Zirconium oxide (NP) - ionic liquid as an efficient media for the domino Knoevenagel hetero Diels-Alder reaction with unactivated alkynes

Solvent-free Knoevenagel reaction catalysed by reusable pyrrolidinium base protic ionic liquids (PyrrILs): synthesis of long-chain alkylidenes

In this work, an efficient and reusable pyrrolidinium ionic liquid (PyrrIL) catalysis system was developed and used in a Knoevenagel condensation reaction of long-chain aldehydes with several 1,3-dicarbonyl compounds.

Recent Advances in Inverse-Electron-Demand Hetero-Diels-Alder Reactions of 1-Oxa-1,3-Butadienes

This review is an endeavor to highlight the progress in the inverse-electron-demand hetero-Diels-Alder reactions of 1-oxa-1,3-butadienes in recent years. The huge number of examples of 1-oxadienes cycloadditions found in the literature clearly demonstrates the incessant importance of this transformation in pyran ring synthesis. This type of reaction is today one of the most important methods for the synthesis of dihydropyrans which are the key building blocks in structuring of carbohydrate and other natural products. Two different modes, inter- and intramolecular, of inverse-electron-demand hetero-Diels-Alder reactions of 1-oxadienes are discussed. The domino Knoevenagel hetero-Diels-Alder reactions are also described. In recent years the use of chiral Lewis acids, chiral organocatalysts, new optically active heterodienes or dienophiles have provided enormous progress in asymmetric synthesis. Solvent-free and aqueous hetero-Diels-Alder reactions of 1-oxabutadienes were also investigated. The reactivity of reactants, selectivity of cycloadditions, and chemical stability in aqueous solutions and under physiological conditions were taken into account to show the potential application of the described reactions in bioorthogonal chemistry. New bioorthogonal ligation by click inverse-electron-demand hetero-Diels-Alder cycloaddition of in situ-generated 1-oxa-1,3-butadienes and vinyl ethers was developed. It seems that some of the hetero-Diels-Alder reactions described in this review can be applied in bioorthogonal chemistry because they are selective, non-toxic, and can function in biological conditions taking into account pH, an aqueous environment, and temperature.

A domino synthetic approach for new, angular pyrazol- and isoxazol-heterocycles using [DBU][Ac] as an effective reaction medium

Some new, angular pyrazol- and isoxazol-heterocycles have been synthesized by the reaction of pyrazolone/isoxazolone with typical ketone-based substrates—O-alkenyloxy/alkynyloxy-acetophenones.