Chitosan supported Zn(II) mixed ligand complexes as heterogeneous catalysts for one-pot synthesis of amides from ketones via Beckmann rearrangement

A novel heterogeneous biocatalyst based on graphene oxide for synthesis of pyran derivatives

Graphene oxide modified with tryptophan (GO-Trp) has been introduced as a new heterogeneous acid-base biocatalyst for synthesis of some pyran derivatives. GO was prepared according to the Hummer's method and tryptophan as a low-cost green amino acid is covalently bonded to the surface of GO without any organic or toxic reagents in a green way. The new catalyst was characterized by different spectroscopic methods such as Fourier transform infrared, X-ray diffraction (XRD), etc. …. The results of XRD patterns showed an increase in the distance between the GO plates in the presence of the modifying agent which specifies the presence of amino acid between the GO layers. XPS analysis also confirmed successful modification through the presence of C-N bonds in the structure of the catalyst. In addition, improvements in thermal stability and changes in the morphology of the samples were observed using thermogravimetric analysis and Field emission scanning electron microscopy analysis respectively. Evaluation of the catalyst performance in the synthesis of some benzo[b]pyran and pyrano[3,2-c] chromene derivatives showed presentable results. Seven benzo[b]pyran (4a-4g) and five pyrano[3,2-c] chromene (4h-4l) derivatives were synthesized. GO-Trp as a safe, natural and efficient catalyst, could be reused up to 5 runs for synthesis of pyran derivatives without any significant decrease in its potency. High purity of the products and desirable yields are other points that make the present work more attractive.

A review study on green synthesis of chitosan derived schiff bases and their applications

Chitosan is a bio-degradable, bio-compatible, non-toxic, and renewable biopolymer. The reactive amino group of chitosan has gained importance because using these amino groups can help achieve the different types of structural modification in chitosan. Chemical modification of chitosan via imine functionalization results in the formation of a chitosan Schiff base. The present review covers the green synthesis of chitosan Schiff bases using non-conventional green methods such as microwave irradiation, green solvent, ultrasound irradiation, and one-pot synthesis. These methods are energy-efficient and greener versions of the conventional condensation methods. Scientists have paid significant attention to the chitosan Schiff base because of its unique properties and versatility. These molecules display various biological applications, including antioxidant, antimicrobial, anticancer, antibacterial, and anti-fungal. In addition to biological applications, chitosan Schiff base also has other applications like corrosion inhibition, catalysis, metal ion adsorption, and as a sensor. Available literature particularly shows the different methods for the synthesis of chitosan Schiff bases and their different applications. This review gives detailed insight regarding sustainable approaches to the synthesis of chitosan derived Schiff bases and their applications in various emerging fields.

Chitosan-dibenzylideneacetone based Schiff base: Evaluation of antimicrobial activity and in-vitro cytotoxicity on MCF-7 and L-132

This study holds significant importance as it explores the synthesis and characterization of two chitosan dibenzylideneacetone Schiff bases. Various analytical techniques, such as UV-visible spectroscopy, FTIR, XRD, TGA, DSC, SEM, and elemental analysis, were employed to thoroughly examine these derivatives. The antimicrobial activity of the chitosan derivatives was evaluated against a range of bacterial and fungal strains, while cytotoxicity tests were conducted on MCF-7, L-132, and VERO cell lines. In the antimicrobial tests, the chitosan derivatives exhibited remarkable antibacterial properties against S. aureus, E. coli, and Pseudomonas aeruginosa, as well as potent antifungal properties against Candida albicans and Aspergillus fumigatus. The cytotoxicity assessment revealed that the dibenzylideneacetone chitosan Schiff base (CHDBA) showed significant effectiveness against the L-132 cell line, surpassing the efficacy of doxorubicin by 2.44 times. Moreover, it exhibited substantial activity against the L-132 and MCF-7 cell lines, with IC50 values of 55.29 μg/mL and 185.8 μg/mL, respectively. Notably, none of the chitosan derivatives demonstrated cytotoxicity towards the normal cell line, indicating their non-toxic nature and safe usability. Based on these findings, it is evident that CHDBA holds promise for further development as a potential treatment option for breast cancer and lung cancer.

Magnetic chitosan stabilized palladium nanostructures: Potential catalysts for aqueous Suzuki coupling reactions

This work describes the preparation of palladium-based catalyst supported on magnetic chitosan (Pd@IO-Chitosan) for Suzuki Miyaura C-C coupling reaction. The Pd@IO-Chitosan catalyst was characterized using different spectroscopic and microscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) Spectroscopy and X-ray photoelectron spectroscopy (XPS). Pd@IO-Chitosan was further analysed by thermogravimetric analysis (TGA) in order to determine its thermal behavior. The catalyst comprised Pd, PdO species stabilised by chitosan that facilitated Suzuki coupling reactions. Palladium loading as low as 0.0055 mol% was found to be effective for aqueous Suzuki cross-couplings with excellent yields of over 99%. The catalyst could be recycled and reused at least 12 times with no significant decrease in its catalytic activity.

Pristine and modified chitosan as solid catalysts for catalysis and biodiesel production: A minireview

Chitosan is one of the readily available polymers with relatively high abundance, biodegradable and sustainable materials with divergent functional groups that are employed in broad range of applications. Chitosan is widely used in many fields like adsorption, drug carrier for therapeutic activity, environmental remediation, drug formulation and among others. One of the unique features of chitosan is that it can be transformed to other forms like beads, films, flakes, sponges and fibres depending upon the applications. This review is aimed at showing the potential applications of chitosan and its modified solids in organic transformations. The number of existing articles is organized based on the nature of materials and subsequently with the types of reactions. After a brief description on the structural features of chitosan, properties, characterization methods including various analytical/microscopic techniques and some of the best practices to be followed in catalysis are also discussed. The next section of this review describes the catalytic activity of native chitosan without any modifications while the subsequent sections provide the catalytic activity of chitosan derivatives, chitosan covalently modified with metal complexes/salts through linkers and chitosan as support for metal nanoparticles (NPs). These sections discuss number of organic reactions that include Knoevenagel condensation, oxidation, reduction, heterocycles synthesis, cross-coupling reactions and pollutant degradation among others. A separate section provides the catalytic applications of chitosan and its modified forms for the production of fatty acid methyl esters (FAME) through esterification/transesterification reactions. The final section summarizes our views on the future directions of this field in the coming years.

Palladium nanoparticles immobilized on a magnetic chitosan-anchored Schiff base: applications in Suzuki–Miyaura and Heck–Mizoroki coupling reactions

A palladium nanocatalyst Fe₃O₄@CS-SB-Pd has been synthesized and characterized by FT-IR, XRD, XPS, FESEM, EDX, TEM, TGA, and ICP-AES analysis.