- Hantzsch reaction in urea-formaldehyde resins
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The effect of acetylacetone and ammonia in urea-formaldehyde resins on the reactions occurring in their presence was examined. The formation of 2,6-dimethyl-3,5-diacetyl-l,4-dihydropyridine in urea-formaldehyde resins was confirmed by 1H NMR spectroscopy.
- Kotova,Maslosh,Pekhtereva,Chervinskii
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- Environmentally friendly and efficient synthesis of various 1,4-dihydropyridines in pure water
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An environmentally friendly and efficient synthesis of a series of 1,4-dihydropyridines was developed by the practical one-pot reactions of aldehydes with ammonium acetate and 1,3-dicarbonyl compounds such as alkyl acetoacetate, 5,5-dimethyl-1,3-cyclohexanedione, 1,3-cyclohexanedione, and 2,4-pentanedione in water without any additives under refluxing conditions.
- Wang, Guan-Wu,Xia, Jing-Jing,Miao, Chun-Bao,Wu, Xue-Liang
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- Artificial Z-scheme constructed with a supramolecular metal complex and semiconductor for the photocatalytic reduction of CO2
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A hybrid for the visible-light-driven photocatalytic reduction of CO 2 using methanol as a reducing agent was developed by combining two different types of photocatalysts: a Ru(II) dinuclear complex (RuBLRu′) used for CO2 reduction is adsorbed onto Ag-loaded TaON (Ag/TaON) for methanol oxidation. Isotope experiments clearly showed that this hybrid photocatalyst mainly produced HCOOH (TN = 41 for 9 h irradiation) from CO 2 and HCHO from methanol. Therefore, it converted light energy into chemical energy (ΔG = +83.0 kJ/mol). Photocatalytic reaction proceeds by the stepwise excitation of Ag/TaON and the Ru dinuclear complex on Ag/TaON, similar to the photosynthesis Z-scheme.
- Sekizawa, Keita,Maeda, Kazuhiko,Domen, Kazunari,Koike, Kazuhide,Ishitani, Osamu
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- Quantitative determination of formaldehyde by spectrophotometry utilizing multivariate curve resolution alternating least squares
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Formaldehyde is a vastly used material in industry. Nowadays, it is proven that formaldehyde is toxic and carcinogenic. Thus providing a reliable method for its quantitative determination is very important. This study proposes a UV-Vis spectrophotometric based method for determination of formaldehyde. The method is based on reaction between the analyte and Fluoral P. Spectral changes during the time were mathematically analyzed using a chemometrics technique, called "multivariate curve resolution alternating least squares" (MCRALS). Data processing by this chemometrics technique enhanced the reliability of the UV-Vis spectrophotometry for quantitative analysis of formaldehyde in real samples.
- Khanmohammadi, Mohammadreza,Dalali, Nasser,Karami, Farshad,Garmarudi, Amir Bagheri,Nemati, Hossein
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- Photoinduced proton transfer promoted by peripheral subunits for some Hantzsch esters
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It is noted that, for a small series of 3,5-diacetyl-1,4-dihydrolutidine (DDL) derivatives and the corresponding Hantzsch esters, the presence of methyl groups at the 2,6-positions serves to extinguish fluorescence in solution but not in the solid state. Emission is weakly activated and affected by changes in solvent polarity. The latter situation arises because the optical transition involves intramolecular charge transfer. Calculations, both semiempirical and DFT, indicate that, in all cases, rotation of the carbonyl function is facile and that the dihydropyridine ring is planar. These calculations also indicate that the 2,6-methyl groups do not affect the generic structure of the molecule. It is proposed that illumination increases the molecular dipole moment and pushes electron density toward the carbonyl oxygen atom. Proton transfer can now occur from one of the methyl groups, leading to formation of a relatively low-energy, neutral intermediate, followed by a second proton transfer step that forms the enol. Reaction profiles computed for the ground-state species indicate that this route is highly favored relative to hydrogen transfer from the 4-position. The barriers for light-induced proton transfer are greatly reduced relative to the ground-state process but such large-scale structural transformations are hindered in the solid state. A rigid analogue that cannot form an enol is highly emissive in solution, supporting the conclusion that proton transfer is in competition to fluorescence in solution. (Figure Presented).
- Azizi, Sbastien,Ulrich, Gilles,Guglielmino, Maud,Le Calv, Stphane,Hagon, Jerry P.,Harriman, Anthony,Ziessel, Raymond
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- Synthesis and photochemistry of novel 3,5-diacetyl-1,4-dihydropyridines
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Some novel 3,5-diacetyl-1,4-dihydropyridine derivatives were synthesized; their photochemical behaviour was studied under oxygen or argon atmosphere. Irradiation of these compounds resulted in the aromatization of the ring and formation of 3,5-diacetylpyr
- Memarian, Hamid R.,Sadeghi, Majid M.,Momeni, Ahmad R.,Doepp, Dietrich
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- Azachalcone derivatives and their bis substituted analogs as novel antimycobacterial agents
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Fifteen novel substituted azachalcone derivatives and their bis substituted analogs were prepared from 3,5-diacetyl-2,6-dimethylpyridine by the Claisen-Schmidt condensation. The influence of the reaction conditions on the yield of mono- and bischalcones was studied to optimize the reaction. Spectral characteristics along with preliminary results of antimycobacterial activity of selected compounds are given.
- Kozmik, Vaclav,Lhotak, Pavel,Odlerova, Zelmira,Palecek, Jaroslav
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- Synthesis and Analgesic Activity of bis(3,4-dihydroquinoxalin-2(1H)-one) and bis(3,4-dihydro-2H-1,4-benzoxazin-2-one) Derivatives
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[Figure not available: see fulltext.] An ester condensation between 3,5-diacetyl-2,6-dimethylpyridine and an excess of diethyl oxalate was used for the preparation of 4,4'(2,6-dimethylpyridine-3,5-diyl)bis(2-hydroxy-4-oxobut-2-enoate). The synthesized hyd
- Kulakov, Ivan V.,Karbainova, Anastasiya A.,Shulgau, Zarina T.,Seilkhanov, Tulegen M.,Gatilov, Yurii V.,Fisyuk, Alexander S.
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- Chemical aromatization of 19-hydroxyandrosta-1,4-diene-3,17-dione with acid or alkaline: Elimination of the 19-hydroxymethyl group as formaldehyde
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In order to determine whether or not a 19-hydroxymethyl group of 19-hydroxyandrosta-1,4-diene-3,17-dione (2, 19-hydroxy ADD), an intermediate of aromatase-catalyzed estrone formation from ADD, a suicide substrate of aromatase, is eliminated as formaldehyde, we examine chemical nature of removal of the 19-hydroxymethyl group. 19-Acetate 3 and 19-tert-butyldimethylsiloxy compound 4 are known to convert rapidly to estrone with treatment of NaOH or n-Bu4NF. Since compound 2 was unstable and unobtainable under these conditions, compounds 3 and 4 as equivalents to compound 2 were used in this study. The acetate 3 with 5 mol/l HCl in acetone and 10% KOH in MeOH along with the silyl ether 4 with 5 mol/l HCl in acetone and 1 mol/l n-Bu4NF in THF gave formaldehyde and estrone in which a ratio of the aldehyde to estrone was near 1. This result indicates that the 19-hydroxymethyl groups of compound 3 and 4 are eliminated as formaldehyde along with estrone derived from the steroid skeleton under the acid or base treatment. The findings suggest that a single hydroxylation at the 19 carbon of ADD (1) would be, chemically, all that was required for estrone formation.
- Numazawa, Mitsuteru,Yamashita, Kouwa,Kimura, Nao,Takahashi, Madoka
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- Laccase-catalyzed oxidation of Hantzsch 1,4-dihydropyridines to pyridines and a new one pot synthesis of pyridines
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The laccase-catalyzed oxidation of 1,4-dihydropyridines to pyridines using aerial O2 as the oxidant exclusively delivers pyridines with yields up to 95% under mild reaction conditions. Combination of the Hantzsch 1,4-dihydropyridine synthesis with the newly developed laccase-catalyzed oxidation forms the basis of a facile and environmentally benign method for the synthesis of pyridines in one pot.
- Abdel-Mohsen, Heba T.,Conrad, Juergen,Beifuss, Uwe
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- A cholesterol benzoate RRS probe for the determination of trace ammonium ions
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The measurement of NH4+ has attracted considerable attention with the increase of NH4+ emissions in sewage caused by human activities. So far, a variety of photometric and fluorescence methods for the detection of NH4+ have been researched and summarized, but there is no report about the use of liquid crystals (LCs) cholesteryl benzoate (CB) as a resonance Rayleigh scattering (RRS) probe to determine ammonium ions. In the NaAc-HAc buffer solution with pH = 4.80, the yellow compounds 3,5 diacetyl-1,4 dihydrolutidine (DDL) generated by the reaction of NH4+ with acetylacetone (AT) and formaldehyde (HCHO) act as the energy receiver and CB as the donor. Because the RRS spectrum of CB overlaps with the DDL absorption spectrum, resonance Rayleigh scattering energy transfer (RRS-ET) occurs. When the NH4+ concentration increased, the generated DDL increased, and the RRS-ET also increased, so the RRS intensity of the system at 395 nm decreased. For this reason, a fast and sensitive CB RRS-ET method was established to apply to the detection of NH4+ in water. The detection range was 1.00 × 10?3 ? 4.66 μg/mL, and the detection limit was 6.62 × 10?3 μg/mL. Using this method to analyze and detect NH4+ in environmental water samples, the precision and recovery rate were between 1.30–9.30% and 95.5–109.9%, respectively. Therefore, this method has the advantages of sensitivity and simplicity.
- Chen, Shuxin,Jiang, Zhiliang,Liao, Liping,Lv, Xiaowen,Wen, Guiqing,Xiao, Yang
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- Application of ammonium acetate as a dual rule reagent-catalyst in synthesis of new symmetrical terpyridines
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Herein, we present a green, efficient and simple synthetic route to the new symmetrical terpyridines by using ammonium acetate (NH4OAc) as catalytically active reagent. Various techniques including Fourier transform infrared (FT‐IR) spectroscop
- Gu, Yanlong,Torabi, Morteza,Yarie, Meysam,Zolfigol, Mohammad Ali
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- Frustrated Lewis Pair Catalyzed Dehydrogenative Oxidation of Indolines and Other Heterocycles
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An acceptorless dehydrogenation of heterocycles catalyzed by frustrated Lewis pairs (FLPs) was developed. Oxidation with concomitant liberation of molecular hydrogen proceeded in high to excellent yields for N-protected indolines as well as four other substrate classes. The mechanism of this unprecedented FLP-catalyzed reaction was investigated by mechanistic studies, characterization of reaction intermediates by NMR spectroscopy and X-ray crystal analysis, and by quantum-mechanical calculations. Hydrogen liberation from the ammonium hydridoborate intermediate is the rate-determining step of the oxidation. The addition of a weaker Lewis acid as a hydride shuttle increased the reaction rate by a factor of 2.28 through a second catalytic cycle.
- Maier, Alexander F. G.,Tussing, Sebastian,Schneider, Tobias,Fl?rke, Ulrich,Qu, Zheng -Wang,Grimme, Stefan,Paradies, Jan
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supporting information
p. 12219 - 12223
(2016/10/13)
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- One-pot, three-component synthesis of 1,4-dihydropyridines in PEG-400
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A series of Hantzsch 1,4-dihydropyridines were synthesized by one-pot condensation of aldehyde, β-dicarbonyl compound, and ammonium acetate in polyethylene glycol (PEG-400) at 90°C. This method has the advantages of good yields, less pollution, and simple reaction conditions. Copyright
- Wang, Xicun,Gong, Haipeng,Quan, Zhengjun,Li, Lei,Ye, Helin
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experimental part
p. 3251 - 3258
(2011/09/30)
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- Direct amino acid-catalyzed cascade reductive alkylation of arylacetonitriles: High-yielding synthesis of ibuprofen analogs
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A novel approach for a one-pot, three-component reductive alkylation (TCRA) reaction of arylacetonitriles-containing electron-withdrawing groups with aldehydes/ketones and 1,4-dihydropyridine via iminium-catalysis has been developed. Many TCRA reaction products have direct applications in agricultural and pharmaceutical chemistry.
- Ramachary, Dhevalapally B.,Shiva Prasad
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supporting information; experimental part
p. 5246 - 5251
(2010/11/03)
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- One-pot synthesis and aromatization of 1,4-dihydropyridines in refluxing water
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A series of 1,4-dihydropyridines were synthesized in an environmentally benign method, by reacting aldehydes with acetoacetate esters or acetylacetone and ammonium acetate in refluxing water. The thus formed 1,4-dihydropyridines was subsequently oxidized in one-pot to the corresponding pyridine derivatives by either ferric chloride or potassium permanganate. Georg Thieme Verlag Stuttgart.
- Xia, Jing-Jing,Wang, Guan-Wu
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p. 2379 - 2383
(2007/10/03)
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- Low-emission formaldehyde donor preparations and use thereof
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The invention relates to a preservative with reduced formaldehyde emission which comprisesa) at least one formal andb) at least one emission-reducing additive which is chosen from urea, urea derivatives, amino acids, guanidine and guanidine derivatives, where the preservative(i) comprises no iodopropynyl compound and(ii) no derivative of IH-benzimidazol-2-carbamic acid, and to a process for the preparation of the preservative and to the use of the preservative in a technical product.
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- Hydrogen transfer from hantzsch 1,4-dihydropyridines to carbon-carbon double bonds under microwave irradiation
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1,4-Dihydropyridines (DHPs) have been used in the reduction of carbon-carbon double bonds under microwave irradiation without solvent. The efficiency of the reactions is dramatically dependent on the steric effects in the DHPs and on the electronic effects in the olefins.
- Torchy, Severine,Cordonnier, Guy,Barbry, Didier,Vanden Eynde, Jean Jacques
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p. 528 - 533
(2007/10/03)
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- PREPARATION OF NEW ORGANIC LUMINOPHORES BASED ON 3,5-DIACETYLPYRIDINES
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The reaction of acetylacetone or sodium salt of oxymethyleneacetone with corresponding aldehydes has been used to prepare 3,5-diacetyl-1,4-dihydropyridines III which have been oxidized to diacetylpyridines VII.These compounds have been transformed by an acid-catalyzed reaction with benzaldehyde into the chalcones VIII which have been utilized for the Kroehnke synthesis of luminophoric terpyridines I and II.
- Lhotak, Pavel,Kurfuerst, Antonin
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p. 1937 - 1946
(2007/10/02)
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- UREAS IN ORGANIC SYNTHESIS. II. SYNTHESIS OF HYDROGENATED ACRIDINE-1,8-DIONES AND 1,4-DIHYDROPYRIDINES BY REACTION OF UREAS WITH 1,3-DICARBONYL COMPOUNDS.
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Urea and its methyl derivatives are convenient reagents in a new single-stage method for the synthesis of compounds of the 1,4-dihydropyridine and pyridine series.Like benzaldehyde, under the discovered conditions benzyl alcohol gives hydrogenated 9-phenyltetramethylacridine-1,8-dione in reaction with urea and dimedone.
- Bakibaev, A. A.,Filimonov, V. D.
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p. 736 - 740
(2007/10/02)
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- The mechanism of the reaction of the Nash and the Sawicki aldehyde reagent
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Synthetic and chromatographic studies are presented on the Nash and Sawicki colorimetric methods for quantitating formaldehyde.It is shown that the actual color-forming agent in the Nash method is an isolable iminodione formed in situ by reaciton of the t
- Compton, Bruce Jon,Purdy, William C.
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p. 2207 - 2211
(2007/10/02)
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