Day: January 5, 2023

Preparation of pyridostigmine bromide labeled with carbon-14 and tritium was written by Kepler, J. A.;Twine, C. E.;Austin, R. D.. And the article was included in Journal of Labelled Compounds and Radiopharmaceuticals in 1992.Safety of 2,6-Dibromo-3-hydroxypyridine This article mentions the following:

[2-¹⁴C]Pyridostigmine bromide (I, X = ¹⁴C, R = Me, R¹ = H) was prepared in 17.6% radiochem. yield with specific activity of 18 mCi/mmol. The reaction sequence involved preparation of 2-furan[¹⁴C]carboxylic acid by carbonation of 2-lithiofuran, followed by conversion to 2-amino[¹⁴C]methylfuran by lithium aluminum hydride reduction of its carboxamide. Oxidative rearrangement of 2-amino[¹⁴C]methylfuran gave 3-hydroxy[2-¹⁴C]pyridine which was converted to [2-¹⁴C]pyridostigmine bromide by reaction with dimethylcarbamyl chloride and quaternization with bromomethane. Pyridostigmine bromide I (X = C, R = ¹⁴CH₃, R¹ = H) labeled in the Me group of the carbamate function was prepared in 73% yield with specific activity of 37.6 mCi/mmol by reaction of bis-3-pyridyl carbonate with [¹⁴C]dimethylamine followed by quaternization with bromomethane. [6-³H]Pyridostigmine bromide (I, X = C, R = Me, R¹ = ³H) with specific activity of 22.5 mCi/mmol was prepared by catalytic halogen-tritium replacement of 2,6-dibromo-3-dimethylcarbamyloxypyridine followed by quaternization with bromomethane and back-exchanging the labile 2-tritium. In the experiment, the researchers used many compounds, for example, 2,6-Dibromo-3-hydroxypyridine (cas: 6602-33-1Safety of 2,6-Dibromo-3-hydroxypyridine).

2,6-Dibromo-3-hydroxypyridine (cas: 6602-33-1) belongs to pyridine derivatives. Pyridine has a conjugated system of six π electrons that are delocalized over the ring. The molecule is planar and, thus, follows the Hückel criteria for aromatic systems. 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.Safety of 2,6-Dibromo-3-hydroxypyridine

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Comparative basicities of substituted pyridines and electronegativity series in pyridines was written by Grandberg, I. I.;Faizova, G. K.;Kost, A. N.. And the article was included in Khimiya Geterotsiklicheskikh Soedinenii in 1966.Reference of 4783-68-0 This article mentions the following:

From a comparison of the pKa values of pyridine and 74 substituted pyridines (I), the effects of substituent groups on basicity were distinguished. For 2-substituents the order of decreasing basicity is: Cl > Br ≥ I > PhO > Ac > MeO > m-O2NC6H4 > p-O2NC6H4 > CHO > 2,4-(O2N)2C6H3CH2 > Ph > CH(OH)Ph > CPh:CH2 > vinyl > H > benzyl > 1-cyclohexen-1-yl ≥ CMe:CH2 > CH2OH > Me2CHCH2 ≥ HOCH2CH2 > iso-Pr ≥ Me. For 3-substituents the corresponding order is: NO2 > Cl > Br > CO2Et > Ac > CHO > CCH > Ph > MeO > vinyl > H > OH > Me ≥ Et ≥ iso-Pr ≥ Me2CHCH2. For 4-substituents the order is: NO2 > Cl > CO2Et > Ac > CCPh > CHO > p-O2NC6H4 > m-O2NC6H4 > CH:CHC6H4NO2-p > H > vinyl > benzyl > Ph > CH:CHC6H4Cl-p > CH:CHPh > CH:CHC6H4Me-p > iso-Bu > CH:CHC6H4Pr-iso-p ≥ Me ≥ Et ≥ iso-Pr ≥ CH:CHC6H4OMe-p > MeO. Some data are given also for pyridine oxides. The results were interpreted in terms of inductive and mesomeric effects. The latter were found to be more important at the 4-position than at the 2-position. Hydroxy substitution in the 3-position showed a pronounced mesomeric effect. Hydroxy substitution in the 2- and 4-positions was not studied because of pyridone tautomerism. In the experiment, the researchers used many compounds, for example, 2-Phenoxypyridine (cas: 4783-68-0Reference of 4783-68-0).

2-Phenoxypyridine (cas: 4783-68-0) 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 groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.Reference of 4783-68-0

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

The selenium dioxide oxidation of 2,3- and 3,4-dimethylpyridines was written by Dunn, A. D.. And the article was included in Organic Preparations and Procedures International in 1999.Application In Synthesis of Methyl 3-methylpicolinate This article mentions the following:

The SeO₂ oxidation of 2,3-dimethylpyridine gave 3-methyl-2-pyridinecarboxaldehyde and 3-methyl-2-pyridinecarboxylic acid, isolated as its Me ester. The aldehyde was converted to its oxime which was dehydrated to the carbonitrile. 3,4-Dimethylpyridine similarly gave 3-methylisonicotinaldehyde and the acid and nitrile. In the experiment, the researchers used many compounds, for example, Methyl 3-methylpicolinate (cas: 59718-84-2Application In Synthesis of Methyl 3-methylpicolinate).

Methyl 3-methylpicolinate (cas: 59718-84-2) 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. 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 Methyl 3-methylpicolinate

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

How Hydrogen Bonding Amplifies Isomeric Differences in Pyridones toward Strong Changes in Acidity and Tautomerism was written by Buechner, Robby;Fondell, Mattis;Mascarenhas, Eric J.;Pietzsch, Annette;Vaz da Cruz, Vinicius;Foehlisch, Alexander. And the article was included in Journal of Physical Chemistry B in 2021.Product Details of 626-64-2 This article mentions the following:

Steric hindrance of hydration and hydrogen bond enhancement by localized charges have been identified as key factors for the massive chem. differences between the hydroxypyridine/pyridone isomers in aqueous solution While all isomers occur mainly in the hydroxypyridine form in the gas phase, they differ by more than 3 orders of magnitude both in their acidity and tautomeric equilibrium constants upon hydration. By monitoring the electronic and solvation structures as a function of the protonation state and the O^– substitution position on the pyridine ring, the amplification of the isomeric differences in aqueous solution has been investigated. Near-edge X-ray absorption fine structure (NEXAFS) measurements at the N K-edge served as the probe of the chem. state. The combination of mol. dynamics simulations, complete active space SCF (CASSCF), and time-dependent d. functional theory (TD-DFT) spectral calculations contributes to unraveling the principles of tautomerism and acidity in multiple biochem. systems based on tautomerism. In the experiment, the researchers used many compounds, for example, Pyridin-4-ol (cas: 626-64-2Product Details of 626-64-2).

Pyridin-4-ol (cas: 626-64-2) 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). 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.Product Details of 626-64-2

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Reaction of aromatic N-oxides with dipolarophiles. XII. Stereoselective exo cycloaddition of 3,5-lutidine N-oxide with N-substituted maleimides and a frontier molecular orbital and mechanistic study was written by Hisano, Takuzo;Harano, Kazunobu;Matsuoka, Toshikazu;Yamada, Hirotoshi;Kurihara, Masahiko. And the article was included in Chemical & Pharmaceutical Bulletin in 1987.Reference of 3718-65-8 This article mentions the following:

Pericyclic reactions of 3,5-lutidine N-oxide with N-phenylmaleimides were investigated. The primary cycloadducts are thermally labile and undergo 1,5-sigmatropic rearrangement to give the 2,3-dihydropyridine derivatives The proton NMR structural assignment of the 1,5-sigmatropy products implies that the primary cycloaddition proceeds through an exo transition state. The reaction behavior is discussed in terms of frontier MO theory, based on MINDO/3 and CNDO/2 calculations and kinetic data. The reaction falls into the category of a normal-type cycloaddition and the exo cycloaddition is brought about by the unfavorable secondary orbital interaction. In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Reference of 3718-65-8).

3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. Pyridines are an important class of heterocycles and occur in polysubstituted forms in many naturally occurring biologically active compounds, drug molecules and chiral ligands. Pyridine groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.Reference of 3718-65-8

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Thermodynamics of protonation of pyridine N-oxide and its methyl-substituted derivatives in aqueous media was written by Klofutar, C.;Paljk, S.;Kremser, D.. And the article was included in Spectrochimica Acta, Part A: Molecular and Biomolecular Spectroscopy in 1973.Safety of 3,5-Dimethylpyridine 1-oxide This article mentions the following:

Thermodn. protonation constants of pyridine N-oxide and its Me derivatives are measured spectrophotometrically from 20-60°. The substituent effect on the free energy of proton ionization is additive, and an approx. linear relation exists between the pKa values of pyridine N-oxides and those of the pyridines. The changes of reaction enthalpy and entropy are discussed in terms of internal and external contributions of thermodn. functions. In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Safety of 3,5-Dimethylpyridine 1-oxide).

3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. Pyridines are an important class of heterocycles and occur in polysubstituted forms in many naturally occurring biologically active compounds, drug molecules and chiral ligands. Halopyridines are particularly attractive synthetic building blocks in a variety of cross-coupling methods, including the Suzuki-Miyaura cross-coupling reaction.Safety of 3,5-Dimethylpyridine 1-oxide

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Oxidative chlorination of 4-pentenols and other functionalized hydrocarbons was written by Bruecher, Oliver;Hartung, Jens. And the article was included in Tetrahedron in 2014.Name: Pyridinehydrochloride This article mentions the following:

Substituted 4-pentenols undergo regio- and stereoselective chlorocyclization, when treated in solutions of di-Me carbonate with chloride, a terminal oxidant, and a buffered proton source. Effective oxidants for liberating chlorine-like reactivity from chloride in the temperature range between 20 and 40 °C are tert-Bu hydroperoxide, activated by a titanium(IV) or a molybdenum(VI) ONO-chelate complex, and potassium monoperoxysulfate from the ternary salt 2KHSO₅·KHSO₄·K₂SO₄ (oxone). Substituents in the flexible part of the alkenol direct oxidative chlorocyclization 2,5-trans- and 2,4-cis-selectively. (E)-Configuration at the alkene translates anti-specifically into relative configuration of substituents at the β-chlorohydrin ether entity. A Ph group bound to the terminal alkene carbon alters the inherent 5-exo-specificity for chlorocyclization of terminal 4-pentenols toward 6-endo-selectivity, as exemplified by synthesis of trans-3-chloro-2-phenyltetrahydropyran from (E)-5-phenyl-4-penten-1-ol in up to 74% yield. Competition kinetics show that 5-exo-chlorocyclization of 1-phenyl-4-penten-1-ol occurs at 40 °C 600 times faster than electrophilic aromatic chlorosubstitution of anisole. Prenyl-type alkenols undergo allylic chlorination with an ene-type selectivity, as exemplified in synthesis of a building block for the fragrance component rose oxide from citronellol. In the experiment, the researchers used many compounds, for example, Pyridinehydrochloride (cas: 628-13-7Name: Pyridinehydrochloride).

Pyridinehydrochloride (cas: 628-13-7) belongs to pyridine derivatives. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Pyridine groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.Name: Pyridinehydrochloride

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Structural considerations for charge-enhanced Bronsted acid catalysts was written by Payne, Curtis;Kass, Steven R.. And the article was included in Journal of Physical Organic Chemistry in 2020.SDS of cas: 626-64-2 This article mentions the following:

All three N-methylated and N-protonated hydroxypyridinium BAr^F₄^– salt isomers were synthesized and their hydrogen bond donating abilities were investigated. DFT and G4 theory computations along with IR spectroscopic measurements were found to be effective methods for predicting the catalytic activities of these O-H and N-H Bronsted acids. A UV-vis titration approach for rapidly quantifying hydrogen bond donating ability revealed that carbon-hydrogen bonds also can participate in electrostatic interactions, but the presence of multiple equilibrium complexes results in a limitation of this method. In the methylated series of hydroxypyridines, the ortho and para isomers displayed modest rate enhancements relative to the meta derivative Protonation introduces a new acidic site and the ortho hydroxypyridinium ion salt is a significantly more active catalyst than all of the other species examined This is indicative of bidentate activation by the N-H and O-H acidic sites, and suggests a new design strategy for improving charge-enhanced catalysts. In the experiment, the researchers used many compounds, for example, Pyridin-4-ol (cas: 626-64-2SDS of cas: 626-64-2).

Pyridin-4-ol (cas: 626-64-2) 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 groups exist in countless molecules, and their applications include catalysis, drug design, molecular recognition, and natural product synthesis.SDS of cas: 626-64-2

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Palladium-Catalyzed Oxidative Olefination of Phenols Bearing Removable Directing Groups under Molecular Oxygen was written by Liu, Bin;Jiang, Huai-Zhi;Shi, Bing-Feng. And the article was included in Journal of Organic Chemistry in 2014.SDS of cas: 4783-68-0 This article mentions the following:

An efficient Pd(II)-catalyzed oxidative olefination of phenols bearing removable directing groups with mol. oxygen as the sole oxidant has been developed. E.g., in presence of Pd(OAc)₂ under atm. O₂, oxidative olefination of 2-phenoxypyridine with Et acrylate gave 73% (E)-I and (E,E)-II (13.6:1). This reaction protocol provides an efficient and robust synthetic tool for the synthesis of o-alkenyl phenols under mild conditions. In the experiment, the researchers used many compounds, for example, 2-Phenoxypyridine (cas: 4783-68-0SDS of cas: 4783-68-0).

2-Phenoxypyridine (cas: 4783-68-0) belongs to pyridine derivatives. Pyridine has a conjugated system of six π electrons that are delocalized over the ring. The molecule is planar and, thus, follows the Hückel criteria for aromatic systems. 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. SDS of cas: 4783-68-0

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem

Lithium trihydroxy/triisopropoxy-2-pyridylborate salts (LTBS): synthesis, isolation, and use in modified Suzuki-Miyaura cross-coupling reactions was written by Chen, Kuanchiang;Peterson, Richard;Math, Shivanand K.;LaMunyon, James B.;Testa, Charles A.;Cefalo, Dustin R.. And the article was included in Tetrahedron Letters in 2012.Quality Control of 2-Bromo-3-(trifluoromethyl)pyridine This article mentions the following:

We describe herein shelf-stable, isolable, and characterizable pyridyl lithium trihydroxy and triisopropoxy 2-borate salts (LTBS) for use in modified Suzuki-Miyaura cross-coupling reactions that can be produced in quantities greater than one hundred grams. For example, 2-bromo-3-fluoro-6-methylpyridine was reacted with triisopropoxyborane and n-butyllithium then hydrolyzed to give lithium (3-fluoro-6-methylpyridin-2-yl)trihydroxyborate in 100% yield. Pyridyl LTBS provide a viable cross-coupling alternative to unstable 2-pyridylboronic acids, boronates, and trifluoroborate salt derivatives We also demonstrate the synthesis and cross-coupling of shelf-stable LTBS reagents of other sp²-hybridized nitrogen-containing heterocycles including thiazole, pyrazine, quinoline, and isoquinoline heterocycles. In the experiment, the researchers used many compounds, for example, 2-Bromo-3-(trifluoromethyl)pyridine (cas: 175205-82-0Quality Control of 2-Bromo-3-(trifluoromethyl)pyridine).

2-Bromo-3-(trifluoromethyl)pyridine (cas: 175205-82-0) 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. 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. Quality Control of 2-Bromo-3-(trifluoromethyl)pyridine

Referemce:
Pyridine – Wikipedia,
Pyridine | C5H5N – PubChem