排序方式: 共有29条查询结果,搜索用时 15 毫秒
21.
Igor Yu. Grishin Nikolai A. Arutiunov Dmitrii A. Aksenov Nicolai A. Aksenov Alexander V. Aksenov Amina Z. Gasanova Elena A. Sorokina Carolyn Lower Michael Rubin 《Molecules (Basel, Switzerland)》2022,27(6)
3-(1H-Indol-3-yl)benzofuran-2(3H)-ones were efficiently accessed via polyphosphoric acid-mediated condensation of 3-(2-nitrovinyl)-1H-indoles with phenols. 相似文献
22.
Dr. Isaac G. Sonsona Dr. Juan V. Alegre-Requena Dr. Eugenia Marqués-López Prof. Dr. M. Concepción Gimeno Prof. Dr. Raquel P. Herrera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5469-5478
The first asymmetric catalyzed aza-Henry reaction of hydrazones is presented. In this process, quinine was used as the catalyst to synthesize different alkyl substituted β-nitrohydrazides with ee up to 77 %. This ee was improved up to 94 % by a further recrystallization and the opposite enantiomer can be obtained by using quinidine as the catalyst, opening exciting possibilities in fields in which the control of chirality is vital, such as the pharmaceutical industry. Additionally, experimental and ab initio studies were performed to understand the reaction mechanism. The experimental results revealed an unexpected secondary kinetic isotope effect (KIE) that is explained by the calculated reaction pathway, which shows that the protonation of the initial hydrazone and the C−C bond forming reaction occur during a concerted process. This concerted mechanism makes the catalysis conceptually different to traditional base-promoted Henry and aza-Henry reactions. 相似文献
23.
24.
József Kaizer Norbert Durkó Miklós Czaun Gábor Speier 《Reaction Kinetics and Catalysis Letters》2006,88(1):193-202
Summary The oxygenation of the potassium salts of alkylnitronates in absolute DMSO leads to potassium nitrite (nitrate) and the corresponding
aldehydes or ketones at 40°C. Kinetic measurements for potassium 1-propylnitronate (K-1-PN) resulted in the rate law -d[K-1-PN]/dt = k2[K-1-PN][O2]. The rate constant, activation enthalpy, and entropy at 313.16 K are as follows: k/M-1 s-1 = (1.43±0.04), DH‡/kJ mol-1 = 57±10 DS‡/J mol-1 K-1 = -60±32. The presence of superoxide ion as a result of a SET from the nitronate to dioxygen was proved by NBT test. 相似文献
25.
Excess volumes of V
E
of binary liquid mixtures of quinoline with each of the nitroalkanes have been measured at 30°C as a function of composition using a continuous dilution dilatometer. The excess volumes are negative over the whole mole-fraction range for all the mixtures except quinoline + nitromethane, which exhibits positive V
E
over the whole range. V
E
results have been analyzed in the light of the Prigogine-Flory-Patterson theory, which divides V
E
into three contributions. The agreement between experimental and theoretical values is reasonably good. 相似文献
26.
Nicolai A. Aksenov Alexander V. Aksenov Igor A. Kurenkov Nikita K. Kirillov Dmitrii A. Aksenov Nikolai A. Arutiunov Daria S. Aksenova Michael Rubin 《Molecules (Basel, Switzerland)》2022,27(9)
A highly efficient and expeditious one-pot approach towards 2-(3-oxoindolin-2-yl)acetonitriles was designed, which involves a base-assisted aldol reaction of ortho-nitroacetophenones, followed by hydrocyanation, triggering an unusual reductive cyclization reaction. 相似文献
27.
Nicholas Backstrom Neil A. Burton C. Ian F. Watt 《Journal of Physical Organic Chemistry》2010,23(8):711-722
Rate constants and kinetic isotope effects have been determined for the formation of nitronate anions from the ethers 1‐(2‐methoxyphenyl)‐2‐nitropropane, 7 (X = H, L = H and D) and 1‐(2‐methoxy‐5‐nitrophenyl)‐2‐nitropropane, 7 (X = NO2, L = H and D), and from the corresponding phenols, 1‐(2‐hydroxyphenyl)‐2‐nitropropane, 3 (X = H, L = H and D), and 1‐(2‐hydroxy‐5‐nitrophenyl)‐2‐nitropropane, 3 (X = NO2, L = H and D), in aqueous basic medium. For the ethers 7 , rates of deprotonation by hydroxide are comparable with those found for deprotonations of 2‐nitropropane, with kH/kD (25 °C) = 7.7 and 7.8, respectively. In both the cases, the isotope effects are conventionally temperature dependent. For the corresponding phenols 3 , conditions have been established under which the deprotonations of the nitroalkane are dominated by intramolecular deprotonation by the kinetically first‐formed phenolate anion, with an estimated effective molarity EM ~ 250. For 3 (X = H, L = H or D), kH/kD (25 °C) = 7.8, with E ? E = 6.9 kJ mol?1 and AH/AD = 0.5. For 3 (X = NO2, L = H or D), rates of intramolecular deprotonation are reduced 30‐fold, and an elevated kinetic isotope effect is found (kH/kD (25 °C) = 10.7). Activation parameters (E ? E = 17.8 kJ mol?1 and AH/AD = 0.008) are compatible with an enhanced tunnelling contribution to reactivity in the H‐isotopomer. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
28.
1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way. 相似文献
29.
A fast new entry for the stereoselective construction of γ-substituted vinyl sulfones is presented. The key for success is the use of a readily available chiral secondary amine catalyst that allows the use of base-sensitive β-nitroethyl sulfones as masked β-sulfonyl vinyl anions in conjugate additions. The method performed in a three-step one-pot operation gives access to a great variety of vinyl sulfones in good yields and with excellent enantioselectivities. The method has also been extended to other relatively base-sensitive β-electron-withdrawing-substituted nitroalkanes to afford products with manifold functionality, providing a quick entry to very attractive synthetic intermediates for organic synthesis. 相似文献