Category: 22468-26-4

The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《4-Hydroxypipecolic acid from Acacia species, and its stereoisomers》. Authors are Clark-Lewis, J. W.; Mortimer, P. I..The article about the compound:4-Hydroxypicolinic acidcas:22468-26-4,SMILESS:O=C(O)C1=NC=CC(O)=C1).Safety of 4-Hydroxypicolinic acid. Through the article, more information about this compound (cas:22468-26-4) is conveyed.

The title compound was isolated on a preparative scale from Acacia oswaldii leaves and separated from the accompanying acids through the Et2O soluble N-nitroso derivative (I). Hydrolysis of I and separation on an ion exchange column gave (-)-pipecolic acid (II) and the hydroxy acid, which was shown by unequivocal degradations to be (-)-trans-4-hydroxy-L-pipecolic acid (III). III was converted by stereospecific transformations into cis-4-hydroxy-L- (IV) and -D-pipecolic acid (V), so that 3 of the 4 optically active forms of 4-hydroxypipecolic acid were now available. A. oswaldii leaves (5.5 g.) extracted with alc. and chromatographed on sulfonated polystyrene gave 95 g. amino acids. The imino acids were extracted into Et2O as the N-nitroso derivatives The imino acids (46 g.) dissolved in 58 cc. refluxing H2O, the solution diluted with alc., and cooled gave 4-hydroxypipecolic acid. Purification gave 23 g. III, m. 285-6° (decomposition); II was obtained as the HCl salt, m. 256-8° (6.5 g. from 17.3 kg. leaves), [α]18D -10.5° (c 8, H2O). Separation of II and III was also achieved by selective elution from Zeo-Karb 225; III was eluted with 0.02-0.4N HCl, and II (and proline) with 0.4-0.8N acid. The mother liquors from III from 20 kg. leaves treated this way, and the column finally washed with 1.6N HCl gave 1.66 g. compound, m. 231-4° (decomposition), [α]24D 15° (c 1, H2O). Milled heartwood of A. excelsa (2094 g.) similarly worked up gave 4 g. III and 0.35 g. II. Similar extractions of other samples of A. excelsa heartwood gave 0.017-0.08% III and 0.001-0.01% II. III (0.01-0.03%) was also obtained from A. mollissima heartwood and sapwood. III isolated as described above was obtained as prisms, m. 294° (decomposition) (alc.), [α]20D -13° (c 1, H2O). III did not react with HIO4; the 1-(2,4-dinitrophenyl) derivative formed prisms, m. 183°; Cu salt, blue prisms, m. 229° (decomposition). III on paper chromatograms sprayed with ninhydrin and heated 5-10 min. at 100-10° gave a greyish green to brownish purple color. III 1-benzoyl derivative obtained in 60-70% yield m. 174°, [α]15D -54° (c 1, alc.). Benzoylation of III with excess BzCl did not yield the dibenzoate. Heating the 1-benzoyl derivative of III caused epimerization at the 2-C atom. p-MeC6H4SO2Cl (0.95 g.) in Me2CO with 0.58 g. III gave 0.7 g. (-)-trans-4-hydroxy-1-p-toluenesulfonyl-L-pipecolic acid, m. 162° (EtOAc-C6H6), [α]19D -16° (c 1, alc.). PhNCO (0.6 g.) was added slowly during 10 min. to 0.58 g. III in 4 cc. N NaOH, diphenylurea precipitated, and the solution acidified to give 0.48 g. (-)-trans-4-hydroxy-1-phenylcarbamoyl-L-pipecolic acid (VI), m. 181-97°, [α]26D -24.5° (c 1, alc.). VI (1.49 g.) in refluxing H2O gave 1.05 g. (-)-trans-4′-hydroxy-3-phenylpiperidino[1′,2′:1,5] hydantoin (VII), prisms, m. 204-5°, [α]23D -53° (c 1, alc.). VII (0.61 g.) dissolved in 4.63 cc. N NaOH and the solution diluted gave [α]D -17°, [α]D -40° (after 3 hrs.) and [α]D -45.4° after 24 hrs. III (0.725 g.) in 25 cc. 50% aqueous C5H5N adjusted to pH 10 with 1.4 cc. N NaOH, 1.2 cc. phenylisothiocyanate added, the mixture shaken, extracted with C6H6, the aqueous layer acidified, and the solid collected gave 0.56 g. (-)-trans-3-phenyl-4′-phenylthiocarbamoyloxypiperidino[1′,2′:1,5]-2-thiohydantoin, m. 213-14°(alc.), [α]22D -74° (c 0.2, alc.). III (0.051 g.), 0.023 g. red P, and 1 cc. HI heated 6 hrs. at 145° in a sealed tube gave 0.0076 g. II. III (2 g.), 0.32 g. red P, and 20 cc. HI heated 12 hrs. at 150° in 4 sealed tubes and the solutions combined contained II and other components. The materials separated on Zeo-Karb gave 0.22 g. II.HCl. III (0.02 g.), 0.007 g. red P, and 0.2 HI was heated 12 hrs. at 145°, evaporated, the residue dissolved in H2O, and examined by paper chromatography; III was absent and the chromatogram showed II and compounds that were apparently 4-iodopipecolic acids. In the 2nd experiment the reduction mixture treated with Ag2CO3, the solids removed, and the aqueous phase chromatographed showed the presence of 2-amino-4-pentenoic acid (VIII) and baikiain (IX). VIII gave a purple color with ninhydrin at 110-15° and IX gave a gray-green color with ninhydrin and a pink color with isatin. III (0.02 g.) was heated 9 hrs. at 145° with 0.0035 g. red P, and 0.2 cc. HI, evaporated, the residue treated in H2O with Ag2CO3 and the Ag salts separated Half the supernatant solution was hydrogenated over PtO2 3 hrs. and chromatograms showed the presence of 2-aminopentanoic acid (norvaline), II, and a minor component. III (2 g.) in 8 cc. PhAc heated 1.5 hrs. at 190°, diluted with Et2O, and extracted with 2N HCl gave 0.52 g. 4-hydroxypiperidine, m. 55-65°; dimorphic 1-p-toluenesulfonate, m. 114-15° or 123-4°. CrO3 (8N) in 7.5 cc. aqueous H2SO4 added to 2.18 g. III in 150 cc. AcOH, left 1.5 hrs. at 20°, MeOH added, the next day the solution decanted, the solutions from 4 such reactions evaporated, diluted, and the components separated on Zeo-Karb gave β-alanine and II. The oxo acid fractions were combined and evaporated to give 1.28 g. 4-oxo-L-pipecolic acid-HCl-H2O (X), decomposing 203°, [α]21D 3.8° (c 2, H2O). The HCl salt (0.4 g.) eluted from a Zeo-Karb 225 column with N NH4OH gave 0.19 g. (-)-4-oxo-L-pipecolic acid, prisms, decomposing 240°, [α]23D -14.8° (c 1, H2O). β-Alanine fractions collected and evaporated gave 0.59 g. containing II, converted into 0.27 g. of the phenylcarbamoyl derivatives Authentic N-phenylcarbamoyl-β-alanine was obtained as blades, m. 173-4° (H2O). PhNCO (0.3 g.) added during 15 min. to 0.4 g. X in 8 cc. 0.5N NaOH, and the filtrate acidified gave 4′-oxo-3-phenylpiperidino(1′,2′:1,5)hydantoin (XI), m. 187°. XI (0.1 g.) in alc. showed mutarotation after 23 hrs. XI exhibited [α]23D -87° (c 0.366, alc.). X (2 g.) in 20 cc. H2O at pH 9 treated 1 hr. at room temperature with 0.112 g. NaBH4 and the product treated on Zeo-Karb 225 gave IV.H2O, plates, m. 265° (decomposition), [α]23D -17° (c 1.1, H2O). IV.2H2O m. 265° (decomposition); Cu salt, blue plates, m. 245° (decomposition); N-(2,4-dinitrophenyl) derivative (62%), prisms, m. 134° (aqueous alc.). BzCl (0.15 g.) added portionwise to 0.163 g. IV.H2O in 3.2 cc. 0.7N NaOH, and the filtrate acidified gave, after 14 hrs. at 0°, 0.119 g. N-benzoyl derivative, blades, m. 104°, [α]23D -39.5° (c 1, alc.). The same product was obtained when 2.2 equivalents BzCl were used. Me 4-chloropicolinate (3.43 g.) in PhCH2OH treated portionwise with 1 g. Na in 30 cc. PhCH2OH, the mixture refluxed 45 min., 50 cc. H2O, 100 cc. Et2O, and 50 cc. 2N HCl added, the mixture shaken, the Et2O washed with dilute HCl, the acidic extracts combined, washed, and 50 cc. 5N NaOH added, and the mixture stored at 0° gave 3.65 g. Na 4-benzyloxypicolinate. Acidification gave 2.4 g. 4-benzyloxypicolinic acid (XII), prisms, m. 172° (alc.); 83% HCl.H2O salt, m. 162°. The HCl salt heated at 200° gave a liquid distillate consisting of PhCH2Cl and 0.15 g. 4-hydroxypicolinic acid (XIII), prisms, m. 258° (decomposition). Hydrogenation of 1 g. XII in 20 cc. 5N HCl at room temperature over PtO2 during 29 hrs. gave 0.52 g. XIII, m. 255-8°. Hydrogenation was inhibited in 1.5N NH3 but in AcOH at 65° hydrogenation gave II and III. XII (6.46 g.) in 50 cc. H2O hydrogenated 24 hrs. at 105°/70 atm. over 0.285 g. PtO2 and the acids isolated from the soluble mixture of 1.91 g. by paper chromatography gave after 24 hrs. bands of II and 4-hydroxypipecolic acids. The product (0.29 g.) in dilute HCl was concentrated to give 0.075 g. (±)-cis-4-hydroxypipecolic acid-HCl, prisms, m. 253-5° (decomposition). III (6 mg.) heated 9 hrs. at 145° in a sealed tube with 0.1 cc. N NaOH gave a mixture of cis and trans isomers; a trace of the epimer was similarly formed by heating in H2O alone, but not in N HCl. The epimeric mixture of imino acids formed by heating 5 mg. III in 0.3 cc. saturated aqueous Ba(OH)3 12 hrs. at 155° in a sealed tube was compared with a number of compounds III 1-benzoyl derivative (2.49 g.) heated 5 min. at 200°, refluxed 6.5 hrs. with 100 cc. 6N HCl, BzOH removed, and the aqueous layer paper chromatographed showed the presence of cis and trans-4-hydroxy acids in equal amounts III (2.9 g.) refluxed 4 hrs. with 30 cc. AcOH and 10.2 cc. Ac2O gave 1.1 g. (±)-1-acetyl-4-hydroxy-D-pipecolic lactone (XIV), plates, m. 148-9° (EtOAc), [α]24D 181° (c 1, alc.). XIV (1 g.) refluxed 3 hrs. with 50 cc. 2N HCl gave 0.74 g. V.2H2O, m. 266-9° (decomposition), [α]24D 17° (c 1, H2O). II was obtained from A. excelsa heartwood in prisms, m. 273-5° (decomposition); HCl salt, [α]22D -10.5° (c 6, H2O). N-Benzoyl-L-pipecolic acid crystallized as prisms, m. 133°, [α]22D -72° (c 1, alc.). 1-Phenylcarbamoyl-L-pipecolic acid (80%) formed prisms, m. 178°, [α]20D -39°. Recrystallization from refluxing H2O gave the optically inactive phenylhydantoin (XV), m. 159-60°. (±)-Pipecolic acid-HCl (m. 258-60°) was obtained in 91% yield by hydrogenation of 5 g. picolinic acid in 20 cc. 5N HCl over 0.2 g. PtO2 24 hrs. at 25 atm./60°. This salt (0.66 g.) in 8 cc. N NaOH treated with 0.59 g. PhNCO gave 0.81 g. (±)-1-phenylcarbamoylpipecolic acid, m. 138° and 156-8°. Recrystallization after refluxing 1 hr. with H2O gave XV. Et β-ethoxycarbonylaminopropionate (38.1 g.) and 34.4 g. Et fumarate were added successively to 350 cc. C6H6 and 4.6 g. Na (the temperature rose to b.p. during 45 min.) the mixture finally refluxed 0.5 hr., diluted with Et2O, extracted with Et2O, washed, the strongly acidic solution saturated with NaCl, extracted with EtOAc, washed, dried, and the solvent evaporated gave 53.5 g. oil. The oil dissolved in 10N HCl, evaporated, and the residue refluxed 4.5 hrs. with 150 cc. alc. saturated with HCl gave 24.2 g. Et 1-ethoxycarbonyl-3-oxopyrrolidine-2-ylacetate (XVI), b0.3 122-8°; semicarbazone, m. 124°; dimorphic 2,4-dinitrophenylhydrazone, orange plates, m. 112-13°, or prisms, m. 135°. NaBH4 (0.38 g.) in 1 cc. H2O added during 10 min. at 15° to 4.86 g. XVI gave after chromatography 0.51 g. 3-hydroxypyrrolidin-2-ylacetic acid-H2O, prisms, m. 215-16° (decomposition); N-(2,4-dinitrophenyl) derivative, prisms, m. 205° (aqueous alc.). The imino acid was recovered after treatment with HNO2. The phenylcarbamoyl derivative lost the elements of H2O to give the lactone, prisms, m. 168°. The lactone was recovered after heating 8 hrs. on a steam bath with 3N HCl.

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Most of the compounds have physiologically active properties, and their biological properties are often attributed to the heteroatoms contained in their molecules, and most of these heteroatoms also appear in cyclic structures. A Journal, Journal of Agricultural and Food Chemistry called UV ozonation of paraquat, Author is Kearney, Philip C.; Ruth, John M.; Zeng, Qiang; Mazzocchi, Paul, which mentions a compound: 22468-26-4, SMILESS is O=C(O)C1=NC=CC(O)=C1, Molecular C6H5NO3, Category: chiral-catalyst.

The use of UV irradiation in the presence of O2 or O3 was investigated as a method for degrading paraquat (I) [4685-14-7] prior to soil disposal. A solution of 1500 ppm of formulated I was slowly degraded after 7 h in a unit containing 66 low-pressure Hg vapor lamps with a maximum energy output at 254 nm. Addition of acetone  [67-64-1] as a photosensitizer accelerated the rate of oxidative cleavage of I in laboratory-scale studies. Loss of 14C from [methyl-14C]I was observed in I solutions at 150 ppm, but not at 1500 ppm. Reaction products identified from I were 4-carboxy-1-methylpyridinium ion  [36455-39-7] at 1500 ppm by HPLC, 4-picolinic acid  [55-22-1], hydroxy-4-picolinic acid  [22468-26-4], succinic acid  [110-15-6], N-formylglycine  [2491-15-8], malic acid  [6915-15-7], and oxalic acid  [144-62-7] as their Me3Si derivatives, and 4,4′-bipyridyl in dilute solutions by gas chromatog.-mass spectrometry.

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In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Substituted quinolines as inhibitors of L-glutamate transport into synaptic vesicles, published in 1998-07-31, which mentions a compound: 22468-26-4, Name is 4-Hydroxypicolinic acid, Molecular C6H5NO3, Category: chiral-catalyst.

This study investigated the structure-activity relationships and kinetic properties of a library of kynurenate analogs as inhibitors of 3H-L-glutamate transport into rat forebrain synaptic vesicles. The lack of inhibitory activity observed with the majority of the monocyclic pyridine derivatives suggested that the second aromatic ring of the quinoline-based compounds played a significant role in binding to the transporter. A total of two kynurenate derivatives, xanthurenate and 7-chlorokynurenate, differing only in the carbocyclic ring substituents, were identified as potent competitive inhibitors, exhibiting Ki values of 0.19 and 0.59 mM, resp. The Km value for L-glutamate was found to be 2.46 mM. Parallel experiments demonstrated that while none of the kynurenate analogs tested effectively inhibited the synaptosomal transport of 3H-D-aspartate, some cross-reactivity was observed with the EAA ionotropic receptors. Mol. modeling studies were carried out with the identified inhibitors and glutamate in an attempt to preliminarily define the pharmacophore of the vesicular transporter. It is hypothesized that the ability of the kynurenate analogs to bind to the transporter may be tied to the capacity of the quinoline carbocyclic ring to mimic the neg. charge of the γ-carboxylate of glutamate. A total of two low energy solution conformers of glutamate were identified that exhibited marked functional group overlap with the most potent inhibitor, xanthurenate. These results help to further refine the pharmacol. specificity of the glutamate binding site on the vesicular transporter and identify a series of inhibitors with which to investigate transporter function.

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HPLC of Formula: 22468-26-4. So far, in addition to halogen atoms, other non-metallic atoms can become part of the aromatic heterocycle, and the target ring system is still aromatic. Compound: 4-Hydroxypicolinic acid, is researched, Molecular C6H5NO3, CAS is 22468-26-4, about Gas chromatography/mass spectrometry of paraquat UV-ozonation products.

The chromatog. and mass spectral properties of 13 compounds isolated from the reaction of uv and O3 on paraquat  [4685-14-7] are described. The products were extracted from the acidified reaction mixture and converted to TMS derivatives The identified products were the di-TMS ester of oxalic acid (m/z 234), the TMS ester of 4-picolinic acid (m/z 195e, the di-TMS ester of succinic acid (m/z 262e, the di-TMS derivative of N-formylglycine, 4,4′-bipyridyl (m/z 156), the tri-TMS derivative of malic acid (m/z 350), and the di-TMS derivative of a hydroxy-4-picolinic acid. Structural features and tentative identification of some of the remaining compounds are discussed. The most prominent peak on the chromatogram has a probable mol. ion at m/z 219, isomeric to the di-TMS derivative of glycine. The structures presented suggest that demethylation, ring oxidation, and fragmentation of 1 or both rings of the bipyridinium di-cation occur during uv-ozonation of paraquat.

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In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called 4-(Tetrazolylalkyl)piperidine-2-carboxylic acids. Potent and selective N-methyl-D-aspartic acid receptor antagonists with a short duration of action, published in 1991-01-31, which mentions a compound: 22468-26-4, Name is 4-Hydroxypicolinic acid, Molecular C6H5NO3, Product Details of 22468-26-4.

A series of trans- and cis-4-(tetrazolylalkyl)piperidine-2-carboxylic acids I (R = H, Me) and II (n = 1, R = H, Me; n = 2-4, R = H) as potent and selective N-methyl-D-aspartic acid (NMDA) receptor antagonists were prepared and evaluated in vitro in both receptor binding assays and in a cortical-wedge preparation to determine affinity, potency, and selectivity. The new amino acids were also evaluated in vivo for their ability to block NMDA-induced convulsions in neonatal rats and NMDA-induced lethality in mice. The most potent compound of this series was I (R = H). I (R = H) blocked both NMDA-induced convulsions in neonatal rats and NMDA-induced lethality in mice. This is the first example of an NMDA receptor antagonist that incorporates a tetrazole moiety as an ω-acid bioisostere. These amino acid antagonists are also unique from their phosphonic acid counterparts in that they have a shorter duration of action in vivo.

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Quality Control of 4-Hydroxypicolinic acid. The protonation of heteroatoms in aromatic heterocycles can be divided into two categories: lone pairs of electrons are in the aromatic ring conjugated system; and lone pairs of electrons do not participate. Compound: 4-Hydroxypicolinic acid, is researched, Molecular C6H5NO3, CAS is 22468-26-4, about A hydroxypipecolic acid from thrift (Armeria maritima). Author is Fowden, L..

A hydroxypipecolic acid has been isolated from thrift and shown to be identical with a substance isolated from Acacia by Virtanen and Kari (C.A. 50, 4943e), who provisionally characterized it as 4-hydroxypipecolic acid (I). I has been synthesized by catalytic hydrogenation of 4-hydroxypicolinic acid with H and PtO. 3-Hydroxypipecolic acid was also synthesized in a like manner from 3-hydroxypicolinic acid. Oxidation of the 4- and 3-isomers yielded β-alanine, glycine, and aspartic acids and β-alanine, glycine, γ-aminobutyric, and aspartic acids, resp. Comparisons with synthetic 4- and 3-isomers indicated that the isolated imino acid may be the 3-isomer. Strictly identical behavior of natural and synthetic 3-isomer could not be demonstrated since the 2 substances differed in stereoisomeric composition

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Heterocyclic compounds can be divided into two categories: alicyclic heterocycles and aromatic heterocycles. Compounds whose heterocycles in the molecular skeleton cannot reflect aromaticity are called alicyclic heterocyclic compounds. Compound: 22468-26-4, is researched, Molecular C6H5NO3, about Plume Image Profiling of UV Laser Desorbed Biomolecules, the main research direction is UV laser desorption biomol plume fluorescence imaging mass spectrometry.Category: chiral-catalyst.

An exptl. system, based upon the techniques of UV and IR laser desorption with time of flight mass spectrometry, has been constructed to enable the production and characterization of neutral biomol. targets. The feasibility of the laser desorption technique for the purpose of radiation interaction experiments is investigated here. Fluorescent dye tagging and laser induced fluorescence imaging has been used to help characterize the laser produced plumes of biomols. revealing their spatial d. profiles and temporal evolution. Peak target thicknesses of 2×1012 mols. cm-2 were obtained 30 μs after laser desorption. (c) 2008 American Institute of Physics.

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Category: chiral-catalyst. The reaction of aromatic heterocyclic molecules with protons is called protonation. Aromatic heterocycles are more basic than benzene due to the participation of heteroatoms. Compound: 4-Hydroxypicolinic acid, is researched, Molecular C6H5NO3, CAS is 22468-26-4, about Chemical optimization of whole-cell transfer hydrogenation using carbonic anhydrase as host protein. Author is Rebelein, Johannes G.; Cotelle, Yoann; Garabedian, Brett; Ward, Thomas R..

Artificial metalloenzymes combine a synthetic metallo-cofactor with a protein scaffold and can catalyze abiotic reactions in vivo. Herein, we report on our efforts to valorize human carbonic anhydrase II as a scaffold for whole-cell transfer hydrogenation. Two platforms were tested: periplasmic compartmentalization and surface display in Escherichia coli. A chem. optimization of an IrCp* cofactor was performed. This led to 90 turnovers in the cell, affording a 69-fold increase in periplasmic product formation over the previously reported, sulfonamide-bearing IrCp* cofactor. These findings highlight the versatility of carbonic anhydrase as a promising scaffold for whole-cell catalysis with artificial metalloenzymes.

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Most of the compounds have physiologically active properties, and their biological properties are often attributed to the heteroatoms contained in their molecules, and most of these heteroatoms also appear in cyclic structures. A Journal, Organometallics called CO2 Hydrogenation and Formic Acid Dehydrogenation Using Ir Catalysts with Amide-Based Ligands, Author is Kanega, Ryoichi; Ertem, Mehmed Z.; Onishi, Naoya; Szalda, David J.; Fujita, Etsuko; Himeda, Yuichiro, which mentions a compound: 22468-26-4, SMILESS is O=C(O)C1=NC=CC(O)=C1, Molecular C6H5NO3, COA of Formula: C6H5NO3.

A series of Ir catalysts [Cp*Ir(H2O)(QCXNHR)][SO4] (1-16; Q = 2-pyridyl, 4-hydroxy-2-pyridyl, 6-hydroxy-2-pyridyl, 2-imidazolyl, 1-pyrazolyl; X = O, S, NH; R = H, Me, Ph, 4-hydroxyphenyl) bearing amide-based ligands were isolated or generated in situ by a deprotonated amide moiety with the hypotheses that strong electron-donating ability of the coordinated anionic nitrogen atom and the proton-responsive OH group near the metal center will improve the catalytic activity for CO2 hydrogenation and formic acid (FA) dehydrogenation. The effects of the modifications of the ligand architecture on the catalytic activity were investigated for CO2 hydrogenation at ambient conditions (25° with 0.1 MPa H2/CO2 (volume/volume = 1/1)) and under slightly harsher conditions (50° with 1.0 MPa H2/CO2) in basic aqueous solutions together with deuterium kinetic isotope effects (KIEs) with selected catalysts. Complex [Cp*Ir(L12)(H2O)][HSO4] (12, L12 = 6-hydroxy-N-phenylpicolinamidate) that has an anionic coordinating N atom and an OH group in the second coordination sphere, exhibits a TOF of 198 h-1 based on the initial 1 h of reaction. This TOF which, to the best of our knowledge, is the highest value ever reported under ambient conditions in basic aqueous solutions However, complex [Cp*Ir(L10)(H2O)][HSO4] (L10 = 4-hydroxy-N-methylpicolinamidate) performs better in long-term CO2 hydrogenation (up to a TON of 14700 with [Ir] = 10μM after 348 h and the final formate concentration of 0.643 M with [Ir] = 250μM.) at ambient conditions. Further, the catalytic activity for FA dehydrogenation was examined under three different conditions (pH 1.6, 2.3 and 3.5). The complex 12 in any of these conditions is less active compared to the picolinamidate catalysts without ortho-OH, owing to its instability. Theor. calculations were performed to examine the catalytic mechanism, and a step-by-step mechanism has been proposed for both CO2 hydrogenation and FA dehydrogenation reactions. D. functional theory calculations of [Cp*Ir(L3)(H2O)][HSO4] (L3 = picolinamidate) and the X-ray structure of the [Cp*Ir(L7)(H)]•H2O (L7 = N-methylpicolinamidate) complex imply a pH-dependent conformational change from N,N coordination to N,O coordination upon lowering the pH of the aqueous solution

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The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《The reaction with nitrous acid of certain derivatives of 4-aminopyridines, substituted in position 2 or 2 and 6. V. 4-Aminopicolinic acid and its amide and 2-cyano-4-aminopyridine》. Authors are Talik, Tadeusz; Plazek, Edwin.The article about the compound:4-Hydroxypicolinic acidcas:22468-26-4,SMILESS:O=C(O)C1=NC=CC(O)=C1).Reference of 4-Hydroxypicolinic acid. Through the article, more information about this compound (cas:22468-26-4) is conveyed.

cf. CA 53, 18954d. 4-Aminopyridine (I) derivatives with a CO2H, CONH2, or CN group in position 2 do not form stable diazonium compounds The 2-cyano derivative (II) of I, m. 145°, yield 92%, was prepared by heating 90 min. on steam bath 5 g. 4-aminopicolinic acid (III) amide (IV), m. 169°, 5 g. P2O5, 30 ml. POCl3, and 10 ml. PCl3, and crystallizing from water after addition of (NH4)2CO3. IV (63%) was prepared by reduction of 4-nitro-2-cyanopyridine N-oxide (V), m. 181°, with FeSO4 and aqueous NH3 solution V (62%) was obtained by boiling the resp. 2-iodo derivative with CuCN in pyridine. III m. 319° (decomposition) [260° as given by Graf (CA 31, 22149]. By action of HNO2 or gaseous N oxides on III, IV, or II in H2SO4 there was formed 4-hydroxypicolinic acid, m. 159°; amide m. 253°. An aqueous IV or II solution saturated with HCl reacted with NaNO2 to give 4-chloropicolinamide, m. 161°, 79% and 46%, resp.

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