Recent Advances in the Synthesis of Coumarin Derivatives via Knoevenagel Condensation: A Review

Despite prior reports of several really effective catalytic and non-catalytic approaches towards Biginelli’s 3,4-dihydropyrimidin-2(1H)-ones, an overwhelming number of new catalysts for the Biginelli reaction have been recently published. Most of the catalysts are somewhat exotic, expensive, harmful and even uneffective in the absence of acidic additives. Herein we reduce the “yet-another-one-catalyst” idea to absurdity by proposing NaCl promotes the reaction that actually requires no catalyst, neither rare nor expensive.

A chemical placebo: NaCl as an effective, cheapest, non-acidic and greener catalyst for Biginelli-type 3,4-dihydropyrimidin-2(1H)-ones (-thiones) synthesis.

Isoxazole, constituting an important family of five-membered heterocycles with one oxygen atom and one nitrogen atom at adjacent positions is of immense importance because of its wide spectrum of biological activities and therapeutic potential. It is, therefore, of prime importance that the development of new synthetic strategies and designing of new isoxazole derivatives should be based on the most recent knowledge emerging from the latest research. This review is an endeavor to highlight the progress in the chemistry and biological activity of isoxazole derivatives which could provide a low-height flying bird's eye view of isoxazole derivatives to the medicinal chemists for the development of clinically viable drugs using this information.

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The synthetic and therapeutic expedition of isoxazole and its analogs

New magnetic nanocomposites of ZrO2–Al2O3–Fe3O4 as green solid acid catalysts in organic reactions

The Pechmann reaction introduces one of the most significant and simple methods for the synthesis of a variety of heterocyclic compounds, particularly coumarin derivatives. In 1883, a German chemist, Hans von Pechmann synthesized coumarins from the reaction of phenols with a carboxylic acid or ester containing a β-carbonyl group. In this article, we try to highlight the various aspects, issues, and applications of this reaction.

Pechmann Reaction in the Synthesis of Coumarin Derivatives

Microwave assisted synthesis of coumarins via potassium carbonate catalyzed knoevenagel condensation in 1-n-butyl-3-methylimidazolium bromide ionic liquid

Efficient and Convenient Method for the Synthesis of Isoxazoles in Ionic Liquid

Microwave Assisted Synthesis of Coumarins via Potassium Carbonate Catalyzed Knoevenagel Condensation in 1-n-Butyl-3-methylimidazolium Bromide Ionic Liquid.

An efficient and cost-effective method has been developed for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones by a one-pot three-component cyclocondensation reaction of a 1,3-dicarbonyl compound, an aldehyde, and (thio)urea using titanium(IV) chloride as catalyst under solvent-free conditions. Addition of TiCl4 to a mixture of the neat reactants afforded the products more quickly and in better yields as compared to traditional methodologies. This methodology presents an improvement of the classical Biginelli three-component condensation, and it is more convenient being inexpensive and proceeding under milder conditions and with shorter reaction times.

Titanium(IV) Chloride Catalyzed One-Pot Synthesis of 3,4-Dihydropyrimidin-2-(1h)-ones under Solvent-Free Conditions via Three-Component Biginelli Reaction

Hamid Gholipur

Papers

Microwave assisted synthesis of coumarins via potassium carbonate catalyzed knoevenagel condensation in 1-n-butyl-3-methylimidazolium bromide ionic liquid

Efficient and Convenient Method for the Synthesis of Isoxazoles in Ionic Liquid

Microwave Assisted Synthesis of Coumarins via Potassium Carbonate Catalyzed Knoevenagel Condensation in 1-n-Butyl-3-methylimidazolium Bromide Ionic Liquid.

Titanium(IV) Chloride Catalyzed One-Pot Synthesis of 3,4-Dihydropyrimidin-2-(1h)-ones under Solvent-Free Conditions via Three-Component Biginelli Reaction

Efficient and Convenient Method for the Synthesis of Isoxazoles in Ionic Liquid.