Electronically Robust Self-Assembled Supramolecular Gel as a Potential Material in Triboelectric Nanogenerators.

A series of self-assembling gluconamide conjugated naphthalimide amphiphiles (GCNA) was synthesized and the self-assembly of GCNA into gel rendered an increased electron density in naphthalimide moiety with an overall change in energy of 15.33×10-32  J via J-type aggregation. SEM analysis and X-ray diffraction underpinning the nanofibrillar formation, and rheological measurements confirmed the processablity and material fabrication. The enriched electron density in the aggregated GCNA4 via cooperative intermolecular non-covalent interactions makes it as effective electron donor in the fabrication of triboelectric nanogenerators (TENG). The TENG based on GCNA4-polydimethylsiloxane (PDMS) triboelectric pair generated an output voltage, current and power density of ∼250 V, 40 µA and ∼622 mW/m2 respectively, which is almost 2.4 times better in performance than the amorphous GCNA4 based TENG. The fabricated TENG can power-up 240 LEDs, wrist watch, thermometer, calculator and hygrometer.

Rapid Assembly of Functionalized 2H-Chromenes and 1,2-Dihydroquinolines via Microwave-Assisted Secondary Amine-Catalyzed Cascade Annulation of 2-O/N-Propargylarylaldehydes with 2,6-Dialkylphenols.

An efficient, secondary amine-catalyzed cascade annulation of 2-O/N-propargylarylaldehydes with 2,6-dialkylphenols was established to access biologically relevant functionalized 2H-chromenes and 1,2-dihydroquinolines tethered with a synthetically useful p-quinone methide scaffold in high yields under microwave irradiation and conventional heating conditions. The microwave-assisted strategy was convenient, clean, rapid, and high yielding in which the reactions were completed in just 15 min, and the yields obtained were up to 95%. This highly atom-economical domino process constructed two new C-C double bonds and a six-membered O/N-heterocyclic ring in a single synthetic operation. Its mechanism process was rationalized as involving sequential iminium ion formation, nucleophilic addition, and intramolecular annulation steps. Furthermore, the synthesized 2H-chromene derivatives were transformed into valuable indeno[2,1-c]chromenes, 5H-indeno[2,1-c]quinolines, and oxireno[2,3-c]chromene via a palladium-catalyzed double C-H bond activation process and epoxidation, respectively.

Diversity-Oriented Synthesis of Benzo[f][1,4]oxazepine-, 2H-Chromene-, and 1,2-Dihydroquinoline-Fused Polycyclic Nitrogen Heterocycles under Microwave-Assisted Conditions.

An efficient, diversity-oriented synthesis of oxazepino[5,4-b]quinazolin-9-ones, 6H-chromeno[4,3-b]quinolines, and dibenzo[b,h][1,6]naphthyridines was established involving a substrate-based approach under microwave-assisted and conventional heating conditions in high yields (up to 88%). The CuBr2-catalyzed, chemoselective cascade annulation of O-propargylated 2-hydroxybenzaldehydes and 2-aminobenzamides delivered oxazepino[5,4-b]quinazolin-9-ones involving a 6-exo-trig cyclization-air oxidation-1,3-proton shift-7-exo-dig cyclization sequence. This one-pot process showed excellent atom economy (-H2O) and constructed two new heterocyclic rings (six- and seven-membered) and three new C-N bonds in a single synthetic operation. On the other side of diversification, the reaction between O/N-propargylated 2-hydroxy/aminobenzaldehydes and 2-aminobenzyl alcohols delivered 6H-chromeno[4,3-b]quinolines and dibenzo[b,h][1,6]naphthyridines involving sequential imine formation-[4 + 2] hetero-Diels-Alder reaction-aromatization steps. The influence of microwave assistance was superior to conventional heating, where the reactions were clean, rapid, and completed in 15 min, and the conventional heating required a longer reaction time at a relatively elevated temperature.

A microwave-assisted intramolecular aminopalladation-triggered domino sequence: an atom economical route to 5,10-dihydroindeno[1,2-b]indoles.

A microwave-assisted, palladium(II)-catalyzed cascade reaction of 2-alkynylanilines tethered with an α,ß-unsaturated carbonyl moiety was established to access 5,10-dihydroindeno[1,2-b]indoles in high yields (up to 84%) in a short reaction time. This operationally simple cascade process shows 100% atom economy and allows the construction of two new five-membered rings and two new (1 C-C and 1 C-N) bonds in a single synthetic attempt. The mechanistic pathway of this reaction is visualized involving intramolecular aminopalladation (5-endo-dig) followed by carbopalladation (olefin insertion) and protonolysis steps. A systematic comparison between microwave irradiation and conventional heating methods was also performed to demonstrate the supremacy of the microwave-assisted approach. This domino reaction requires no protecting groups for the amino group and the palladium catalyst needs no ligands. To the best of our knowledge, this is the first report on microwave-assisted nucleopalladation-initiated cascade transformation.

Direct Access to Bridged Tetrahydroquinolines and Chromanes via an InCl3-Catalyzed Sequential Three-Component Cascade.

A sequential three-component cascade process was developed for the synthesis of bridged tetrahydroquinolines and chromanes bearing 2,6-methanobenzo[d][1,3]diazocine and 2,6-methanobenzo[g][1,3]oxazocine scaffolds, respectively, in good yields from readily available materials. The InCl3-catalyzed reaction progressed via enamine formation, Michael addition, intramolecular cyclization, and intramolecular iminium ion cyclization steps. Notably, this high atom economic approach (-2H2O) allowed the generation of four new bonds (1 C-C and 3 C-N or 1 C-C, 1 C-O and 2 C-N) and two heterocyclic rings in a single operation.

Regioselective synthesis of tetrahydroquinolines via syn- and anti-nucleopalladation-initiated cascade processes.

Palladium(ii)-catalyzed regioselective syn-chloropalladation and anti-acetoxypalladation-initiated cascade processes were developed for the synthesis of functionalized tetrahydroquinolines. A series of N-propargyl arylamines tethered with an α,ß-unsaturated carbonyl scaffold underwent atom economical cascade reactions to deliver chloro- and acetoxy-substituted tetrahydroquinolines bearing an exocyclic double bond in high yields. A mechanism is proposed for these cascade processes involving a sequential syn-chloropalladation or anti-acetoxypalladation of alkynes followed by intramolecular olefin insertion (6-exo-trig) and protonolysis steps. The reaction was completely regioselective and the terminal aryl/alkyl group of the propargyl moiety dictated the regiochemistry of the initial nucleopalladation. The role of the bidentate nitrogen ligand is crucial to trigger the acetoxypalladation-initiated cascade sequence in contrast to the chloropalladation-initiated process.

Diastereoselective ABB' Three-Component Synthesis of Highly Functionalized Spirooxindoles Bearing Five Consecutive Asymmetric Carbons.

The synthesis of spirooxindoles bearing tetrahydro-4 H-cyclopenta[ b]furan framework was established starting from isatin-derived aldehydes and 2 equiv of 1,3-dicarbonyl compounds involving a piperidine-catalyzed ABB' three-component domino process. This reaction was highly diastereoselective affording a single diastereomer of spirooxindoles with five consecutive asymmetric carbons including spiro and tetrasubstituted carbon centers. In addition, this waste-free (-2H2O) reaction showed high atom economy and step economy by creating four new bonds, including three C-C bonds and one C-O bond, and two rings (one carbo- and one heterocyclic) in a single operation. The mechanism of this three-component domino process involved sequential Knoevenagel condensation-Michael addition-intramolecular oxa-Michael addition-intramolecular aldol reactions.

Synthesis of 5,6-Dihydrodibenzo[b,h][1,6]naphthyridines via Copper Bromide Catalyzed Intramolecular [4 + 2] Hetero-Diels-Alder Reactions.

A highly efficient synthesis of 5,6-dihydrodibenzo[b,h][1,6]naphthyridines was achieved by reaction between 2-(N-propargylamino)benzaldehydes and arylamines in the presence of CuBr2. The in situ generated electron-deficient heterodienes bearing a tethered alkyne partner underwent an intramolecular inverse electron-demand hetero-Diels-Alder reaction followed by air oxidation to furnish the products in high yields. This reaction tolerated a large number of substituents to afford diverse products under mild conditions. This strategy was also successfully extended to the synthesis of 12,13-dihydro-6H-benzo[h]chromeno[3,4-b][1,6]naphthyridin-6-ones starting from 3-amino-2H-chromen-2-one, again in high yields.

Synthesis of 6,12-Epiminodibenzo[b,f][1,5]diazocines via an Ytterbium Triflate-Catalyzed, AB2 Three-Component Reaction.

An efficient and selective procedure for the synthesis of epiminodibenzo[b,f][1,5]diazocines involving a AB2 three-component reaction is developed. Two equivalents of suitably substituted 2-aminoarylaldehydes reacted with arylamines in the presence of Yb(OTf)3 to afford the desired products in high yields. The reaction is highly atom-economic and waste-free, in addition to allowing the generation of two heterocyclic rings and four C-N bonds in a single operation. Significantly, this approach is complementary to the existing literature procedures, affording arylamine-derived products that could not be accessed previously. A plausible mechanism is proposed involving an imine formation-intermolecular annulation-intramolecular iminium ion cyclization sequence.

Metal-free oxidative amidation of aldehydes with aminopyridines employing aqueous hydrogen peroxide.

The first metal free report on the amidation of aldehydes with aminopyridines was accomplished using simple aqueous hydrogen peroxide (aq. H2O2) as the oxidant. No catalysts or additives were needed for this transformation and the reaction proceeded in water, an environmentally benign reaction medium. Green oxidant and reaction conditions, and the ability to construct diverse N-(pyridin-2-yl)benzamide by this elegant method render it a practical alternative for the synthesis of these amides.

Remediation of Dyes Using Supramolecular Material Derived from Carbohydrate Based π-Gelator Using the Bottom-Up Assembly Approach.

As a consequence of rapid population growth, the earth has faced numerous environmental sustainability issues and crises, water pollution is one of the important points of concern because of industrialization. In particular, effluents discharged from dying industries are rated top among the various industrial effluents, especially by their volume and composition. Annually >7.5 × 105 metric tons of different dyes are produced and consumed in different industries. In order to dye 1 kg of fabric, approximately 100-150 L of water is required, and after the dying process, it is discharged as an effluent either on a landfill or in water bodies. It is our responsibility to conserve environmental sustainability. In this line, we have developed a simple protocol to generate carbohydrate-based amphiphile using D-sorbitol, and pyrene-1-carboxaldehyde in good yield. This carbohydrate-based π-gelator is prone to forming a gel in various solvents and oils by the bottom-up assembly process. Morphological analysis of the self-assembled structure was identified by using optical microscopy and SEM. The viscoelastic behavior of the gel was examined by using rheology. In this paper, we explored the dye adsorption and desorption characteristics of the gel. Further, we have developed a cartridge based on cellulose using a template-assisted assembly phenomenon and demonstrated its potential in adsorbing dyes such as methylene blue, crystal violet, rhodamine B, and Congo red.

Palladium-catalyzed intramolecular oxypalladation-initiated cascade: solvent-dependent chemodivergent approach to functionalized benzazepines and tetrahydroquinolines.

Palladium-catalyzed, solvent-dependent intramolecular oxypalladation-triggered domino sequences of internal alkynes bearing tethered nucleophilic carboxylic ester and electrophilic enone functionalities were developed for the chemodivergent synthesis of two completely distinct biologically significant complex molecules including isochromenone-fused benzazepines and isobenzofuranone-fused tetrahydroquinolines/chromanes in a single synthetic operation.

Iodine-catalyzed three-component annulation: access to highly fluorescent trisubstituted thiophenes.

An efficient synthesis of highly fluorescent trisubstituted thiophenes was achieved via iodine-catalyzed, base-promoted annulation employing elemental sulfur as a sulfur source. The compounds exhibit excellent photophysical properties like solid-state fluorescence, high quantum yield and solvatochromism. As these thiophene derivatives have potential application in the development of optoelectronic devices, gram-scale synthesis of the desired heterocycles was demonstrated.

Hybrid hydrogels derived from renewable resources as a smart stimuli responsive soft material for drug delivery applications.

The design and synthesis of amphiphilic molecules play a crucial role in fabricating smart functional materials via self-assembly. Especially, biologically significant natural molecules and their structural analogues have inspired chemists and made a major contribution to the development of advanced smart materials. In this report, a series of amphiphilic N-acyl amides were synthesized from natural precursors using a simple synthetic protocol. Interestingly, the self-assembly of amphiphiles 6a and 7a furnished a hydrogel and oleogel in vegetable oils. Morphological analysis of gels revealed the existence of a 3-dimensional fibrous network. Thermoresponsive and thixotropic behavior of these gels were evaluated using rheological analysis. A composite gel prepared by the encapsulation of curcumin in the hydrogel formed from 7a displayed a gel-sol transition in response to pH and could act as a dual channel responsive drug carrier.

First Report of Rust on Osmorhiza Longistylis Caused by Puccinia Pimpinellae in India.

Osmorhiza longistylis (Torr.) DC., commonly known as sweet cicely, is a dominant plant species in the wastelands of the Bhaderwah Valley of District Doda in the states of Jammu and Kashmir (India). The plant is a perennial herb found abundantly near water streams and irrigation channels. The herb has medicinal value and is being used to treat digestive disorders and used as an antiseptic wash. During a disease survey in July 2010, leaf samples collected from Bhaderwah (Gwari Research Farm of Regional Horticulture Research Substation-Bhaderwah (Doda), SKUAST-Jammu) had symptoms of a rust disease. Rust symptoms appeared as small, cream colored flecks on the lower surfaces of leaves. Numerous hypophyllous, narrow, linear lesions were observed. These lesions slowly enlarged and formed light brown, erumpent, and seriately arranged sori surrounded by yellow haloes. Sori originated beneath the epidermis but ruptured through the host epidermis on sporulation. In later stages, infection extended to the stem, flowering buds, inflorescence, and fruit seeds (1,3). Teliospores were uniformly two celled, reticulate with a yellowish brown wall, obovoid-ellipsoid or oblong-ellipsoid, and 30 to 40 × 20 to 27 µm. Aeciospores were subglobose and verrucose. Urediniospores were subglobose with a yellowish brown color and 23 to 30 × 21 to 27 µm. Uredia, telia, and aecia were observed on infected leaves (2). Infected plant material has been deposited and identified at the Herbarium Crytogamae Indiae Orientalis (HCIO 50095), New Delhi. To our knowledge, this is the first report of rust on O. longistylis caused by Puccinia pimpinellae from India. References: (1) K. M. Ghoneem et al. Plant Pathol. J. (Faisalabad) 8:165, 2009. (2) W. E. I. A. Saber et al. Afr. J. Microbiol. Res. 3:153, 2009. (3) W. I. A. Saber et al. Plant Pathol. J. (Faisalabad) 8:32, 2009.

N-Heterocyclic Carbene Catalyzed Synthesis of Trisubstituted Epoxides via Tandem Amidation/Epoxidation Sequence.

A tandem amidation/epoxidation sequence between various substituted chalcones and N,N-dimethylformamide (DMF) for the synthesis of trisubstituted epoxides employing N-heterocyclic carbene catalysis was developed. This reaction was performed under metal-free conditions in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant. Trisubstituted epoxides bearing a ketone and an amide functionality (N,N-dimethyl formyl group) were synthesized starting from a wide range of chalcones in moderate to good yields with excellent diastereoselectivity.

An injectable self-healing anesthetic glycolipid-based oleogel with antibiofilm and diabetic wound skin repair properties.

Globally, wound infections are considered as one of the major healthcare problems owing to the delayed healing process in diabetic patients and microbial contamination. Thus, the development of advanced materials for wound skin repair is of great research interest. Even though several biomaterials were identified as wound healing agents, gel-based scaffolds derived from either polymer or small molecules have displayed promising wound closure mechanism. Herein, for the first time, we report an injectable and self-healing self-assembled anesthetic oleogel derived from glycolipid, which exhibits antibiofilm and wound closure performance in diabetic rat. Glycolipid derived by the reaction of hydrophobic vinyl ester with α-chloralose in the presence of novozyme 435 undergoes spontaneous self-assembly in paraffin oil furnished an oleogel displaying self-healing behavior. In addition, we have prepared composite gel by encapsulating curcumin in the 3D fibrous network of oleogel. More interestingly, glycolipid in its native form demoed potential in disassembling methicillin-resistant Staphylococcus aureus, methicillin-susceptible Staphylococcus aureus, and Pseudomonas aeruginosa biofilms. Both oleogel and composite gel enhanced the wound skin repair in diabetic induced Wistar rats by promoting collagen synthesis, controlling free radical generation and further regulating tissue remodeling phases. Altogether, the reported supramolecular self-assembled anesthetic glycolipid could be potentially used for diabetic skin wound repair and to treat bacterial biofilm related infections.

Glycolipid-Based Oleogels and Organogels: Promising Nanostructured Structuring Agents.

Over the past few decades, the scientific community is actively involved in the development of edible structuring agents suitable for food, cosmetics, agricultural, pharmaceutical, and biotechnology applications. In particular, edible oil structuring using simple amphiphiles would be the best alternative for the currently used trans and saturated fatty acids, which cause deleterious health effects and cardiovascular problems. In this report, we have made an attempt to address the aforementioned consequences, by synthesizing a new class of structuring agents by a judicious combination of δ-gluconolactone and ricinoleic acid, compounds classified as GRAS, using simple steps in good yield. To our delight, the synthesized glycolipids self-assemble in a wide variety of vegetable oils and commercially viable glycerol, ethylene glycol, and polyethylene glycol via various intermolecular interactions to form a gel. The morphology of molecular gels was investigated by optical microscopy and FESEM analysis, which reveal the existence of a tubular architecture with a diameter ranging from 75 to 150 nm. Rheological studies disclosed the viscoelastic nature, thermal processability, and thixotropic behavior of both oleogels and organogels. Altogether, self-assembled oleogel and organogel reported in this paper would potentially be used in food, agricultural, cosmetics, pharmaceutical, and biotechnological applications.

Smart supramolecular gels of enolizable amphiphilic glycosylfuran.

The implementation of a novel approach in the development of stimuli responsive supramolecular gels is an important objective that challenges material chemists and biologists in order to access an exclusively new category of smart materials. In this report, non-toxic, bio-based amphiphilic glycosylfurans were designed and synthesized using a biocatalyst, Novozyme 435, an immobilized lipase B from Candida antarctica. The self-assembly of these compounds generated oleogels and hydrogels. To our delight, these bio-based amphiphilic glycosylfurans furnished an in situ stimuli responsive hydrogel with simultaneous encapsulation of various biologically relevant molecules and ions. For the first time we are reporting hydrogelation via in situ molecular tuning followed by a self-sorting mechanism. The sol-to-gel transition in the reported smart hydrogel was observed by the addition of acidic buffer of pH 4.0, which could be potentially used for the stimuli responsive delivery of a signalling molecule, H2S and other biomolecules that regulate many physiological and pathological processes.

Oxidant-free, three-component synthesis of 7-amino-6H-benzo[c]chromen-6-ones under green conditions.

An oxidant-free three-component synthesis of biologically significant 7-amino-6H-benzo[c]chromen-6-ones was established involving a Sc(OTf)3 catalyzed three-component reaction between primary amines, ß-ketoesters and 2-hydroxychalcones under green conditions. In this strategy, both the B and C rings of 6H-benzo[c]chromen-6-ones were constructed simultaneously starting from acyclic precursors by generating four new bonds including two C-C, one C-N and one C-O in a single synthetic operation. The mechanism of this sequential cascade process involves the initial formation of a ß-enaminone intermediate followed by Michael addition with 2-hydroxychalcone, intramolecular cyclization, dehydration, lactonization and aromatization steps. Unlike the related literature approaches, this reaction delivered the products without the addition of any external oxidants to achieve the key aromatization step.