A catalyst- and solvent-free protocol for the sustainable synthesis of fused 4H-pyran derivatives

Unraveling the access to the regioselective synthesis of highly functionalized pyranopyrazoles using an ionic liquid catalyst

An efficient and green strategy for the regioselective synthesis of highly functionalized pyranopyrazole via one-pot condensation of 3-methyl-1-phenyl-5-pyrazolone or EAA and hydrazine hydrate, substituted aromatic aldehydes with NMSM [(E)-N-Methyl-1-(methylthio)-2-nitro-ethenamine] in the existence of IL [(EMIM)Ac] as catalyst with solvent-free condition (SFC) is described. This domino protocol produces biologically substantial heterocycles through Knoevenagel condensation proceeded by Michael addition and O-cyclization with an eradication of methanethiol group, which create the one stereo-center and creation of "C-C, C-N, C-O, C=C, C=N, bonds." The final product is produced by exceptionally easy filtering after the reaction mass was triturated with ethanol. The strategy's noteworthy features include the use of biodegradable IL catalyst, excellent to exceptional yield with rapid reaction times, applicability to a wide range of substrate, clear reaction profile, and straightforward workup process.

A close look into the biological and synthetic aspects of fused pyrazole derivatives

The fusion of pyrazole scaffold with other skeletons creates a class of attractive molecules, demonstrating significant biological and chemical potentiality in the development of medicinal chemistry. Over the past few decades, numerous biologically active molecules featuring fused pyrazole moieties have been excavated and synthesized, some of which represented by sildenafil have been marketed as drugs, and the biological importance together with chemical synthesis strategies of fused pyrazole compounds, including structural modification based on lead compounds, have been steadily progressing. In this review, we focused our attention on the biological importance of fused pyrazoles and highlighted recent progress in the synthesis of this framework over the past 10 years. What' s more, the limitations, challenges, and future prospects were proposed, wishing to provide references for the development of pyrazole fused frameworks in the field of medicinal chemistry. Contents.

Copper-Catalyzed Cascade Annulation of o-Hydroxyphenyl Propargylamines with Pyrazolin-5-ones to Access Pyrano[2,3-c]pyrazoles

An efficient copper-catalyzed cascade annulation of o-hydroxyphenyl propargylamines and pyrazolin-5-ones is described. This methodology leads to the rapid assembly of a series of valuable pyrano[2,3-c]pyrazoles with good yields across a wide range of substrates in a simple fashion. This novel reaction involves the formation of alkynyl ortho-quinone methides, a 1,4-conjugate addition, and a subsequent 6-endo cyclization process. The mechanistic elucidation is well supported by control experiment and literature precedents.