Showing papers on "Pyran published in 2021"

A Review of Recent Advances in the Green Synthesis of Azole- and Pyran-based Fused Heterocycles Using MCRs and Sustainable Catalysts

Abstract: Nitrogen, oxygen and sulfur-containing fused heterocycles are of great importance because of their exciting and diverse biological activities. The construction of the carbonnitrogen and carbon-oxygen through a multicomponent reaction approach by using ecofriendly reusable heterogeneous catalysts are of significant importance as it opens avenues for the introduction of nitrogen and oxygen in organic molecules. Thus, green methodologies have gained particular significance in this field; today, green chemistry is considered a tool for introducing sustainable concepts at the fundamental level. This review emphasizes and discusses the current progress on the applications of eco-friendly, recyclable heterogeneous catalysts for the synthesis of different heterocyclic fused systems and their green protocols. We paid particular attention to the specific integration of carbon-nitrogen, and carbon-oxygen bond-forming fused heterocycles by a one-pot approach by evaluating the literature between 2012 and the middle of 2020. The efficiency of the catalyst is assessed in terms of reaction time, yield and possible reusability. The MCR and heterogeneous catalyst strategies have demonstrated broader scope, economical and viability for the green and sustainable processes in the field of synthetic organic chemistry.

Design of High-Contrast Mechanochromic Materials Based on Aggregation-Induced Emissive Pyran Derivatives Guided by Polymorph Predictions

Abstract: High-contrast mechanochromic (MC) materials are prominent candidates for sensor, security, and memory applications; however, the development of materials with a large luminescence change (Δλem > 10...

Novel nano-architectured carbon quantum dots (CQDs) with phosphorous acid tags as an efficient catalyst for the synthesis of multisubstituted 4H-pyran with indole moieties under mild conditions

Abstract: In this work, a new nano-structured catalyst with phosphorus acid moieties, synthesized by the reaction of carbon quantum dots (CQDs) and phosphorus acid under refluxing EtOH. The structure and morphology of CQDs–N(CH2PO3H2)2 were fully characterized using various techniques such as Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric (TG) analysis, fluorescence and X-ray diffraction (XRD) measurements. The new CQDs–N(CH2PO3H2)2 catalyst was successfully used for the synthesis of 2-amino-6-(2-methyl-1H-indol-3-yl)-4-phenyl-4H-pyran-3,5-dicarbonitriles by the one-pot reaction of various aromatic aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitrile derivatives and malononitrile in refluxing EtOH and/or ultrasonic irradiation conditions.

Nano-SiO2/DBN: an efficacious and reusable catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran derivatives

Abstract: The nano-sized particles enhance the exposed surface area of the active part of the catalyst, thereby increasing the contact between precursors and catalyst considerably. In this study, nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en was synthesized, characterized and used as a heterogeneous nanocatalyst for the synthesis of tetrahydrobenzo[b]pyran derivatives. Fourier Transform Infrared Spectroscopy, Field Emission Scanning Electron Microscopy, Brunauer–Emmett–Teller plot, Energy Dispersive X-ray Spectroscopy and Thermo Gravimetric Analysis were used to discern nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en. Tetrahydrobenzo[b]pyrans were synthesized by using nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en via one-pot three-component condensation of malononitrile, aldehydes and dimedone in H2O/EtOH at 60 °C. The results indicate that tetrahydrobenzo[b]pyrans were synthesized in good to high yields and short reaction times. The fundamental privileges of this method are short reaction time, plain procedure, recyclability of catalyst and high yields of products.

Photoexcited Na2 eosin Y as direct hydrogen atom transfer (HAT) photocatalyst promoted photochemical metal-free synthesis of tetrahydrobenzo[b]pyran scaffolds via visible light-mediated under air atmosphere

Abstract: Background eosin Y is a metal-free organic dye with easy availability that has gained a wide application in recent years, having economic and ecological superiority for substituting transition-metal-based photocatalysts. Method a green three-component tandem strategy for synthesizing tetrahydrobenzo[b]pyran scaffolds through Knoevenagel-Michael cyclocondensation is reported using Na2 eosin Y-derived photoexcited states functions as a direct hydrogen atom transfer (HAT) catalyst via visible light-mediated in aqueous ethanol at ambient temperature under air atmosphere. Findings this study paves the new role for further use of a metal-free organic dye with commercial availability and inexpensiveness, Na2 eosin Y in photochemical synthesis with use of the lowest amount of catalyst, energy-effectiveness, excellent yields, operational simplicity, time-saving aspects of the reaction and high atom economy, thus meeting some features of sustainable and green chemistry.

Zr@IL-Fe3O4 MNPs as an efficient and green heterogeneous magnetic nanocatalyst for the one-pot three-component synthesis of highly substituted pyran derivatives under solvent-free conditions

Abstract: The present study was conducted to synthesize Zr@IL-Fe3O4 MNPs as a new magnetically recoverable heterogeneous catalyst, which was then characterized by Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The catalytic behavior of the Zr@IL-Fe3O4 MNPs was efficiently used for the synthesis of highly substituted pyran derivatives via a one-pot three-component condensation of 4-hydroxycoumarin/dimedone, malononitrile, and arylaldehydes under solvent-free conditions. This new methodology demonstrated some important features, including short reaction times, excellent yields, lower loading of the catalyst, easy work-up, and recyclability of the catalyst for a minimum of six times without any noticeable decrease in catalytic activity.

Lewis acid-catalyzed [4 + 2] cycloaddition of 3-alkyl-2-vinylindoles with β,γ-unsaturated α-ketoesters

Abstract: A Lewis acid-catalyzed [4 + 2] cycloaddition of 3-alkyl-2-vinylindoles with β,γ-unsaturated α-ketoesters has been established in the presence of Sc(OTf)3, which afforded a series of indole-containing pyran derivatives in generally good yields (up to 90% yield) with excellent diastereoselectivities (up to >95:5 dr) under mild conditions. This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles, but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.

Novel Pyran-Linked Phthalazinone-Pyrazole Hybrids: Synthesis, Cytotoxicity Evaluation, Molecular Modeling, and Descriptor Studies.

Abstract: A series of novel pyran-linked phthalazinone-pyrazole hybrids were designed and synthesized by a facile one-pot three-component reaction employing substituted phthalazinone, 1H-pyrazole-5-carbaldehyde, and active methylene compounds. Optimization studies led to the identification of L-proline and ethanol as efficient catalyst and solvent, respectively. This was followed by evaluation of anticancer activity against solid tumor cell lines of lung and cervical carcinoma that displayed IC50 values in the range of 9.8-41.6 µM. Molecular modeling studies were performed, and crucial interactions with the target protein were identified. The drug likeliness nature of the compounds and molecular descriptors such as molecular flexibility, complexity, and shape index were also calculated to understand the potential of the synthesized molecules to act as lead-like molecule upon further detailed biological investigations as well as 3D-QSAR studies.

Correction to "Three-Component Condensation of Pyridinium Ylides, β-Ketonitriles, and Aldehydes with Divergent Regioselectivity: Synthesis of 4,5-Dihydrofuran-3- and 2H-Pyran-5-carbonitriles".

Abstract: A library of trans-4,5-dihydrofuran-3-carbonitriles was synthesized in a diastereoselective manner in good yields by the three-component reaction of β-ketonitriles, carbonyl- and semistabilized pyridinium ylide precursors, and aldehydes in the presence of piperidine. This one-pot transformation generates two C-C and one C-O bond and proceeds through a cascade Knoevenagel condensation, a Michael addition, and intramolecular SN2 cyclization. Formation of cyclopropanecarbonitrile derivatives, which in some cases were obtained as major products, was found to be a competing reaction. The use of arylglyoxals changes regioselectivity and leads to 2-hydroxy-2H-pyran-5-carbonitriles.

Nucleophilic Vinylic Substitution in Perfluoroacylchromenes. Diastereoselective Synthesis of Push–Pull Enamino Ketones

Abstract: The reactions of 2-perfluoroacyl-1H-benzo[f]chromenes and 6,7-dimethyl-3-trifluoroacetyl-4H-chromene with primary aliphatic amines and ammonia afforded a series of enamino ketones containing a (2-hydroxynaphthalen-1-yl)methyl or 2-hydroxybenzyl substituent in the α-position with respect to the carbonyl group. These reactions involved opening of the pyran ring, which followed aza-Michael addition as the initial step. The obtained enamino ketones were found to exist in DMSO solution as single E isomers.

Three-component synthesis of 4H-pyran scaffolds accelerated by a gabapentin-based natural deep eutectic solvent

Abstract: The development of environmentally benign synthetic protocols has attracted increasing attention in recent organic syntheses. As a part of this concept, our group synthesized a new natural deep eutectic solvent (NADES) by using gabapentin and choline chloride. After characterization by FTIR, 1H and 13C NMR, and mass spectra, the prepared NADES was utilized as an efficacious catalyst for the synthesis of 4H-pyran scaffolds such as tetrahydrobenzo[b]pyran and pyrano[2,3-d]pyrimidinone(thione) derivatives. The use of inexpensive and bio-compatible reagents for the synthesis of the catalyst, a simple and green procedure for the preparation of the catalyst and products, short reaction times, high yields of the products, and applicability to large-scale synthesis are the prominent features of this protocol. Also, the catalyst could be recovered easily and recycled up to five times without significant loss of its catalytic activity.

Nanostructured coumarin-based cobalt complex as an efficient, heterogeneous and recyclable catalyst for the three-component synthesis of benzo[b]pyran and 3,4-dihydropyrano[c]chromene derivatives

Abstract: An improved one-pot three-component reaction of carbonyl compounds (dimedon, 4-hydroxy coumarin and 1,3-cyclohexadion) with malononitrile and aryl aldehydes in aqueous media (H2O:EtOH) as a solvent with short reaction time for the synthesis of benzo[b]pyran and 3,4- dihydropyrano[c]chromane derivatives by using nanostructured coumarin-based cobalt complex as an efficient heterogeneous catalyst. The salient features of this new protocol include simple procedure, high yields, easy isolation of products without need to column chromatography and short reaction times. Also, the nanocatalyst was recovered by adding EtOH and reused five times without significant loss of its catalytic activity. Biological impact assessments of the complex were conducted by DNA cleavage ability assay and eukaryotic cell toxicity measurement. Although the complex showed single-strand DNA breakage under oxidative conditions, its high polar nature revealed a marked decrease in cell toxicity data due to the restriction on cell entry.