An environmentally benign,green, and efficient ionic liquid catalyzed synthesis of Quinoline derivatives via Knoevenagel condensation

The present investigation is in the interest of one-pot, environmentally friendly and efficient protocol for the synthesis of quinoline derivatives from 2-aminoarylketones and active methylene compounds in the presence of L-proline and ionic liquid 1,3-dimethylimidazolium methyl sulfate [MMIm][MSO₄]. The Ionic liquid which is used as a catalyst can be reused several times. The results obtained by using [MMIm][MSO₄] were also compared with those described in the literature. The advantages of the method are shorter reaction time, milder conditions, easy workup and better yields. The catalyst [MMIm][MSO₄] can be recovered for the subsequent reactions and reused without any appreciable loss of efficiency. This method of synthesis widens the applicability of Ionic liquids in heterocyclic compounds.     

An efficient synthesis of 9-anthrone lactone derivatives via the Knoevenagel condensation and intramolecular cyclization

One-step synthesis of 9-anthrone lactone derivatives from 1-acetyloxyanthraquinone with a variety of dicarbonyl substrates in the presence of K₂CO₃ by Knovenagel condensation and intramolecular cyclization is developed. Possible reaction mechanisms have been investigated using the density functional theory (DFT), which has been widely used in the study of reaction mechanism. The strategy could be useful for the synthesis of the core structure of marine natural product aspergiolide.     

An efficient synthesis of 2-Aminoethylidene-1,1-Bisphosphonates derivatives via Michael addition reaction

A facile, rapid and cheap synthetic strategy towards a wide range of novel 2-aminoethylidene-1,1-bisphosphonate derivatives was developed through the Michael addition reaction of various aromatic amines, aromatic amides as well as nucleoside analogues with tetraethyl ethenylidene-1,1-bisphosphonate. All the newly obtained compounds were characterized by ¹H, ³¹P, ¹³C NMR spectroscopy, IR and HR MS.     

One-pot efficient green synthesis of 1,4-dihydro-quinoxaline-2,3-dione derivatives

An efficient synthesis of the potential pharmacophore 1,4-dihydro-quinoxaline-2,3-dione (1) has been achieved in a one-pot reaction at room temperature from substitutedo-phenylene diamine and oxalic acid under solvent-free conditions by a simple grinding method with unsurpassed atom economy. Thermal and powder X-ray diffraction analysis was carried out for some hydrated crystals.     

A Novel Approach towards 2,3,5-Trisubstituted Thiophenes via tandem Michael addition/intramolecular Knoevenagel condensation

Starting from the easily available, highly functionalized acetylenic ketories 4a–i (Scheme 1), novel 2,3,5-trisubstituted thiophenes 1a–i (Scheme 2) were synthesized in good yields using a tandem Michael-addition/intramolecular Knoevenagel-condensation strategy, featuring Cs₂CO₃/MgSO₄ (1:2) as an efficient base to effect the cyclization. Subsequent simple one-step transformations yielded 2,3-disubstituted thiophene-5-carbaidehydes 7a–c , carboxylic-acid derivatives 8, 9 , and 11 , and alcohol 10 (Scheme 3). These molecules constitute interesting novel thiophene-containing building blocks, useful for the preparation of low-molecular-weight compound libraries by combinatorial and parallel-chemistry techniques.     

One-pot synthesis of hydrazine derivatives from aldehydes via radical addition reactions

A one-pot procedure for the synthesis of hydrazine derivatives from aldehydes via radical addition reactions was developed. Lewis acids promoted both the condensation between aldehydes and benzhydrazide, and the alkyl radical addition to the Cdbnd?N bond of hydrazones, affording moderate-to-high yields of hydrazine derivatives. The present process provides a tin-free radical, sustainable, and eco-friendly synthetic method.     

The efficient enantioselective synthesis of dihydropyrans via organocatalytic Michael addition reactions

An asymmetric Michael addition of α-cyanoketones to α,β-unsaturated aldehydes to form chiral dihydropyrans catalyzed by l-diphenylprolinol trimethylsilyl ether is presented. A series of 3,4-dihydropyrans were obtained in excellent yields (up to 91%) and enantioselectivities (up to 98% ee). A plausible mechanism for this process is proposed.     

Knoevenagel reaction: alum-mediated efficient green condensation of active methylene compounds with arylaldehydes

Abstract

A solvent-free stirred mixture of active methylene compounds, arylaldehyde and 10 mol% alum at 80°C afforded Knoevenagel products in excellent yields. The use of a green catalyst, the solvent-free conditions, and shorter reaction times are the main features of this efficient protocol.     

Enantioselective solution- and solid-phase synthesis of glutamic acid derivatives via Michael addition reactions

The enantioselective conjugate addition of Schiff base ester derivatives to Michael acceptors either in solution (56–89% e.e.) or on solid-phase (34–82% e.e.) gave optically active unnatural α-amino acid derivatives. The reaction was conducted in the presence of chiral, non-racemic quaternary salts derived from the cinchona alkaloids using neutral, non-ionic phosphazene bases.     

Pyrylium-based porous organic polymers via Knoevenagel condensation for efficient visible-light-driven heterogeneous photodegradation

Pyrylium salts are a type of representative and convincing example of versatility and variety not only as a nodal point in organic transformations but also as an attractive building block in functional organic materials. Herein, we report an effective synthetic protocol to fabricate a new pyrylium-containing porous organic polymers (POPs), named TMP-P, via Knoevenagel condensation with 2,4,6-trimethylpyrylium salt (TMP) as the key building block and 1,4-phthalaldehyde as the linker. The resulting ionic polymer TMP-P exhibited efficient visible-light-driven heterogeneous photodegradation of Rhodamine B, owing to the presence of wide visible light absorption and a narrow optical band gap triggered pyrylium core in the framework.     

“On-water” synthesis of 3-substituted indoles via Knoevenagel/Michael addition sequence catalyzed by Cu doped ZnS NPs

Cu doped ZnS NPs represent a green catalyst for an ‘on-water’ one-pot rapid synthesis of 3-substituted indole derivatives via Knoevenagel/Michael addition reaction of indane-1,3-dione, aromatic aldehydes, and indole. The catalytic activity of Cu doped ZnS NPs was about sevenfold higher as compared to the ZnS NPs. The Cu doped ZnS NPs catalyst could be recovered and reused for five reaction cycles, giving a total TOF = 201 h⁻¹.     

One-pot synthesis of adamantane derivatives by domino Michael reactions from ethyl 2,4-dioxocyclohexanecarboxylate

Adamantane derivatives were constructed by the one-pot reaction of ethyl 2,4-dioxocyclohexanecarboxylate with 2-phenylethyl 2-(acetoxymethyl)acrylate or 2-(acetoxymethyl)-1-phenyl-2-propen-1-one via domino Michael reactions and a Dieckmann condensation or an aldol-type reaction (four-bond formation). This is the first one-pot construction of adamantane derivatives from cyclohexanone derivatives not involving enamines.     

Novel codeinone derivatives via Michael addition of barbituric acids

Two novel adducts of codeinone with barbituric and 2-thiobarbituric acids have been synthesized via Michael addition. The compounds were spectroscopically elucidated by means of IR-LD spectroscopy of oriented samples as a suspension in nematic liquid crystals, UV spectroscopy and ¹H and ¹³C NMR spectroscopy. The 2-thiobarbituric adduct was characterized by X-ray crystallography. HPLC tandem mass spectrometry (HPLC ESI MS/MS) and thermal methods were also employed. Quantum chemical calculations have been performed with a view to obtaining the electronic structure and vibrational properties of the novel compounds.     

Organosulfur phosphonium salt-mediated synthesis of functionalized thiopyran derivatives

Methyl 4-oxotetrahydro-2H-thiopyran-3-carboxylate as a CH-acid undergoes a mild reaction with acetylenic esters in the presence of triphenylphosphine to produce phosphorus ylides possessing thiopyran-4-one ring moiety. The resulted phosphorus ylides when heated in toluene afforded functionalized thiopyran derivatives through intramolecular Wittig reaction.     

One-pot conversion of alkyl aldehydes into substituted propanoic acids via Knoevenagel condensation with Meldrum’s acid

Reaction of a range of alkyl aldehydes and Meldrum’s acid in triethylammonium formate (TEAF) at 100 °C generates substituted propanoic acids in a single step.     

Highly efficient Knoevenagel condensation reactions catalyzed by a proline-functionalized polyacrylonitrile fiber

A new proline-functionalized fiber catalyst was employed for the first time to catalyze the Knoevenagel condensation reactions between aromatic aldehydes and ethyl cyanoacetate or malononitrile.This fiber catalyst exhibits a high efficiency(0.5-2 mol% of catalyst with yields of 90%-99%) and excellent reusability(up to 20 times) without the need for additional treatments.     

One-pot, three-component synthesis of five-membered cyclic nitrones by addition/cyclization/condensation domino reaction

A new approach to five-membered cyclic nitrones connected with the incorporation of a planar aromatic ring system into the structure is described. This procedure is based on an allenyloxime one-pot domino transformation under simple base catalysis in alcoholic and aqueous solvents. The structure of obtained nitrones was studied by X-ray analysis and the reactivity of products in 1,3-dipolar cycloadditions was tested.     

Diastereoselective synthesis of a highly substituted cis-decahydroquinoline via a Knoevenagel condensation

A diastereoselective approach to 3,7,8-trisubstituted cis-decahydroquinolines is described. This ring system forms the core of rings B and E of the norditerpenoid alkaloid methyllycaconitine. This approach starts with a known disubstituted cyclohexene. The remaining carbons are attached via a Knoevenagel condensation followed by an intramolecular lactam formation. The stereochemistry of the substituents is controlled by the cis-substitution of the starting cyclohexene ring.     

One-pot synthesis of dihydropyrimidines via eco-friendly phosphorus derivatives catalysis

A straightforward, cost effective and eco-friendly protocol for the Biginelli reaction relying on the use of readily available hypophosphorous acid is presented. The methodology developed displays improvements compared to existing methods, is high-yielding, robust and was applied to a panel of dihydropyrimidines and thio-derivatives with various substituents. Related urea derivatives such as guanidines, benzimidazoles and benzothiazoles also reacted efficiently to afford more complex scaffolds. Thus, this rapid and convenient catalysis allows access to a wide diversity of structures including original biologically relevant heterocycles.