116241-61-3Relevant articles and documents
Ruthenium (II) and iridium (III) complexes of N-heterocyclic carbene and pyridinol derived bidentate chelates: Synthesis, characterization, and reactivity
Gerlach, Deidra L.,Siek, Sopheavy,Burks, Dalton B.,Tesh, Jamie M.,Thompson, Courtney R.,Vasquez, Robert M.,White, Nicholas J.,Zeller, Matthias,Grotjahn, Douglas B.,Papish, Elizabeth T.
, p. 442 - 450 (2017)
We report the synthesis and characterization of new ruthenium(II) and iridium(III) complexes of a new bidentate chelate, NHCR′-pyOR (OR?=?OMe, OtBu, OH and R′?=?Me, Et). Synthesis and characterization studies were done on the following compounds: four ligand precursors (1–4); two silver complexes of these NHCR′-pyOR ligands (5–7); six ruthenium complexes of the type [η6-(p-cymene)Ru(NHCR′-pyOR)Cl]X with R′?=?Me, Et and R?=?Me, tBu, H and X?=?OTf?, PF6? and PO2F2? (8–13); and two iridium complexes, [Cp?Ir(NHCMe-pyOtBu)Cl]PF6 (14) and [Cp?Ir(NHCMe-pyOH)Cl]PO2F2 (15). The complexes are air stable and were isolated in moderate yield. However, for the PF6? salts, hydrolysis of the PF6? counter anion to PO2F2? during t-butyl ether deprotection was observed. Most of the complexes were characterized by 1H and 13C NMR, MS, IR, and X-ray diffraction. The ruthenium complexes [η6-(p-cymene)Ru(NHCMe-pyOR)Cl]OTf (R?=?Me (8) and tBu (9)) were tested for their ability to accelerate CO2 hydrogenation and formic acid dehydrogenation. However, our studies show that the complexes transform during the reaction and these complexes are best thought of as pre-catalysts.
Iridium and ruthenium complexes of N-heterocyclic carbene- and pyridinol-derived chelates as catalysts for aqueous carbon dioxide hydrogenation and formic acid dehydrogenation: The role of the alkali metal
Siek, Sopheavy,Burks, Dalton B.,Gerlach, Deidra L.,Liang, Guangchao,Tesh, Jamie M.,Thompson, Courtney R.,Qu, Fengrui,Shankwitz, Jennifer E.,Vasquez, Robert M.,Chambers, Nicole,Szulczewski, Gregory J.,Grotjahn, Douglas B.,Webster, Charles Edwin,Papish, Elizabeth T.
, p. 1091 - 1106 (2017)
Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible, that energy can be released on demand. Some of the most effective transition metal catalysts for CO2 hydrogenation have featured pyridin-2-ol-based ligands (e.g., 6,6'-dihydroxybipyridine (6,6'-dhbp)) for both their proton-responsive features and for metal-ligand bifunctional catalysis. We aimed to compare bidentate pyridin-2-ol based ligands with a new scaffold featuring an N-heterocyclic carbene (NHC) bound to pyridin-2-ol. Toward this aim, we have synthesized a series of [CpIr(NHC-pyOR)Cl]OTf complexes where R = tBu (1), H (2), or Me (3). For comparison, we tested analogous bipyderived iridium complexes as catalysts, specifically [CpIr(6,6'-dxbp)Cl]OTf, where x = hydroxy (4Ir) or methoxy (5Ir); 4Ir was reported previously, but 5Ir is new. The analogous ruthenium complexes were also tested using [(η6-cymene)Ru(6,6'-dxbp)Cl]OTf, where x = hydroxy (4Ru) or methoxy (5Ru); 4Ru and 5Ru were both reported previously. All new complexes were fully characterized by spectroscopic and analytical methods and by single-crystal X-ray diffraction for 1, 2, 3, 5Ir, and for two [Ag(NHC-pyOR)2]OTf complexes 6 (R = tBu) and 7 (R = Me). The aqueous catalytic studies of both CO2 hydrogenation and formic acid dehydrogenation were performed with catalysts 1-5. In general, NHC-pyOR complexes 1-3 were modest precatalysts for both reactions. NHC complexes 1-3 all underwent transformations under basic CO2 hydrogenation conditions, and for 3, we trapped a product of its transformation, 3SP, which we characterized crystallographically., we trapped a product of its transformation, 3SP, which we characterized crystallographically.. For CO2 hydrogenation with base and dxbp-based catalysts, we observed that x = hydroxy (4Ir) is 5-8 times more active than x = methoxy (5Ir). Notably, ruthenium complex 4Ru showed 95% of the activity of 4Ir. For formic acid dehydrogenation, the trends were quite different with catalytic activity showing 4Ir Z> 4Ru and 4Ir ≈ 5Ir Secondary coordination sphere effects are important under basic hydrogenation conditions where the OH groups of 6,6'-dhbp are deprotonated and alkali metals can bind and help to activate CO2. Computational DFT studies have confirmed these trends and have been used to study the mechanisms of both CO2 hydrogenation and formic acid dehydrogenation.
Novel synthesis method for ortho-alkane superseded pyridine
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Paragraph 0018; 0019; 0020; 0021, (2017/07/19)
The invention relates to a novel synthesis method for ortho-alkane superseded pyridine. According to the method, ortho halogenated pyridine serves as raw materials, the ortho halogenated pyridine and corresponding alcohol react to obtain the ortho-alkane superseded pyridine under the action of sodium hydroxide. The reaction has universality for the ortho halogenated pyridine, and the method is simple and practical. Influence of consumption of the sodium hydroxide on mono-substitution and di-substitution in the reaction is inspected, alkoxy mono-substitution products and alkoxy di-substitution production are acquired, and a novel simply-operated, economical and favorable process for synthesis ortho-alkane superseded pyridine is provided.
C-H FLUORINATION OF HETEROCYCLES WITH SILVER (II) FLUORIDE
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Paragraph 00153, (2015/02/19)
The present invention provides compositions and methods for the selective C-H fluorination of nitrogen-containing heteroarenes with AgF2, which has previously been considered too reactive for practical, selective C-H fluorination. Fluorinated heteroarenes are prevalent in numerous pharmaceuticals, agrochemicals and materials. However, the reactions used to introduce fluorine into these molecules require pre-functionalized substrates or the use of F2 gas. The present invention provides a mild and general method for the C-H fluorination of nitrogen-containing heteroarene compounds to 2-fluoro-heteroarenes with commercially available AgF2. In various embodiments, these reactions occur at ambient temperature within one hour and occur with exclusive selectivity for fluorination at the 2-position. Exemplary reaction conditions are effective for fluorinating diazine heteroarenes to form a single fluorinated isomer.
Selective C-H fluorination of pyridines and diazines inspired by a classic amination reaction
Fier, Patrick S.,Hartwig, John F.
, p. 956 - 960 (2013/12/04)
Fluorinated heterocycles are prevalent in pharmaceuticals, agrochemicals, and materials. However, reactions that incorporate fluorine into heteroarenes are limited in scope and can be hazardous. We present a broadly applicable and safe method for the site-selective fluorination of a single carbon-hydrogen bond in pyridines and diazines using commercially available silver(II) fluoride. The reactions occur at ambient temperature within 1 hour with exclusive selectivity for fluorination adjacent to nitrogen. The mild conditions allow access to fluorinated derivatives of medicinally important compounds, as well as a range of 2-substituted pyridines prepared by subsequent nucleophilic displacement of fluoride. Mechanistic studies demonstrate that the pathway of a classic pyridine amination can be adapted for selective fluorination of a broad range of nitrogen heterocycles.
Preparation of 2-Fluoropyridines via Base-Induced Decomposition of N-Fluoropyridinium Salts
Umemoto, Teruo,Tomizawa, Ginjiro
, p. 1726 - 1731 (2007/10/02)
N-Fluoropyridinium salts with either BF4-, SbF6-, or PF6- as a counteranion were treated with excess base such as triethylamine at room temperature to give 2-fluoropyridine in good yield.This method was succesfully applied to the preparation of 2-fluoropyridine derivatives possessing electron-donating or -withdrawing substituents using substituted N-fluoropyridinium tetrafluoroborates.Pyridine-F2 compounds produced through reactions of pyridines with molecular fluorine were also treated with base to give 2-fluoropyridines but in low yields.These reactions are considered to occur through a carbene mechanism as follows: a novel N-F-containing cyclic carbene (3), generated from the N-fluoropyridinium salts by 2-proton abstraction, reacts with fluorine atoms from counteranions such as BF4-, SbF6-, or PF6-, followed by elimination of F- from the N-F moiety, to yield 2-fluoropyridines.Previously reported findings in reactions of pyridines with molecular fluorine are explained on the basis of this mechanism.
