Lalthazuala Rokhum

Selective Monoesterification of Symmetrical Diols Using Resin-Bound Triphenylphosphine.

Coupling reactions to make esters and amides are among the most widely used organic transformations. We report efficient procedures for amide bond formation and for the monoesterification of symmetrical diols in excellent yields without any requirement for high dilution or slow addition using resin-bound triarylphosphonium iodide. Easy purification, low moisture sensitivity, and good to excellent yields of the products are the major advantages of this protocol.

A microwave-assisted highly practical chemoselective esterification and amidation of carboxylic acids

The ubiquitousness of esters and amide functionalities makes their coupling reaction one of the most sought-after organic transformations. Herein, we have described an efficient microwave-assisted synthesis of esters and amides. Soluble triphenylphosphine, in conjugation with molecular iodine, gave the desired products without the requirement for a base/catalyst. In addition, a solid-phase synthetic route is incorporated for the said conversion, which has added advantages over solution-phase pathways, such as low moisture sensitivity, easy handling, isolation of the product by simple filtration, and reusability. In short, our method is simple, mild, green, and highly chemoselective in nature.

Exploiting waste: towards a sustainable production of biodiesel using Musa acuminata peel ash as a heterogeneous catalyst

Today, biodiesel, a renewable, non-toxic and environmentally friendly fuel, is attracting increasing attention worldwide as an alternative to fossil fuel. In the present study, waste biomass-derived banana peel ash served as a heterogeneous catalyst for converting soybean oil into biodiesel at room temperature. The catalyst was well-characterized using IR, XRD, XRF, XPS, SEM, EDX, TEM, TGA and BET analysis techniques to assess its chemical composition, structure and morphology. The TEM-EDX, XPS and XRF analyses revealed the presence of several alkali metals and alkaline earth metals, which probably provide the basic sites for the transesterification reactions to produce biodiesel. A high biodiesel yield of 98.95% was achieved under the optimized reaction conditions. The catalyst has the advantage of being a waste material hence cost-free, easily prepared, biogenic, highly efficient, labor-effective and environmentally friendly; making it a potential candidate as a “green catalyst” for low cost production of biodiesel on the industrial scale.

Magnetic Fe3O4@silica sulfuric acid nanoparticles promoted regioselective protection/deprotection of alcohols with dihydropyran under solvent-free conditions

Protection (and deprotection) of hydroxyl groups via tetrahydropyranylation was carried out effectively using a catalytic amount of Fe3O4 supported silica sulphuric acid nanoparticles (Fe3O4@SiO2@SO3H) under solvent-free conditions. The synthesized nanocatalyst was characterized by XRD, TEM, FT-IR etc. A wide range of tetrahydropyranylated alcohol derivatives were synthesized using this heterogeneous magnetic nanocatalyst within 10–20 min with high yields. In addition, tetrahydropyranyl ethers could also be deprotected to the parent alcoholic compounds in the presence of MeOH using the same catalyst. After completion of the reactions, the catalyst was easily separated from the reaction medium using an external magnet, which ameliorated the overall synthetic process. The catalyst was recovered and reused for five successive reactions without any appreciable loss in its activity. Mild reactions conditions, operational simplicity, solvent free conditions, high selectivity, easy recyclability of the magnetic nanocatalyst, and high yields can be considered as the advantageous features of our procedure.

Polymer supported DMAP: an easily recyclable organocatalyst for highly atom-economical Henry reaction under solvent-free conditions

Polymer supported catalysts are regarded as a borderline class of catalysts, which retains the advantages of homogeneous catalysts while securing the ease of recovery by simple filtration and workup of heterogeneous systems. Additionally, such catalysts are less hygroscopic due to the long polymer backbone. Here we have demonstrated that a catalytic amount of polymer supported DMAP (10 mol%) can lead to excellent conversion of an equimolar mixture of aldehyde and nitroalkane exclusively into β-nitroalcohols via the Henry reaction. Unlike most of the commonly used catalysts, polymer supported DMAP can be recovered by simple filtration and reused several times, thereby reducing the operational cost. High synthetic efficiency, total atom economy, near quantitative yields, mild reaction conditions, operational simplicity, easy recovery and reusability of the catalyst, solvent-free reaction conditions and avoidance of traditional reaction workup make the protocol highly significant from Green and Sustainable Chemistry perspectives.

A mild and highly chemoselective iodination of alcohol using polymer supported DMAP

AbstractThe synthesis of organic compounds using polymer supported catalysts and reagents, where the required product is always in solution, has been of great interest in recent years, both in industries and academia especially in pharmaceutical research. Here, a simple and efficient method for conversion of alcohols into their iodides in high yield using polymer supported 4-(Dimethylamino)pyridine (DMAP) is described. Polymer supported DMAP is used in catalytic amount and is recovered and reused several times. Additionally, this method is highly chemoselective. Graphical AbstractA mild and highly selective iodination of alcohols using polymer supported 4-(Dimethylamino)pyridine (DMAP) in catalytic amount is reported. The base catalyst can be easily recovered by simple filtration and reused several times without appreciable loss in activity.

Waste snail shell derived heterogeneous catalyst for biodiesel production by the transesterification of soybean oil

A waste snail shell (Pila spp.) derived catalyst was used to produce biodiesel from soybean oil at room temperature for the first time. The snail shell was calcined at different temperatures of 400–1000 °C. The synthesized catalysts underwent XRD, SEM, TEM, EDS, FTIR, XRF, TG/DTA and N2 adsorption–desorption isotherm (BET) analysis. The major component CaO was determined at a calcination temperature of 900 °C as depicted in the XRD results. 100% conversion of soybean oil to methyl ester biodiesel was obtained, as confirmed by 1H NMR. A biodiesel yield of 98% was achieved under optimized reaction conditions such as a calcination temperature of 900 °C, a catalyst loading of 3 wt%, a reaction time of 7 h and a methanol to oil ratio of 6 : 1, and biodiesel conversion was confirmed by FT-NMR and IR spectroscopies. A total of 9 fatty acid methyl esters (FAMEs) were identified in the synthesized biodiesel by the retention time and fragmentation pattern data of GC-MS analysis. The catalyst was recycled 8 times without appreciable loss in its catalytic activity. A high biodiesel yield of 98% was obtained under these optimised conditions. The catalyst has the advantage of being a waste material, therefore it is easily prepared, cost free, highly efficient, biogenic, labor effective and environmentally friendly, making it a potential candidate as a green catalyst for low cost production of biodiesel at an industrial scale.

Green biosynthesis, characterisation and antimicrobial activities of silver nanoparticles using fruit extract of Solanum viarum

Green synthesis of nanoparticles is considered an efficient method when compared with chemical and physical methods because of its bulk production, eco-friendliness and low cost norms. The present study reports, for the first time, green synthesis of silver nanoparticles (AgNPs) at room temperature using Solanum viarum fruit extract. The visual appearance of brownish colour with an absorption band at 450 nm, as detected by ultraviolet-visible spectrophotometer analysis, confirmed the formation of AgNPs. X-ray diffraction confirmed the AgNPs to be crystalline with a face-centred lattice. The transmission electron microscopy-energy dispersive X-ray spectroscopy image showed the AgNPs are poly-dispersed and are mostly spherical and oval in shape with particle size ranging from 2 to 40 nm. Furthermore, Fourier transform-infrared spectra of the synthesised AgNPs confirmed the presence of phytoconstituents as a capping agent. The antimicrobial activity study showed that the AgNPs exhibited high microbial activity against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus susp. aureus, Aspergillus niger, and Candida albicans. The highest antimicrobial activity of AgNPs synthesised by S. viarum fruit extract was observed in P. aeruginosa, S. aureus susp. aureus and C. albicans with zone of inhibition, 26.67 mm.