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The article discusses the use of H6P2W18O62·18H2O as a recyclable catalyst for the synthesis of tetrahydrobenzo[b]pyrans. The Wells-Dawson type heteropolyacid catalyst is effective in producing these compounds through a three-component reaction in aqueous ethanol at reflux. The method is environmentally friendly, with high yields and the ability to recover and reuse the catalyst. The research aims to contribute to the greening of pyran synthesis and enhance knowledge of Wells-Dawson catalysis of heterocyclic systems. [Extracted from the article]

The article discusses the use of glycerol, a by-product of the biodiesel industry, as a solvent for the catalyst-free synthesis of 2-amino-4H-chromenes. Glycerol's advantages include low toxicity, reusability, and cost-effectiveness. The method described in the article offers high yields, avoids hazardous catalysts and solvents, and allows for simple work-up without chromatography. Glycerol can be recycled and reused through multiple reaction cycles without significant loss of activity, making it an environmentally friendly medium for chemical synthesis. [Extracted from the article]

This article explores the use of Acridine Yellow G (AYG) as a photocatalyst for the synthesis of pyrano[2,3-d]pyrimidines in water. The researchers discovered that AYG was most effective as a catalyst at a loading of 0.2 mol%. The reaction yielded a compound called 4a with a 96% yield. The method was successful with various substrates and the resulting products were easily obtained and purified. The article also provides a plausible mechanism for the photocatalytic process and includes optimization studies for the solvent and light source. Additionally, the article discusses the application of AYG as a photocatalyst in a tandem Knoevenagel-Michael radical cyclocondensation reaction. The study found that visible light could be used as an energy source at room temperature in an air atmosphere for reactions in an aqueous medium. The method was efficient, utilized non-toxic solvents, and achieved excellent yields. Furthermore, the reaction could be scaled up to meet industrial and environmental requirements. [Extracted from the article]

Background: Typically, organic dyes show lower excited state lifetimes, a key hindrance in the development of efficient photoredox processes. Due to their distinctive qualities and efficiency, a particular class of organic chromophores has drawn considerable interest from the scientific community. Thermally activated delayed fluorescence (TADF), is only seen in molecules with a minimal energy gap (usually less than 0.2 eV) between their lowest two excited states, i.e., singlet excited state (Si) and triplet excited state (TJ, is a distinctive property of the molecules under study. Isophthalonitriles are a promising family of chromophores for use as organic photocatalysts because of the ease with which their redox potentials may be adjusted and the prolonged singlet excited states resulting from TADF. Methods: A sustainable process for the photosynthesis of polyfunctionalized dihydro-2-oxypyrroles has been developed using the Michael-Mannich cyclocondensation of amines, dialkyl acetylenedicarboxylates, and formaldehyde. The development of a green radical synthesis strategy for this family of chemicals is discussed in detail in the current work. This work used a novel halogenated dicyanobenzene-based photosensitizer was used as a photocatalyst. It was dissolved in ethanol, exposed to air at ambient temperature, and triggered by a blue light-emitting diode as a renewable energy source. This project's main goal is to use a novel conveniently accessible, reasonably priced donor-acceptor (D-A) based on halogenated cyanoarene. Findings: When exposed to visible light, the 3DPAFIPN [2,4,6tris(diphenylamino)-5-fluoroisophthalonitrile] photocatalyst, which is a thermally activated delayed fluorescence (TADF), can induce single-electron transfer (SET), providing a simple and green method that is highly effective, energy-efficient, and environmentally friendly. Also, we calculated the turnover number (TON) and turnover frequency (TOF) for polyfunctionalized dihydro-2oxypyrroles. Gram-scale cyclization has also been shown to be a practical technique for use in industrial applications. [ABSTRACT FROM AUTHOR]

This document provides a concise summary of an article discussing the use of photocatalysis in organic synthesis, specifically focusing on the synthesis of tetrahydrobenzo[b]pyrans using a carbazole-based photocatalyst called 4CzIPN. The article highlights the advantages of photocatalysis and the diverse applications of tetrahydrobenzo[b]pyrans. It also describes the optimization of the synthesis process and concludes that 4CzIPN is an effective photocatalyst for this purpose. The document includes experimental details and data on the synthesized compounds, and acknowledges the support of the Research Council of the Apadana Institute of Higher Education. [Extracted from the article]

A green radical synthetic approach for the production of tetrahydrobenzo[b]pyran scaffolds, which utilizes a Knoevenagel–Michael cyclocondensation reaction of aldehydes, malononitrile, and dimedone, has been devised. This innovative technique has been designed to achieve environmental sustainability. A novel single-electron transfer photocatalyst was employed for the synthesis in an aqueous ethanol solution under an air atmosphere at room temperature and stimulated with blue LED illumination serving as a renewable energy source. The objective of this undertaking is to cultivate a metal-free donor–acceptor (D–A) photocatalyst that is highly affordable and universally accessible. 9-Mesityl-10-methylacridinium perchlorate (Mes-Acr-Me+ClO4−) is recognized for its expeditious and effortless applicability, high efficiency in yielding products, low energy consumption, and commendable eco-friendliness. This capability facilitates the investigation into the temporal alterations of environmental and chemical constituents. A research inquiry was conducted with the primary objective of determining the turnover number and turnover frequency associated with tetrahydrobenzo[b]pyran scaffolds. Furthermore, the attainment of cyclization at a gram-scale level offers substantiation for its feasibility as a viable solution for industrial implementation. [ABSTRACT FROM AUTHOR]

A highly versatile and convenient synthetic route for biologically active α-amino acid, glutamic acid catalyzed facile and mild preparation of polyfunctionalized dihydro-2-oxypyrroles via one-pot, four condensation domino reaction between aromatic/aliphatic amines, dialkyl acetylenedicarboxylates and formaldehyde have been studied. The route includes green, biodegradable and inexpensive α-amino acid catalyst, high atom-economy, simplicity of operation and work-up procedures, without chromatographic purification steps. The solid catalyst, non-toxic or hazardous, easily handled with mild reaction conditions and excellent yields are the notable benefits of the highly efficient and expedient synthesis of these products.

A sustainable methodology for the synthesis of pyrano [2,3-d] pyrimidine scaffolds have been developed, employing the Knoevenagel-Michael tandem cyclocondensation reaction of barbituric acid/1,3-dimethylbarbituric acid, malononitrile, and aryl aldehydes. This study elucidates the advancement of a sustainable and environmentally conscious approach to synthesizing this category of chemical compounds. In the present investigation, a novel photosensitizer comprising proflavine (PFH+) bio-photocatalyst was employed in an aqueous medium, subjected to air atmosphere at room temperature, and stimulated by a blue-light-emitting diode (LED) to harness renewable energy. The fundamental objective of this initiative is to utilize a photosensitizer (PS) biocatalyst that has been recently developed, can be conveniently acquired, and is priced affordably. The proflavine (PFH+) photocatalyst, demonstrates the ability to initiate photoinduced-electron transfer (PET) through exposure to visible light. This property endows the photocatalyst with a practical and efficient method of achieving high effectiveness, energy efficiency, and environmentally friendly outcomes. The current research endeavor has the objective of examining the turnover number (TON) and turnover frequency (TOF) pertaining to pyrano [2,3-d] pyrimidine scaffolds. Moreover, it has been validated that cyclization at the gram-scale is a feasible approach that can be employed in various industrial settings. [ABSTRACT FROM AUTHOR]

Caffeine was found to be a natural and green and biodegradable catalyst for the one-pot, three-component condensation Biginelli reaction of β-keto esters, aromatic aldehydes and urea/thiourea to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones/thiones derivatives under solvent-free conditions. The remarkable features of this green procedure are high yields, short reaction times, simplicity of operation and work-up procedures, the availability and easy handling of this solid catalyst, avoidance of hazardous or toxic catalysts and organic solvents and economic availability of the catalyst.