- Synthesis, characterization, crystal structure, Hirshfeld surface analysis, antioxidant properties and DFT calculations of a novel pyrazole derivative: Ethyl 1-(2,4-dimethylphenyl)-3-methyl-5-phenyl-1H-pyrazole-4-carboxylate
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An effective route for the direct synthesis of substituted pyrazole through 3+2 annulation method was described. (E)-ethyl 2-benzylidene-3-oxobutanoate was prepared from ethyl acetoacetate and benzaldehyde via Knoevenagel approach. The cyclocondensation r
- Kumar, A. Dileep,Kumar, K. Ajay,Kumara, Karthik,Lokanath, N. K.,Naveen, S.,Warad, Ismail,Zarrouk, Abdelkader
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Read Online
- Amino-based metal-organic frameworks as stable, highly active basic catalysts
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Metal-organic frameworks (MOFs) with non-coordinated amino groups, i.e. IRMOF-3 and amino-functionalized MIL-53, are stable solid basic catalysts in the Knoevenagel condensation of ethyl cyanoacetate and ethyl acetoacetate with benzaldehyde. IRMOF-3D
- Gascon, Jorge,Aktay, Ugur,Hernandez-Alonso, Maria D.,van Klink, Gerard P.M.,Kapteijn, Freek
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Read Online
- Immobilized proton sponge on inorganic carriers: The synergic effect of the support on catalytic activity
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1,8-bis(dimethylaminonaphthalene) (DMAN), a proton sponge, was grafted onto amorphous and pure-silica MCM-41. The results show that DMAN supported on MCM-41 is an excellent base catalyst for the Knoevenagel condensation between benzaldehyde and different active methylene compounds as well as for the Claisen-Schmidt condensation of benzaldehyde and 2′-hydroxyacetophenone to chalcones and flavanones. The influence of the solvent and the polarity of the support on the activity of the catalysts was studied. It was found that the activity of the supported catalyst is directly related to the polarity of the inorganic support. Moreover, the support can also preactivate the reagents by interaction of the carbonyl groups with the weakly acidic silanol groups of the MCM-41. This preactivation step enables DMAN, anchored onto MCM-41, to abstract protons with a higher pKa than that of the DMAN. Finally, the study of the deactivation and recycling of the DMAN anchored onto MCM-41 catalysts showed that it is a stable material with respect to deactivation and leaching and results in comparable rates in successive batch reactions.
- Corma,Iborra,Rodriguez,Sanchez
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Read Online
- The Knoevenagel reaction in water catalyzed by zwitterionic liquids
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Three hydroxyl functionalized zwitterionic liquids (ZILs) were found to be novel recyclable catalysts for the Knoevenagel condensation between aldehydes or ketones and active methylene compounds in aqueous medium. Both aldehydes and ketones gave satisfactory results. The products could simply be separated from the catalysts/water, and the catalysts could be recycled six times without noticeably decreasing the catalytic activity.
- Fang, Dong,Fei, Zheng-Hao,Liu, Zu-Liang
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Read Online
- Binary caesium-lanthanum oxide supported on MCM-41: A new stable heterogeneous basic catalyst
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Heterogeneous mesoporous stable basic catalysts have been prepared by wet or solid-state impregnation of MCM-41 with caesium acetate and lanthanum nitrate followed by thermal decomposition. 133Cs MAS NMR data of CsLa/MCM-41 show an increase in
- Kloetstra,Van Laren,Van Bekkum
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Read Online
- On the enantioselective phosphoric-acid-catalyzed hantzsch synthesis of polyhydroquinolines
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A reinvestigation of a chiral phosphoric-acid-catalyzed four-component Hantzsch enantioselective synthesis of polyhydroquinolines reported in 2009 is presented. In our hands, when the reaction was performed with fidelity to the original report using a chiral enantiopure phosphoric acid catalyst, no enantioselectivity was observed. Unlike in the original report, enantioselectivity results are backed by baseline separation of the enantiomers by HPLC analyses on chiral stationary phase with UV and chiroptical detection.
- Bonne, Damien,Bressy, Cyril,Bugaut, Xavier,Constantieux, Thierry,Jean, Marion,Lemaitre, Clément,Quinonero, Ophélie,Rodriguez, Jean,Roussel, Christian,Vanthuyne, Nicolas
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supporting information
p. 3394 - 3398
(2021/05/29)
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- Asymmetric Synthesis of Pentasubstituted Cyclohexanes through Diphenylprolinol Silyl Ether Mediated Domino Michael/Michael Reaction
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An asymmetric domino Michael/Michael reaction of α,β-unsaturated aldehydes 1 and α-acetyl-β-substituted-α,β-unsaturated esters 2 catalyzed by diphenylprolinol silyl ether was developed. This is a formal carbo [4+2] cycloaddition reaction affording penta-s
- Hayashi, Yujiro,Matoba, Hiroaki,Mori, Naoki,Odoh, Amaechi Shedrack,Umekubo, Nariyoshi,Aidanp??, Louise
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supporting information
p. 6670 - 6673
(2021/12/31)
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- Highly Active Bisamino Functionalized Zr(IV)-UiO-67 Metal-Organic Framework for Cascade Catalysis
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This work reports the synthesis and characterization of Zr(IV)-based UiO-67-(NH2)2 (called 1) metal-organic framework. Activated 1 (named 1') was shown to be an efficient tandem catalyst in the conversion of benzaldehydedimethyl acet
- Das, Aniruddha,Anbu, Nagaraj,Mostakim,Dhakshinamoorthy, Amarajothi,Biswas, Shyam
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supporting information
p. 2830 - 2834
(2020/07/04)
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- Metal free biomimetic deaminative direct C-C coupling of unprotected primary amines with active methylene compounds
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An unprecedented direct C-C coupling reaction of unprotected primary amines with active methylene compounds is reported. The reaction involves a biomimetic deamination of amines which was achieved under conditions free of metallic reagents and strong oxidizing agents. A wide range of primary amines was reacted with different active methylene compounds to provide structurally diverse trisubstituted alkenes and dihydropyridines. A kinetic study revealed an activation barrier of 10.1 kcal mol-1 for the conversion of a key intermediate of the reaction.
- Ghosh, Santanu,Jana, Chandan K.
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supporting information
p. 10153 - 10157
(2019/12/26)
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- Highly Efficient Synthesis of Substituted 3,4-Dihydropyrimidin-2-(1H)-ones (DHPMs) Catalyzed by Hf(OTf)4: Mechanistic insights into reaction pathways under metal Lewis acid catalysis and solvent-free conditions
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In our studies on the catalytic activity of Group IVB transition metal Lewis acids, Hf(OTf)4 was identified as a highly potent catalyst for”one-pot, three-component” Biginelli reaction. More importantly, it was found that solvent-free conditions, in contrast to solvent-based conditions, could dramatically promote the Hf(OTf)4-catalyzed formation of 3,4-dihydro-pyrimidin-2-(1H)-ones. To provide a mechanistic explanation, we closely examined the catalytic effects of Hf(OTf)4 on all three potential reaction pathways in both “sequential bimolecular condensations” and “one-pot, three-component” manners. The experimental results showed that the synergistic effects of solvent-free conditions and Hf(OTf)4 catalysis not only drastically accelerate Biginelli reaction by enhancing the imine route and activating the enamine route but also avoid the formation of Knoevenagel adduct, which may lead to an undesired byproduct. In addition, 1H-MMR tracing of the H-D exchange reaction of methyl acetoacetate in MeOH-d4 indicated that Hf(IV) cation may significantly accelerate ketone-enol tautomerization and activate the β-ketone moiety, thereby contributing to the overall reaction rate.
- Kong, Rui,Han, Shuai-Bo,Wei, Jing-Ying,Peng, Xiao-Chong,Xie, Zhen-Biao,Gong, Shan-Shan,Sun, Qi
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- The Employment of Sodium Hydride as a Michael Donor in Palladium-catalyzed Reductions of α, β-Unsaturated Carbonyl Compounds
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Sodium hydride was employed as a Michael donor under the catalysis of PdCl2 for 1,4-conjugate reductions of α, β-unsaturated carbonyl compounds, which features operational simplicity, mild conditions and high atom-economy. The merits of NaH as a reductant were demonstrated by the one-pot or cascade reactions for the syntheses of complex molecules. (Figure presented.).
- Liu, Ye,Mao, Yujian,Hu, Yanwei,Gui, Jingjing,Wang, Liang,Wang, Wei,Zhang, Shilei
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supporting information
p. 1554 - 1558
(2019/02/16)
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- Cross-linked polystyrene-TiCl4 complex as a reusable Lewis acid catalyst for solvent-free Knoevenagel condensations of 1,3-dicarbonyl compounds with aldehydes
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Cross-linked polystyrene copolymer beads with the average particle size in the range of (50–80 mesh size) were prepared by a new method, characterized and functionalized with titanium tetrachloride to afford the corresponding polystyrene?titanium tetrachloride complex in one step reaction and characterized by FT-IR, UV, TGA, DSC, XRD, SEM, BET. This polymer metal complex (PS/TiCl4) was used as a heterogeneous, recoverable, reusable Lewis acid for solvent-free Knoevenagel condensations of 1,3-diketones with aromatic aldehydes under green and mild conditions. The rate of reactions was found to decrease with an increasing percentage of crosslinking and the mesh size of the copolymer beads. This complex showed good stability and catalytic activity in the Knoevenagel reactions.
- Rahmatpour, Ali,Goodarzi, Niloofar
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- Four-component synthesis of polyhydroquinolines under catalyst- and solvent-free conventional heating conditions: mechanistic studies
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A convenient and environmentally friendly procedure for the synthesis of polyhydroquinolines via a one-pot, four component condensation of different aromatic aldehydes with dimedone, ethyl acetoacetate and ammonium acetate has been developed. Upon heating
- Mayurachayakul, Pipattra,Pluempanupat, Wanchai,Srisuwannaket, Choladda,Chantarasriwong, Oraphin
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p. 56764 - 56770
(2017/12/27)
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- Base-free Knoevenagel condensation catalyzed by copper metal surfaces
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For the first time Knoevenagel condensation has been catalyzed by elemental copper with unexpected activity and excellent isolated yields. Inexpensive, widely available copper powder was used to catalyze the condensation of cyanoacetate and benzaldehyde under mild conditions. To ensure general applicability, a wide variety of different substrates was successfully reacted.
- Schneider,Zeltner,Kr?nzlin,Grass,Stark
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supporting information
p. 10695 - 10698
(2015/06/30)
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- Raman spectroscopy as a tool for monitoring mesoscale continuous-flow organic synthesis: Equipment interface and assessment in four medicinally-relevant reactions
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An apparatus is reported for real-time Raman monitoring of reactions performed using continuous-flow processing. Its capability is assessed by studying four reactions, all involving formation of products bearing α,β-unsaturated carbonyl moieties; synthesi
- Hamlin, Trevor A.,Leadbeater, Nicholas E.
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supporting information
p. 1843 - 1852
(2013/10/22)
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- Stereoselective synthesis of α-ylidene-β-dicarbonyl compounds: A mild PhI(OAc)2-mediated dehydrogenation process
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PhI(OAc)2-mediated dehydrogenation of α-alkyl-β-dicarbonyl compound has been developed to afford α-ylidene-β- dicarbonyl compounds with high stereoselectivity under mild conditions. This process provides a complementary entry to stereoselectivity for the Knoevenagel reaction.
- Fan, Liyan,Chen, Wen,Tang, Kunshan,Wu, Dongbei
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p. 940 - 942
(2012/11/06)
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- Biocatalytic Knoevenagel reaction using alkaline protease from Bacillus licheniformis
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BLAP (alkaline protease from Bacillus licheniformis) was used as a biocatalyst in the Knoevenagel condensations of aromatic, hetero-aromatic and α;β-unsaturated aldehydes with less reactive acetylacetone or ethyl acetoacetate. The reactions were performed in organic solvent in the presence of water. The functionalized trisubstituted alkenes and α,β,γ, δ-unsaturated carbonyl compounds could be obtained in moderate to good yields with E/Z selectivities up to >99:1. This biocatalytic reaction provided an alternative pathway for Knoevenagel condensation, which also demonstrates a novel case of unnatural activity of existing enzymes.
- Xie, Bang-Hua,Guan, Zhi,He, Yan-Hong
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experimental part
p. 238 - 244
(2012/06/30)
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- Strong organic bases as building blocks of mesoporous hybrid catalysts for C-C forming bond reactions
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1,8-Bis(tetramethylguanidino)naphthalene (TMGN), a neutral organic base that combines the properties of guanidine and the properties of proton sponges, was used as a building block to produce organic-inorganic silica-based mesoporous hybrids with strong basic properties. The TMGN-based mesoporous hybrids (TMGN/SiO2) were prepared by a sol-gel route working at a neutral pH and low temperatures, which avoided the use of SDAs. TMGN has been modified in order to have two terminal reactive silyl groups able to perform co-condensation with a conventional organosilane (TMOS) used as a silicon source. This synthesis has allowed us to directly introduce the unmodified, functionalized TMGN as part of the walls of the mesoporous silica by a one-pot synthesis. TMGN/SiO2 hybrid materials present excellent catalytic properties for C-C bond forming reactions: Knoevenagel, Henry (nitroaldol), and Claisen-Schmidt condensations. The activity of the hybrid materials is higher than that of the counterpart homogeneous catalyst. The TMGN/SiO2 hybrid catalyst was synthesized using 1,8-bis(tetramethylguanidino)naphthalene (TMGN). It combines the properties of guanidine and of proton sponges. A functionalized TMGN builder was introduced directly into a nonordered mesoporous silica by the NH4F-catalyzed sol-gel route. This catalyst shows good catalytic performances in C-C bond forming reactions. Copyright
- Gianotti, Enrica,Diaz, Urbano,Velty, Alexandra,Corma, Avelino
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p. 5175 - 5185
(2013/01/15)
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- Efficient solvent-free knoevenagel condensation between -diketone and aldehyde catalyzed by silica sulfuric acid
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Silica sulfuric acid has been utilized as an efficient heterogeneous recyclable catalyst for Knoevenagel condensation between poorly reactive β-diketones and aldehydes under solvent-free conditions. This protocol also works well with more reactive β-ketoesters. The condensation is efficient, clean, and mild. The scope and generality of the Knoevenagel condensation were investigated. The procedure led only to the Knoevenagel product, and no side product derived from a subsequent Michael βaddition of -diketone to alkene was detected at rt. Increasing temperature led to a subsequent Michael addition, and it was applied to the efficient synthesis of 9-aryl-1,8-dioxo- octahydroxanthene derivatives.
- Zhang, Fuyi,Wang, Yu-Xin,Yang, Feng-Ling,Zhang, Hong-Yu,Zhao, Yu-Fen
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scheme or table
p. 347 - 356
(2011/04/16)
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- An efficient iodine-catalysed Knoevenagel condensation reaction in the presence of acetic anhydride
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A mild, simple and efficient iodine catalysed system has been developed for the Knoevenagel condensation of 1,3-dicarbonyl compounds with various aromatic aldehydes in the presence of acetic anhydride. The reaction gave good to excellent yields for a broad range of substrates.
- Li, Zhong-Xian,Liu, Xiao-Pei,Qiu, Zhen,Xu, Dan,Yu, Xue-Jun
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experimental part
p. 35 - 36
(2011/04/24)
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- Efficient synthetic method of Z-selective 2-halo-1,3-dienes from reactions of allenols possessing ethoxycarbonyl and vinyl group with indium trihalide
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An efficient synthetic method of Z-selective 3-ethoxycarbonyl-2-halo-1,3- dienes and 3-vinyl-2-halo-1,3-dienes was developed from the reaction of allenols having ethoxycarbonyl and vinyl group with indium trihalides at room temperature in CH2Cl
- Eom, Dahan,Kim, Sung Hong,Lee, Phil Ho
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scheme or table
p. 645 - 649
(2010/08/06)
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- A simple method for the preparation of functionalized trisubstituted alkenes and α,β,γ,δ-unsaturated carbonyl compounds by using natural amino acid l-tryptophan
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Primary natural amino acid l-tryptophan was used, for the first time, as a catalyst in Knoevenagel condensations of aliphatic, aromatic, hetero-aromatic and α,β-unsaturated aldehydes with less reactive acetylacetone and ethyl acetoacetate. The reactions were carried out at room temperature and gave good yields. It is a convenient entry for preparation of functionalized trisubstituted alkenes and α,β,γ,δ-unsaturated carbonyl compounds.
- Hu, Ying,He, Yan-Hong,Guan, Zhi
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scheme or table
p. 656 - 659
(2010/11/05)
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- Domino imino-aldol-aza-Michael reaction: One-pot diastereo- and enantioselective synthesis of piperidines
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Addition of α-arylmethylidene- or α-alkylidene-β-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to subst
- Ghorai, Manas K.,Halder, Sandipan,Das, Raj Kumar
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supporting information; experimental part
p. 7061 - 7072
(2010/12/25)
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- Solvent-free NbCl5 catalyzed condensation of 1,3-dicarbonyl compounds and aldehydes: a facile synthesis of trisubstituted alkenes
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A simple preparation of trisubstituted alkenes by condensation of β-diketones or β-ketoesters with aldehydes in presence of NbCl5 as a Lewis acid catalyst in solvent-free conditions is described.
- Yadav,Bhunia, Dinesh C.,Singh, Vinay K.,Srihari
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experimental part
p. 2470 - 2473
(2009/08/09)
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- Nano-silica PAMAM dendrimer as a novel catalyst for Knoevenagel reactions
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A nano-silica dendrimer, poly(amidoamine)-grafted nanosilica (nano-PAMAM), catalyzed the Knoevenagel reaction of aryl and aliphatic aldehydes with various active methylene compounds at room temperature in good yields. The reaction conditions were mild eno
- Hagiwara, Hisahiro,Sekifuji, Masayoshi,Tsubokawa, Norio,Hoshi, Takashi,Suzuki, Toshio
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p. 926 - 927,2
(2020/08/31)
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- Cu(OTf)2 catalyzed Biginelli type condensation of aldehydes, β-keto esters and carbamates: Synthesis of 3,4-dihydro[1,3]oxazin-2-ones
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Cu(OTf)2 catalyzes effectively a new multicomponent reaction comprising aldehydes, β-ketoester and methyl carbamate in acetonitrile to afford substituted 3,4-dihydro[1,3]oxazin-2-ones in 60-82% yields. These compounds have been found to show inhibition activity against HL-60 cancer cell.
- Jagdale, Arun R.,Paraskar, Abhimanyu S.,Sudalai, Arumugam
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p. 1091 - 1095
(2008/12/23)
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- Synthesis of ethyl 5-hydroxyisoxazolidine-4-carboxylates via michael addition/intramolecular hemiketalisation
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The 1,4-addition of N,O-bis(trimethylsilyl)hydroxylamine to alkylideneacetoacetates gave, in high yield, new 5-hydroxyisoxazolidine-4- carboxylates. The results of the accurate computational investigation on the mechanism at the DFT level are in complete
- Benfatti, Fides,Bottoni, Andrea,Cardillo, Giuliana,Gentilucci, Luca,Monari, Magda,Mosconi, Elisa,Stenta, Marco,Tolomelli, Alessandra
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scheme or table
p. 6119 - 6127
(2009/05/31)
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- An efficient method for the selective iodination of ?±,?2- unsaturated ketones
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An efficient approach to ?±,?2-unsaturated ?±'-iodo ketones directly from ?±,?2-unsaturated ketones by selective iodination at the ?±'-position, without effect on the double bond and the activated benzene ring, in the presence of copper (II) oxide/iodine is described. The present method has the advantages of high yields, short reaction times, inexpensive reagents, mild reaction conditions, ease of manipulation, and the formation of cleaner products. ? Georg Thieme Verlag Stuttgart ?· New York.
- Wang, Zihua,Yin, Guodong,Qin, Jing,Gao, Meng,Cao, Liping,Wu, Anxin
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scheme or table
p. 3675 - 3681
(2009/06/18)
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- Rearrangement of propargylic esters: Metal-based stereospecific synthesis of (E)- and (Z)-knoevenagel derivatives
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Alkoxy-substituted propargylic esters undergo regioselective 1,3-acyloxy migration in the presence of Pt(II) and Cu(I) catalysts, allowing the preparation of α-ylidene-β-keto and -malonate esters. The reaction proved to also be stereodivergent as the Pt(II) and the Cu(I) catalysts perform the isomerization with complementary Z/E selectivity. Moreover, alkynyl-conjugated Knoevenagel products are produced from (bisalkynyl)methyl acetates. In such a case, the reaction is chemoselective as the 1,3-acetyl migration takes place through the alkoxyalkyne group in preference over the phenylalkyne group. The resulting (E)-alkynylenone unit suffers metal-catalyzed cyclization into the furyl ring, generating a copper(I) carbene species. Copyright
- Barluenga, Jose,Riesgo, Lorena,Vicente, Ruben,Lopez, Luis A.,Tomas, Miguel
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p. 7772 - 7773
(2008/02/08)
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- Neat reaction technology: A green tool
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A solvent free approach for organic synthesis is described which involve microwave exposure of neat reactants. A variety of cyclization and condensation are carried out including the efficient one pot assembly of heterocyclic molecules from in situ genera
- Kidwai, Mazaahir,Mothsra, Poonam
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p. 2330 - 2336
(2007/10/03)
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- Synthesis of some new unsymmetrically substituted 1,4-dihydropyridines
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A series of some new 3,5-unsymmetrically substituted 1,4-dihydropyridines have been synthesized, which have ethoxycarbonyl and acetyl groups on 3- and 5-positions, respectively. A three-step procedure has been examined to increase the yield of the desired products, by suppressing the formation of the symmetrically substituted 3,5-diacetyl-1,4-dihydropyridines and 3,5-diethoxycarbonyl-1,4-dihydropyridines.
- Memarian, Hamid R.,Abdoli-Senejani, Masumeh,D?pp, Dietrich
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- Neat reaction technology for the synthesis of novel 1,5-benzodiazepines
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A convenient, solvent-free, green approach is described for the synthesis of novel 1,5-benzodiazepines by the reaction of ethylacetoacetate, aldehyde, and o-phenylenediamine without any catalyst at pH 7. Copyright Taylor & Francis Group, LLC.
- Kidwai, Mazaahir,Mothsra, Poonam
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p. 817 - 824
(2007/10/03)
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- Organic Reactions in Ionic Liquids: Knoevenagel Condensation Catalyzed by Ethylenediammonium Diacetate
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The moisture and air stable ionic liquids 1-butyl-3-methylimidazonium tetrafluoroborate [bmim]BF4 and 1-butyl-3-methylimidazonium hexafluorophosphate [bmim]PF6 were used as 'green' recycle alternatives to volatile organic solvents (VOCs) for ethylenediammonium diacetate (EDDA) catalyzed Knoevenagel condensation between aldehydes or ketones with active methylene compounds. Both aldehydes and ketones gave satisfactory results. The ionic liquids containing catalyst EDDA were recycled several times with no decrease in yields and reaction rates. In the case of 2-hydroxybenzaldehyde, the reactions led to the formation of 3-substituted coumarins under standard reaction conditions.
- Su, Ce,Chen, Zhen-Chu,Zheng, Qin-Guo
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p. 555 - 559
(2007/10/03)
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- Potassium triiodide. A new and efficient catalyst for carbon-carbon bond formation in aqueous media
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Potassium triiodide catalyses the condensation of carbonyl compounds with active methylene compounds in aqueous media to afford E olefinic products in high yields.
- Thakur, Ashim J.,Prajapati, Dipak,Gogoi, Baikuntha J.,Sandhu, Jagir S.
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p. 258 - 259
(2007/10/03)
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- Research on heterocyclic compounds. XLIII. Synthetic studies on 1,4-dihydropyridine derivatives
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In order to obtain N-benzyl-3,5-dicarbethoxy-2,6-dimethyl-4-phenyl-1,4-dihydropyridine 1 as a lead compound of pharmacological interest, the classical Hantzsch synthetic method and the modified Collie procedure were used. However, only a very low yield of
- Rimoli, Maria Grazia,Avallone, Lucia,Zanarone, Serena,Abignente, Enrico,Mangoni, Alfonso
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p. 1117 - 1122
(2007/10/03)
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- An easy-to-use heterogeneous catalyst for the knoevenagel condensation
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Physical mixtures of alkali and earth alkali metal carbonates and commercially available zeolites were investigated as solid catalysts for the Knoevenagel condensation. Best results for the model reaction between benzaldehyde and ethyl cyanoacetate were o
- Siebenhaar,Casagrande,Studer,Blaser
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p. 566 - 569
(2007/10/03)
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- L-aryl(heteryl)-2-ethoxycarbonyl-3-trimethylsiloxy-1,3-butadienes in diene synthesis. Synthesis of 2-hydroxy-4-aryl(heteryl)-9,10-anthraquinone derivatives
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A high reactivity in the (4+2)-cycloaddition of synthesized l-aryI(heteryl)-2-ethoxycarbonyl-3-trimethylsil-oxy-1,3-butadienes was revealed. The regio- and stereoselectivity of the cycloaddition to unsymmetrical dienophiles was studied. A general preparat
- Shults,Petrova,Rybalova,Gatilov,Tolstikov
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p. 845 - 855
(2007/10/03)
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- Cadmium Iodide as a New Catalyst for Knoevenagel Condensations
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Cadmium iodide catalyses the condensation of aldehydes with active methylene compounds, in the absence of solvent, to afford olefinic products in high yields.
- Prajapati, Dipak,Sandhu, Jagir S.
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p. 739 - 740
(2007/10/02)
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- Bismuth(III) chloride as a New Catalyst for Knoevenagel Condensation in the Absence of Solvent
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The Knoevenagel condensation of various aldehydes was carried out under heterogeneous catalysts conditions using bismuth(III) chloride in absence of solvent.The method gives high yields of Knoevenagel products.
- Prajapati, Dipak,Sandhu, Jagir S.
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p. 1945 - 1946
(2007/10/02)
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- XXXIV. THE CYCLIC ANALOGS OF LEVUGLANDINS. STUDY OF THE STRUCTURAL CHARACTERISTICS OF THE ALLYL-ALCOHOL SIDE CHAIN
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Some reactions of 5-methyl-2-methoxy-4-ethoxycarbonyl-3R-2,3-dihydrofurans were studied in a development of the synthetic approach to new cyclic analogs of levuglandins.A path was developed for the construction of the "lower" chain.
- Tolstikov, G. A.,Miftakhov, M. S.,Valeev, F. A.,Khalikov, R. M.,Akhmetvaleev, R. R.,Khalilov, L. M.
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p. 1853 - 1861
(2007/10/02)
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- SYNTHESIS OF HETEROCYCLIC COMPOUNDS. XXXVI. PREPARATION OF ALKYL SUBSTITUTED PYRANCARBONITRLES.
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The cyclization of the ketonitriles obtained from the reaction of suitably substituted propenones with propanedinitrile leads to alkyl substituted 4H-pyrans.Some of the starting propenones had to be prepared by base promoted opening of an isoxazole ring in the presence of an aldehyde.An exception to the general synthesis is also reported.
- Soto, Jose L.,Seoane, Carlos,Martin, Nazario,Quinteiro, Margarita
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- Selective γ-Substitution of α,β-Unsaturated Esters via α-Trimethylsilyl β,γ-Unsaturated Esters
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In order to achieve selective γ-substitution of α,β-unsaturated esters, we investigated the directive effect of silicon in the reaction of various electrophiles with α-trimethylsilyl β,γ-unsaturated esters.These esters were prepared by nickel-catalyzed vinylation reactions of the lithium enolate of ethyl α-(trimethylsilyl)acetate.The α-silyl β,γ-unsaturated esters reacted with a variety of electrophiles (aldehydes, ketones, acetals, ketals, acid chlorides, and chloro thioethers) in the presence of Lewis acids (titanium tetrachloride and trimethylsilyl trifluoromethanesulfonate) to give exclusively the γ-substituted product in moderate to good yields.In some cases, the primary substitution products underwent additional conversions under the reaction conditions, such as the cyclization of the δ-hydroxyl or δ-keto enoates to dihydropyrones or pyrones, respectively.These α-silyl β,γ-unsaturated esters are effective reagents for achieving complete γ-selective substitution of α,β-unsaturated ester systems.
- Albaugh-Robertson, Pamela,Katzenellenbogen, John A.
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p. 5288 - 5302
(2007/10/02)
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