Enantioselective C−H Functionalization Reactions under Gold Catalysis

Transition metal-catalyzed enantioselective functionalization of ubiquitous C−H bonds has proven to be promising field as it offers the construction of chiral molecular complexity in a step- and atom-economical manner. In recent years, gold has emerged as an attractive contender for catalyzing such reactions. The unique reactivities and selectivities offered by gold catalysts have been exploited to access numerous asymmetric transformations based on gold-catalyzed C−H functionalization processes. Herein, this review critically highlights the major advances and discoveries made in the enantioselective C−H functionalization under gold catalysis which is accompanied by mechanistic insights at appropriate places.     

Synthesis and characterization of chitosan-hydroxyapatite composite for bone graft applications

In the current work chitosan-hydroxyapatite composites were synthesized using the method of co-precipitation for bone grafting. The composite samples were characterized using SEM, EDS and UTM. The composites showed a good Ca:P ratio of 2.10, indicating a sufficient level of osteoconductive of the composites. The EDS peaks showed a strong presence of carbon, oxygen, calcium and phosphorous with insignificant impurities. The UTM tests revealed compressive modulus of 80 ?MPa desired for various human bones. Also, grey rational analysis was used to optimize the process parameters. The results thus obtained show an improvement over previously reported results of bone grafts using other materials and procedures. Thus, the work can serve as a viable alternative to traditional bone grafting techniques, such as allografts and autografts, which face problems of biocompatibility and affordability.     

Synthesis and bio-evaluation of novel 2-arylquinoxaline

2-Arylquinoxalines were synthesized by the condensation of α-chloroacetophenone and o-phenylenediamine (1:1) using pyridine as catalyst in THF at room temperature. All the compounds were characterized by spectral data. Furthermore, these are screened for in vivo anti-inflammatory activity by carrageenan induced rat hind paw edema methods all the compounds were displayed significant anti-inflammatory activity. The title compounds were also shown good antibacterial and antifungal activity.     

Intensification of degradation of acetamiprid by the combination of ultrasonic cavitation with other advanced oxidation processes (AOPs)

The degradation of acetamiprid has been studied using ultrasonic cavitation (US) and its combination with H₂O₂, Fenton's reagents and photo-Fenton process. Initially, the optimization of operational parameters has been carried out to enhance the performance of US. Maximum degradation of acetamiprid was obtained at ultrasonic power density of 0.22 ?W/mL, operating pH of 2.5 and acetamiprid concentration of 10 ?ppm. Further, the rate of degradation of acetamiprid obtained by US (0.807 ?× ?10^-3 min^-1) was intensified by combining it with hydrogen peroxide (4.925 ?× ?10^-3 min^-1), Fenton's reagent (5.593 ?× ?10^-3 min^-1) and photo-Fenton process (39.907 ?× ?10^-3 min^-1) with synergistic coefficients of 5.58, 3.14 and 2.04 respectively. The comparison of US and various US based combined processes have been carried out on the basis of mineralization study and cavitational yield. Maximum extent of mineralization of 52.25% and cavitational yield of 5.288 ?× ?10^-12 ?mol/J were observed for US ?+ ?photo-Fenton process. Further, the cost of electricity of 4.128 USD/L and power consumption of 41.650 ?kWh/L obtained in the case of US has significantly reduced to 0.233 USD/L and 2.358 ?kWh/L respectively for US ?+ ?photo-Fenton process. The study of effect of radical scavenger (sodium bicarbonate) has confirmed that degradation of acetamiprid using US based combined processes is controlled by OH^? radical attack. Comparison of cavitational yield, power consumption and cost of electricity of US and US based combined processes has indicated US ?+ ?photo-Fenton process to be the most energy efficient and cost effective process for the degradation of acetamiprid.     

Interplay of Anion-π+ and π+-π+ Interactions in Novel Pyrido[2,1-a]isoquinolinium-Based AIEgens - Substituent- and Counterion-Dependent Fluorescence Modulation and Applications in Live Cell Mitochondrial Imaging**

Recently, the concept of anion-π⁺ interactions has witnessed unique applications in the field of AIEgen development. In this contribution, we disclose a consolidated study of a library of N-doped ionic AIEgens accessed through silver-mediated cyclization of pyridino-alkynes. A thorough photophysical, computational and crystallographic study has been conducted to rationalize the observed substituent- and counterion-dependent fluorescence properties of these luminogens. We further elucidate the prominent role of anion-π⁺ interactions, π⁺-π⁺ interactions and other non-covalent interactions, in inhibiting the undesired ACQ effect. Finally, we have also demonstrated the application of selected AIEgens for imaging of mitochondria in live cells.     

Greener approach for process intensification of iron haematinics by membrane nanofiltration

Iron haematinics are high-volume, low-cost drug products used to treat anaemia. For the preparation of iron haematinics, the manufacturers depend heavily on multipurpose-batch or semi-batch reactors. Here, process intensification of haematinics was carried out using membrane nanofiltration as a major operation. A total of three haematinics namely, iron (III) hydroxide polymaltose, iron gluconate, and iron sucrose complex were prepared, and the process intensified on dead-end filtration set up by using a polymeric membrane. Iron (III) hydroxide polymaltose experimental results were compared with commercially available standard. The membrane performance was characterized by various parameters such as flux, permeability, flux decline ratio, flux recovery ratio, percentage retention, fouling, etc., at different transmembrane pressures. The membrane surface was analysed by Scanning Electron Microscopy (SEM) to understand its morphology and fouling. The iron concentration was detected in the permeate stream using inductively coupled plasma optical emission (ICP-OES) spectroscopy to detect %retention (>99.99%) under all experimental conditions tested. The study led to optimized conditions for haematinics concentration by a membrane at a 10-bar trans-membrane pressure, which was applied for the preparation of iron gluconate salt. Overall, the study resulted in a green process with increased productivity.     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

Screening of Rubiaceae and Apocynaceae extracts for mosquito larvicidal potential

Rubiaceae and Apocynaceae families are well known for the expression of cyclotides having insecticidal properties. Leaves and flowers extracts of plants from the families Rubiaceae (Ixora coccinea) and Apocynaceae (Allamanda violacea) were evaluated for mosquito larvicidal effect against early IVth instars of Aedes aegypti and Anopheles stephensi. Two forms of plant extracts, one untreated and the other treated with heat and proteolytic enzyme were used for assay. After primary assay, the extract showing more than 50% inhibition was further used for quantification purpose. LC₅₀ and LC₉₀ values of all the extracts were found to be reduced with the treated form. Phytochemical analysis of plant extracts was performed. Primary confirmation for the presence of cyclotides was done by Lowry test, thin layer chromatography and haemolytic assay. This novel approach merits use of plant extracts in mosquito control programmes.     

Hydrazide–Hydrazone Small Molecules as AIEgens: Illuminating Mitochondria in Cancer Cells

Aggregation-induced-emission luminogens (AIEgens) have gained considerable attention as interesting tools for several biomedical applications, especially for bioimaging due to their brightness and photostability. Numerous AIEgens have been developed for lighting up the subcellular organelles to understand their forms and functions not only healthy but also unhealthy states, such as in cancer cells. However, there is lack of easily synthesizable, biocompatible small molecules for illuminating mitochondria (powerhouses) inside cells. To address this issue, an easy and short synthesis of new biocompatible hydrazide–hydrazone-based small molecules with remarkable aggregation-induced emission (AIE) properties is described. These small-molecule AIEgens showed hitherto unobserved AIE properties due to dual intramolecular H-bonding confirmed by theoretical calculation, pH- and temperature-dependent fluorescence and X-ray crystallographic studies. Confocal microscopy showed that these AIEgens were internalized into the HeLa cervical cancer cells without showing any cytotoxicity. One of the AIEgens was tagged with a triphenylphosphine (TPP) moiety, which successfully localized in the mitochondria of HeLa cells in a selective way compared to L929 noncancerous fibroblast cells. These unique hydrazide–hydrazone-based biocompatible AIEgens can serve as powerful tools to illuminate multiple subcellular organelles to elucidate their forms and functions in cancer cells for next-generation biomedical applications.