C7-Decorated indoles are important structural motifs present in a plethora of bioactive and pharmaceutical compounds. Early stage developments for C7 modifications were realized through directed ...metallation (DOM) and subsequent quenching with suitable electrophiles or by halogenation with Cu(
ii
) halides. Direct C-7 functionalization of indoles is comparatively difficult compared to functionalization at C-2 and C-3 positions owing to the inherent reactivity of the pyrrole-type ring. However, recently transition-metal-catalyzed auxiliary assisted site-selective C-7 functionalization of indoles has emerged as an elegant synthetic tool for carbon-carbon and carbon-heteroatom bond formation to diversify the indoles. This article covers the advancement, application and mechanistic underpinnings of the evolved transformations of the otherwise inert C7-H bond up to October 2018.
The advancement and future prospects of transition-metal-catalyzed auxiliary assisted regioselective C7-functionalization of indoles/indolines are covered in this article.
The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these ...dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.
Display omitted
•Spindle-like Nd & V codoped ZnO was prepared via ultrasonic assisted sol-gel route.•Materials were characterized by different analytical techniques.•The activity was tested by ...studying the degradation of different pollutants.•Co-doped ZnO showed better activity than mono and undoped samples.•Mechanism of enhanced photocatalytic activity was proposed.
Synthesis of visible light active photocatalyst with desirable control on recombination of charge carriers is prerequisite for photocatalysis. The simultaneous doping of two metals into oxide semiconductor materials is considered to be an efficient strategy to alleviate the charge carrier recombination and to improve the photocatalytic activity. Herein, a visible light driven Nd-V-ZnO with spindle-like shape was synthesized by an ultrasonic assisted sol-gel method and characterized by XRD, SEM-EDS, TEM, UV–Vis DRS, FTIR and TGA-DTA techniques. The shift in optical response as well in XRD peaks validates the incorporation of metal ions into ZnO. The photocatalytic activity of synthesized materials was investigated by studying the degradation of three different pollutants such as rhodamine B (RhB), methyl orange (MO), and paracetamol in aqueous suspension with visible light illumination. The modified ZnO photocatalyst with 4% Nd and 1% V content shows excellent photocatalytic for the degradation of organic compounds. The substantial improvement in photocatalytic activity could be attributed to the extended visible light response and long-lived photogenerated charge carriers. In addition, the scavenging studies and photoluminescence terephthalic acid probe method revealed •OH as the main reactive species involved in the degradation reaction. In addition, 4% Nd-V-ZnO photocatalyst showed reasonable photocatalytic activity for the degradation of RhB even after 4 cycle runs. A probable photocatalytic mechanism based on the radical trapping experiments for the degradation of pollutants has also been proposed.
Metallaphotoredox catalysis represents the combination of two activation modes: metal‐catalyzed C−H functionalization and visible‐light‐induced photocatalysis. This appealing dual catalysis technique ...has evolved as a versatile platform that has paved the way for diverse low‐energy pathways for a plethora of synthetic transformations. The synergistic combination of two “green” approaches has garnered enormous interest owing to the development of sustainable strategies. In the recent past, significant advancements have been accomplished in constructing site‐selective C−C and C‐heteroatom bonds. This review outlines the use of photoredox catalysis in directing group‐assisted C−H functionalization reactions. The mechanistic insights of the developments and synthetic applications are addressed.
This review outlines a handful of transformations employing transition‐metal and photoredox catalysis by auxiliary‐assisted C−H activation strategy to assemble synthetic libraries of C−C and C‐heteroatom bonds. The review also features the substrate scope and mechanistic insights of the key methodologies.
The rice–wheat rotation model of crop planting is widely used globally, and worldwide, straw returning is the main method of crop straw treatment. However, the straw return method commonly used in ...the modern rice–wheat rotation system has many adverse effects on the levels and improvement of soil fertility and crop yield, and there is no systematic theory of rice and wheat straw returning to use as a guide. In this paper, we concluded that: in the rice–wheat rotation system, returning 1,500–4,500 kg/ha of rice straw and 2,250–6,750 kg/ha of wheat straw to the field helps increase the organic carbon content and quality of the soil and promotes high annual yields; conventional mixing of straw into the field can increase the organic carbon content of the soil in a short time; long‐term use of concentrated ditch‐buried straw return has obvious advantages over other straw returning methods in increasing the accumulation of soil organic carbon; the combination of little or no tillage plus straw returning helps increase the content and quality of organic carbon in soil; and when the soil water content is 15%–22.5%, it is the most conducive to the accumulation of soil organic carbon. In addition, we also provide relevant suggestions for future research directions on straw returning via systematic analyses and thought processes.
Little or no tillage plus straw returning helps increase the content and quality of soil organic carbon. Appropriate straw returning improves soil quality and annual yields in rice–wheat rotation system.
A cobalt-catalyzed C2-selective amidation of indoles using acyl azides has been accomplished. Isotope experiments suggest that C–H activation is reversible. The use of sustainable Co catalysis, ...functional group diversity, substrate scope, and regioselectivity are the important practical features.
The purpose of this study is to explore the factors that affect rural household food security in northern area of Pakistan. The random sampling technique was applied to collected data from 294 rural ...households through a face to face interview. A binary logistic regression technique was used to determine the factors that influence household food insecurity. The results of our study revealed that age, gender, education, remittances, unemployment, inflation, assets, and disease are important factors determining household food insecurity. Moreover, gender played a dominant role in food insecurity as female headed household were food insecure while male headed household were food secure. The policies should be set to promote education, more focus on female headed household and encourage the inflow of remittances.
Drought stress is reducing the production of crops globally. This research was designed to evaluate the role of titanium dioxide (TiO2 NPs) nanoparticles and calcium phosphate on wheat facing drought ...stress. TiO2 NPs were prepared by green synthesis and their characterization (by UV–visible spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX)) was also done. The results showed that TiO2 NPs worked efficiently and improved plant growth under drought. However, the best results were obtained from combined applications of 40 ppm TiO2 NPs and 40 ppm calcium phosphate on plants. They increased root length (33%), shoot length (53%), fresh weight (48%), and dry weight (44%) of wheat as compared to control. The physiological parameters including chlorophyll content, relative water content, membrane stability index, and osmolyte content (proline and sugar) were also improved. The increase in superoxide dismutase, peroxidase and, catalase activity by the combined application of TiO2 NPs and calcium phosphate was 83% and 78%, 74% and 52%, 81%, and 67% in Pakistan-13 and Zincol-16 respectively, as compared to untreated drought exposed plants. They also enhanced the nutrients uptake (including potassium, phosphorus, and nitrogen) that ultimately improved plant biomass. They also maintained the level of growth hormones in plants. These hormones regulate cellular processes and are responsible for germination, development, and plant reaction in drought stress. The increase in the yield was also significant, hence it is recommended that the 40 ppm concentration of TiO2 NPs along with calcium phosphate improves the productivity of wheat under drought stress.
•Drought stress affects growth, physio-biochemical attributes, activity of enzymatic antioxidants and productivity of wheat plants.•Application of Titanium dioxide nanoparticles (TiO2 NPs) mitigated the negative effects of drought stress.•Calcium supplementation improved the growth and development of wheat plantsunder drought stress.•Combined application of TiO2 NPs and calcium improved all parameters under drought stress.
The transition-metal-aided stereoselective construction of sp
3
-carbon-rich heterocyclic scaffolds using strained-ring systems has received considerable attention in recent years due to the ...prominent presence of these scaffolds in myriad natural products, bioactive molecules, and pharmaceutical components. In this area, the catalytic ring-enlargement of vinylaziridines and vinyloxiranes plays a predominant role when synthesizing high sp
3
-content biorelevant heterocyclic compounds. This article aims to portray recent advancements in the ring-expansion of vinylaziridines and vinyloxiranes for accessing densely functionalized stereoselective heterocycles that have been developed over the past five years, with an emphasis on the substrate scopes and mechanistic insights into the key methodologies, and it is arranged based on the transition metals used and the ring sizes of the heterocyclic scaffolds.
This article covers ring expansions of vinylaziridines and vinyloxiranes developed over the past five years for accessing stereochemically enriched heterocycles.
Current study illustrates the impact assessment of TiO2 nano-particle seed priming on the overall germination, physiology in maize thriving under salinity stress.
Seeds of maize cultivar were soaked ...in 40, 60 and 80 ppm aerated solution of TiO2nano-particle for one day and nano-primed seeds were then exposed to salinity stress, i.e., 200 mM NaCl on paper culture system.
Results indicated that 60 ppm TiO2nano-priming treatment effect positively on the rate of germinate and growth of maize seedling under salinity stress. The experiment was carried out in sand as a growth medium with 60 ppm TiO2 priming. Results exhibited that germination percentage, germination energy, seedling vigor index, lengths of root and shoot, fresh and dry weights of seedling, potassium ion (K+) concentration, relative water content (RWC), total phenolic and proline and contents, superoxide dismutase (SOD), catalase (CAT) and phenylalanine ammonia lyase (PAL) activities were significantly enhanced and mean emergence time (MET), sodium ion (Na+) concentration, membrane electrolyte leakage (MEL) and malondialdehyde (MDA) content were decreased by TiO2 priming as compared to control under salinity stress.
So, nano-priming with TiO2 mitigates the salinity injury in maize and could be a significant alternate strategy to mitigate the deleterious impact of salinity stress in maize.
PDF
