3337-17-5Relevant academic research and scientific papers
Electrochemistry of aqueous pyridinium: Exploration of a key aspect of electrocatalytic reduction of CO2 to methanol
Yan, Yong,Zeitler, Elizabeth L.,Gu, Jing,Hu, Yuan,Bocarsly, Andrew B.
, p. 14020 - 14023 (2013)
The mechanism by which pyridinium (pyrH+) is reduced at a Pt electrode is a matter of recent controversy. The quasireversible cyclic voltammetric wave observed at -0.58 V vs SCE at a Pt electrode was originally proposed to correspond to reduction of pyrH+ to pyridinyl radical (pyrH?). This mechanistic explanation for the observed electrochemistry seems unlikely in light of recent quantum mechanical calculations that predict a very negative reduction potential (-1.37 V vs SCE) for the formation of pyrH?. Several other mechanisms have been proposed to account for the discrepancy in calculated and observed reduction potentials, including surface adsorption of pyrH?, reduction of pyrH+ by two electrons rather than one, and reduction of the pyrH+ proton to a surface hydride rather than a π-based radical product. This final mechanism, which can be described as inner-sphere reduction of pyrH+ to form a surface hydride, is consistent with experimental observations.
Evaluation of Organic Hydride Donors as Reagents for the Reduction of Carbon Dioxide and Metal-Bound Formates
Elton, Timothy E.,Ball, Graham E.,Bhadbhade, Mohan,Field, Leslie D.,Colbran, Stephen B.
supporting information, p. 3972 - 3982 (2018/11/23)
A variety of organic hydride donors (OHDs) have been tested as reagents for the transfer of hydride to iron formato complexes in the activation and reduction of carbon dioxide. Theoretical calculations show that the selection of OHD and solvent is crucial when planning systems involving OHD cooperativity. Strong consideration is given to the likelihood that metal centers may deactivate formate to hydride attack, since, in general, the formate group has more resonance stabilization energy when complexed to a metal center compared to an organoformate or formic acid. It is experimentally demonstrated that 1,2-dihydropyridine is not a competent reducing agent for carbon dioxide.
Chemo- and regioselective catalytic reduction of N-heterocycles by silane
Lee, Sun-Hwa,Gutsulyak, Dmitry V.,Nikonov, Georgii I.
supporting information, p. 4457 - 4464 (2013/09/23)
The ruthenium complex [Cp(iPr3P)Ru(NCCH3) 2]+ (1) catalyzes the regioselective hydrosilylation of pyridines to 1,4-dihydropyridines. Substitution in the 3- and 5-positions is tolerated, whereas pyridines with substituents in the 2-, 4-, and 6-positions are not reduced. Reduction of functionalized pyridines having keto and ester substituents results in a mixture of products. N-Silyl-1,4-dihydropyridine reacts with ketones and aldehydes to give products of N-Si addition across the C=O bond. Hydrosilylation of pyridine in acetone results quantitatively in the addition product PhMe2SiO-CMe2-NC5H 6, which decomposes in hexane to give the parent dihydropyridine HNC5H6. The phenanthroline complex [Cp(phen)Ru(NCCH 3)2]+ (10) catalyzes regioselective 1,4-reduction of phenanthroline by a 3-4-fold excess of silane/water or silane/alcohol mixtures. The Cp* analogue [Cp*(ph n)Ru(NCCH 3)2]+ (9) catalyzes 1,4-regioselective monohydrosilylation of phenanthroline, quinoline, acridine, and 1,3,5-triazine and the 1,2-reduction of isoquinoline. In contrast, 2-substituted phenanthroline, pyrazine, 2-ethylpyridine, 2,6-lutidine, 2,4-lutidine, and pyrimidine are not reduced under these conditions by either of the catalysts studied.
Facile catalytic hydrosilylation of pyridines
Gutsulyak, Dmitry V.,Van Der Est, Art,Nikonov, Georgii I.
supporting information; experimental part, p. 1384 - 1387 (2011/04/21)
Not only surprisingly facile, a hydrosilylation of pyridines under the catalysis of [Cp(iPr3P)Ru(NCCH3)2]+ has the advantages that it is 1,4-regioselective and reversible. The products can be transformed in a variety of ways (see scheme). The related complex [CpRu(NCCH3)3]+ catalyzes the two-hydrogen-atom reduction of phenanthroline by HSiMe2Ph/water.
Trisubstituted heterocyclic compounds and their use as fungicides
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, (2008/06/13)
Compounds of general formula (I): in which:Het represents a five or six membered saturated, partially unsaturated or aromatic ring containing between one and six heteroatoms of the group N, O, S, in which the heterocycle is substituted in an adjacent manner with -P-Q1-T-Q2, -GZ and Y, such that the substituant -GZ is adjacent to both. the other substituants being as defined in the description,process for preparing these compounds,fungicidal compositions comprising these compounds,processes for treating plants by applying these compounds or compositions.
Process for the preparation of optically enriched 4-aryl-3-hydromethyl substituted piperidines to be used as intermediates in the synthesis of paroxetine
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, (2008/06/13)
The subject invention pertains to optically-enriched compounds of formula (1), wherein Ar is a C6-20 aryl group; and R1 and R2 are independently H, alkyl or aryl. The subject invention also pertains to method of preparing these compounds. The subject compounds can be prepared by reduction of the corresponding 1,4-dihydropyridine-3-aldehyde, e.g., using hydrogen an a catalyst. The aldehyde can be prepared by hydrolytic cleavage of an aminal obtainable by the reaction of 3-pyridinecarboxaldehyde and a chiral C-2 symmetric diamine, an then stereoselective introduction of the Ar and COOCHR1 R2 groups. STR1
On the Structure and Mechanism of Formation of the Lansbury Reagent, Lithium Tetrakis(N-dihydropyridyl)aluminate
Tanner, Dennis D.,Yang, Chi-Ming
, p. 1840 - 1846 (2007/10/02)
The reaction of lithium aluminium hydride (LAH) and pyridine yields five lithium tetrakis(N-dihydropyridyl)aluminate (LDPA) isomers.The LDPA isomers are formed reversibly and contain both 1,2- and 1,4-dihydropyridyl ligands.The 1,2-dihydropyridyl ligands are incorporated as the products of kinetic control while the 1,4-dihydropyridyl ligands are formed as the thermodynamic products.When LDPA is synthesized using lithium aluminium deuteride and the deuterated LDPA is placed in pyridine solvent, the ligands exchange with the pyridine in the solvent pool and form pyridine which is deuterated mainly in the 2- and 4-position.A small amount of 3-deuterated pyridine is also detected.The formation of 3-deuteriopyridine suggests that the pyridine radical anion is an intermediate present during the reaction of LAH with pyridine.In support of this suggestion, when LAH and pyridine are mixed, the EPR spectrum of the lithium salt of the pyridyl radical anion is observed.The stepwise addition of ligands to form LDPA is observed (NMR).Five aluminate species are detectable (27Al NMR): LAH , mono-, di-, and -trisubstituted aluminium hydride, and LDPA.The hydrolysis of LDPA in solvent pyridine-d5 yields a mixture of 1,4-, 1,2-, and 2,5-dihydropyridines.The dihydropyridines are stable in the absence of oxygen.
Chiral organoiron complexes and use for assymetric reduction
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, (2008/06/13)
STR1 Compounds having general formula (I) wherein (i) Cp is either a cyclopentadienyl ligand having the formula C5 (R3)5 where the R3 groups are independently hydrogen, methyl or ethyl or an indenyl ligand; (ii) Z is a ligand having the formula X(R4)2 (Y) wherein X is selected from phosphorus, arsenic or antimony; the R4 groups are independently aryl or aroxy and Y is selected from --R5 --NHR5 and --OR5 wherein R5 is a hydrocarbyl group; (iii) the R groups are independently hydrogen, halogen or C1 to C4 alkyl; (iv) R1 is selected from hydrogen, C1 to C6 alkyl, benzyl and --CO2 R6 where R6 is C1 to C6 alkyl; (v) R2 is selected from hydrogen, C1 to C10 alkyl, phenyl and benzyl, and (vi) B is either R or COY wherein Y is selected from --NHR7, --OR7 and --SR7 where R7 is a hydrocarbyl group is provided. The compounds are efficient asymmetric hydrogenating agents for prochiral carbonyl containing compounds when used in single enantiomer form.
1.4-dihydro-4-pyridyl-substituted imidazo (2,1-b) thiazoles and the corresponding thiazines.
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, (2008/06/13)
6-Aryl-2,3-dihydroimidazo[2,1-b]thiazoles and corresponding thiazines act as nucleophiles, either directly or in the form of Grignard reagents, with N-acylpyridinium salts to produce new 6-aryl-5-(N-acyl-1,4-dihydro-4-pyridyl)-2,3-dihydroimidazo-[2,1-b]thiazoles and corresponding thiazines. These are oxidized to give the corresponding pyridyl-substituted imidazo[2,1-b]thiazoles and thiazines, which are active as inhibitors of the 5-lipoxygenase pathway of arachidonic acid metabolism.
RELETIVE REACTIVITIES OF HETEROAROMATIC CATIONS TOWARDS REDUCTION BY 1,4-DIHYDRONICOTINAMIDES
Bunting, John W.,Bolton, Judy L.
, p. 1007 - 1020 (2007/10/02)
Kinetic data are reported for the equilibration of the 1-methyl-3-nitropyridinium cation with its pseudobase (hydroxide adduct) and for the reduction of this cation by 1-benzyl-1,4-dihydronicotinamide.The C-2 hydroxide adduct is kinetically controlled product (pKR+ = 11.6) when this pyridinium cation is mixed with aqueous base, however, this species rearranges to the C-4 adduct as the thermodynamically more stable product (pKR+ = 9.42).The pH-dependence of this equilibration may be analyzed to give kOH = 1600 M-1s-1 for hydroxide ion attack at C-4 of this cation.Reduction of this pyridinium cation by 1-benzyl-1,4-dihydronicotinamide appears to occur exclusively at C-4 with second-order rate constant k2 = 0.72 M-1s-1 and k2H/k2D = 2.0 in 20percent CH3CN - 80percent H2O, ionic strength 1.0, 25 deg C.The reactivities of pyridinium, quinolinium, isoquinolinium, acridinium and phenanthridinium cations of pKR+ = 10.0 towards both hydroxyde ion and 1-benzyl-1,4-dihydronicotinamide are evaluated.Relative reactivities (k2/kOH) for these two processes are shown to be acridinium : quinolinium (C-4) : pyridinium (C-4) : quinolinium (C-2) : isoquinolinium : phenantridinium = 1.6x1E5 : 3400 : 80 4 : 1.0 : O.7 for predominantly aqueous reaction media.These data support the hypothesis that formation of 1,2-dihydropyridine systems upon reduction of heteroaromatic cations by 1,4-dihydronicotinamides occurs via direct one step hydride transfer, while formation of 1,4-dihydropyridines in such processes occurs preferentially by a mechanistically more complex process involving electron transfer.
