Ionic Liquid–Mediated Knoevenagel Condensation of Meldrum's Acid and Aldehydes

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 rate is observed in Brönsted acidic ionic liquid 1‐methylimidazolium trifluoroacetate [Hmim]Tfa, which furnishes quantitative yields with 4–30 min in most of the cases. Furthermore, ionic liquid is easily reused without any appreciable loss in activity.     

Organic Reactions in Ionic Liquids: Ionic Liquid Ethylammonium Nitrate–Promoted Knoevenagel Condensation of Meldrum's Acid With Aromatic Aldehydes

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.     

o-Iodoxy Benzoic Acid–Mediated Synthesis of 3,5-Diarylisoxazoles and Isoxazole-3-carboxylic Acids

A new, convenient, ecofriendly synthesis of 3,5-diarylisoxazoles is reported from α,β-unsaturated ketoximes. Similarly, a novel synthesis of isoxazole carboxylic acids is also reported. Both the methods use efficient, environmentally friendly, and nontoxic iodoxybenzoic acid (IBX) as an oxidative cyclizing reagent. Easy procedure, environmentally benign reaction conditions, and nontoxicity are advantages to the methodology.     

Organic Reactions in Ionic Liquids: Ionic Liquid Promoted Knoevenagel Condensation of Aromatic Aldehydes with (2‐Thio)Barbituric Acid

Abstract

The Knoevenagel condensation of aromatic aldehydes with (2‐thio)barbituric acid proceeded efficiently in reusable ionic liquids, EAN, BmimBF₄, and BmimPF₆ at room temperature in the absence of any catalyst with high yields.     

Synthesis of Substituted Coumarins via Brønsted Acid Mediated Condensation of Allenes with Substituted Phenols or Anisoles

Coumarins were obtained from the condensation of electron-rich arenes with allenes in the presence of TfOH in good yield. Depending on the substituent pattern of allenes employed, the general synthetic method of 4-substituted and 3,4-disubstituted 3-arylcoumarins has been developed. Readily available allenes were employed as the three-carbon atom sources constituting the coumarin skeleton.     

Ionic Liquid–Mediated,One-Pot Synthesis for 4-Thiazolidinones

A convenient one-pot, three-component cyclocondensation mediated by ionic liquid for obtaining 2,3-disubstituted-4-thiazolidinones with excellent yields is reported.     

Single-Pot Synthesis of Spiroannulated Dihydrofurans by Iodine–Ammonium Acetate–Mediated Reaction of Dimedone with Aldehydes

Iodine–ammonium acetate–mediated annealation of dimedone with aldehydes led to facile formation of spirodihydrofuran in good yields through tandem Knoevenagel–Michael iodonation and cyclodehydroiodonation reactions in a single pot.     

Efficient Synthesis of Dicycloalkenopyridines： One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free α,α'-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two α-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one α-methylene position alternatively resulted in 10-ary...     

L-Proline Catalyzed Solvent-Free Knoevenagel Condensation for the Synthesis of 3-Substituted Coumarins

L-Proline was utilized as an efficient organo-catalyst for the environmentally benign synthesis of 3-substituted coumarins by the Knoevenagel condensation of substituted 2-hydroxybenzaldehydes with reactive methylene compounds under solvent free conditions.     

Synthesis of Tetrahydrofuran and Tetrahydropyran Derivatives Catalyzed by Tungstophosphoric Acid in Ionic Liquid

Synthesis of tetrahydrofuran and tetrahydropyran derivatives catalyzed by tungstophosphoric acid （H3PW12040） were conveniently performed with high yield from the corresponding unsaturated alcohols in ionic liquid. Sufuric acid （H2SO4）, trifluoromathanesulfonic acid （TfOH） and p-toluenesulfonic acid （TsOH） were also explored for preparing these products in ionic liquid. The catalysts and ionic liquid can be easily recovered and reused.     

A Simple,Microwave-Assisted,and Solvent-Free Synthesis of 2-Arylbenzothiazoles by Acetic Acid–Promoted Condensation of Aldehydes with 2-Aminothiophenol in Air

An efficient and simple procedure has been developed for the synthesis of various 2-arylbenzothiazoles by acetic acid–promoted condensation of 2 -aminothiophenol with aromatic aldehydes under microwave irradiation and solvent-free conditions in high yields.     

Copper(II) Acetate–Mediated Cross-Coupling of Phenylboronic Acids with Aryloximes: Synthesis of O-Aryloximes

A novel method for the synthesis of O-aryloxime is described. It consisted of the coupling reaction between phenylboronic acids and aryloximes in the presence of catalytic quantities of copper(II) acetate. This reaction takes place in the presence of pyridine under a mild condition (DCE, Rt, 24–36 h) with moderate yield. It represents a good alternative to known methods for O-aryloxime synthesis.     

Determination of Indole-3-acetic Acid and Abscisic Acid by Double-Direction Dispersive Liquid–Liquid Microextraction Coupled with High-Performance Liquid Chromatography

A method for the separation and purification of indole-3-acetic acid and abscisic acid based on double-direction dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography was developed. The reverse-direction dispersive liquid–liquid microextraction procedure was very efficient in the purification of the hormones. The forward-direction dispersive liquid–liquid microextraction procedure was very efficient in the enrichment of the analytes. Under optimum conditions, a linear response was observed over the ranges of 0.2 µg/g to 200.0 µg/g for indole-3-acetic acid and 0.1 µg/g to 200.0 µg/g for abscisic acid, with correlation coefficients of 0.9967 and 0.9983. The limits of detection for indole-3-acetic acid and abscisic acid were 0.02 µg/g and 0.01 µg/g. The recoveries by standard addition were 91.4% and 88.6% for indole-3-acetic acid and abscisic acid with corresponding relative standard deviations of 4.5% and 6.1% (n = 5). The developed method was used for the preconcentration and determination of indole-3-acetic acid and abscisic acid in Arabidopsis thaliana, and satisfactory results were obtained.     

Lewis Acid–Mediated Domino Reaction of 3-Bromomethylthiophenes with Arenes/Heteroarenes

Lewis acid–mediated domino reaction of 3-bromomethylthiophenes with various types of arenes and heteroarenes is reported.     

CuI–Ionic Liquids as Efficient Reaction Media for the Synthesis of Pyran Skeleton via Domino Knoevenagel–Hetero–Diels–Alder Reaction with Unactivated Alkynes

The article describes ionic liquids [bmim][NO₃] in the presence of 30% mol CuI as efficient media for the domino Knoevenagel–hetero–Diels–Alder reaction of o-propargyloxy benzaldehydes as unactivated terminal alkynes with some active methylene compounds. Short reaction time, easy workup, good to excellent yields, and mild conditions are advantages of this new media.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Clean Synthesis in Water：Darzens Condensation Reaction of Aromatic Aldehydes with Phenacyl Chloride

The Darzens condensation reaction of aromatic aldehydes with phenacyl chloride proceeded very efficiently in a water suspension medium in the presence of triethylbenzylammonium chloride and only trans-2,3-epoxy-1,3-diaryl-1-propanones were formed which can be isolated simply by filtration.The structures of these compounds were confirmed by elemental analysis,IR and ^1H NMR spectra.Therir configurations are in agreement with that of the same compounds reported in the literature.Compared to the classical Darzens condensation,this new method has the advantages of good yields,high stereoselectivity,low running cost inexpensive and environmentally benign procedure.     

Asymmetric Synthesis of α-Amino Phosphonic Acids Employing the Condensation of Nitrones with Phosphite Derivatives

Abstract

Chiral α-amino phosphonic acid derivatives were synthesized by condensing an enantiomerically homogeneous diazasilyl phosphite with a series of prochiral nitrones. The reactions proceed under mild conditions with moderate to high enantioselectivities and good yields.     

Condensation of p-Benzoquinone with Anilides of β-Aminocrotonic Acid

Benzofuranone derivatives have been synthesized by the condensation of p-benzoquinone with anilides of -aminocrotonic acids under the conditions of the Nenitzescu reaction.