rapid loss of PNAH was observed by monitoring the absorbance at 350 nm. This was clearly tied to the acid catalysed hydration of PNAH (25,28) as was evidenced by a characteristic isosbestic point at 310-315 nm. For 14, PNAH, and ZnC1, in the same solvent system but with 1 equiv.…”

Section: (A) Synthesesmentioning

confidence: 90%

Nitrogen- and sulfur-containing models for metallo-enzymes. Part I. Synthesis and physical studies of 2(2-pyridyl)-1,3-dithioalkyl-2-propanols, 2(2-pyridyl)- and 2(2-imidazolyl)-1,3-dimercapto-2-propanols

Curtis¹,

Brown²

1981

Can. J. Chem.

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N. J. CURTIS and R. S. BROWN. Can. J. Chem. 59,65 (1981). Several compounds of the title class have been synthesized as small-molecule analogues for the metal-binding sites in such biochemical systems as ADH. The ligands containing pyridine and two thioethers do not bind divalent metals (Co2+, Zn2+, Cu2+, Ni2+), strongly suggesting that thioethers are poorly chelated. However, the analogues containing free SH groups bind divalent metals very strongly, producing complexes with limited solubility at pH values in excess of 6. Titration of the latter ligands in the presence of 1 equiv. Zn2+ indicates the consumption of 3 equiv. OH-by pH 6, one for the &-H + N: ionization, and one for each S-H bound to Zn2+. On the basis of these data the resulting complexes are considered to neutral bis-thiolates. The relationship of these data to the state of ionizat~on of the Zn2+-cysteine SH's in ADH is discussed. N. J. CURTIS et R. S. BROWN. Can. J. Chem. 59,65 (1981). On a synthetise plusieurs composes de la classe de ceux mentionnes dans le titre en tant qu'analogue des petites molecules des sites de liaison metallique de certains systkmes tel le ADH. Les ligands contenant la pyridine et deux thioethers ne se lient pas au metaux bivalents (Co2+, Zn2+, Cu2+, Ni2+) suggerant ainsi fortement que les thiokthers sont chelates faiblement. Cependant les analogues contenant des groupes S H libres se lient fortement aux mktaux bivalents, produisant des complexes B solubilit6 limitee a un pH superieur a 6. Le titrage des derniers ligands en presence de 1 Cq. de Zn2+ demontrent qu'i un pH de 6 , trois eq. de OH-sont utilises; un eq. pour I'ionisation de f i -~+~: et un pour chacun des groupes S-H lie au Zn2+. En se basant sur ces donnees, on en a deduit que les complexes resultant sont des bis-thiolates neutres. On discute de la relation entre ces donnees et I'Ctat d'ionisation de la ZnZ+-cysteine S H dans I'ADH.[Traduit par le journal]

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“…The decomposition of 1,4-dihydropyridines in the presence of acids has been studied by several groups in the past (Ib, [21][22][23][24][25][26] and is known to involve several successive reactions (23)(24)(25). The primary acid decomposition reaction is a twostep process resulting in hydration of the 5,6-double bond, [2] (21, 26).…”

Section: Reactions Of the Dihydvopyridine Ringmentioning

confidence: 99%

“…The 1,4-dihydropyridines 2a through 2k can be divided into three groups based 011 (25)), and can even be used in acetate buffers of p H 5.5 for periods of up to 6 h. The remaining dihydropyridines, 2d, 2e, 2f, and 2i are too labile to be used in acetate buffers but meet the criterion of less than 10% decomposition over 24 h in Tris buffers.…”

Section: Reactions Of the Dihydvopyridine Ringmentioning

confidence: 99%

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The pyridinium–dihydropyridine system. I. Synthesis of a series of substituted pyridinium ions and their 1,4-dihydro reduction products and a determination of their stabilities in aqueous buffers

Norris¹,

Stewart²

1977

Can. J. Chem.

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The 1.4-dihydro derivatives of eleven of these have been prepared and characterized and their stabilities likewise determined. The pyridinium ions are stable in acidic solution but undergo either ring attack or amide or ester hydrolysis undei-basic conclition5. whel-eai the dihydropyridines ~indergo covalent hydration in acid solution. For only four pairs of compounds and one buffer system (Tris) are there pH-!ranges in uhich the pyridinium and dihqdl-opqridine forms are simultaneously stable (less than 10r4 decornposition in 24 h). These compounds have a cai-bamoyl or acetyl group at the 3-position and either a methoxvmethyl. acetonql. or carhamoylmethyl group at the 1-position. The acetic acid catalyzed rates of hqdration of the 1-alkql-3-carbarnoql-1,4-dihydropyridines are corl-elated by a" values uith a P" of 2 . 0 0 . consistent with PI-otonation being the rate-controlling step.

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Acid-Catalyzed Addition of Water to 1,4-Dihydronicotinamide Derivatives^*

Cited by 79 publications

References 12 publications

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Nitrogen- and sulfur-containing models for metallo-enzymes. Part I. Synthesis and physical studies of 2(2-pyridyl)-1,3-dithioalkyl-2-propanols, 2(2-pyridyl)- and 2(2-imidazolyl)-1,3-dimercapto-2-propanols

The pyridinium–dihydropyridine system. I. Synthesis of a series of substituted pyridinium ions and their 1,4-dihydro reduction products and a determination of their stabilities in aqueous buffers

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Acid-Catalyzed Addition of Water to 1,4-Dihydronicotinamide Derivatives*

Cited by 79 publications

References 12 publications

Reduction of CO2 to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Reduction of CO2 to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Nitrogen- and sulfur-containing models for metallo-enzymes. Part I. Synthesis and physical studies of 2(2-pyridyl)-1,3-dithioalkyl-2-propanols, 2(2-pyridyl)- and 2(2-imidazolyl)-1,3-dimercapto-2-propanols

The pyridinium–dihydropyridine system. I. Synthesis of a series of substituted pyridinium ions and their 1,4-dihydro reduction products and a determination of their stabilities in aqueous buffers

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Acid-Catalyzed Addition of Water to 1,4-Dihydronicotinamide Derivatives^*

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine

Reduction of CO₂ to Methanol Catalyzed by a Biomimetic Organo-Hydride Produced from Pyridine