- Bentonite catalyzed an efficient and green synthesis of arylidene meldrum's acid derivatives in aqueous media
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In the present paper, a simple, highly efficient, and environmentally friendly protocol was proposed for the Knoevenagel condensation reaction of aromatic aldehydes using Meldrum’s acid (2,2-dimethyl-4,6-dioxo-1,3-dioxane) with bentonite as an available n
- Yahyazadehfar, Mahdieh,Ahmadi, Sayed Ali,Sheikhhosseini, Enayatollah,Ghazanfari, Dadkhoda
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p. 513 - 519
(2021/07/25)
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- Enantioselective Ammonium Ylide Mediated One-Pot Synthesis of Highly Substituted γ-Butyrolactones
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An ammonium ylide mediated access towards trans-β,γ-disubstituted, all-trans-α,β,γ-trisubstituted, and α,α,β,γ-tetrasubstituted γ-butyrolactones bearing a broad variety of functionalities was developed. Starting from widely accessible benzylidene Meldrum's acid derivatives and α-bromo carbonyl compounds, γ-butyrolactones were obtained in yields between 32–99% with up to excellent diastereoselectivities (>95:5) via a DABCO-mediated [2+1] annulation. Utilization of enantiomerically pure cinchona alkaloid derivatives enables the first asymmetric ammonium ylide mediated method to provide (3R,?4R)-β,γ-disubstituted and (2R,?3R,?4R)-α,β,γ-trisubstituted γ-butyrolactones in moderate to good yields with up to very good enantiomeric ratios (97:3). The scalability of the transformation was proven while determining the absolute configuration. (Figure presented.).
- Drennhaus, Till,?hler, Laura,Djalali, Saveh,H?fmann, Svenja,Müller, Clemens,Pietruszka, J?rg,Worgull, Dennis
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supporting information
p. 2385 - 2396
(2020/04/30)
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- An alternative, practical, and ecological protocol for synthesis of arylidene analogues of Meldrum’s acid as useful intermediates
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This paper presents an ecological protocol for Knoevenagel condensation using a catalytic amount of 4,4′-trimethylenedipiperidine as a versatile, efficient, safe, commercially available, inexpensive, and recyclable organocatalyst by a ball-milling process
- Khaligh, Nader Ghaffari,Mihankhah, Taraneh,Johan, Mohd Rafie
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- Microwave-associate synthesis of Co3O4 nanoparticles as an effcient nanocatalyst for the synthesis of arylidene barbituric and Meldrum's acid derivatives in green media
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In this study, Co3O4 nanocatalysts were constructed in environmentally appropriate conditions using controlled, effective, and facile microwave method. The final nanostructures were characterized by SEM, XRD, and TEM analyses. The products had a small size distribution, homogeneous morphology, and crystallographic structures associated with the formation of Co3O4 nanostructures. Moreover, EDS mapping analysis confirmed the existence of Co and O elements in the final structure, and the magnetic properties of the samples were investigated by VSM. The application of this nanostructure in a catalytic process was further examined, and the results suggested that it could be used as a novel candidate for the synthesis of arylidene barbituric and Meldrum,s acid through Knoevenagel condensation of aldehydes by barbituric and Meldrum,s acid in aqueous media. The high yield of these nanocatalysts would be justified by the nature of the nanostructure as well as the experimental procedure developed in this study, which affected the physicochemical features of the products.
- Yahyazadehfar, Mahdieh,Sheikhhosseini, Enayatollah,Ahmadi, Sayed Ali,Ghazanfari, Dadkhoda
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- A transition metal free expedient approach for the C[dbnd]C bond cleavage of arylidene Meldrum's acid and malononitrile derivatives
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A transition metal free expedient approach for the C[dbnd]C bond cleavage of electron deficient alkenes such as arylidene Meldrum's acid and malononitrile derivatives are discussed. The C[dbnd]C bond of these compound were cleaved to benzoic acid in good yield at high temperature. Most importantly, with oxone in CH3CN/H2O at 45 °C or m-CPBA in DCM or NaClO2 in THF/H2O or PIDA in THF at room temperature furnished benzaldehyde derivatives selectively in excellent yields.
- Suresh, Muthiah,Kumari, Anusueya,Singh, Raj Bahadur
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- With the plaque and A β of the nerve fiber entanglement having affinity to the compound and its preparation method
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The invention provides a compound provided with good affinity and tangled with an Abeta plaque and a nerve fiber. The structural general formula (I) of the compound is as shown in the specification, wherein W is a benzo-hexahydric aromatic ring or a hexah
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Paragraph 0131-0132
(2018/04/26)
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- Synthesis of bis-spiro cyclopropanes based on Meldrum's acid by milling
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Reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid) with various solid aldehydes in the presence of cyanogen bromide and solid sodium ethoxide (EtONa) leads to the selective and efficient formation of bis-spiro cyclopropanes based on Meldrum's acid at the range of 0 °C to room temperature. The products were obtained in good to excellent yields. Structure elucidation is carried out by 1H NMR, 13C NMR, FT-IR spectroscopy, mass analyses and X-ray crystallography techniques. A possible mechanism for the formation of products is also discussed under solvent-free condition.
- Kashani, Elmira,Noroozi Pesyan, Nader,Tun?, Tuncay,Sahin, Ertan
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p. 249 - 256
(2015/03/31)
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- Di- and triarylmethylium ions as probes for the ambident reactivities of carbanions derived from 5-benzylated Meldrum's acid
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The kinetics of the reactions of carbocations with carbanions 1 derived from 5-benzyl-substituted Meldrum's acids 1-H (Meldrum's acid=2,2-dimethyl-1,3- dioxane-4,6-dione) were investigated by UV/Vis spectroscopic methods. Benzhydryl cations Ar2CH+ added exclusively to C-5 of the Meldrum's acid moiety. As the second-order rate constants (kC) of these reactions in DMSO followed the linear free-energy relationship lg k=s N(N+E), the nucleophile-specific reactivity parameters N and s N for the carbanions 1 could be determined. In contrast, trityl cations Ar3C+ reacted differently. While tritylium ions of low electrophilicity (E-2) reacted with 1 through rate-determining β-hydride abstraction, more Lewis acidic tritylium ions initially reacted at the carbonyl oxygen of 1 to form trityl enolates, which subsequently reionized and eventually yielded triarylmethanes and 5-benzylidene Meldrum's acids by hydride transfer.
- Chen, Xi,Tan, Yue,Berionni, Guillaume,Ofial, Armin R.,Mayr, Herbert
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supporting information
p. 11069 - 11077
(2014/10/15)
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- Synthesis of new guanidium-meldrum acid zwitterionic salts and dynamic NMR study of rotational energy barrier around C-NH bond of guanidine moiety
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Synthesis of the Guanidium-Meldrum acid zwitterionic salts was developed through a three component reaction of 2, 2-dimethyl-1, 3-dioxane-4, 6-dione (Meldrum acid), aromatic aldehydes and N, N, N', N'- Tetramethyl-guanidine in benzen at room temperature.
- Aminkhani, Ali
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p. 1791 - 1797
(2015/04/27)
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- Nickel nanoparticles catalyzed chemoselective Knoevenagel condensation of Meldrum's acid and tandem enol lactonizations via cascade cyclization sequence
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A novel protocol has been reported wherein, polyethylene glycol (PEG) stabilized nickel nanoparticles have been used as catalyst for chemoselective Knoevenagel condensation of aromatic aldehydes and Meldrum's acid to give 5-arylidene Meldrum's acid which underwent tandem enol lactonization by Michael addition/cyclization sequence with active methylene compounds in the presence of Ni nanoparticles to give corresponding enol lactone derivatives.
- Khurana, Jitender M.,Vij, Kanika
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experimental part
p. 3666 - 3669
(2011/07/29)
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- Facile Knoevenagel and domino Knoevenagel/Michael reactions using gel-entrapped base catalysts
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An efficient method for Knoevenagel condensation of arenecarbaldehydes with active methylene compounds such as barbituric acid and Meldrum's acid in the presence of gel-entrapped base catalysts is reported. The method has been extended to the one-pot synthesis of arylmethylene-bis[3-hydroxycyclohex-2-en-1- one] derivatives from dimedone (=5,5-dimethylcyclohexane-1,3-dione) and arenecarbaldehydes by using domino Knoevenagel/Michael reaction sequence. Copyright
- Shinde, Shital,Rashinkar, Gajanan,Kumbhar, Arjun,Kamble, Santosh,Salunkhe, Rajashri
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experimental part
p. 1943 - 1951
(2012/01/04)
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- Synthesis and biological evaluation of arylidene analogues of Meldrum's acid as a new class of antimalarial and antioxidant agents
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A series of arylidene analogues of Meldrum's acid were synthesized and evaluated for in vitro antimalarial and antioxidant activities for the first time. The influence of various physico-chemical parameters such as dielectric constant (), donor number (DN
- Sandhu, Harmeet S.,Sapra, Sameer,Gupta, Mukesh,Nepali, Kunal,Gautam, Raju,Yadav, Sunil,Kumar, Raj,Jachak, Sanjay M.,Chugh, Manoj,Gupta, Manish K.,Suri, Om P.,Dhar
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experimental part
p. 5626 - 5633
(2010/09/11)
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- Knoevenagel condensation of aldehydes with Meldrum's acid in ionic liquids
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The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in the recyclable ionic liquid [bmim]BF4 at room temperature in the presence of catalytic amounts of piperidine.
- Tahmassebi, Daryoush,Wilson, Levi J. A.,Kieser, Jerod M.
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experimental part
p. 2605 - 2613
(2009/12/04)
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- Electrophilicity parameters of 5-benzylidene-2,2-dimethyl[1,3]dioxane-4,6- diones (benzylidene meldrum's acids)
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(Chemical Equation Presented) Kinetics of the reactions of four benzylidene Meldrum's acids 1 with acceptor-substituted carbanions 2 were studied photometrically in DMSO at 20°C. The reactions follow second-order kinetics, and the second-order rate consta
- Kaumanns, Oliver,Mayr, Herbert
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p. 2738 - 2745
(2008/09/20)
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- Tandem molybdenum catalyzed hydrosilylations: An expedient synthesis of β-aryl aldehydes
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The synthesis of β-aryl aldehydes utilizing a tandem molybdenum catalyzed hydrosilylation is described. This new functional group interconversion provides an efficient method for the two-carbon homologation of aryl aldehydes.
- Frost, Christopher G.,Hartley, Benjamin C.
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p. 4259 - 4261
(2008/02/12)
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- Ionic liquid-mediated knoevenagel condensation of Meldrum's acid and aldehydes
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A simple, efficient, and green protocol for Knoevenagel condensation of Meldrum's acid and aldehydes in ionic liquid at room temperature without any catalyst is described. The reaction has been performed in different ionic liquids. The enhancement in the
- Darvatkar, Nitin B.,Deorukhkar, Amol R.,Bhilare, Sachin V.,Salunkhe, Manikrao M.
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p. 3043 - 3051
(2007/10/03)
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- Organic reactions in ionic liquids: Ionic liquids ethylammonium nitrate promoted Knoevenagel condensation of aromatic aldehydes with active methylene compounds
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The Knoevenagel condensation of aromatic aldehydes with active methylene compounds proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields.
- Hu, Yi,Chen, Jue,Le, Zhang-Gao,Zheng, Qin-Guo
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p. 739 - 744
(2007/10/03)
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- Organic reactions in ionic liquids: Ionic liquid ethylammonium nitrate-promoted knoevenagel condensation of meldrum's acid with aromatic aldehydes
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The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields. Copyright Taylor & Francis, Inc.
- Hu, Yi,Wei, Ping,Huang, He,Le, Zhang-Gao,Chen, Zhen-Chu
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p. 2955 - 2960
(2007/10/03)
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- Solvent-free Knoevenagel condensations and Michael additions in the solid state and in the melt with quantitative yield
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Numerous Knoevenagel condensations of solid or liquid aromatic aldehydes are performed with four barbituric acids, Meldrum's acid, dimedone, cyanoacetamide, malodinitrile and methyl cyanoacetate in stoichiometric mixtures of the solids or of stoichiometri
- Kaupp, Gerd,Naimi-Jamal, M. Reza,Schmeyers, Jens
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p. 3753 - 3760
(2007/10/03)
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- Knoevenagel condensation of aldehydes with cyclic active methylene compounds in water
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A new route of Knoevenagel condensation of aromatic aldehydes with Meldrum's acid, barbituric acid and dimedone in the presence of cetyltrimethyl ammonium bromide at room temperature in water is described.
- Ren, Zhongjiao,Cao, Weiguo,Tong, Weiqi,Jing, Xiuping
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p. 1947 - 1952
(2007/10/03)
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- Kinetic studies of condensation of aromatic aldehydes with Meldrum's acid
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The condensation reaction of Meldrum's acid with aromatic aldehydes in the presence of a catalyst has been investigated spectrophotometrically at 25-50 °C. The reaction follows overall second order kinetics, first order in each of the reactants. Electron-
- Medien
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p. 1320 - 1326
(2007/10/03)
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- Condensation of aromatic aldehydes with acidic methylene compounds without catalyst
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The condensation of aromatic aldehyde with isopropylidene malonate or 5,5-dimethyl-1,3-cyclohexanedione is carried out in DMF as solvent without catalyst.
- Shi, Daqing,Wang, Yucheng,Lu, Zaisheng,Dai, Guiyuan
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p. 713 - 726
(2007/10/03)
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- 3-Hydroxypyrroles and 1H-Pyrrol-3(2H)-ones. Part 13. Reactions of Methoxymethylene Meldrum's Acids with 3-Hydroxypyrroles, with 3-Methoxypyrroles and with other Active Substrates, and Pyrolytic Heterocyclizations of the Products
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Methoxymethylene Meldrum's acid 2 in acetonitrile solution acts a useful C-electrophile for active substrates such as pyrrole, indole or tertiary enaminones to give substitution products (e.g. 5, 6 or 12, respectively).Primary enaminones react exlusively at the nitrogen atom under these conditions.The effect of the ring substituents on the regiochemistry of electrophilic substitution of 3-hydroxypyrroles and 3-methoxypyrroles was studied using methoxymethylene Meldrum's acid as the electrophile.Flash vacuum pyrolysis of the Meldrum's acid derivatives obtained in many of these reactions gave access to a range of heterocyclic systems, including the pyridone 48, quinolinedione 43, benzazepinedione 41 and fused pyrones 50, 52 and 54.
- Derbyshire, Paul A.,Hunter, Gordon A.,McNab, Hamish,Monahan, Lilian C.
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p. 2017 - 2026
(2007/10/02)
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- New Aspects in the Reaction of Azomethines with Cyclic CH-Acidic Compounds
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Treatment of substituted benzylidene anilines 1a - f with cyclic CH-acidic compounds 2a - m in ethanol at room temperature yields in addition/elimination reactions the corresponding arylidene derivatives 4 and the 2:1 adducts 5.The addition products 3, which are formed as intermediates, could not be isolated in any case.The donor/acceptor effect of the substituents on the benzylidene moiety influences to a significant extent the reactivity towards the azomethine carbon. Keywords.Azomethine; CH-Acidic compound; Addition/elimination reaction.
- Hennig, Lothar,Alva-Astudillo, Mario,Mann, Gerhard,Kappe, Thomas
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p. 571 - 580
(2007/10/02)
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- Nucleophilic Addition to Olefins. 21. Substituent and Solvent Effects on the Reaction of Benzylidene Meldrum's Acids with Piperidine and Morpholine
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Rate (k1) and equilibrium constants (K1) for piperidine and morpholine addition to benzylidene Meldrum's acid (BMA) and substituted BMA's (Z=4-NO2, 3-Cl, 4-CN, 4-OMe, 4-NMe2, 4-NEt2) were determined in water and in 50percent, 70percent, and 90percent aqueous Me2SO.The equilibrium for addition is highly favorable, with K1 values (piperidine) as high as 7.8*107M-1, which is the highest value measured in a series of olefins of the type PhCH=CXY.The rates are also quite high (k1 up to 2.1*106M-1s-1), indicating a relatively high intrinsic rate constant (k0=k1 for K1=1) which ranks BMA second among seven PhCH=CXY-type olefins with respect to kinetic reactivity.This ranking is "reasonable" based on a correlation between k0 for nucleophilic addition to PhCH=CXY and k0 for deprotonation of carbon acids of the type CH2XY.βnucn (d log k1/ d log K1, variation of amine) is very amall, particularly in aqueous solution.This result appears to be part of a trend toward lower βnucn values with increasing thermodynamic stability of the adducts of PhCH=CXY. αnucn (d log k1/ d log K1, variation of Z) is significantly larger than βnucn, implying a substantial imbalance in these reactions.However, after correction of αnucn for the effect of the developing positive charge on the amine nitrogen the remaining "true" imbalance is quite small.The small imbalance as well as the high k0 value are consistent with the Meldrum's acid anion deriving most of its exceptional stability from its bislactone structure rather than from resonance.Strong ?-donor substituents (4-NMe2, 4-NEt2) have a strong stabilizing effect on the olefin, leading to a large reduction in K1.Contrary to expectations based on the principle of nonperfect synchronization (PNS), this resonance effect does not lead to a strong reduction of the intrinsic rate constant, probably because the polarization in the olefin (Me2N+=C6H4+CHC(COO)2-C(CH3)2) helps in partially offsetting the PNS effect caused by delayed development of resonance on the carbanionic side of the adduct
- Bernasconi, Claude F.,Panda, Markandeswar
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p. 3042 - 3050
(2007/10/02)
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