Knoevenagel-Michael Cyclocondensation Research Articles

Partially reduced-linked covalent organic frameworks: A new approach for heterogeneous catalysis and naked-eye HCl sensing

Compared to the traditionally made imine-linked covalent organic frameworks (COFs), amine-linked COFs provided by in-situ reduction of the linkages represent significant potential for advanced applications, including catalysis and sensing. The current paper deals with preparing a partially reduced COF with secondary amine groups (IR-COF) via in-situ reduction of imine linkages as a dual-functional material adopted for heterogeneous catalysis and acid-sensing. This COF was synthesized using formic acid as a reductant and catalyst in a solvothermal reaction between 2,4,6-tris-(4-formyl-phenoxy)-1,3,5-triazine and p-phenylenediamine. The IR-COF was used as a basic organocatalyst for the efficient synthesis of tetrahydro-4H-chromenes through the Knoevenagel-Michael cyclocondensation. Excellent yields, short reaction times, easy workup, absence of toxic organic solvents, easy recovery, and reusability of the catalyst are outstanding aspects of this catalytic method, making it convenient and useful for fine chemical synthesis. Moreover, the immediate naked-eye color change of IR-COF upon exposure to the hydrochloric acid by protonating the secondary amine groups was investigated. The (time-dependent) density functional theory (TD)DFT PBE/DNP+ method was used to investigate the mechanism of color change during the sensing. The appearance of a new absorption band at higher wavelengths upon protonation is proved to be due to intermolecular or interlayer electron transitions.

A new role for concentrated solar radiation (CSR) as a renewable heat source for the catalyst-solvent free synthesis of tetrahydrobenzo[b]pyran scaffolds

Increased energy consumption as a result of population growth and industrialization necessitates the use of renewable energy sources in the field of chemistry. Nonrenewable energy sources release not only greenhouse gases but also other hazardous pollutants that are damaging to all living things. This plainly mandates the researchers' use of a renewable energy source that is both environmentally friendly and cost-effective. This study shows that a renewable energy source (sunlight) can be used to synthesize tetrahydrobenzo[b]pyran scaffolds using the Knoevenagel–Michael cyclocondensation of aldehyde derivatives, malononitrile, and dimedone via a three-condensation domino reaction. This research establishes a new role for solar energy as a renewable energy source for the synthesis of tetrahydrobenzo[b]pyran scaffolds under catalyst-solvent-free conditions, with outstanding yields, shorter reaction time, and great atom economy. This cyclization may also be done on a gram scale with free, safe, and clean energy from concentrated solar radiation (CSR), indicating the reaction's potential for industrial applications.

Fe3O4@iron-based metal-organic framework nanocomposite [Fe3O4@MOF (Fe) NC] as a recyclable magnetic nano-organocatalyst for the environment-friendly synthesis of pyrano[2,3-d]pyrimidine derivatives.

Various pyrano[2,3-d]pyrimidines were synthesized by the multicomponent reaction of aldehydes, malononitrile, and acidic C-H compounds such as barbituric acid through the tandem Knoevenagel-Michael cyclocondensation pathway in an environmentally friendly reactive medium in the presence of a recoverable nanocomposite. This nanocomposite includes Fe3O4 nanoparticles placed on an organometallic framework. The synthesized Fe3O4@iron-based metal-organic framework nanocomposite was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, a vibrating sample magnetometer, and thermogravimetric analysis.

Photochemical synthesis of pyrano[2,3-d]pyrimidine scaffolds using photoexcited organic dye, Na2 eosin Y as direct hydrogen atom transfer (HAT) photocatalyst via visible light-mediated under air atmosphere

The Knoevenagel-Michael cyclocondensation of barbituric acid/1,3-dimethylbarbituric acid, malononitrile, and arylaldehyde derivatives was used to construct a multicomponent green tandem method for the metal-free synthesis of pyrano[2,3-d]pyrimidine scaffolds. At room temperature in aqueous ethanol, photo-excited state functions generated from Na2 eosin Y were employed as direct hydrogen atom transfer (HAT) catalysts by visible light mediated in the air atmosphere. This research looks towards expanding the use of a non-metallic organic dye that is both affordable and readily available. Because of its good yields, energy-effectiveness, high atom economy, time-saving qualities of the reaction, and operational simplicity, Na2 eosin Y is photochemically produced with the least amount of a catalyst. As a result, various ecological and sustainable chemical properties are met. Surprisingly, such cyclization may be carried out on a gram scale, indicating the reaction's potential industrial application.

Polyethylene glycol (PEG-400) as a recyclable and biodegradable reaction medium for green synthesis of 2-amino-4H-chromenes

A helpful manufactured course to the one-pot green synthesis of 2-amino-4H-chromenes through a tandem Knoevenagel-Michael cyclocondensation reaction of aldehydes, malononitrile, and resorcinol in polyethylene glycol (PEG-400) as accessible and biodegradable media have been detailed. All responses are completed in a brief time and the items are gotten in fabulous yields. The striking highlights of this eco-friendly approach are biodegradable media, fabulous yields, simple work-up without requires for column chromatographic separation, and no poisonous organic solvents, evasion of harmful reagents, one-pot strategy, and effortlessness of operation. Additionally, PEG-400 is exceedingly steady and can be reused for four sequential runs without major basic changes or misfortune of movement, which has been exceptionally advantageous in tending to natural concerns.

Synthesis of dihydropyrano[2,3-c]pyrazole scaffolds by methylene blue (MB+) as a photo-redox catalyst via a single-electron transfer (SET)/energy transfer (EnT) pathway

A new environmentally friendly plan was created to make dihydropyrano [2,3-c]pyrazole structures without using metals. This plan involves combining ethyl acetoacetate, hydrazine hydrate, aldehyde derivatives, and malononitrile in a radical tandem Knoevenagel-Michael cyclocondensation reaction. We used metal-free methylene blue (MB+) to create special functions that respond to light. These functions can transfer electrons and energy in water at room temperature using light as a source of energy in the air. The amount of product made is pretty consistent (between 81 and 98 %, with an average of 91.8 %), and it gets made quickly (between 3 and 7 min, with an average of 5.3 min). The important thing mentioned in the conversation is that the process can handle different types of chemicals while still being fast and giving good results. The results show that this special technique is a successful and easy way to get good results in just one step. Methylene blue is used with very little amount to make a chemical reaction happen. This leads to high amounts of product, saves energy, and is good for the environment. It helps use up all the starting materials efficiently, saves time by not needing to separate chromatography, and reduces waste. This photocatalyst is easy to use. This creates many different types of characteristics in the environment and chemicals that last a long time. The turnover number (TON) and turnover frequency (TOF) of dihydropyrano [2,3-c]pyrazole scaffolds were calculated. It is interesting that cyclization on a gram scale can be achieved, showing that this technique can be used in industries.

Recyclable mesalamine-functionalized magnetic nanoparticles (mesalamine/GPTMS@SiO2@Fe3O4) for tandem Knoevenagel-Michael cyclocondensation: grinding technique for the synthesis of biologically active 2-amino-4H-benzo[b]pyran derivatives.

In the present study, mesalamine-functionalized on magnetic nanoparticles (mesalamine/GPTMS@SiO2@Fe3O4) is fabricated as an efficient and magnetically recoverable nanocatalyst. The as-prepared nanocatalyst was successfully synthesized in three steps using a convenient and low-cost method via modification of the surface of Fe3O4 nanoparticles with silica and GPTMS, respectively, to afford GPTMS@SiO2@Fe3O4. Finally, treatment with mesalamine as a powerful antioxidant generates the final nanocatalyst. Then, its structure was characterized by FT-IR, SEM, TEM, EDX, XRD, BET, VSM, and TGA techniques. The average size was found to be approximately 38 nm using TEM analysis and the average crystallite size was found to be approximately 27.02 nm using XRD analysis. In particular, the synthesized nanocatalyst exhibited strong thermal stability up to 400 °C and high magnetization properties. The activity of the synthesized nanocatalyst was evaluated in the tandem Knoevenagel-Michael cyclocondensation of various aromatic aldehydes, dimedone and malononitrile under a dry grinding method at room temperature to provide biologically active 2-amino-4H-benzo[b]pyran derivatives products in a short time with good yields. The presented procedure offers several advantages including gram-scale synthesis, good green chemistry metrics (GCM), easy fabrication of the catalyst, atom economy (AE), no use of column chromatography, and avoiding the generation of toxic materials. Furthermore, the nanocatalyst can be reused for 8 cycles with no loss of performance by using an external magnet.

Mortar–Pestle Grinding Technique as an Efficient and Green Method Accelerates the Tandem Knoevenagel–Michael Cyclocondensation Reaction in the Presence of Ethylenediamine Immobilized on the Magnetite Nanoparticles

In this research, we successfully designed and synthesized a new core-shell-structured inorganic-organic hybrid magnetic nanocatalyst via the ethylene diamine immobilized to the core-shell Fe3O4 nanomagnetic particles (Fe3O4@SiO2@(CH2)3/EDA). A variety of analyses such as fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), elemental mapping (WDS), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and Brunauer-Emmet-Teller (BET) were used to characterize the as-synthesized nanocatalysts. The activity of this as-synthesized nanocatalysts can be successfully used in the grinding synthesis of various aldehydes, malononitrile and dimedone under solvent- and metal-free conditions at room temperature to give 2-amino-4H-benzo[b]pyran derivatives within high purity and excellent yields. Easy fabrication of Fe3O4@SiO2@(CH2)3/EDA, waste reduction, effective for large scale synthesis, simple work-up procedure, adherence to the basics of green chemistry, high catalytic efficiency in very small amounts (0.05 g), environmentally friendly and based on natural ingredients are the great advantages of the current method. In particular, due to the super magnetic behavior of the catalyst, it can be easily recovered with the use of an external magnet from the reaction mixture, and it can be reused over 7 successive times with no decrease in the yields and activity.

Methylene Blue as a Photo-Redox Catalyst: The Development Synthesis of Tetrahydrobenzo[b]pyran Scaffolds via a Single-Electron Transfer/Energy Transfer.

In a green tandem reaction using aldehyde derivatives, malononitrile, and dimedone, a radical tandem Knoevenagel–Michael cyclocondensation reaction of tetrahydrobenzo[b]pyran scaffolds was developed. Using visible light as a sustainable energy source, methylene blue (MB+)-derived photo-excited state functions were employed in an aqueous solution as single-electron transfer (SET) and energy transfer catalysts. The range of yields is quite uniform (81–98%, average 92.18%), and the range of reaction time is very fast (2–7 min, average 3.7 min), and the point mentioned in the discussion is that the procedure tolerates a range of donating and withdrawing groups, while still giving very excellent yields. The reaction is fairly insensitive to the nature of the substituents. Research conducted in this project aims to develop a non-metallic cationic dye that is both inexpensive and widely available for more widespread use. In addition to energy efficiency and environmental friendliness, methylene blue also offers an excellent atom economy, time-saving features, and ease of use. As a result, a wide range of long-term chemical and environmental properties can be obtained. The turnover number and turnover frequency of tetrahydrobenzo[b]pyran scaffolds have been computed. Surprisingly, gram-scale cyclization is a possibility, implying that the technology may be applied in industries.

The development of knoevenagel-michael cyclocondensation through a single-electron transfer (SET)/energy transfer (EnT) pathway in the use of methylene blue (MB+) as a photo-redox catalyst

Through the Knoevenagel-Michael cyclocondensation of malononitrile, aryl aldehydes, and resorcinol, a multicomponent green tandem method for the metal-free synthesis of 2-amino-4H-chromene scaffolds was developed. At room temperature in an aqueous solvent, photo-excited state functions formed from methylene blue (MB+) were used as single-electron transfer (SET) and energy transfer (EnT) catalysts using visible light as a renewable energy source in the air atmosphere. This research looks toward expanding the use of a non-metal cationic dye that is both affordable and readily available. Methylene blue is catalyzed by photochemical means using the least amount of catalyst, which results in excellent yields, energy efficiency, environmental friendliness, high atom economy, time-saving features, and ease of operation. As a result, various ecological and sustainable chemical properties are met. Surprisingly, such cyclization may be carried out on a gram scale, indicating the reaction's potential industrial application.

New Role for Photoexcited Na2 Eosin Y via the Direct Hydrogen Atom Transfer Process in Photochemical Visible-Light-Induced Synthesis of 2-Amino-4H-Chromene Scaffolds Under Air Atmosphere.

The Knoevenagel–Michael cyclocondensation of malononitrile, aryl aldehydes, and resorcinol was used as a multicomponent green tandem strategy for the metal-free synthesis of 2-amino-4H-chromene scaffolds. Through a visible-light-induced process, the photo-excited state functions derived from Na2 eosin Y were used as direct hydrogen atom transfer catalysts in aqueous ethanol at ambient temperature. The purpose of this study was to examine the further use of an organic dye that does not contain metal and is inexpensive and commercially available. Na2 eosin Y is synthesized by photochemical means using the least amount of catalyst, which results in excellent yields, energy efficiency, and environmental friendliness, high atom economy, time-saving features, and ease of operation. As a result, some properties of green and sustainable chemistry are met. This kind of cyclization can be performed on a gram scale, indicating the potential utility of this reaction in industry.

Catalyst-Free and Solvent-Free Visible Light Assisted Synthesis of Tetrahydrobenzo[b]Pyran Scaffolds at Room Temperature

A catalyst-free and solvent-free three-component tandem strategy for synthesizing tetrahydrobenzo[b]pyran scaffolds through Knoevenagel–Michael cyclocondensation is reported using visible light irradiation as a green promoter at room temperature. The prominent benefits of the existing protocol are catalyst-free, solvent-free, using commercially accessible, inexpensive preliminary substances, operational simplicity, energy-effectiveness, great yields, high atom-economy, thus meeting some features of sustainability and green chemistry.

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

Backgroundeosin 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. Methoda 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. Findingsthis 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.

Per-6-NH2-β-CD as Supramolecular Host and Reusable Aminocyclodextrin Promoted Solvent-Free Synthesis of 2-Amino-4H-Chromene Scaffolds at Room Temperature

Aminocyclodextrins are homogeneous CD derivatives modified by per substitution at the primary face with amino pendant groups, and this manifests combined hydrophobic and electrostatic binding of guest molecules relative to native CDs. A green multi-component tandem strategy for solvent-free synthesizing 2-amino-4H-chromene scaffolds by Knoevenagel-Michael cyclocondensation of aryl aldehydes, malononitrile and resorcinol is reported via supramolecular host and reusable per-6-amino-β-cyclodextrin at room temperature. The isolated products were checked for its purity by TLC. The final product was characterized by 1HNMR spectrometry. This study paves the use of supramolecular host and reusable aminocyclodextrin for producing of 2-amino-4H-chromene scaffolds with use of the commercially accessible inexpensive preliminary substances, energy-effectiveness, reusable catalyst, excellent yields, operational simplicity, time-saving aspects of the reaction, easy work-up, solvent-free conditions, high atom economy, green reaction conditions thus meeting some features of sustainability and green chemistry. Also, per-6-amino-β-cyclodextrin was so stable that they were capable of being used for six consecutive times with no significant change in structure and any activity loss. These characteristics have caused this procedure to be highly beneficial in facing the environmental worries and industrial needs.

Magnetic Nanoparticles Functionalized with Copper Hydroxyproline Complexes as an Efficient, Recoverable, and Recyclable Nanocatalyst: Synthesis and Its Catalytic Application in a Tandem Knoevenagel–Michael Cyclocondensation Reaction

A novel catalyst has been afforded by attaching of a Cu(proline)2 complex to magnetic nanoparticles through cheap, simple, and readily available chemicals. This catalyst was characterized by Fourier transform infrared, energy-dispersive X-ray, X-ray diffraction, vibrating-sample magnetometry, transmission electron microscopy, scanning electron microscopy, and inductively coupled plasma analyses. The catalytic activity of the Fe3O4@NH2@TCT@HProCu nanocatalyst was investigated in a green and effective synthesis of pyran derivatives in high yields by applying three-component reactions of malononitrile, dimedone, and aldehydes in ethanol. Conversion was high under optimal conditions. The obtained nanocatalyst could be easily separated from the mixture of the reaction and was recyclable nine times via a simple magnet without considerable reduction of its catalytic efficiency. Operational simplicity, high product yields, environmental friendliness, ecofriendliness, economical processing, and easy workup are the features of this methodology.

New role for photoexcited organic dye, Na2 eosin Y via the direct hydrogen atom transfer (HAT) process in photochemical visible-light-induced synthesis of spiroacenaphthylenes and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones under air atmosphere

A green multi-component tandem strategy for metal-free synthesizing spiroacenaphthylenes and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones by Knoevenagel-Michael cyclocondensation is reported via organic dye Na2 eosin Y-derived photoexcited states functions as a direct hydrogen atom transfer (HAT) catalyst via visible light-mediated in aqueous ethyl lactate at ambient temperature under air atmosphere. 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. Notably, this cyclization is also runnable on gram scale, which highlights the potentiality of using this reaction in industrial uses.

A new role for photoexcited Na2 eosin Y as direct hydrogen atom transfer (HAT) photocatalyst in photochemical synthesis of dihydropyrano[2,3-c]pyrazole scaffolds promoted by visible light irradiation under air atmosphere

Evidence indicates that Na2 eosin Y-derived photoexcited states functions as a direct hydrogen atom transfer (HAT) catalyst to synthesize dihydropyrano[2,3-c]pyrazole scaffolds photochemically via four-condensation domino reaction of tandem Knoevenagel-Michael cyclocondensation reaction ethyl acetoacetate, hydrazine hydrate, aryl aldehyde derivatives and malononitrile via visible light-mediated in aqueous ethanol at ambient temperature under air atmosphere. This study paves the new role for further the 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, excellent yields, time-saving aspects of the reaction and high atom economy. Notably, this cyclization is also runnable on the gram scale, which highlights the potentiality of using this reaction in industrial uses.

Catalyst-free and solvent-free visible light irradiation-assisted Knoevenagel–Michael cyclocondensation of aryl aldehydes, malononitrile, and resorcinol at room temperature

Catalyst-free and solvent-free three-component tandem approach can synthesize 2-amino-4H-chromene scaffolds by Knoevenagel–Michael cyclocondensation of aryl aldehydes, malononitrile, and resorcinol via visible light irradiation as a green promoter at room temperature. The significant advantages of the present protocol include energy-effectiveness, catalyst-free, excellent yields, solvent-free, operational simplicity, and high atom-economy, commercially accessible inexpensive preliminary substances, so it meets some features of sustainable and green chemistry.

Supramolecular β-cyclodextrin as a Biodegradable and Reusable Catalyst Promoted Environmentally Friendly Synthesis of Pyrano[2,3-d]pyrimidine Scaffolds via Tandem Knoevenagel–Michael–Cyclocondensation Reaction in Aqueous Media

The catalytic activity of supramolecular β-cyclodextrin as a biodegradable and reusable catalyst was studied for the synthesis of pyrano[2,3-d]pyrimidine scaffolds in aqueous media. This green and eco-safe domino approach revealed simplicity, use of biodegradable and highly efficient catalyst, avoidance of toxic organic solvents, versatility and high stability of the catalyst combined with excellent yields, easy work-up procedures with no necessity of chromatographic purification steps, the reusability of the catalyst and being in agreement with the green chemistry protocols, and time-saving aspects of the reaction suggest that this method presents real alternatives over conventional reaction protocols.

Catalyst-free, visible light irradiation promoted synthesis of spiroacenaphthylenes and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones in aqueous ethyl lactate

Catalyst-free three-component tandem approach can synthesize spiroacenaphthylenes and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones by Knoevenagel-Michael cyclocondensation via visible light irradiation in aqueous ethyl lactate at room temperature. The significant advantages of the present protocol include energy-effectiveness, catalyst-free, excellent yields, operational simplicity, high atom-economy, commercially accessible, inexpensive preliminary substances, so it meets some features of sustainablility and green chemistry.