L-Proline-Functionalized Fe3 O4 Nanoparticles as an Efficient Nanomagnetic Organocatalyst for Highly Stereoselective One-Pot Two-Step Tandem Synthesis of Substituted Cyclopropanes

Synergistic effect of silver NPs immobilized on Fe3O4@L-proline magnetic nanocomposite toward the photocatalytic degradation of Victoria blue and reduction of organic pollutants

The surface of magnetite (Fe₃O₄) nanoparticles was subject to modification through the incorporation of L-proline (LP) by simple co-precipitation method in which silver nanoparticles were deposited by in situ method, thereby yielding the Fe₃O₄@LP-Ag nanocatalyst. The fabricated nanocatalyst was characterized using an array of techniques including Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), and UV-Vis spectroscopy. The results evince that the immobilization of LP on the Fe₃O₄ magnetic support facilitated the dispersion and stabilization of Ag NPs. The SPION@LP-Ag nanophotocatalyst exhibited exceptional catalytic efficiency facilitating the reduction of MO, MB, p-NP, p-NA, NB, and CR in the presence of NaBH₄. The rate constants obtained from the pseudo-first-order equation were 0.78, 0.41, 0.34, 0.27, 0.45, 0.44, and 0.34 min^-1 for CR, p-NP, NB, MB, MO, and p-NA, respectively. Additionally, the Langmuir-Hinshelwood model was deemed the most probable mechanism for catalytic reduction. The novelty of this study lies in the use of L-proline immobilized on Fe₃O₄ MNPs as a stabilizing agent for the in-situ deposition of silver nanoparticles, resulting in the synthesis of Fe₃O₄@LP-Ag nanocatalyst. This nanocatalyst exhibits high catalytic efficacy for the reduction of multiple organic pollutants and azo dyes, which can be attributed to the synergistic effects between the magnetic support and the catalytic activity of the silver nanoparticles. The easy recyclability and low cost of the Fe₃O₄@LP-Ag nanocatalyst further enhance its potential application in environmental remediation.

Indane-1,3-Dione: From Synthetic Strategies to Applications

Indane-1,3-dione is a versatile building block used in numerous applications ranging from biosensing, bioactivity, bioimaging to electronics or photopolymerization. In this review, an overview of the different chemical reactions enabling access to this scaffold but also to the most common derivatives of indane-1,3-dione are presented. Parallel to this, the different applications in which indane-1,3-dione-based structures have been used are also presented, evidencing the versatility of this structure.

Copper acetate catalysed C-C bond formation en route to the synthesis of spiro indanedione cyclopropylpyrazolones

This article reports the synthesis of spiro compounds based on an indanedione-cyclopropane-pyrazolone framework. The reaction relied upon the Michael-initiated ring closure strategy and was carried out under Cu(OAc)₂ catalysis, assisted by an oxygen atmosphere and the base Et₃N. The final compounds were obtained as an inseparable mixture in most cases with modest to good yields using diverse substrates. Among the two plausible routes, computational studies indicated the feasibility of a route which involves a four-membered Cu containing intermediate. Given the generic nature of the developed method, it may be utilised to synthesise other analogous spiro systems.

NMR relaxation time measurements of solvent effects in an organocatalysed asymmetric aldol reaction over silica SBA-15 supported proline

The behaviour of solvents in solid-supported proline organocatalysts is explored using NMR relaxation measurements coupled with reaction screening. Solvents with a lower affinity for the solid surface lead to a higher reactivity.

Simultaneous Fe3O4 Nanoparticle Formation and Catalyst-Driven Hydrothermal Cellulose Degradation

Breakdown and utilization of cellulose are critical for the bioenergy sector; however, current cellulose-to-energy conversion schemes often consume large quantities of unrecoverable chemicals, or are expensive, due to the need for enzymes or high temperatures. In this paper, we demonstrate a new method for converting cellulose into soluble compounds using a mixture of Fe²⁺ and Fe³⁺ as catalytic centers for the breakdown, yielding Fe₃O₄ nanoparticles during the hydrothermal process. Iron precursors transformed more than 61% of microcrystalline cellulose into solutes, with the composition of the solute changing with the initial Fe³⁺ concentration. The primary products of the breakdown of cellulose were a range of aldaric acids with different molecular weights. The nanoparticles have concentration-dependent tuneable sizes between 6.7 and 15.8 nm in diameter. The production of value-added nanomaterials at low temperatures improves upon the economics of traditional cellulose-to-energy conversion schemes with the precursor value increasing rather than deteriorating over time.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Highly diastereoselective spiro-cyclopropanation of 2-arylidene-1,3-indanediones and dimethylsulfonium ylides

High diastereoselectivity, mild conditions and excellent functional group compatibility.

Annulations involving 2-arylidene-1,3-indanediones: stereoselective synthesis of spiro- and fused scaffolds

Stereoselective annulations of 2-arylidene-1,3-indanediones towards spiro-carbocycles as well as spiro/fused heterocycles based on various cycloadditions and tandem annulations are described.