Effective one‐pot synthesis of tetrahydrobenzo[ b ]pyran derivatives using nickel Schiff‐base complex immobilized on iron oxide nanoparticles

A facile one-pot synthesis of tetrahydrobenzo[b]pyrans and 2-amino-4H-chromenes under green conditions

This research developed a new nanocatalyst by incorporating nanocopper iodide onto the surface of a layered double hydroxides modified. This new nanocatalyst enables the green synthesis of tetrahydrobenzo[b]pyrans and 2-amino-4H-chromene derivatives through a one-pot, three-component reaction, demonstrating remarkable activity and selectivity. Key advantages of this method include increased products yield (86-96%), rapid reaction kinetics (5-23 minutes), low reaction temperature (40 °C), synthesis of new products, straightforward purification methods, catalyst recyclability (up to 4 cycles), and solvent-free conditions.

Recent Progress in the Multicomponent Synthesis of Pyran Derivatives by Sustainable Catalysts under Green Conditions

Pyrans are one of the most significant skeletons of oxygen-containing heterocyclic molecules, which exhibit a broad spectrum of medicinal applications and are constituents of diverse natural product analogues. Various biological applications of these pyran analogues contributed to the growth advances in these oxygen-containing molecules. Green one-pot methodologies for synthesising these heterocyclic molecules have received significant attention. This review focuses on the recent developments in synthesising pyran ring derivatives using reusable catalysts and emphasises the multicomponent reaction strategies using green protocols. The advantages of the catalysts in terms of yields, reaction conditions, and recyclability are discussed.

Metformin functionalized dendritic fibrous nanosilica (KCC-1-nPr-Met) as an innovative and green nanocatalyst for the efficient synthesis of tetrahydro-4H-chromene derivatives

An innovative nanocatalyst (KCC-1-nPr-Met) has been prepared from the covalent attachment of metformin on the channels and the pores of n-propyl amine functionalized dendritic fibrous nanosilica (DFNS) and used towards efficient, green, and high yield synthesis of tetrahydro-4H-chromenes derivatives by one-pot three-component reaction of aromatic aldehydes, malononitrile, and dimedone in H₂ O-EtOH at room temperature. The designed nanocatalyst has been characterized by energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and adsorption/desorption analysis (BET) techniques. Also, field emission scanning electron microscopy (FE-SEM) was used to study the morphology of prepared nanocatalyst. The engineered nanocatalyst with uniform fibrous spheres has dendritic structure, high pore volume (0.35 cm³ /g), and great surface area (178 m² /g). Hence, the specific dendritic structure of the prepared nanocatalyst not only improve the diffusion ability of the reactants and products, but also, increase the availability of dynamic sites in the pores and channels of the catalyst. According to the obtained results, a unique strategy was proposed towards the synthesis of important biologically active scaffolds in the presence of nontoxic and environmental friendly nanocatalyst and media. Milder reaction conditions (room temperature), shorter reaction times (5-30 minutes), excellent yields (92%-98%) of the products with higher purity, very simple workup procedure, and using of EtOH: H₂ O as a green solvent are the advantages of the presented work.

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

BACKGROUND

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.

RESULTS

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.

CONCLUSIONS

The fundamental privileges of this method are short reaction time, plain procedure, recyclability of catalyst and high yields of products.