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A non-noble metal-based bifunctional Fe–Ni/MMT nanocomposites exhibit excellent H2 generation capability from the methanolysis of NaBH4 at a rate of 16,200 mL min−1 g−1Fe–Ni with 10%Fe–Ni loading on MMT support. Moreover, the evolved H2 from this catalytic process is efficiently utilized for the one-pot step-wise synthesis of secondary amines from nitrobenzene and aldehydes using NaBH4 as a source of hydrogen at room temperature. Circumventing the reduction of aldehyde and triggering the formation of imine intermediate through sequential addition of reactants in a time dependent manner has resulted in the excellent yields for aliphatic, aromatic and heterocyclic amines (91–98%). The catalytic activity of Fe–Ni/MMT nanocomposite is ascribed to synergic association of Fe–Ni NPs, Lewis and Bronsted acidity as well as adsorptive nature of MMT. Thus, a simple, facile and greener route is developed for the synthesis of secondary amines with an efficient H2 generation non-noble metal catalyst and easily accessible H-donor at room temperature.

Nanoceria is considered to be a promising material for the modulation of its pro-and anti-oxidant activities due to its tuneable Ce3+/Ce4+ ratios under different physiological conditions. In the present study, we explored the feasibility of CeO2 NPs as a pro-drug and drug carrying vehicle towards receptor-mediated targeted delivery of doxorubicin (DOX) to MCF-7 cancer cells. The surface-engineered, substancilly smaller sized (3–4 nm) particles of CeO2-loaded DOX-nanoconjugates possess excellent dispersibility in water, with surface charges in the range of +17.03 to −7.68 mV. The functionalised nanoceria exhibits a quasi-reversible Ce3+/Ce4+ redox couple at a considerably lower redox potential, while the amount of DOX loaded on the nanoceria was found to be in the range of 2.3–12%. The DNA binding and cleavage activities of CeO2 NPs suggest their beneficial binding with phosphate linkages that induces DNA damage. Uncoated and PEGylated CeO2 NPs possess significant anticancer activity against MCF-7, with the latter exhibiting better activity at 2.5 μg mL−1 due to its interference in cellular redox reactions induced by reactive oxygen species (ROS). Moreover, the synergic conjugation of nanoceria with DOX resulted in excellent cytotoxicity of these nanoconjugates against MCF-7 cells at an extremely low concentration (57.5 ng mL−1) of DOX. This feature can be ascribed to the enhanced uptake of nanoceria as well as site targeting of DOX nanoconjugates facilitated by the folic acid (FA) via folate receptors. Thus, it may be concluded that nanoceria behaves in a dual manner both as a pro-drug and an efficient nanocarrier for delivery of DOX at a specific site.

The hydrazones of nonsteroidal anti-inflammatory drugs (NSAIDs) diclofenac and ibuprofen are synthesized with aldehydes of pyridine and imidazole and are characterized by 1H, 13C and mass spectroscopy. Cu(II) complexes of hydrazones constructed from these ligands possess square planar geometry for bidentate diclofenac-hydrazone and tridentate ibuprofen-hydrazone conjugates with [Cu(L)2] and [Cu(L)Cl] compositions, respectively. The observed irreversible Cu(II)/Cu(I) redox couple in the range of +0.20 to +0.61 V is due to the substantial distortion in the square-planar geometry. ESR studies indicate the appreciably covalent character within M–L bonding due to extensive delocalization of electron from dx2–-y2 orbital. The hydrazone–NSAID conjugates exhibit substantial cytotoxicity against A-549, HCT-116 and MDA-MB-231 cancer cell lines with ibuprofen-imidazole-hydrazone ligand possessing the lowest IC50 (2.26 µM) amongst the synthesized NSAID-conjugates. Interestingly, its Cu(II) complex also displays excellent anticancer activity against MDA-MB- 231 with IC50 value of 3.58 µM. Such a feature may be ascribed to the synergistic association of Cu(II)–NSAID–hydrazone linkage. Thus, conjugation of NSAID with hydrazone and its complexation with a bioactive metal ion may be regarded as a potential strategy for designing of non-platinum anticancer agents.

A simple, facile, and convenient route is adopted for the synthesis of 4,9-dimethoxynaphthalide (4,9-DMN); an analog of naturally occurring naphthalene lactone family. It is achieved without involving a tedious and hazardous lithiation step using 3-(bromomethyl)-1,4-dimethoxy-2-naphthaldehyde as key intermediate through base catalyzed oxidative cyclization resulting in a five-membered lactone ring. This compound exhibits significant anti-fungal activity against Candida albicans while it is found to be less toxic towards MCF-7 cancer cell line with IC50 value less than 250 µM.

Direct one-pot hydrogenation of furfural (FFR) to cyclopentanone (CPO) was investigated over different silica-supported Pd catalysts. Among these, 4% Pd on fumed silica (4%Pd/f-SiO2) showed remarkable results, achieving almost 98% furfural (FFR) conversion with ∼89% selectivity and 87% yield to cyclopentanone at 165 °C and 500 psig H2 pressure. More interestingly, the fumed-silica-supported catalyst tuned the selectivity toward the rearrangement product, i.e., cyclopentanone, whereas all of the other supports were found to give ring hydrogenation as well as side chain hydrogenation products due to their parent Brönsted acidity and specific support properties. X-ray diffraction data revealed the presence of different phases of the face-centered cubic lattice of metallic Pd along with lowest crystallite size of 15.6 nm in the case of the silica-supported Pd catalyst. However, Pd particle size was found to be in the range of 5–13 nm with even dispersion over the silica support, confirmed by high-resolution transmission electron microscopy analysis. While studying the effect of reaction parameters, it was observed that lower temperature gave low furfural conversion of 58% with only 51% CPO selectivity. Similarly, higher H2 pressure lowered CPO selectivity with subsequent increase in 2-methyl furan and ring hydrogenation product 2-methyl furan and 2-methyl tetrahydrofuran. Thus, as per the requirement, the product selectivity can be tuned by varying the type of support and/or the reaction parameters suitably. With the help of several control experiments and the characterization data, a plausible reaction pathway was proposed for the selective formation of cyclopentanone.

The acid functionality of montmorillonite clay K 10 (MMT-K 10) was found to play a key role to give 1,2-pentanediol (1,2-PeDO) in Pd catalysed furfural hydrogenation. Among various Pd loadings on MMT-K 10, 3% Pd/MMT-K 10 catalyst exhibited excellent performance giving almost complete conversion of FFR and the highest selectivity of 66% to 1,2-PeDO. Py-IR of the catalyst evidenced the presence of Bronsted acidity which was responsible in C5-O cleavage of furan ring after the formation of furfuryl alcohol which is the first step intermediate in FFR hydrogenation. At a lower temperature of 140 °C, highest selectivity of 56% was achieved for FAL while increase in temperature to 220 °C, enhanced the selectivity to 1,2-PeDO. Keeping the temperature constant at 220 °C, increase in H 2 pressure from 500 to 750 psig, resulted in decrease in 1,2-PeDO selectivity from 66 to 34% with proportionate increase in THFAL selectivity. Thus as per the requirement, the product selectivities can be tailored by varying the reaction parameters suitably. Several control experiments were also performed the results of which combined with the characterization data allowed to propose a plausible reaction pathway for the formation of 1,2-PeDO.

Dihydrobenzofuran as one of the active ingredients of the naturally occurring motif is synthesized by using in situ generation of ortho allyl phenols. Aryl allyl ethers on reacting with catalytic amounts of non noble metal iron (III) chloride supported on MCM-41 under moderate reaction conditions yield dihydrobenzofuran. First step via Claisen rearrangement gives ortho allyl phenol followed by its in situ cyclization to yield dihydrobenzofuran in very good yields. Both Lewis as well as Brønsted acidity of the catalyst as evidenced by Py-FTIR studies was found to catalyze the cascade synthesis of dihydrobenzofuran. The scope of the present strategy was successfully demonstrated for several substrates with varying electronic effects for the synthesis of corresponding dihydrobenzofuran with high yields in a range of 71–86%. Keywords: Claisen rearrangement, Dihydrobenzofuran, Aryl allyl ether, MCM-41, Ferric chloride

Various iridium supported carbon catalysts were prepared and screened for the direct hydrogenation of furfural (FFR) to 2-methyl furan (2-MF). Amongst these, 5% Ir/C showed excellent results with complete FFR conversion and highest selectivity of 95% to 2-MF at a very low H2 pressure of 100 psig. Metallic (Ir°) and oxide (IrO2) phases of Ir catalyzed the first step hydrogenation involving FFR to FAL and subsequent hydrogenation to 2-MF, respectively. This was confirmed by XPS analysis and some control experiments. At a low temperature of 140 °C, almost equal selectivities of FAL (42%) and 2-MF (43%) were observed, while the higher temperature (220 °C) favored selective hydrodeoxygenation. At optimized temperature, 2-MF was formed selectively while higher pressure and higher catalyst loading favored ring hydrogenation of furfural rather than side chain hydrogenation. With the combination of several control experimental results and detailed catalyst characterization, a plausible reaction pathway has been proposed for the selective formation of 2-MF. The selectivity to various other products in FFR hydrogenation can be manipulated by tailoring the reaction conditions over the same catalyst.

The present work describes the improved photocatalytic activity of cetyl trimethylammonium bromide (CTAB)-assisted Bi2WO6 (CBTH) toward the synthesis of bioactive benzazoles. X-ray diffraction analysis of CBTH suggests that crystal growth has occurred along the (200) plane, whereas field-emission scanning electron microscopy images confirm two-dimensional rose bud morphology and high-resolution transmission electron microscopy analysis suggests the formation of thin nanosheets possessing an orthorhombic structure. Temperature-programmed desorption of ammonia and Py-IR measurements indicate substantial acidity with the generation of Brønsted acid sites on the surface of CBTH. Raman spectra of CBTH also corroborate these observations with the formation of defects within [Bi2O2]2+ layers, resulting in decreased thickness and shapes of nanoplates. These beneficial properties are explored toward the photochemical synthesis of benzazoles using a 35 W tungsten lamp and a CBTH photocatalyst, resulting in better yields at lesser exposure time. It is observed that the catalytic activity is retained up to five consecutive cycles with marginal decrease in % yield. Such a feature can be ascribed to the photostability of the photocatalyst even after continuous exposure to light, implying that the surface active sites remained unaltered as evident from the X-ray photoelectron spectroscopy analysis of pre- and post-characterization of CBTH. Moreover, decrease in the surface hydroxyl groups after five catalytic cycles also accounts for the generation of enhanced Brønsted sites owing to the presence of Bi–O on the surface of CBTH. It exhibits better catalytic activity as compared to other photocatalysts employed for the synthesis of benzazoles. Thus, CBTH serves as a robust photocatalyst for the facile synthesis of these heterocycles in a sustainable manner.

Four Ru(II) complexes with tridentate ligands viz. (4-hydroxy-N′-(pyridin-2-yl-ethylene) benzohydrazide [Ru(L1)(PPh3)2(Cl)] (1), N′-(pyridin-2-yl-methylene) nicotinohydrazide [Ru(L2)(PPh3)2(Cl)] (2), N′-(1H-imidazol-2-yl-methylene)-4-hydroxybenzohydrazide [Ru(L3)(PPh3)2(Cl)] (3), and N′-(1H-imidazol-2-yl-methylene) nicotinohydrazide [Ru(L4)(PPh3)2(Cl)] (4) have been synthesized and characterized. The methoxy-derivative of L3H (abbreviated as L3H*) exists in E configuration with torsional angle of 179.4° around C7-N8-N9-C10 linkage. Single crystal structures of acetonitrile coordinated ruthenium complexes of 1 and 3 having compositins as [Ru(L1)(PPh3)2(CH3CN)]Cl (1a) and [Ru(L3)(PPh3)2(CH3CN)]Cl (3a) revealed coordination of tridentate ligands with significantly distorted octahedral geometry constructed by imine nitrogen, heterocyclic nitrogen, and enolate amide oxygen, forming a cis-planar ring with trans-placement of two PPh3 groups and a coordinated acetonitrile. Ligands (L1H-L4H) and their ruth...

Single step conversion of furfural to ring hydrogenation and decarbonylation products, 2-methyltetrahydrofuran (2-MeTHF) and tetrahydrofuran (THF) in high selectivity was achieved by controlling the particle size of Pd/C catalyst. The particle size variation of Pd/C catalysts in the range of 3.8 to 22 nm could be achieved by employing different reducing agents. Of particular interest was the NaBH4 reduced catalyst (Pd−B/C), which gave the lowest crystallite size of 4.8 nm due to incorporation of B into the inner lattices of Pd−Pd. This phase was evidenced by a characteristic XRD peak of Pd−B at 2θ=38.85 O as well as a shift of (111) peak (40.07 O) of Pd towards the lower value (39.8 O). As compared to formaldehyde reduced catalyst (Pd−F/C), Pd−B/C catalyst completely suppressed the formation of furfuryl alcohol to give > 65 % selectivity to 2-MeTHF and THF. At 180 OC, almost equal distribution of side chain hydrogenation and ring opening products, 2-MF (45 %) and PeDO (37 %), respectively, was observed while, higher temperature clearly favoured ring hydrogenation and decarbonylation reactions to give 2-MeTHF and THF.

Removal of the protecting allyl group from allyl aryl ethers in the presence of other oxygen protecting groups was successfully achieved using a solid acid supported on the high surface area material MCM-41. The catalyst showed excellent activity in the presence of various electron withdrawing, electron donating, and oxidizable functional groups. The methodology is also very useful for the removal of protecting allyl groups of various natural products such as vanillin, isovanillin, and other oxygen functionalized aldehydes and ketones.

Bimetallic nanoparticles have diverse applications in catalytic processes owing to the differences in individual properties that contribute to their increased catalytic activity. To further improve the efficiency, they are dispersed in an inert support that enhances the catalytic activity toward organic transformations. In this study, we report simple, facile, and cost-effective chemical route for the fabrication of nanocomposites with Fe–Ni bimetallic nanoparticles supported on montmorillonite (MMT) possessing variation in the Fe and Ni content. These composites are characterized with X-ray diffraction, transmission electron microscopy surface area, and NH3-TPD. Fe–Ni bimetallic nanoparticles are well-dispersed within MMT structure having particle sizes of about 30–40 nm. Among various compositions of Fe–Ni/MMT catalysts, composite with 25% Fe and 25% Ni exhibits >99% LA conversion with 98% selectivity to GVL within 1 h. IPA is found to be better solvent for levulinic acid (LA) to γ-valerolactone (GVL) c...

A facile, one-pot three component catalytic method is developed for the synthesis of N-substituted tetrazole using RuO2/MMT nanocomposite. It is characterized with low and wide angle XRD which suggests that RuO2 nanoparticles are evenly dispersed on the surface of MMT while FESEM images indicate a spherical morphology having size in the range of 40-50 nm. The catalytic efficiency is evaluated for three component one-pot synthesis of the tetrazole using various amine, sodium azide and triethyl-ortho-formate under solvent free condition. This strategy has resulted in good to excellent yields (84 – 97%) of N-substituted tetrazoles within moderate reaction time. Moreover, the catalyst possesses excellent reusability up to five cycles with only 5% decrease in the yield of tetrazole after 5th cycle. The beneficial catalytic activity of the bifunctional nanocomposite is attributed to the uniformly dispersed RuO2 nanoparticles on the surface of MMT where RuO2 site is responsible for coordination of isocyanide intermediate while strong acidic character of MMT induces condensation and cyclization steps in a synergic manner. Thus, it can be argued that RuO2/MMT nanocomposite possesses potential applications for Multi Component Reactions (MCR) in terms of efficient and sustainable manner.

A sustainable process of catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to γ-valerolactone (GVL) was investigated over Ni on various supports (Al2O3, ZnO, MMT and SiO2) in the presence of isopropanol (IPA) as the H-donor. Among these, the montmorillonite (MMT) supported Ni catalyst showed almost complete LA conversion (>99%) and selectivity (>99%) to GVL within 1 h. XRD and XPS results showed that the concentration of the metallic species significantly enhanced (two to four times) in the recovered sample as compared to the freshly prepared Ni/MMT. This was due to the in situ reduction of Ni2+ species present on the catalyst surface, through liberated H2 under the reaction conditions. The strong acid strength of MMT, evidenced by NH3-TPD and py-IR, facilitated the esterification of LA as well as cyclization to GVL. The conversion–selectivity pattern was found to decrease in the IPA–water mixture while, it remained unchanged in the IPA–acetone mixture. Our catalyst could be efficiently recycled up to five times with consistent CTH activity and selectivity to GVL. The plausible mechanism of LA to GVL conversion involves the formation of a levulinate ester with IPA that favours its simultaneous hydrogenation and cyclization in a spontaneous manner to give GVL and regenerating IPA for sustainability.