Month: December 2022

The effect of the substituents on the carbonyl absorptions of 2H-pyrid-2-ones and 2H-thiopyran-2-ones was written by Siddiq, Muhammad. And the article was included in Pakistan Journal of Scientific and Industrial Research in 1988.Synthetic Route of C5H3Br2NO This article mentions the following:

The IR spectra of a number of substituted 2H-pyrid-2-ones and 2H-thiopyran-2-ones have been measured in the carbonyl stretching vibration region and interpreted in terms of the chem. effect of the substituents. In general, the presence of electron withdrawing substituents at the 1-, 3-, or 3,5-positions and electron donating substituents at the 1-, 4-, or 5-positions of the 2-pyridone have been found to raise and lower the carbonyl absorption, resp. The substituted 2H-thiopyran-2-ones show an appreciable decrease in their carbonyl absorptions as compared to the corresponding 2-pyridones. In the experiment, the researchers used many compounds, for example, 3,5-Dibromo-2-hydroxypyridine (cas: 13472-81-6Synthetic Route of C5H3Br2NO).

3,5-Dibromo-2-hydroxypyridine (cas: 13472-81-6) belongs to pyridine derivatives. Pyridine has a dipole moment and a weaker resonant stabilization than benzene (resonance energy 117 kJ·mol−1 in pyridine vs. 150 kJ·mol−1 in benzene). Reduced pyridines, namely tetrahydropyridines, dihydropyridines and piperidines, are found in numerous natural and synthetic compounds. The synthesis and reactivity of these compounds have often been driven by the fact many of these compounds have interesting and unique pharmacological properties. Synthetic Route of C5H3Br2NO

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Synthesis, CYP 450 evaluation, and docking simulation of novel 4-aminopyridine and coumarin derivatives was written by Ghalehshahi, Hajar G.;Balalaie, Saeed;Sohbati, Hamid R.;Azizian, Homa;Alavijeh, Mohammad S.. And the article was included in Archiv der Pharmazie (Weinheim, Germany) in 2019.Computed Properties of C7H7ClN2 This article mentions the following:

Four series of novel compounds based on 4-aminopyridine, glatiramer acetate, pyrone, and coumarin backbones were sufficiently synthesized and identified by spectroscopic methods. CYP enzyme inhibition assays of five predominate human P 450 isoenzymes indicate that all compounds, except for 4-hydrazide pyridine 1c, seem to be less toxic than 4-aminopyridine. Further investigation of the compounds using mol. docking experiments revealed different, the same, or stronger binding modes for most of the synthesized compounds, with both polar and hydrophobic interactions with the 1WDA and 1J95 receptors compared to benzoyl L-arginine amide and 4-aminopyridine, resp. These results introduce the synthesized compounds as K⁺ channel blockers that could be considered for in vivo CNS disease studies. In the experiment, the researchers used many compounds, for example, 1-(Cyanomethyl)pyridin-1-ium chloride (cas: 17281-59-3Computed Properties of C7H7ClN2).

1-(Cyanomethyl)pyridin-1-ium chloride (cas: 17281-59-3) belongs to pyridine derivatives. The ring atoms in the pyridine molecule are sp2-hybridized. The nitrogen is involved in the π-bonding aromatic system using its unhybridized p orbital. The lone pair is in an sp2 orbital, projecting outward from the ring in the same plane as the σ bonds. Pyridine, its benzo and pyridine-based compounds play diverse roles in organic chemistry. Pyridine-based materials are valued for their optical and physical properties as well as their medical potential. Computed Properties of C7H7ClN2

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Regioselective Amidomethylation of 4-Chloro-3-fluoropyridine by Metalation and Minisci-Type Reactions was written by Papaioannou, Nikolaos;Fray, M. Jonathan;Rennhack, Andreas;Sanderson, Thomas J.;Stokes, Jamie E.. And the article was included in Journal of Organic Chemistry in 2020.COA of Formula: C6H6FN This article mentions the following:

The synthesis of a series of 2-amidomethylated pyridines (3-8) was investigated, starting from 4-chloro-3-fluoropyridine. Kinetic deprotonation at -75°C followed by reaction with DMF gave 2-formyl-4-chloro-3-fluoropyridine 10 regioselectively, which was converted to 2-aminomethyl analog 1 via sulfinamide 2. Alternatively, Minisci-type amidomethylation under Ag⁺/persulfate or photoredox-mediated conditions using a series of amino acid derivatives gave (3-8, 19, and 34) in 30-74% yield and isomer ratios in the range 6.7:1 to > 50:1. The latter methods gave overall yields similar to that of the deprotonation approach, but were shorter and more amenable to scale-up. In particular, N-Boc analog 8 was obtained in a single step. The amidomethylations of another six 3-fluoropyridines under the photoredox conditions were briefly examined In the experiment, the researchers used many compounds, for example, 3-Fluoro-4-methylpyridine (cas: 399-88-2COA of Formula: C6H6FN).

3-Fluoro-4-methylpyridine (cas: 399-88-2) belongs to pyridine derivatives. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Many analogues of pyridine are known where N is replaced by other heteroatoms . Substitution of one C–H in pyridine with a second N gives rise to the diazine heterocycles (C4H4N2), with the names pyridazine, pyrimidine, and pyrazine.COA of Formula: C6H6FN

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Discovery of a Novel Highly Selective Histamine H4 Receptor Antagonist for the Treatment of Atopic Dermatitis was written by Ko, Kwangseok;Kim, Hye-Jung;Ho, Pil-Su;Lee, Soon Ok;Lee, Ji-Eun;Min, Cho-Rong;Kim, Yu Chul;Yoon, Ju-Han;Park, Eun-Jung;Kwon, Young-Jin;Yun, Jee-Hun;Yoon, Dong-Oh;Kim, Jung-Sook;Park, Woul-Seong;Oh, Seung-Su;Song, Yu-Mi;Cho, Woon-Ki;Morikawa, Kazumi;Lee, Kyoung-June;Park, Chan-Hee. And the article was included in Journal of Medicinal Chemistry in 2018.Application In Synthesis of 5,6-Dichloro-3-nitropyridin-2-amine This article mentions the following:

The histamine H4 receptor (H4R), a member of the G-protein coupled receptor family, has been considered as a potential therapeutic target for treating atopic dermatitis (AD). A large number of H4R antagonists have been disclosed, but no efficient agents controlling both pruritus and inflammation in AD have been developed yet. Here, we have discovered a novel class of orally available H4R antagonists showing strong anti-itching and anti-inflammation activity as well as excellent selectivity against off-targets. A pharmacophore-based virtual screening system constructed in house successfully identified initial hit compound 9, and the subsequent homol. model-guided optimization efficiently led us to discover pyrido[2,3-e]tetrazolo[1,5-a]pyrazine analog 48 as a novel chemotype of a potent and highly selective H4R antagonist. Importantly, orally administered compound 48 exhibits remarkable efficacy on antipruritus and anti-inflammation with a favorable pharmacokinetic (PK) profile in several mouse models of AD. Thus, these data strongly suggest that our compound 48 is a promising clin. candidate for treatment of AD. In the experiment, the researchers used many compounds, for example, 5,6-Dichloro-3-nitropyridin-2-amine (cas: 203794-33-6Application In Synthesis of 5,6-Dichloro-3-nitropyridin-2-amine).

5,6-Dichloro-3-nitropyridin-2-amine (cas: 203794-33-6) belongs to pyridine derivatives. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Several pyridine derivatives play important roles in biological systems. While its biosynthesis is not fully understood, nicotinic acid (vitamin B3) occurs in some bacteria, fungi, and mammals.Application In Synthesis of 5,6-Dichloro-3-nitropyridin-2-amine

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

N-Oxides of the methylpyridines. III. Action of acetic an-hydride on the N-oxides of 3-picoline and 3,5-lutidine was written by Rooyen, G. F. van;Brink, C. V. D. M.;Villiers, P. A. de. And the article was included in Tydskrif vir Natuurwetenskappe in 1964.Application of 3718-65-8 This article mentions the following:

3-Picoline (I) N-oxide [Ochiai, CA 48, 3359i), except that the reaction was catalyzed by concentrated H₂SO₄] (70.1 g.) and 108 g. Ac₂O refluxed 4 hrs. at 140-50°, the mixture concentrated in vacuo, treated with 20 ml. H₂O, and again concentrated in vacuo, the residue made alk. with concentrated aqueous Na₂CO₃ and extracted with CHCl₃, the extract dried and concentratedin vacuo [the residue (A) was saved], and the distillate refractionated gave an oil which treated with excess saturated aqueous picric acid gave 0-2% I picrate, m. 145-7°, and 11% 3 other picrates of unidentified bases, m. 184-6°, 204-5.5°, and 281-2°; the picrate m. 1846° was converted to the free base, m. 145-7° (C₆H₆). Residue A dissolved in H₂O, made strongly alk. with concentrated aqueous NaOH, and extracted with CHCl₃ [the aqueous soluble solution (A) was saved], the extract evaporated, the residue extracted with cyclohexane, and the extract purified by chromatography on Al₂O₃ gave 5-10% 3-methyl-N-(5-methyl-2-pyridyl)-2-pyridone (II), m. 107.5-8.5° (cyclohexane); the residue remaining after extraction with cyclohexane chromatographed on Al₂O₃ with 3:2 CCl₄-C₆H₆ and eluted with CCl₄-C₆H₆ and then CHCl₃ gave an oil, whose picrate m. 137.5-8.5°, after rechromatography of the oil, and whose HgCl₂ complex m. 151-3° (the oil may possibly be 5,5′-dimethyl-2,2′-bipyridyl); further elution with EtOH gave 0.5% 2-amino-5-methylpyridine (IIa) (picrate m. 247.5-9.5°; HgCl₂ complex m. 159-60°). Solution A acidified with HCl, made slightly alk. with aqueous NH₃ (Congo paper), extracted with CHCl3, evaporated in vacuo, the residue extracted with CHCl₃, and the combined CHCl₃ extracts concentrated gave 10.03 g. crude 5-methyl-2-pyridone (III), which recrystallized from 1:1 C₆H₆-hexane gave III, m. 185-6° (C₆H₆-hexane) (picrate m. 1467.5°; HgCl₂ complex m. 206.5-8.5°); the mother liquor chromatographed on activated Al₂O₃ and the column eluted with C₆H₆ gave a mixture (IIIa) of III and 3-methyl-2-pyridone (IV); further elution with CHCl₃ gave addnl. III, and 10% AcOH elulion gave some IV and a small amount unidentified compound, m. 226.5-31.0°. Repeated chromatography of IIIa gave 3.46 g. IV, m. 140-1.5° (C₆H₆); picrate m. 157.5-9.0°; HgCl₂ complex m. 131.5-2.0°. 3,5-Lutidine (V) N-oxide (VI) (Kambara, et al., CA 46, 1795f) (37.9 g.) refluxed 2.25 hrs. at 160° with 36 g. Ac₂O, 10 ml. Ac₂O added, and the mixture heated 2.75 hrs. while gradually allowing the temperature to drop to 146° and worked up gave a CHCl₃ distillate containing no products and 32 g. oily alkali-insoluble fraction (A) and a 7.85 g. semi-crystalline alk.-soluble fraction (B). Fraction A chromatographed on activated Al₂O₃ and eluted with CCl₄ gave 23.7 g. oil, which extracted with petr. ether gave 7.32 g. petr. ethersol. I (picrate m. 244-5°) and 7% petr. ether-insoluble 3,5-dimethyl-N-(3,5-dimethyl-2-pyridyl)-2-pyridone, m. 104-5° (1:1 C₆H₆ hexane); further elution with C₆H₆ gave 2.7 g. unchanged VI (picrate m. 135-6.5°). Fraction B chromatographed on Al₂O₃ and eluted with CHCl₃ gave 4% 3,5-dimethyl-2-pyridone, m. 118.5-19.5° (hexane); picrate m. 208.5-10.0°. 5-Methyl-2bromopyridine [m. 152.5° (3:1 C₆H₆-CHCl₃); picrate m. 1267.5°] (0.85 g.), 0.65 g. IV Na derivative, and 25 mg.Cu powder refluxed 5 hrs. and worked up (CA 51, 5067h) gave 300 mg. II, m. 107.5-8.5° (cyclohexane). II (300 mg.), 1.5 g. NaOH, and 1 ml. H₂O refluxed 20 min. at 145-50° and the mixture cooled, diluted with 10 ml. H₂O, acidified with dilute HCl, made just alk. with aqueous NH₃, and extracted with CHCl₃ gave (from the extract) oily IIa; picrate m. 247.5-9.5°. Ir and uv data were given. In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Application of 3718-65-8).

3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. Pyridine is diamagnetic and has a diamagnetic susceptibility of −48.7 × 10−6 cm3·mol−1.The molecular electric dipole moment is 2.2 debyes. The standard enthalpy of formation is 100.2 kJ·mol−1 in the liquid phase and 140.4 kJ·mol−1 in the gas phase. Pyridine groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.Application of 3718-65-8

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Design, Synthesis, and Biological Evaluation of Novel Matrix Metalloproteinase Inhibitors As Potent Antihemorrhagic Agents: From Hit Identification to an Optimized Lead was written by Orbe, Josune;Sanchez-Arias, Juan A.;Rabal, Obdulia;Rodriguez, Jose A.;Salicio, Agustina;Ugarte, Ana;Belzunce, Miriam;Xu, Musheng;Wu, Wei;Tan, Haizhong;Ma, Hongyu;Paramo, Jose A.;Oyarzabal, Julen. And the article was included in Journal of Medicinal Chemistry in 2015.Reference of 51834-97-0 This article mentions the following:

Growing evidence suggests that matrix metalloproteinases (MMP) are involved in thrombus dissolution; then, considering that new therapeutic strategies are required for controlling hemorrhage, we hypothesized that MMP inhibition may reduce bleeding by delaying fibrinolysis. Thus, we designed and synthesized a novel series of MMP inhibitors to identify potential candidates for acute treatment of bleeding. Structure-based and knowledge-based strategies were utilized to design this novel chem. series, α-spiropiperidine hydroxamates, of potent and soluble (>75 μg/mL) pan-MMP inhibitors. The initial hit was progressed to an optimal lead I. Racemic I showed a remarkable in vitro phenotypic response and outstanding in vivo efficacy; in fact, the mouse bleeding time at 1 mg/kg was 0.85 min compared to 29.28 min using saline. In addition, I displayed an optimal ADME and safety profile (e.g., no thrombus formation). Its corresponding enantiomers were separated, leading to the preclin. candidate (R)-I. In the experiment, the researchers used many compounds, for example, 5-Hydroxy-2-methoxylpyridine (cas: 51834-97-0Reference of 51834-97-0).

5-Hydroxy-2-methoxylpyridine (cas: 51834-97-0) belongs to pyridine derivatives. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Pyridine derivatives are also useful as small-molecule α-helix mimetics that inhibit protein-protein interactions, as well as functionally selective GABA ligands.Reference of 51834-97-0

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Application of pyridinium ionic liquids in extraction of total flavonoids from seabuckthorn leaves was written by Zhao, San-hu;Wang, Ming-shan;Qiao, Yong-sheng;Dong, Zhi-yun;Liu, Gai-mei. And the article was included in Huaxue Shiji in 2018.Formula: C17H30BrN This article mentions the following:

In this work, six kinds of pyridinium ionic liquids were prepared and their aqueous solution was applied in extraction total flavonoids from seabuckthorn leaves. The results showed that using 1 mol/L aqueous solution of N-dodecyl pyridinium bromide as the extraction agent to extract the total flavonoids from the seabuckthorn leaves dried naturally, under the microwave irradiation at 50°C, the extraction rate 3.65% was obtained after 5 min. Based on the method of pharmacopoeia, using ethanol as extraction agent, the extraction rate was only 2.72% after 3 h. So the microwave-assisted extraction total flavonoid with pyridinium ionic liquids as extraction agents is an efficient and convenient method. In the experiment, the researchers used many compounds, for example, 1-Dodecylpyridin-1-ium bromide (cas: 104-73-4Formula: C17H30BrN).

1-Dodecylpyridin-1-ium bromide (cas: 104-73-4) belongs to pyridine derivatives. Pyridine is diamagnetic and has a diamagnetic susceptibility of −48.7 × 10−6 cm3·mol−1.The molecular electric dipole moment is 2.2 debyes. The standard enthalpy of formation is 100.2 kJ·mol−1 in the liquid phase and 140.4 kJ·mol−1 in the gas phase. One of the examples of pyridines is the well-known alkaloid lithoprimidine, which is an A3 adenosine receptor antagonist and N,N-dimethylaminopyridine (DMAP) analog, commonly used in organic synthesis.Formula: C17H30BrN

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Discrete half-sandwich Ir, Rh-based organometallic molecular boxes: synthesis, characterization, and their properties was written by Han, Ying-Feng;Lin, Yue-Jian;Jin, Guo-Xin. And the article was included in Dalton Transactions in 2011.SDS of cas: 15420-02-7 This article mentions the following:

The treatment of binuclear complexes [Cp^*₂M₂(μ-QA)Cl₂] (M = Ir, 2a; M = Rh, 2b) (H₂QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifunctional pyridyl-based ligands (4,4′-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt)) in the presence of AgOTf (OTf = CF₃SO₃) in CH₃OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp^*₄M₄(μ-QA)₂(μ-L)₂](OTf)₄ (M = Ir, 3a–7a; M = Rh, 3b–7b), resp. The mol. structure of [Cp^*₄Ir₄(μ-QA)₂(μ-pyrazine)₂](OTf)₄ (3a) has been determined by single-crystal x-ray anal., revealing that the metal centers were connected by pyrazine and bis-bidentate QA^2- ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 Å. Complexes 3a and 3b were found to exhibit selective trapping of halocarbons properties. In the experiment, the researchers used many compounds, for example, 2,5-Di(pyridin-4-yl)-1,3,4-oxadiazole (cas: 15420-02-7SDS of cas: 15420-02-7).

2,5-Di(pyridin-4-yl)-1,3,4-oxadiazole (cas: 15420-02-7) belongs to pyridine derivatives. Pyridine has a dipole moment and a weaker resonant stabilization than benzene (resonance energy 117 kJ·mol−1 in pyridine vs. 150 kJ·mol−1 in benzene). Pyridine groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.SDS of cas: 15420-02-7

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Alkylation of pyridine 1-oxides and related compounds with activated acetylenes. A novel molecular rearrangement of heteroaromatic N-oxides was written by Abramovitch, Rudolph A.;Grins, George;Rogers, Richard B.;Shinkai, Ichiro. And the article was included in Journal of the American Chemical Society in 1976.Computed Properties of C7H9NO This article mentions the following:

The reaction of pyridine 1-oxide with phenylcyanoacetylene gives the 3-alkylated derivative (I) as the main product together with minor amounts of II, III and IV. With substituted pyridine 1-oxides and with quinoline 1-oxide the products of 3-alkylation are also formed unless the 3 and 5 positions are blocked. The 3-alkylated products arise from the initial 1,2-dihydro adduct by a [σ2s + π2a + π4s] rearrangement, followed by regiosp. cyclopropane ring opening to the 3-alkylated derivatives In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Computed Properties of C7H9NO).

3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. The ring atoms in the pyridine molecule are sp2-hybridized. The nitrogen is involved in the π-bonding aromatic system using its unhybridized p orbital. The lone pair is in an sp2 orbital, projecting outward from the ring in the same plane as the σ bonds. One of the examples of pyridines is the well-known alkaloid lithoprimidine, which is an A3 adenosine receptor antagonist and N,N-dimethylaminopyridine (DMAP) analog, commonly used in organic synthesis.Computed Properties of C7H9NO

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Structure activity relationship of pyridoxazinone substituted RHS analogs of oxabicyclooctane-linked 1,5-naphthyridinyl novel bacterial topoisomerase inhibitors as broad-spectrum antibacterial agents (Part-6) was written by Singh, Sheo B.;Kaelin, David E.;Wu, Jin;Miesel, Lynn;Tan, Christopher M.;Meinke, Peter T.;Olsen, David B.;Lagrutta, Armando;Wei, Changqing;Liao, Yonggang;Peng, Xuanjia;Wang, Xiu;Fukuda, Hideyuki;Kishii, Ryuta;Takei, Masaya;Yajima, Masanobu;Shibue, Taku;Shibata, Takeshi;Ohata, Kohei;Nishimura, Akinori;Fukuda, Yasumichi. And the article was included in Bioorganic & Medicinal Chemistry Letters in 2015.Category: pyridine-derivatives This article mentions the following:

Oxabicyclooctane linked 1,5-naphthyridinyl-pyridoxazinones are novel broad-spectrum bacterial topoisomerase inhibitors (NBTIs) targeting bacterial DNA gyrase and topoisomerase IV at a site different than quinolones. Due to lack of cross-resistance to known antibiotics they present excellent opportunity to combat drug-resistant bacteria. A structure activity relationship of the pyridoxazinone moiety is described in this Letter. Chem. synthesis and activities of NBTIs with substitutions at C-3, C-4 and C-7 of the pyridoxazinone moiety with halogens, alkyl groups and methoxy group has been described. In addition, substitutions of the linker NH proton and its transformation into amide analogs of AM-8085 and AM-8191 have been reported. Fluoro, chloro, and Me groups at C-3 of the pyridoxazinone moiety retained the potency and spectrum. In addition, a C-3 fluoro analog showed 4-fold better oral efficacy (ED₅₀ 3.9 mg/kg) as compared to the parent AM-8085 in a murine bacteremia model of infection of Staphylococcus aureus. Even modest polarity (e.g., methoxy) is not tolerated at C-3 of the pyridoxazinone unit. The basicity and NH group of the linker is important for the activity when CH₂ is at the linker position-8. However, amides (with linker position-8 ketone) with a position-7 NH or N-Me group retained potency and spectrum suggesting that neither basicity nor hydrogen-donor properties of the linker amide NH is essential for the activity. This would suggest likely an altered binding mode of the linker position-7,8 amide containing compounds The amides showed highly improved hERG (functional IC₅₀ >30 μM) profile. In the experiment, the researchers used many compounds, for example, 3-Fluoro-4-methylpyridine (cas: 399-88-2Category: pyridine-derivatives).

3-Fluoro-4-methylpyridine (cas: 399-88-2) belongs to pyridine derivatives. Pyridine is diamagnetic and has a diamagnetic susceptibility of −48.7 × 10−6 cm3·mol−1.The molecular electric dipole moment is 2.2 debyes. The standard enthalpy of formation is 100.2 kJ·mol−1 in the liquid phase and 140.4 kJ·mol−1 in the gas phase. Halopyridines are particularly attractive synthetic building blocks in a variety of cross-coupling methods, including the Suzuki-Miyaura cross-coupling reaction.Category: pyridine-derivatives

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem