Month: April 2022

The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Kinetics of the cyanide-cystine reaction》. Authors are Gawron, Oscar; Fernando, Joseph.The article about the compound:2-Amino-4,5-dihydrothiazole-4-carboxylic acidcas:2150-55-2,SMILESS:O=C(C1N=C(N)SC1)O).SDS of cas: 2150-55-2. Through the article, more information about this compound (cas:2150-55-2) is conveyed.

The kinetics of the cystine-cyanide reaction was studied in 0.04M KOH at pH 12.5 by a spectrophotometric method. The reaction was bimol., with cyclization of the thiocyanato product much faster than the reverse reaction. Activation parameters at 35° were: Ea, 16.8 kcal./mole; ΔH*, 16.1 kcal./mole; and ΔS*, -7.4 e.u. The entropy of activation was about the same as that for the cyanide-S8 reaction but about 20 e.u. less than that for the cystine-SO3–reaction; this indicated the activated complex for cystine-SO3– is more crowded than that for cystine-CN-.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Name: 2-Amino-4,5-dihydrothiazole-4-carboxylic acid. The mechanism of aromatic electrophilic substitution of aromatic heterocycles is consistent with that of benzene. Compound: 2-Amino-4,5-dihydrothiazole-4-carboxylic acid, is researched, Molecular C4H6N2O2S, CAS is 2150-55-2, about Spectrophotometric analysis of the cyanide metabolite 2-aminothiazoline-4-carboxylic acid (ATCA). Author is Baskin, Steven I.; Petrikovics, Ilona; Platoff, Gennady E.; Rockwood, Gary A.; Logue, Brian A..

Methods of directly evaluating cyanide levels are limited by the volatility of cyanide and by the difficulty of establishing steady-state cyanide levels with time. We investigated the measurement of a stable, toxic metabolite, 2-aminothiazoline-4-carboxylic acid (ATCA), in an attempt to circumvent the challenge of directly determining cyanide concentrations in aqueous media. This study was focused on the spectrophotometric ATCA determination in the presence of cyanide, thiocyanate (SCN-), cysteine, rhodanese, thiosulfate, and other sulfur donors. The method involves a thiazolidine ring opening in the presence of p-(hydroxy-mercury)-benzoate, followed by the reaction with diphenylthiocarbazone (dithizone). The product is spectrophotometrically analyzed at 625 nm in CCl4. The calibration curve was linear with a regression line of Y = 0.0022x (R2 = 0.9971). Interference of cyanide antidotes with the method was determined Cyanide, thiosulfate, butanethiosulfonate (BTS), and rhodanese did not appreciably interfere with the anal., but SCN- and cysteine significantly shifted the standard curve. This sensitive spectrophotometric method has shown promise as a substitute for the measurement of the less stable cyanide.

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Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

The chemical properties of alicyclic heterocycles are similar to those of the corresponding chain compounds. Compound: 4-Aminopyrimidine, is researched, Molecular C4H5N3, CAS is 591-54-8, about Development of an Aryl Amination Catalyst with Broad Scope Guided by Consideration of Catalyst Stability, the main research direction is dialkylbiaryl monosphosphine ligand preparation amination coupling catalyst.Formula: C4H5N3.

The authors have developed a new dialkylbiaryl monophosphine ligand, GPhos, that supports a palladium catalyst capable of promoting carbon-nitrogen cross-coupling reactions between a variety of primary amines and aryl halides; in many cases, these reactions can be carried out at room temperature The reaction development was guided by the idea that the productivity of catalysts employing BrettPhos-like ligands is limited by their lack of stability at room temperature Specifically, it was hypothesized that primary amine and N-heteroaromatic substrates can displace the phosphine ligand, leading to the formation of catalytically dormant palladium complexes that reactivate only upon heating. This notion was supported by the synthesis and kinetic study of a putative off-cycle Pd complex. Consideration of this off-cycle species, together with the identification of substrate classes that are not effectively coupled at room temperature using previous catalysts, led to the design of a new dialkylbiaryl monophosphine ligand. An Ot-Bu substituent was added ortho to the dialkylphosphino group of the ligand framework to improve the stability of the most active catalyst conformer. To offset the increased size of this substituent, the authors also removed the para i-Pr group of the non-phosphorus-containing ring, which allowed the catalyst to accommodate binding of even very large α-tertiary primary amine nucleophiles. In comparison to previous catalysts, the GPhos-supported catalyst exhibits better reactivity both under ambient conditions and at elevated temperatures Its use allows for the coupling of a range of amine nucleophiles, including (1) unhindered, (2) five-membered-ring N-heterocycle-containing, and (3) α-tertiary primary amines, each of which previously required a different catalyst to achieve optimal results.

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Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

HPLC of Formula: 118994-89-1. Aromatic compounds can be divided into two categories: single heterocycles and fused heterocycles. Compound: Ethyl oxazole-5-carboxylate, is researched, Molecular C6H7NO3, CAS is 118994-89-1, about Synthetic studies on bengazoles of marine sponge origin. Synthesis of the core bis-oxazole fragments. Author is Chittari, Pabba; Hamada, Yasumasa; Shioiri, Takayuki.

The core bis-oxazole fragment I (R = OCH2OMe, R1 = CHO) was constructed by the coupling of 5-formyloxazole with lithiated 5-(silyoxymethyl)oxazoles, oxidation of the resulting bis(oxazolyl)methanol (II), followed by the asym. reduction with (R)-(+)-BINAL-H as key steps. Addnl., preparation of bis-oxazole fragment I (R = H, R1 = CH2OSiPh2CMe3) was accomplished by the Barton-McCombie radical deoxygenation reaction of II.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

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.Ren, Ji-Wei; Tong, Meng-Nan; Zhao, Yu-Fen; Ni, Feng researched the compound: 4-Aminopyrimidine( cas:591-54-8 ).Electric Literature of C4H5N3.They published the article 《Synthesis of Dipeptide, Amide, and Ester without Racemization by Oxalyl Chloride and Catalytic Triphenylphosphine Oxide》 about this compound( cas:591-54-8 ) in Organic Letters. Keywords: dipeptide preparation diastereoselective; amino acid ester amidation triphenylphosphine oxide catalyst; ester preparation enantioselective; amide preparation enantioselective diastereoselective; amine phenylpropanoic acid amidation triphenylphosphine oxide catalyst; alc amino acid esterification triphenylphosphine oxide catalyst. We’ll tell you more about this compound (cas:591-54-8).

An efficient triphenylphosphine oxide-catalyzed amidation and esterification for the rapid synthesis of a series of dipeptides ((2S,2S)/(2S,2R))-RNHCH(R1)C(O)N(R2)CH(C(O)OR3)R4 [R = (tert-butoxy)carbonyl, (9H-fluoren-9-ylmethoxy)carbonyl, (benzyloxy)carbonyl; R1 = Me, Bn, [(acetamidomethyl)sulfanyl]methyl, (tert-butoxy)methyl, etc.; R2 = H; R3 = Me, t-Bu; R4 = 2-methylpropyl, propan-2-yl, Bn; R2R4 = -(CH2)3-], amides (S)-R5N(R6)C(O)C(R7)(CH3)C6H5 (R5 = 2-methylpropyl, 3,4-dicyanophenyl, pyridin-4-yl, 1-(tert-butoxy)-1-oxo-3-phenylpropan-2-yl, etc.; R6 = H; R5R6 = -(CH2)2N(Boc)(CH2)2-; R7 = H, Me) and esters (S)-(Fmoc)NHCH(R1)C(O)OR8 (R1 = Me, Bn; R8 = Me, Ph, cyclohexyl, etc.) is described. This reaction is applicable to challenging couplings of hindered carboxylic acids (S)-RNHCH(R1)C(O)OH, C6H5C(CH3)(R7)C(O)OH, and (S)-(Fmoc)NHCH(R1)C(O)OH with weakly nucleophilic amines ((S)/(R))-NH(R2)CH(C(O)OR3)R4, R5NH(R6) or alcs., R8OH giving the products in good yields (67-90%) without racemization. This system employs the highly reactive intermediate Ph3PCl2 as the activator of the carboxylate in a catalytic manner and drives the reaction to completion in a short reaction time (less than 10 min).

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Application In Synthesis of 2-Amino-4,5-dihydrothiazole-4-carboxylic acid. The fused heterocycle is formed by combining a benzene ring with a single heterocycle, or two or more single heterocycles. Compound: 2-Amino-4,5-dihydrothiazole-4-carboxylic acid, is researched, Molecular C4H6N2O2S, CAS is 2150-55-2, about Enzymatic production of cystine in commercial plant. Author is Yamamoto, Yasushi; Fujita, Itsuo; Horino, Issei; Kouda, Tohru; Akashi, Kunihiko.

For the enzymic production of cystine in a com. plant, the improvement of reaction process, the purification procedure, and the removal process of hydrogen sulfide were studied. Fed-batch process was adapted to the enzymic reaction and optimized. In the purification process, contaminating Fe ion was excluded from cystine products by adding chelating agent and the co-produced hydrogen sulfide was removed by an oxidation method. An improved process was realized in the industrial plant.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Yang, Ke; Zhang, Cheng; Wang, Peng; Zhang, Yan; Ge, Haibo published the article 《Nickel-catalyzed decarboxylative acylation of heteroarenes by sp2 C-H functionalization》. Keywords: oxoglyoxylic acid oxazole decarboxylative acylation nickel catalyst; oxazole ketone preparation; acylation; decarboxylation; heteroarenes; nickel; sp2 CH bond functionalization.They researched the compound: Ethyl oxazole-5-carboxylate( cas:118994-89-1 ).Category: pyrazines. Aromatic heterocyclic compounds can be divided into two categories: single heterocyclic and fused heterocyclic. In addition, there is a lot of other information about this compound (cas:118994-89-1) here.

Nickel-catalyzed ligand-free decarboxylative cross-coupling of azole derivatives with α-oxoglyoxylic acids was developed. This work represents the first example of decarboxylative cross-coupling reactions, in a C-H bond functionalization manner, through nickel catalysis, and tolerates various functional groups. Addnl., this approach provides an efficient access to (ox)azole ketones, an important structural motif in many medicinal compounds with a broad range of biol. activities. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

HPLC of Formula: 118994-89-1. 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: Ethyl oxazole-5-carboxylate, is researched, Molecular C6H7NO3, CAS is 118994-89-1, about Continuous flow as an enabling technology: a fast and versatile entry to functionalized glyoxal derivatives. Author is Lima, Fabio; Meisenbach, Mark; Schenkel, Berthold; Sedelmeier, Joerg.

Two complementary strategies employing organolithium chem. for the synthesis of glyoxal derivatives RC(O)R1R2 (R = methoxymethyl, 3,5-difluorophenyl, pyridin-2-yl, quinolin-6-yl, etc.; R1 = Cl, OEt, H; R2 = Cl, OEt, 3-chlorophenyl) were reported. Micro-mixer technol. allows for the generation of unstable organometallic intermediates and their instantaneous in-line quenching with esters as electrophiles RC(O)OEt. Selective mono-addition was observed via putative stabilized tetrahedral intermediates. Advantages offered by flow chem. technologies facilitate direct and efficient access to masked 1,2-dicarbonyl compounds while mitigating undesired byproduct formation. These two approaches enable the production of advanced and valuable synthetic building blocks for heterocyclic chem. with throughputs of grams per min.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

The preparation of ester heterocycles mostly uses heteroatoms as nucleophilic sites, which are achieved by intramolecular substitution or addition reactions. Compound: 5-Amino-2-fluoropyridine( cas:1827-27-6 ) is researched.SDS of cas: 1827-27-6.Li, Qilan; Lomonosova, Elena; Donlin, Maureen J.; Cao, Feng; O’Dea, Austin; Milleson, Brienna; Berkowitz, Alex J.; Baucom, John-Charles; Stasiak, John P.; Schiavone, Daniel V.; Abdelmessih, Rudolf G.; Lyubimova, Anastasiya; Fraboni, Americo J.; Bejcek, Lauren P.; Villa, Juan A.; Gallicchio, Emilio; Murelli, Ryan P.; Tavis, John E. published the article 《Amide-containing α-hydroxytropolones as inhibitors of hepatitis B virus replication》 about this compound( cas:1827-27-6 ) in Antiviral Research. Keywords: hepatitis B virus replication amide alpha hydroxytropolone; Hepatitis B Virus; Molecular modeling; Ribonuclease H; α-Hydroxytropolones. Let’s learn more about this compound (cas:1827-27-6).

The Hepatitis B Virus (HBV) RNase H (RNaseH) is a promising but unexploited drug target. Here, we synthesized and analyzed a library of 57 amide-containing α-hydroxytropolones (αHTs) as potential leads for HBV drug development. Fifty percent effective concentrations ranged from 0.31 to 54μM, with selectivity indexes in cell culture of up to 80. Activity against the HBV RNaseH was confirmed in semi-quant. enzymic assays with recombinant HBV RNaseH. The compounds were overall poorly active against human RNase H1, with 50% inhibitory concentrations of 5.1 to >1,000μM. The aHTs had modest activity against growth of the fungal pathogen Cryptococcus neoformans, but had very limited activity against growth of the Gram – bacterium Escherichia coli and the Gram + bacterium Staphylococcus aureus, indicating substantial selectivity for HBV. A mol. model of the HBV RNaseH templated against the Ty3 RNaseH was generated. Docking the compounds to the RNaseH revealed the anticipated binding pose with the divalent cation coordinating motif on the compounds chelating the two Mn++ ions modeled into the active site. These studies reveal that that amide aHTs can be strong, specific HBV inhibitors that merit further assessment toward becoming anti-HBV drugs.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

SDS of cas: 1827-27-6. Aromatic heterocyclic compounds can also be classified according to the number of heteroatoms contained in the heterocycle: single heteroatom, two heteroatoms, three heteroatoms and four heteroatoms. Compound: 5-Amino-2-fluoropyridine, is researched, Molecular C5H5FN2, CAS is 1827-27-6, about Design, synthesis and evaluation of pyrazolopyrimidinone derivatives as novel PDE9A inhibitors for treatment of Alzheimer’s disease. Author is Zhang, Pei; Jiang, Mei-Yan; Le, Mei-Ling; Zhang, Bei; Zhou, Qian; Wu, Yinuo; Zhang, Chen; Luo, Hai-Bin.

Phosphodiesterase-9 (PDE9) is a promising target for the treatment of Alzheimer’s disease (AD). To discover efficient PDE9 inhibitors with good metabolic stability and solubility, a series of novel pyrazolopyrimidinone derivatives were designed with the assistance of mol. docking and dynamics simulations. All the fourteen synthesized compounds gave excellent inhibition ratio against PDE9 at 10 nM. Compound (R)-N-(1H-benzo[d]imidazol-5-yl)-2-((1-cyclopentyl-4-oxo-4,5-dihydro-1H-pyrazolo [3,4-d]pyrimidin-6-yl)amino)propanamide with the IC50 of 2.0 nM against PDE9, showed good metabolic stability (t1/2 of 57 min) in the RLM as well as good solubility (195 mg/L). The anal. on binding modes of targeted compounds may provide insight for further structural modification.

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Reference:
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem