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A sustainable and environmentally benign biogenic technique for one-step synthesis of Ni-NPs (NiC2O4·2H2O-NPs) using Portulaca oleracea (purslane) leaf extract has been disclosed for the first time.

In this work, a uniquely designed imidazolium-based dicationic ionic liquid (IL) was synthesized as a greener template and applied for the synthesis of ZSM-5 zeolite as a heterogeneous catalyst for...

A greener approach for the synthesis of various functionalized biaryl frameworks in good to excellent yield through palladium-catalyzed denitrogenative cross-coupling of aryl halides with arylhydrazines under mild reaction conditions was developed. Catalytic system is free from the aid of expensive ligands and external oxidants. Biogenically prepared palladium nanoparticles (Pd NPs) immobilized cellulose based dip catalyst displayed excellent reactivity and selectivity toward the synthesis of a broad array of symmetrical and unsymmetrical biaryls through C–N bond cleavage in air as green oxidant. In addition, recyclability in denitrogenative cross-coupling reaction was also studied which showed excellent recycling performance and the dip catalyst remained stable even after several reuses. Thus, our newly developed strategy was successfully applied for constructing wide-ranging functional groups tolerated biaryls using arylhydrazines and aryl halides as coupling partners which is most useful for practical applications in synthetic chemistry.

An eco-friendly green method for a one-step synthesis of palladium nanoparticles and their synthetic utility are reported. Phytochemicals like amines, alcohols, and phenols present in the Areca Nut Husk extract facilitate the reduction of Pd(II) to Pd(0). The phytochemicals serve as stabilising agents and ligands for palladium reduction and the need for an external ligand is avoided. The Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy of newly synthesized palladium nanoparticles revealed a spherical morphology. The catalytic activity of the nanoparticles was tested for 1,2-difunctionalization of ynamides, Heck coupling, denitrogenative coupling of phenylhydrazine and C–H arylation of indole. Moreover, catalyst recyclability, control experiments, mechanistic elucidation, and gram-scale synthesis are elaborated.

A regioselective C2 arylation of indoles, benzothiophene and benzofuran without directing group has been accomplished using economically cheap Pd NPs and NHC-Pd@MNPs catalyst. The reusable catalyst is efficiently employed to access C2 arylated heterocycles in good to excellent yield. The reusability of the catalyst is studied up to five cycles and a gram-scale synthesis has been achieved. The reaction mechanism is well supported by control experiments and literature precedents.

A robust synthesis approach to develop CuO/ZnO nanocomposites using microwave-epoxide-assisted hydrothermal synthesis and their proficiency toward H2S gas-sensing application are reported. The low-cost metal salts (Cu and Zn) as precursors in aqueous media and epoxide (propylene oxide) as a proton scavenger/gelation agent are used for the formation of mixed metal hydroxides. The obtained sol was treated using the microwave hydrothermal process to yield the high-surface area (34.71 m2/g) CuO/ZnO nanocomposite. The developed nanocomposites (1.25-10 mol % Cu doping) showcase hexagonal ZnO and monoclinic CuO structures, with an average crystallite size in the range of 18-29 nm wrt Cu doping in the ZnO matrix. The optimized nanocomposite (2.5 mol % Cu doping) showed a lowest crystallite size of 21.64 nm, which reduced further to 18.06 nm upon graphene oxide addition. Morphological analyses (scanning electron microscopy and transmission electron microscopy) exhibited rounded grains along with copious channels typical for sol-gel-based materials . Elemental mapping displayed the good dispersion of Cu in the ZnO matrix. When these materials are employed as a gas sensor, they demonstrated high sensitivity and selectivity toward H2S gas in comparison with the reducing gases and volatile organic compounds under investigation. The systematic doping of Cu in the ZnO matrix exhibited an improved response from 76.66 to 94.28%, with reduction in operating temperature from 300 to 250 °C. The 2.5 mol % doped Cu in ZnO was found to impart a response of 23 s for 25 ppm of H2S. Gas-sensing properties are described using an interplay of epoxide-assisted sol-gel chemistry and structural and morphological properties of the developed material.

The catalyst-free regioselective [3+2]-cycloaddition of α,β-unsaturated N-arylnitrones with alkenes are developed. The series of synthetically important functionalized isoxazolidines are prepared in good to excellent yields by step economic pathway under ligand and transition-metal-free conditions. The regioselective cycloaddition pathway supported by control experiment and computational study.

An exclusive synthesis of benzo-oxazine, benzo-oxazepine, and benzo-oxazocine from aryl propanal and 2-(hydroxyamino)phenyl alcohol under metal-free conditions is described. O atom transfer and formation of new C═O, C-N, and C-O bonds occur at room temperature to form six-, seven-, and eight-membered heterocycles under one-pot reaction conditions without using an external oxidant and base. The photophysical properties are studied using ultraviolet-visible absorption and photoluminescence. The mechanistic elucidation is well supported by control experiment and literature precedents.

Biowaste resources are the promising renewable raw materials for green and economical purpose. In this context, usage of cellulose fibers as linear and flexible bio-polymer derived from waste lignocellulosic biomass has gained much attention in various applications due to their extensive properties such as eco-friendly, low cost, easy availability, low energy consumption, bio-degradability, high tensile strength and could be recyclable compared to other synthetic fibers those are expensive and non-decomposable in nature. In the present work, biogenically prepared palladium nanoparticles from waste banana pseudostem extract are immobilized on cellulose fibers, isolated from waste banana pseudostem as dip catalyst through green protocol for the first time. The synthesized new dip catalyst was characterized by ATR-IR, FE-SEM, EDS, ICP-OES, HR-TEM, p-XRD, TG/DTA, UV–Vis, GC–MS, XPS and BET surface area analysis. Catalytic potential and reusability of newly developed dip catalyst has been studied in Suzuki–Miyaura cross-coupling reactions for the synthesis of various functional groups tolerated biaryls for practical applications. In addition, an analgesic non-steroidal anti-inflammatory drug molecule Felbinac was synthesized in greener reaction conditions by using dip catalyst with good yield.

In this paper, highly stable, powerful, and recyclable magnetic nanoparticles tethered N-heterocyclic carbene-palladium(II) ((CH3)3-NHC-Pd@Fe3O4) as magnetic nanocatalyst was successfully synthesized from a simplistic multistep synthesis under aerobic conditions through easily available low-cost chemicals. Newly synthesized (CH3)3-NHC-Pd@Fe3O4 magnetic nanocatalyst was characterized from various analytical tools and catalytic potential of the (CH3)3-NHC-Pd@Fe3O4 magnetic nanocatalyst was studied for the catalytic reduction of toxic 4-nitrophenol (4-NP), hexavalent chromium (Cr(VI)), Methylene Blue (MB) and Methyl Orange (MO) at room temperature in aqueous media. UV-Visible spectroscopy was employed to monitor the reduction reactions. New (CH3)3-NHC-Pd@Fe3O4 magnetic nanocatalyst exhibited excellent catalytic activity for the reduction of toxic environmental pollutants. Moreover, (CH3)3-NHC-Pd@Fe3O4 magnetic nanocatalyst could be easily and rapidly separated from the reaction mixture with the help of an external magnet and recycled minimum five times in reduction of 4-NP, MB, MO and four times in Cr(VI) without significant loss of catalytic potential and remains stable even after reuse.

We report a facile, green synthesis of graphene/Ag/ZnO nanocomposites and their use as acetone sensors via a medicinal plant extraction assisted precipitation process. The choice of plant extract in combination with metal nitrates led to self-sustaining colloid chemistry. Along with the green synthesis strategy, structural, morphological and gas sensing properties are described.

In the current work, a new stable and powerful magnetic nanoparticle supported Schiff base-palladium(II) (MNPs@SB-Pd) nanomagnetic catalyst was synthesized. The structural feature of the MNPs@SB-Pd nanomagnetic catalyst was properly characterized using a combination of attenuated total reflectance infrared spectroscopy (ATR-IR), ultraviolet–visible spectroscopy (UV–Visible), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller surface area analysis (BET). The air- and moisture stable prepared MNPs@SB-Pd nanomagnetic catalyst was applied in C–C bond formation through Suzuki-Miyaura cross-coupling reactions and reduction of nitroarenes. Use of green medium, eco-friendly, waste-free, efficient preparation leading to high yield of products, short reaction time and cost effective catalyst are the major benefits of the method presented. In addition, the MNPs@SB-Pd nanomagnetic catalyst was easily separated from the reaction mixture with the help of an external magnetic field and reused for five consecutive cycles in Suzuki-Miyaura cross-coupling and ten consecutive cycles in reduction of nitroarene reactions with no significant loss of catalytic efficiency.

In the current work, palladium nanoparticles (Pd NPs) were prepared from palladium acetate biogenically using the aqueous-ethanolic extract of black pepper (Piper nigrum) and characterized by various analytical techniques like XRD, FE-SEM, EDS, TEM, ATR-IR, UV–Vis spectroscopy, BET, TGA and ICP-OES analysis. The reduction of Pd(II) to Pd(0) is achieved by the action of various phytochemicals present in the black pepper extract like phenols, acids, pellitorine, ethyl piperonyl cyanoacetate, piperine and N-isobutyl-tetradeca-2,4-dienamide. The biosynthesized Pd NPs shown excellent catalytic activity in aryl halide cyanation and Hiyama cross-coupling reactions. Also, less toxic potassium hexacyanoferrate(II) trihydrate was used as cyanide source in aryl halide cyanation and Hiyama cross-coupling was performed under fluoride free condition. Both reactions proceeded well with Pd NPs under ligand free circumstances to give good to excellent yields. The Pd NPs were recovered after each reaction and recycled up to five times in aryl halide cyanation and ten times in Hiyama cross-coupling without considerable loss in the activity. Green synthesis of palladium nanoparticles: applications in aryl halide cyanation and Hiyama cross-coupling reaction under ligand free conditions.

In the present work, we report the synthesis of low-cost mesoporous biomass carbon (BC) from waste radish leaves for the first time with a specific surface area of 703.99 m2g−1 and was employed as support in the preparation of palladium-based (BC-TPEA@Pd) heterogeneous catalyst. The prepared BC-TPEA@Pd heterogeneous catalyst was fully characterized by numerous analytical techniques. Moreover, we have developed a greener reaction protocol for Suzuki-Miyaura cross-coupling reactions using the basic extract of radish leaves with base/ligand/promoter/additives free reaction conditions. The newly developed reaction protocol offers greener reaction conditions, efficient, economical and highly recyclable methodology for the synthesis of substituted biaryls for commercial applications. Additionally, BC-TPEA@Pd catalyst shows high performance as supercapacitor electrode material in an aqueous electrolyte- based two electrode cell with a specific capacitance of 129.36F/g at a current density of 0.25 A/g and a 96.14 % of original capacitance retention after 2500 GCD cycles.

A transition metal-free, four-component one-pot synthesis of polyfunctionalized fluorinated β-keto-imidates via the functionalized hydration of alkynes has been described. The intermediate 1,3-ketoamino moiety was obtained from easily accessible arylpropioladehyde and arlyhydroxylamine and was treated with Selectfluor delivering fluorinated β-keto-imidates. A wide variety of functional groups are tolerated under mild reaction conditions and the product applicability is highlighted.

The present work demonstrates basicity controlled MgCo2O4 spinel oxides as promising catalysts for fixation of CO2 into epoxides at atmospheric pressure. Four different MgCo2O4 nanostructures were synthesized using different interlayer anions (chloride, nitrate, acetate, sulphate) present in the metal salt precursors which strongly altered their basicity and played a stimulating role in their catalytic efficiency. The characterization results of all four MgCo2O4 nanostructures revealed effect on morphology, surface area and developed diversely exposed Lewis basic (O2−) sites on the catalyst surface. Particularly, [MgCo2O4]-[Cl−] nanostructures prepared using chloride (Cl−) anion showed porous 3D-flower morphology with high pore diameter and highly exposed basic sites. Catalytic activity studies revealed that [MgCo2O4]-[Cl−] catalyst in presence of base, exhibited 95% conversion of styrene oxide and 96% selectivity towards styrene carbonate at atmospheric pressure. The enhanced activity of [MgCo2O4]-[Cl−] was due to the relatively smaller size of Cl− anion which replaced the hydroxyl groups in the Brucite-like structure and exposed maximum number of basic (O2−) sites during the thermal decomposition of the Mg-Co DH-[Cl−] precursor. Additionally, various reaction parameters were investigated to optimize reaction conditions. The obtained results with [MgCo2O4]-[Cl−] and base suggested that this catalytic system showed good tolerance for a broad substrate scope in good yields and demonstrated good reusability with retention in activity and physicochemical properties for eight recycles. A plausible mechanism was proposed to support the activation of epoxide and CO2 by the unique cooperation of active Lewis acidic and basic sites present in [MgCo2O4]-[Cl−] for formation of cyclic carbonates at atmospheric pressure.

A series of 1,3,4–trisubstituted–1,2,3–triazolium iodide salts (4a–c) were synthesized via a three–step reaction sequence. Corresponding anilines (1a–c) were converted to azides (2a–c) which were then treated with phenylacetylene with “Click” chemistry to access 1,4–disubstituted–1,2,3–triazoles (3a–c). Subsequent methylation of 1,4–disubstituted–1,2,3–triazoles (3a–c) yielded 1,3,4–trisubstituted–1,2,3–triazoliumiodide salts (4a–c) in appreciable yields. All the synthesized compounds were characterized by 1H and 13C NMR, ATR–IR spectroscopic techniques and elemental analyses. Additionally, the structure of 1–(4–chlorophenyl)–4–phenyl–1,2,3–triazole (3b) was confirmed by single crystal X–ray diffraction analysis. The catalytic activity of 4a–c in a catalytic system consisting of 1,3,4–trisubstituted–1,2,3–triazoliumiodide salt/palladium(II) acetate/base were investigated towards Suzuki–Miyaura and Heck–Mizoroki cross–coupling reactions. The Suzuki–Miyaura cross–coupling reactions were carried out under mild reaction conditions with good to excellent yields, whereas Heck–Mizoroki cross–coupling reactions were performed at elevated temperature with moderate yields. Further, in situ method skips the synthetic procedure of preparing the palladium(II) complexes and hence is more economical and less tedious.

We have developed the Cp*Rh(III)-catalyzed cyclization reaction of arylnitrones with diazo compounds to obtain N-hydroxyindoline products under mild conditions. The substrate scope and functional group compatibility were examined with the demonstration of synthetic utility.

The first example of Rh(III)-catalyzed cyclization of arylnitrones to indolines under external oxidant-free conditions is presented. An intermolecular coupling of arylnitrones with internal alkynes is made possible by the dual role of the Cp*Rh(III) catalyst mediating both the C-H bond activation and O-atom transfer. Synthetically important and pharmacologically privileged indoline derivatives were obtained in good yields with high diastereoselectivity.

The greener approach for the synthesis of biaryl using palladium nanoparticle (Pd–NPs) catalyzed denitrogenative coupling between aryl hydrazine and aryl halides under ligand-free condition has been described. The phytochemicals of the black pepper extract plays a dual role in reduction of PdII to Pd0 and acts as stabilizing agent for Pd–NPs. The electronically diver's arylhydrazines and commercially available aryl halides are used for the synthesis of symmetrical and unsymmetrical biaryls in good to excellent yield. The mechanism is well supported by control experiment and the recyclability, turnover number and turnover frequency of biogenically synthesized Pd–NPs is studied.

Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and Zn(II) assists the hydrolysis of key oxonium intermediate.

We have developed a borane-catalyzed regio- and stereoselective hydrosilylation of internal ynamides for the first time. The scope of ynamide substrates and silane reactants was broad under mild reaction conditions, affording synthetically versatile β-silyl (Z)-enamide products. The observed stereoselectivity was reasoned to be due to the β-silicon effect on a postulated ketene iminium intermediate.

We have developed the Cp*Rh(III)-catalyzed cyclization reaction of arylnitrones with diazo compounds to obtain N-hydroxyindoline products under mild conditions. The substrate scope and functional group compatibility were examined with the demonstration of synthetic utility.

We report two viable routes for the 1,2-difunctionalization of aminoalkynes using only oxidants. In the presence of a gold catalyst, nitrones enable the oxoamination of aminoalkynes 1 to form 2-aminoamides 2. With a suitable gold catalyst, nitrosobenzenes implement an alkyne/nitroso metathesis of the same substrates to give 2-oxoiminylamides 3. These two novel oxidations also provide 1,2-aminoalcohols with opposite regioselectivity via NaBH(4) reduction in situ.

The first example of Rh(III)-catalyzed cyclization of arylnitrones to indolines under external oxidant-free conditions is presented. An intermolecular coupling of arylnitrones with internal alkynes is made possible by the dual role of the Cp*Rh(III) catalyst mediating both the C–H bond activation and O-atom transfer. Synthetically important and pharmacologically privileged indoline derivatives were obtained in good yields with high diastereoselectivity.

Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and Zn(II) assists the hydrolysis of key oxonium intermediate.

The reaction proceeds as well with 3-en-1-ynamides who bear alternative withdrawing groups like tosyl instead of mesyl at the nitrogen.

Gold-catalyzed formal [4+1]-cycloadditions between 3-en-1-ynamides 1 and 8-methylquinoline oxide are reported. The success of this reaction relies on a hypothetic oxa-Nazarov cyclization on gold-stabilized allylic cations. Preliminary results on a new 1,2-difunctionalization of 3-en-1-ynamide are also reported.