Zn(L-proline)2as a powerful and reusable organometallic catalyst for the very fast synthesis of 2-amino-4H-benzo[g]chromene derivatives under solvent-free conditions

Ni-Unsymmetrical Salen Complex-Catalyzed One-Pot Multicomponent Reactions for Efficient Synthesis of Biologically Active 2-Amino-3-cyano-4H-pyrans

In this report, four new Ni(II)-unsymmetrical salen complexes, [NiL1-4], were prepared by refluxing Ni(Ac)2·4H2O with unsymmetrical salen ligands, H2L1-4. All of the synthesized ligands and complexes were characterized by various physicochemical methods. Also, the solid-state structures of [NiL1], [NiL2], and [NiL4] were defined through single-crystal X-ray diffraction methods. The catalytic potential of [NiL1-4] was investigated by economic and environmentally friendly one-pot-three-component reactions (using reagent: 1,3-dicarbonyls, malononitrile, benzaldehyde, or its derivatives) for the synthesis of biologically active 2-amino-3-cyano-4H-pyran derivatives (total 16 derivatives). After optimization of the reaction conditions, this new synthetic protocol by taking Ni(II)-unsymmetrical salen complexes as catalysts shows excellent conversion with a maximum yield of up to 98% of the effective catalytic products within 1 h of reaction time. In addition, it was observed that the aromatic aldehyde containing an electron-withdrawing group as a ring substituent shows better conversion (up to 98%), and the electron-donating group substituent shows similar or less conversion compared to benzaldehyde under the optimized reaction conditions. From the comparison of results between all these Ni complexes, it was found that the efficiency of the catalytic performance follows the order [NiL1] > [NiL3] > [NiL2] > [NiL4]. A possible reaction pathway was predicted and established through UV-vis spectroscopy. Intermediate II proposed in the reaction pathway was also trapped and characterized through 1H and 13C NMR.

Construction of a Dual-Functionalized Acid-Base Nanocatalyst via HEPES Buffer Functionalized on Fe3O4 as a Reusable Catalyst for Annulation Reactions

Herein, we present a highly efficient dual-functionalized acid-base nanocatalyst, denoted as Fe3O4@GLYMO-HEPES, featuring sulfuric acid and tertiary amines as its dual functional components. This catalyst is synthesized through the immobilization of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as the source of these functionalities onto magnetite (Fe3O4) using 3-glycidoxypropyltriethoxysilane (GLYMO) as a linker. Characterization studies confirm the integrity of the Fe3O4 core, with the GLYMO-HEPES coating exhibiting no phase changes. Furthermore, Fe3O4@GLYMO-HEPES nanoparticles demonstrate a uniform size distribution without aggregation. Notably, the catalyst exhibits remarkable stability up to 200 °C and possesses a saturation magnetization value of 31.5 emu/g, facilitating easy recovery via magnetic separation. These findings underscore the potential of Fe3O4@GLYMO-HEPES as a versatile and recyclable nanocatalyst for various applications. Its catalytic ability was evaluated in the synthesis of various pyrano[2,3-c]pyrazoles and 2-amino-3-cyano-4H-chromenes through a tandem Knorr-Knoevenagel-Michael-Thorpe-Ziegler-type heterocyclization mechanism, using different aldehydes. A wide range of fused heterocycles was synthesized having good to excellent yields. The process is cost-effective, safe, sustainable, and scalable, and the catalyst can be reused up to five times. The prepared catalyst was found to be highly stable and heterogeneous and showed good recyclability.

Magnetically retrievable nanocatalyst Fe3O4@CPTMO@dithizone-Ni for the fabrication of 4H-benzo[h]chromenes under green medium

In the research, the core-shell procedure synthesized a novel magnetically separable heterogeneous nanocatalyst with high stability named Fe3O4@CPTMO@dithizone-Ni. In this method, Fe3O4 was modified as a magnetic core using surfactant (SDS) and polyethylene glycol (PEG) coating; after functionalizing the magnetic nanoparticles with 3-chloropropyl-tri-methoxysilane and dithizone, Ni metal was immobilized. The prepared catalyst was identified and specified utilizing diverse physicochemical techniques involving FT-IR, XRD, SEM, EMA, BET, ICP, EDS, TGA, Raman, and TEM. In the following, to vouch for the efficiency of the obtaining catalyst for the green synthesis of 4H-benzo[h]chromenes utilizing the three-component, one-pot condensation reaction of α-naphthol, aryl glyoxal, and malononitrile as precursors were evaluated. The catalyst exhibited high recyclability with a slight reduction in activity at least eight series without a substantial decrease in stability and efficiency. The synthesized nanocatalyst was evaluated in various conditions such as different solvents, etc. the best of these conditions is the initial concentration of 30 mg of nanocatalyst with water as a solvent in 3 min with 98% yield. The prominent merits of the present research include easy separation of the catalyst without centrifugation, high-accessible raw precursors, cost-effectiveness, environmental friendliness, green reaction status, quick reaction, and excellent product yields.

Wood ash biocatalyst as a novel green catalyst and its application for the synthesis of benzochromene derivatives

Wood ash is a naturally alkaline derived substance containing organic and inorganic constituents. This study investigates the catalytic activity of wood ash as a heterogeneous catalyst for the synthesis of benzochromene derivatives. Several wood ash catalysts, comprising calcium- and potassium-rich carbonates, were prepared from different natural resources under various combustion temperatures. The prepared catalysts were characterized by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction techniques. Catalytic efficiency of the resultant catalysts was tested in the synthesis of benzochromene derivatives. The experimental studies clarified that the catalyst prepared at 850 °C could efficiently expedite the formation of three-component synthesis of benzochromene derivatives in water at 80 °C with high yields. Indeed, alkali, alkaline metal, and metal oxides such as Al₂O₃, SiO₂, MgO, CaO, and Fe₂O₃, are widely utilized as both catalyst and catalyst support in the heterogeneous catalytic processes. The prepared wood ash catalysts (possessing metal oxides, e.g., CuO, Al₂O₃, SiO₂, and CaO) could effectively prompt the electrophilic activity of the carbonyl groups during the nucleophilic attack intermediate, enhancing the efficiency of the reactions.

One-pot multicomponent green LED photoinduced synthesis of chromeno[4,3-b]chromenes catalyzed by a new nanophotocatalyst histaminium tetrachlorozincate

Histaminium tetrachlorozincate nanoparticles are prepared, characterized and applied as an effective and recoverable photocatalyst in the one-pot, green and multi-component synthesis of various chromenes by the reaction of dimedone and/or 1,3-cyclohexanedione, arylaldehyde and 4-hydroxycoumarin in high yields under solventless conditions at ambient temperature. This new catalyst is characterized by FT-IR, XRD, EDX, NMR, SEM and TEM techniques. The incorporation of histaminium ions into the framework of ZnCl₄²⁻ significantly affected the photocatalytic activity of tetrachlorozincate such that good reusability and recyclability are attained. Moreover, reactive species such as ˙O₂⁻ and hydroxyl radicals have proved to be active species in the presented photocatalytic reaction. In addition, the hot filtration test confirms enough stability of the photocatalyst and no significant leaching and destruction of the framework in the course of the reaction. The major advantages of the presented methodology include easy work-up, cost effectiveness, nontoxic nature, broad substrate scope, 100% atom economy, ease of separation, and environment friendly reaction conditions. Finally, the catalyst could be reused many times without significant loss of activity.

(His.)ZnCl₄ nanocatalyst is realized for the preparation of chromenes with a green LED. ˙O₂⁻, OH˙ and h⁺ are reactive species for this reaction. Complementary tests assured good stability and reusability of the nanophotocatalyst.

Eco-friendly synthesis of chromeno[4,3-b]chromenes with a new photosensitized WO3/ZnO@NH2-EY nanocatalyst

A new heterogeneous photoredox nanocatalyst WO₃/ZnO@NH₂-EY (EY: eosin Y) was fabricated and characterized employing some instrumental techniques such as XRD, FT-IR, ICP, TGA, and SEM. The photocatalytic efficiency of the prepared material was investigated in the preparation of various chromeno[4,3-b]chromenes via a simple and practical method. The chromene derivatives were prepared through the condensation of aromatic aldehydes, dimedone, and coumarin under an open-air atmosphere in the presence of a green LED under solventless conditions. The significant advantages of this new method include low reaction time, easy work-up, cost-effective, wide substrate scope, excellent yield, and complete atom economy of the final products. Moreover, the prepared photocatalyst could be frequently recovered up to four times with only a little decrease in the catalytic activity. Furthermore, the progress of the condensation reaction is demonstrated to occur via a radical mechanism, which shows that reactive species such as ˙O₂⁻ and OH˙ together with h⁺ would be involved in the photocatalytic process. Stability and reusability studies also warranty good reproducibility of the nanocatalyst for at least 4 runs. Eventually, a hot filtration test ensured that the nanohybrid catalyst is stable in the reaction medium and its catalytic activity originates from the whole undecomposed conjugated composite.

WO₃/ZnO@NH₂-EY is disclosed in the preparation of chromenes under air in the presence of a green LED. ˙O₂⁻, OH˙, and h⁺ are proposed as reactive species and hot filtration test assured stability and reusability of the nanocatalyst.

Organotellurium compounds: an overview of synthetic methodologies

In wake of emerging applications of organotellurium compounds in biological and material science avenues, the current review describes their key synthetic methodologies while focusing the synthesis of organotellurium compounds through five ligand-to-metal linkages including carbon; carbon-oxygen; carbon-nitrogen; carbon-metal; carbon-sulfur to tellurium. In all of these linkages whether tellurium links with ligands through a complicated or simple pathways, it is often governed through electrophilic substitution reactions. The present study encompasses these major synthetic routes so as to acquire comprehensive understanding of synthetic organotellurium compounds.

Homoleptic and heteroleptic Zn(ii) selone catalysts for thioetherification of aryl halides without scrubbing oxygen

Tetra-coordinated zinc imidazoline selone complexes were synthesized and utilized as potential catalysts in the thioetherification of aryl halides without scrubbing oxygen.

Synthesis, and molecular modeling of bis(3-(piperazine-1-yl)propyl)tungstate (BPPT) nanoparticles, and its first catalytic application for one-pot synthesis of 4H-chromene derivatives

A novel, nano-sized, bis(3-(piperazine-1-yl)propyl)tungstate (BPPT) is introduced as an efficient and reusable organometallic catalyst which is considered as a heterogeneous Bronsted-Lowry base and applied successfully for one-pot synthesis of methyl 2-amino-4-aryl substituted-4H-chromene derivatives with good to excellent yields. BPPT has been prepared via a two-step route from natrium tungstate salt. At first, the oxygens of Na₂WO₄ react with 1-bromo-3-chloropropane via nucleophilic substitution to produce bis(3-choloro propyl)tungstate. Then nucleophilic substitution of piperazine with chlorines produced bis(3-(piperazine-1-yl)propyl) tungstate. Bis(3-(piperazine-1-yl)propyl) tungstate, which was called BPPT, characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and scanning electron microscope (SEM). The catalyst is heterogeneous, green and recyclable. It is a thermally stable and its handling is easy. Its catalytic activity is very high and leads to the production of 4H-pyran derivatives with good to excellent yields in short reaction times. Furthermore, molecular modeling studies and ADMETox prediction revealed that not only it can inhibit acetylcholinesterase enzyme and act as an anti-Alzheimer agent but also has no variation from Lipinski's rule of five and can be a good candidate as anti-Alzheimer agents. These above-mentioned facts can be countered as advantages of the current protocol.

Bis[(l)prolinate-N,O]Zn: A water-soluble and recycle catalyst for various organic transformations

Under the green chemistry perspective, bis[(l)prolinate-N,O]Zn (also called zinc-proline or Zn[(l)-pro]₂) has proven its competence as a promising alternative in a plethora of applications such as catalyst or promoter. Owing to its biodegradable and non-toxic nature of bis[(l)prolinate-N,O]Zn, it is being actively investigated as a water soluble green catalyst for synthetic chemistry. Bis[(l)prolinate-N,O]Zn are readily utilized under mild conditions and have high selectivity and reactivity with broad range of substrate acceptance to make it better reaction medium for a wide variety of organic transformations. This Review summarizes the till date literature on its synthesis, characterization, and its catalytic role in various organic reactions.

A facile one-pot ultrasound assisted for an efficient synthesis of benzo[g]chromenes using Fe3O4/polyethylene glycol (PEG) core/shell nanoparticles

In this research, a general synthetic method for the synthesis of benzo[g]chromenes has been developed using Fe3O4/polyethylene glycol (PEG) core/shell nanoparticle under ultrasonic irradiations. Compared to the conventional methods, ultrasound procedure showed several advantages including mild reaction conditions, high yield products, short reaction times, reusability of the catalyst and little catalyst loading.

Facile synthesis and investigation of 1,8-dioxooctahydroxanthene derivatives as corrosion inhibitors for mild steel in hydrochloric acid solution

For the first time, the corrosion inhibitive performance of some 1,8-dioxooctahydroxanthene derivatives is proposed.

Ultrasound promoted facile one pot synthesis of highly substituted pyran derivatives catalyzed by silica-coated magnetic NiFe2O4nanoparticle-supported H14[NaP5W30O110] under mild conditions

Application of ultrasonic method as a green source of energy to reduce the reaction times compared to conventional processes. NiFe₂O₄@SiO₂–H₁₄[NaP₅W₃₀O₁₁₀] was used as magnetically separable catalyst for synthesis of pyrans with minimum work up.

Green synthesis of tetrahydrobenzo[b]pyrans, pyrano[2,3-c]pyrazoles and spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles catalyzed by nano-structured diphosphate in water

Preparation of nanostructured diphosphate Na₂CaP₂O₇. Avoiding of any acid catalysts. The prepared catalyst is reusable and eco-friendly. The method is easy and contains simple experimental procedure.