- Ynamide-Mediated Intermolecular Esterification
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An ynamide-mediated one-pot, two-step intermolecular esterification via the condensation of carboxylic acids with nucleophilic hydroxyl species was reported. A broad substrate scope with respect to carboxylic acids, alcohols, and phenols was observed. The α-acyloxyenamide intermediates formed by the addition of carboxylic acids to ynamides proved to be effective acylating reagents for the esterification of alcohol and phenol derivatives with the assistance of base catalysis. Notably, the racemization of the α-chiral center of carboxylic acids can be avoided.
- Wang, Xuewei,Yang, Yang,Zhao, Yongli,Wang, Sheng,Hu, Wenchang,Li, Jinmei,Wang, Zihao,Yang, Fengling,Zhao, Junfeng
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p. 6188 - 6194
(2020/05/26)
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- Exploring the influence of designer surfactant hydrophobicity in key C–C/C–N bond forming reactions
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Designer micellar medium was explored for the transformation of diverse anilines to the corresponding densely substituted biologically relevant skatole derivatives in an aqueous medium via 5-exo-trig cyclization reaction. The scope of the reaction was extended to intermolecular Csp2-Csp2 and Csp2-N bond forming reactions in water. Systematic investigations revealed that altering hydrophobicity of surfactant influences the yield of both C–C and C–N bond forming reactions in water.
- Reddy, Singarajanahalli Mundarinti Krishna,Kothandapani, Jagatheeswaran,Sengan, Megarajan,Veerappan, Anbazhagan,Selva Ganesan, Subramaniapillai
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- A novel aromatic carbocation-based coupling reagent for esterification and amidation reactions
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A novel tropylium-based coupling reagent has been developed to facilitate the synthesis of a series of esters, amides, lactones and peptides under mild reaction conditions. Remarkably, this reagent can be used in catalytic amounts in conjunction with a sacrificial reagent, offering a new and efficient method for nucleophilic coupling reactions of carboxylic acids.
- Nguyen, Thanh V.,Lyons, Demelza J.M.
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supporting information
p. 3131 - 3134
(2015/06/17)
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- Influence of electronically and sterically tunable cinnamate ligands on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine) palladium(0) olefin complexes
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A detailed study of the influence of electronic and steric characteristics of cinnamic acid esters on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine)palladium(0) cinnamic acid ester complexes is presented (51 different new complexes included). These complexes show a dynamic behavior on the NMR spectroscopic time scale. Therefore, the rotational barriers of the olefin about the metalolefin bond as well as the dissociation entropy and enthalpy of the olefin and the dissociation mechanism could be determined. These findings are interpreted together with the NMR spectroscopic, IR spectroscopic, and X-ray structural data (7 new structures included) concerning the influence of the different olefin ligands on the complex properties by means of Hammett plots. DFT calculations were performed to support the mechanistic conclusions.
- Buchner, Magnus R.,Bechlars, Bettina,Wahl, Bernhard,Ruhland, Klaus
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experimental part
p. 588 - 601
(2012/03/22)
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- TMSOTf-catalyzed intramolecular seleno-arylation of tethered alkenes: A novel method for the solid-phase synthesis of dihydrocoumarins and coumarins
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TMSOTf-catalyzed intramolecular seleno-arylation of tethered alkenes was performed using polystyrene-supported succinimidyl selenide as the selenium source. This catalytic process provides an efficient method for the regioselective synthesis of dihydrocoumarins possessing a seleno-functionality, followed by traceless cleavage of selenium linker to provide dihydrocoumarins and coumarins in good yields and purities.
- Tang,Li, Wen,Gao, Zhang Yong,Gu, Xi
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body text
p. 631 - 634
(2012/07/03)
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- NHC-catalyzed C-O or C-N bond formation: Efficient approaches to α,β-unsaturated esters and amides
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Simple and efficient NHC-catalyzed transformations of bromoenal or α,β-dibromoenal into α,β-unsaturated esters or amides with high stereoselectivity through C-O or C-N bond formation have been demonstrated. The NHC-catalyzed processes occur under mild con
- Zhang, Bo,Feng, Peng,Cui, Yuxin,Jiao, Ning
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supporting information; experimental part
p. 7280 - 7282
(2012/07/28)
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- Selective synthesis of 3,4-dihydrocoumarins and chalcones from substituted aryl cinnamic esters
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Coumarins are ubiquitous in plant kingdom and have been used as antitumor, antifungals, anticoagulants, insecticides. Chalcones are also widespread in plant kingdom and have been known to possess diverse biological activities; antibacterial, antifungal, antitumor and anti-inflammatory, etc. As they are considered as important natural products, numerous synthetic approaches have been reported up to the present. We devise a new selective method of preparing dihydrocoumarins and chalcones from aryl cinnamates by the selection of reagents. Dihydrocoumarin derivatives were prepared selectively by using intramolecular cyclization catalyzed by p-toluene sulfonic acid. Also, chalcones were prepared by Fries-rearrangement catalyzed by TiCl4. This method can be used for preparing various coumarin & chalcone compounds.
- Jeon, Jae-Ho,Yang, Deok-Mo,Jun, Jong-Gab
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experimental part
p. 65 - 70
(2011/10/31)
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- Conjugate addition of lithium N -phenyl- N -(α-methylbenzyl)amide: Application to the asymmetric synthesis of (R)-(-)-angustureine
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The conjugate addition of lithium (R)-N-phenyl-N-(α-methylbenzyl) amide to a range of α,β-unsaturated 4-methoxyphenyl esters proceeds with excellent levels of diastereoselectivity to give the corresponding β-amino esters in good yield and as single diaste
- Bentley, Scott A.,Davies, Stephen G.,Lee, James A.,Roberts, Paul M.,Thomson, James E.
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supporting information; experimental part
p. 2544 - 2547
(2011/06/25)
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- Preyssler catalyst: An efficient catalyst for esterification of cinnamic acids with phenols and imidoalcohols
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In the present work a series of eco-friendly Preyssler solid acids and their salts H14[NaP5W29MoO110] (PW), H14[NaP5W30O110] (PWMo), K12.5Na1.5[NaP5W30O110]·15H2O (PWK), K12.5Na1.5[NaP5W29MoO110]·15H2O (PWMoK) and 10% silica-supported H14[NaP5W29MoO110] (PWSiO2), and H14[NaP5W30O110] (PWMoSiO2) have been used as catalysts for the direct esterification of cinnamic acids with phenols or 2-(N-phthalimidoethanol). Effects of the reaction conditions were studied, including temperature, reaction time, and type and amount of catalyst. These solids were characterized by several techniques, such as diffuse reflectance spectroscopy, Fourier transformed infrared spectroscopy, optical and scanning electron microcopies, and X-ray diffraction, among others. The most adequate catalyst for performing the title reaction was H14[NaP5W30O110] (PWMo). The catalyst was applied for the synthesis of various substituted cinnamates, giving very good yields.
- Ruiz, Diego M.,Romanelli, Gustavo P.,Vázquez, Patricia G.,Autino, Juan C.
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experimental part
p. 110 - 119
(2010/11/04)
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- Ru(III)-Catalyzed Cyclization of Arene-Alkene Substrates via Intramolecular Electrophilic Hydroarylation
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(Matrix presented) We herein report that RuCl3/AgOTf has proven to be a hydroarylation catalyst with an efficiency and scope superior to previously known methods. This catalyst demonstrated consistent performance with arene-ene substrates of diverse structural features, providing good to excellent yields of cyclization products (chromanes, tetralins, terpenoids, dihydrocoumarins).
- Youn, So Won,Pastine, Stefan J.,Sames, Dalibor
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p. 581 - 584
(2007/10/03)
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- Stereoselectivity and mechanism in the electrohydrodimerisation of esters of cinnamic acid
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Rate constants (kobs) and reaction orders have been determined for the cathodic reduction in DMF solution of 11 cinnamiic acid esters including some derived from chiral alcohols and a dicinnamate derived from trans-cyclohexane-1,2-diol.The cinn
- Fussing, Ingrid,Guellue, Mustafa,Hammerich, Ole,Hussain, Abid,Nielsen, Merete Folmer,Utley, James H. P.
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p. 649 - 658
(2007/10/03)
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- Electrochemical generation and reactions of acyloxytriphenylphosphonium ions
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Constant-current electrolysis, in an undivided cell, of Ph3P in the presence of a carboxylic acid in CH2Cl2 containing 2,6-lutidinium perchlorate as the supporting electrolyte was shown to generate the corresponding acyloxyphosphonium ion, Ph3P+-OCOR, which was converted in situ to esters, amides, and β-lactams under mild conditions.
- Ohmori, Hidenobu,Maeda, Hatsuo,Kikuoka, Masayuki,Maki, Toshihide,Masui, Masaichiro
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p. 767 - 776
(2007/10/02)
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- Metal Ion Effects in Intramolecular Reactions. Effects of Divalent Metal Ions on Intramolecular Acetamido Group Participation in Ester Hydrolysis
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The hydrolysis reactions of a series of esters of α-acetamidocinnamic acid proceed with formation of an oxazolinone intermediate.In 50percent dioxane-H2O (v/v) at 50 deg C, an oxazolinone can be observed spectrophotometrically in the OH- catalyzed cyclization reactions of the α-acetamido-substituted esters with leaving groups of pKa 12.4 or less.In comparison with the OH- catalyzed hydrolysis of the corresponding cinnamate esters, the rate enhancement due to the presence of the acetamido group is a factor of 200 with the trifluoroethyl ester and increases to 2x1E6 with the p-nitrophenyl ester.The plot of log kOH vs ?, the Hammett substituent constant, is linear and has a slope (ρ) of 2.7 (1.8 when ?- is employed) for the cyclization reactions of the phenolic esters, but the ρ value is only 1.4 for the OH- catalyzed hydrolysis of the corresponding cinnamates.The slope of log kOH vs the pKa of the leaving group for the cyclization of the α-acetamidocinnamic acid derivatives, βlg, is -0.9.Thus, there must be considerable C-O bond breaking in the critical transition state for oxazolinone formation.In H2O as the solvent, 6-carboxy-2-pyridylmethyl α-(N-acetylamino)cinnamate and the corresponding 2-pyridylmethyl derivative cyclize rapidly to the oxazolinone with KOH (5xE4)-fold larger than that for hydrolysis of 2-pyridylmethyl cinnamate, even though the leaving group is an aliphatic alcohol.There is significant metal ion catalysis in the cyclization reactions with Cu2+, Ni2+, Co2+ or Zn2+.The binding of the metal ions to the 6-carboxy-substituted derivative is very strong, and saturation occurs at metal ion concentrations less than 0.01 M.A saturating concentration of Cu2+ (0.001 M) enhances the rate of cyclization by a factor of 5x1E4.Thus, the total rate enhancement provided by bifunctional catalysis (Cu2+ and the neighboring acetamido group) is 1E9-fold.Metal ion binding to 2-pyridylmethyl α-(N-acetylamino)cinnamate is weak, but nevertheless, the second-order rate constants kOH are similar to those of the 6-carboxy-substituted ester at equal metal ion concentrations.The metal ions must exert their catalytic effect by stabilizing the leaving group alcohol in the transition state.This appears to be a general mechanism for metal ion catalysis of reactions in which C-O bond breaking is the rate-determining step.
- Fife, Thomas H.,Przystas, Theodore J.,Pujari, Mahesh P.
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p. 8157 - 8163
(2007/10/02)
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- APPLICATION OF THE PHOTO-FRIES REARRANGEMENT OF ARYL DIHYDROCINNAMATES TO THE SYNTHESIS OF FLAVONOIDS
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The photo-Fries rearrangement of aryl dihydrocinnamates is compared with that of the analogous cinnamates from a preparative point of view.The former proceeds with higher conversions, giving the corresponding 2'-hydroxydihydrochalcones in acceptable yields.This process, combined with well established reactions, provides an alternative entry to the synthesis of flavonoids.
- Garcia, Hermenegildo,Iborra, Sara,Miranda, Miguel A.,Primo, Jaime
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p. 1983 - 1989
(2007/10/02)
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