Tunable random laser based on hybrid plasmonic enhancement.

This research investigates the hybridized plasmonic response of silver film combined with dispersed silver (Ag) nanowires (NWs) to random laser emission. The mixture of Rhodamine B (RhB) dye and polyvinyl alcohol (PVA) matrix is taken as the gain medium for random lasing, and the silver combination provides feedback mechanisms for light trapping. Importantly, film roughness and the coupling between localized and extended (delocalized) surface plasmons play a vital role in RL performance evaluation. The laser threshold is strongly influenced by film thickness attributed to surface roughness. Furthermore, the variation in film thickness also supports the wavelength modulation of 9 nm (597 nm to 606 nm), which results from the reabsorption of RhB. Additionally, the intriguing capability of emission wavelength tuning under the variation of temperature facilitates exciting prospects for precise wavelength control in plasmonic devices.

Tunable random lasers via phase transition for information encryption.

Introducing phase transition materials to random systems provides a promising route to create new optoelectronic functionalities of random lasers. Here, a phase transition random laser with switchable lasing modes is reported, which is designed with a thermoresponsive hydrogel as scattering medium. By manipulating the phase transition in hydrogel, random lasing modes can be switched reversibility between incoherent and coherent random lasing. The phenomenon derives from the changing of light scattering properties in different phase states, thus affecting the optical feedback path of random lasing. Besides, based on its controllable and easily detectable time-domain characteristics, the phase transition random laser is applied in information encoding and transmission. It is the first time that the transition from coherent to incoherent random lasing is observed by varying the sample phase states. This work will inspire the design and application of novel random lasers in photoelectric device.

Morpho-physiological characterization and metabolic profiling of rice lines for immunity to counter Helminthosporiumoryzae.

Heliminthosporium oryzae is a necrotrophic fungal pathogen that effect rice crops grown on millions of hectares. We evaluated nine newly establishing rice lines and one local variety for resistance against H. oryzae. Significant (P ≤ 0.05) differences in response to pathogen attack were recorded in all rice lines. Maximum disease resistance was recorded in Kharamana under pathogen attack as compared to uninfected plants. A comparison of decline in shoot length revealed that Kharamana and Sakh experienced minimum lost (9.21%, 17.23%) in shoot length respectively against control while Binicol exhibited highest reduction (35.04%) in shoot length due to H. oryzae attack. Post-infection observations of shoot fresh weight revealed 63% decline in Binicol and declared it as the most susceptible rice line. Sakh, Kharamana and Gervex exhibited minimum fresh weight decrease (19.86%, 19.24% and 17.64% respectively) as compared to other lines under pathogen attack. Maximum chlorophyll-a contents were recorded in Kharamana under control and post pathogen attackconditions. Following the inoculation of H. oryzae, SOD was increased up to 35% and 23% in Kharamana and Sakh. However, minimum POD activity was recorded in Gervex followed by Swarnalata, Kaosen and C-13 in non-inoculated and pathogen-inoculated plants. Significant decrease in ascorbic acid contents (73.7% and 70.8%) was observed in Gervex and Binicol that later contributed in their susceptibility to H. oryzae attack. Pathogen attack caused Significant (P ≤ 0.05) changes in secondary metabolites in all rice lines but minimum total flavonoids, anthocyanin and lignin were observed in Binicol in uninfected plants and attested its susceptibility to pathogen. In post-pathogen attack conditions, Kharamana showed best resistance against pathogen by exhibiting a significantly high and maximum value of morpho-physiological, and biochemical attributes. Our findings suggest that tested resistant lines can be further explored for multiple traits including molecular regulation of defense responses to breed immunity in rice varieties.

Patients' Perception of Long-term Outcome After Laparoscopic Ventral Mesh Rectopexy; Single Tertiary Center Experience.

OBJECTIVE: To assess patients' long-term outcome and satisfaction after laparoscopic ventral mesh rectopexy (LVMR). SUMMARY OF BACKGROUND DATA: Data on the long-term outcome and satisfaction of patients undergoing LVMR are limited. METHODS: Patients who underwent LVMR between 2004 and 2017 were identified from a prospectively maintained database. We attempted to contact all patients by telephone for an interview using a standardized questionnaire to record pre-LVMR symptoms, long-term outcome, and overall satisfaction. RESULTS: Total number of patients who underwent LVMR was 848 and 99(12%) were deceased at follow-up. In the end, 544 (64%) patients were contacted successfully and 478 (56%) were able to complete the questionnaire. Median time elapsed since surgery was 7 years and mean age was 62 years. Patients' reported preoperative symptoms were obstructed defecation syndrome in 40%, fecal incontinence in 22%, combination of obstructed defecation syndrome and fecal incontinence in 21% and other conditions in 17%. Bowel symptoms were reported as improved by 69% of patients and worse by 12%. Pelvic pain was reported to be improved in 47% of the patients after LVMR but new onset of pelvic pain appeared in 15%. Sexual function was reported to be better and worse with equal frequency. Overall, 63% of the patients were satisfied with the outcome and 76% would recommend this procedure to others with similar symptoms. CONCLUSION: LVMR offers acceptable long-term outcomes and satisfaction. There is a mixed impact on pelvic pain and sexual function which requires careful consideration in counseling patients for this procedure.

Toxicity and sublethal effects of diafenthiuron on life table parameters of Musca domestica L. (Diptera: Muscidae).

Housefly, Musca domestica L. (Diptera: Muscidae), is an important insect-pest owing to its disease transmitting capability in both humans and animals e.g. diarrhea, gastroenteritis diseases, lumpy skin disease, cholera. Residual insecticides are widely used to control houseflies that pose serious threat to human and animal health as well as to the environment. The population resurgence after insecticidal spray is also a common problem in many cases. Transgenerational studies can be very helpful to see the fate of insecticidal sprays. In the current study, we determined transgenerational effects of sublethal doses of diafenthiuron using Age-stage two-sex life table analysis, while focusing on potential use of diafenthiuron in baits. After treating adult flies with three different doses of diafenthiuron viz. LC10, LC20 and LC50, the progeny depicted significant changes regarding pre-adult duration (shorter in control), male and female longevity of their progeny were observed (more adult longevity in control). Additionally, population growth parameters viz. intrinsic rate of growth (r) (-0.03-0.12 per day), net reproductive rate (R0) (0.50-9.98), limiting rate of growth (λ) (0.96-1.13 per day) were also significantly reduced in the progeny of treated adults. Based on the decreased biotic potential i.e. intrinsic rate of growth and other population parameters, diafenthiuron can be recommended as an effective insecticide even at lower doses.

Enhanced Harmonics Reactive Power Control Strategy Based on Multilevel Inverter Using ML-FFNN for Dynamic Power Load Management in Microgrid.

The shift of the world in the past two decades towards renewable energy (RES), due to the continuously decreasing fossil fuel reserves and their bad impact on the environment, has attracted researchers all around the world to improve the efficiency of RES and eliminate problems that arise at the point of common coupling (PCC). Harmonics and un-balance in 3-phase voltages because of dynamic and nonlinear loads cause a lagging power factor due to inductive load, active power losses, and instability at the point of common coupling. This also happens due to a lack of system inertia in micro-grids. Passive filters are used to eliminate harmonics at both the electrical converter's input and output sides and improve the system's power factor. A Synchronous Reference Frame (SRF) control method is used to overcome the problem related to grid synchronization. The sine pulse width modulation (SPWM) technique provides gating signals to the switches of the multilevel inverter. A multi-layer feed forward neural network (ML-FFNN) is employed at the output of a system to minimize mean square error (MSE) by removing the errors between target voltages and reference voltages produced at the output of a trained model. Simulations were performed using MATLAB Simulink to highlight the significance of the proposed research study. The simulation results show that our proposed intelligent control scheme used for the suppression of harmonics compensated for reactive power more effectively than the SRF-based control methods. The simulation-based results confirm that the proposed ML-FFNN-based harmonic and reactive power control technique performs 0.752 better in terms of MAE, 0.52 for the case of MSE, and 0.222 when evaluating based on the RMSE.

Nickel-Catalyzed Enantioselective Synthesis of 2,3,4-Trisubstituted 3-Pyrrolines.

The development of synthetic methods to produce highly functionalized chiral 3-pyrrolines is of indisputable importance because of their prevalence in natural and synthetic bioactive molecules. Unfortunately, previous general cycloaddition approaches using allenoates, could not synthesize 3,4-disubstituted 3-pyrrolines. Herein, an original approach to yield 2,3,4-trisubstituted 3-pyrrolines with chirality at the 2-position is presented. A NiII /Fc-i-PrPHOX catalytic system facilitated a redox-neutral highly stereoselective process that exhibited an enantioselectivity of up to 99 %. Enantioenriched 3-pyrrolines can be converted to other valuable classes of N-heterocycles.

Foraging behavior and bait station preference in scavenging termite, Odontotermes obesus (Blattodea: Termitidae).

Termites are a significant pest of buildings, agriculture, and trees, and are mainly controlled by baiting. However, baiting systems are available for only lower termites (Rhinotermitidae) not for higher termites (Termitidae). Termite foraging behavior associated with baiting systems varies among species and families, and plays a significant role in baiting success. Here, foraging behavior of Odontotermes obesus (Blattodea: Termitidae: Macrotermitinae), a fungus-growing higher termite, was investigated relative to three bait-station sizes (small, medium, and large) containing different quantities of food. Significantly more workers recruited to large stations (470/station) compared to medium (246/station) and small (124/station) stations. Abundance of O. obesus in large and medium stations significantly positively correlated with relative humidity whereas negative but non-significant correlations were observed with temperature in large and medium stations. Total and continuous contacts with the stations increased with time and were greater in large stations. Station abandonment due to disturbance was significantly less in large stations (3%) followed by medium (9%) and small stations (20%). Our results suggest that large stations (≈8 litres volume) work best for population management of O. obesus and other related fungus-growing higher termites.

A Scheduling Mechanism Based on Optimization Using IoT-Tasks Orchestration for Efficient Patient Health Monitoring.

Over the past years, numerous Internet of Things (IoT)-based healthcare systems have been developed to monitor patient health conditions, but these traditional systems do not adapt to constraints imposed by revolutionized IoT technology. IoT-based healthcare systems are considered mission-critical applications whose missing deadlines cause critical situations. For example, in patients with chronic diseases or other fatal diseases, a missed task could lead to fatalities. This study presents a smart patient health monitoring system (PHMS) based on an optimized scheduling mechanism using IoT-tasks orchestration architecture to monitor vital signs data of remote patients. The proposed smart PHMS consists of two core modules: a healthcare task scheduling based on optimization and optimization of healthcare services using a real-time IoT-based task orchestration architecture. First, an optimized time-constraint-aware scheduling mechanism using a real-time IoT-based task orchestration architecture is developed to generate autonomous healthcare tasks and effectively handle the deployment of emergent healthcare tasks. Second, an optimization module is developed to optimize the services of the e-Health industry based on objective functions. Furthermore, our study uses Libelium e-Health toolkit to monitors the physiological data of remote patients continuously. The experimental results reveal that an optimized scheduling mechanism reduces the tasks starvation by 14% and tasks failure by 17% compared to a conventional fair emergency first (FEF) scheduling mechanism. The performance analysis results demonstrate the effectiveness of the proposed system, and it suggests that the proposed solution can be an effective and sustainable solution towards monitoring patient's vital signs data in the IoT-based e-Health domain.

Elucidating Cd-mediated distinct rhizospheric and in planta ionomic and physio-biochemical responses of two contrasting Zea mays L. cultivars.

Cadmium (Cd) in soil-plant system can abridge plant growth by initiating alterations in root zones. Hydroponics and rhizoboxes are useful techniques to monitor plant responses against various natural and/or induced metal stresses. However, soil based studies are considered more appropriate in order to devise efficient food safety and remediation strategies. The present research evaluated the Cd-mediated variations in elemental dynamics of rhizospheric soil together with in planta ionomics and morpho-physio-biochemical traits of two differentially Cd responsive maize cultivars. Cd-sensitive (31P41) and Cd-tolerant (3062) cultivars were grown in pots filled with 0, 20, 40, 60 and 80 µg/kg CdCl2 supplemented soil. The results depicted that the maize cultivars significantly influenced the elemental dynamics of rhizosphere as well as in planta mineral accumulation under applied Cd stress. The uptake and translocation of N, P, K, Ca, Mg, Zn and Fe from rhizosphere and root cell sap was significantly higher in Cd stressed cv. 3062 as compared to cv. 31P41. In sensitive cultivar (31P41), Cd toxicity resulted in significantly prominent reduction of biomass, leaf area, chlorophyll, carotenoids, protein contents as well as catalase activity in comparison to tolerant one (3062). Analysis of tolerance indexes (TIs) validated that cv. 3062 exhibited advantageous growth and efficient Cd tolerance due to elevated proline, phenolics and activity of antioxidative machinery as compared to cv. 31P41. The cv. 3062 exhibited 54% and 37% less Cd bio-concentration (BCF) and translocation factors (TF), respectively in comparison to cv. 31P41 under highest Cd stress regime. Lower BCF and TF designated a higher Cd stabilization by tolerant cultivar (3062) in rhizospheric zone and its potential use in future remediation plans.

Toward Accurate Position Estimation Using Learning to Prediction Algorithm in Indoor Navigation.

Internet of Things is advancing, and the augmented role of smart navigation in automating processes is at its vanguard. Smart navigation and location tracking systems are finding increasing use in the area of the mission-critical indoor scenario, logistics, medicine, and security. A demanding emerging area is an Indoor Localization due to the increased fascination towards location-based services. Numerous inertial assessments unit-based indoor localization mechanisms have been suggested in this regard. However, these methods have many shortcomings pertaining to accuracy and consistency. In this study, we propose a novel position estimation system based on learning to the prediction model to address the above challenges. The designed system consists of two modules; learning to prediction module and position estimation using sensor fusion in an indoor environment. The prediction algorithm is attached to the learning module. Moreover, the learning module continuously controls, observes, and enhances the efficiency of the prediction algorithm by evaluating the output and taking into account the exogenous factors that may have an impact on its outcome. On top of that, we reckon a situation where the prediction algorithm can be applied to anticipate the accurate gyroscope and accelerometer reading from the noisy sensor readings. In the designed system, we consider a scenario where the learning module, based on Artificial Neural Network, and Kalman filter are used as a prediction algorithm to predict the actual accelerometer and gyroscope reading from the noisy sensor reading. Moreover, to acquire data, we use the next-generation inertial measurement unit, which contains a 3-axis accelerometer and gyroscope data. Finally, for the performance and accuracy of the proposed system, we carried out numbers of experiments, and we observed that the proposed Kalman filter with learning module performed better than the traditional Kalman filter algorithm in terms of root mean square error metric.

Towards a Remote Monitoring of Patient Vital Signs Based on IoT-Based Blockchain Integrity Management Platforms in Smart Hospitals.

Over the past several years, many healthcare applications have been developed to enhancethe healthcare industry. Recent advancements in information technology and blockchain technologyhave revolutionized electronic healthcare research and industry. The innovation of miniaturizedhealthcare sensors for monitoring patient vital signs has improved and secured the human healthcaresystem. The increase in portable health devices has enhanced the quality of health-monitoringstatus both at an activity/fitness level for self-health tracking and at a medical level, providing moredata to clinicians with potential for earlier diagnosis and guidance of treatment. When sharingpersonal medical information, data security and comfort are essential requirements for interactionwith and collection of electronic medical records. However, it is hard for current systems to meetthese requirements because they have inconsistent security policies and access control structures.The new solutions should be directed towards improving data access, and should be managed bythe government in terms of privacy and security requirements to ensure the reliability of data formedical purposes. Blockchain paves the way for a revolution in the traditional pharmaceuticalindustry and benefits from unique features such as privacy and transparency of data. In this paper,we propose a novel platform for monitoring patient vital signs using smart contracts based onblockchain. The proposed system is designed and developed using hyperledger fabric, which isan enterprise-distributed ledger framework for developing blockchain-based applications. Thisapproach provides several benefits to the patients, such as an extensive, immutable history log, andglobal access to medical information from anywhere at any time. The Libelium e-Health toolkitis used to acquire physiological data. The performance of the designed and developed system isevaluated in terms of transaction per second, transaction latency, and resource utilization usinga standard benchmark tool known as Hyperledger Caliper. It is found that the proposed systemoutperforms the traditional health care system for monitoring patient data.

Modulation of growth and key physiobiochemical attributes after foliar application of zinc sulphate (ZnSO4) on wheat (Triticum aestivum L.) under cadmium (Cd) stress.

A pot experiment was conducted to examine the effect of foliar application of various levels of ZnSO4 on wheat (Triticum aestivum L.) under cadmium (Cd) stress. Seeds of two wheat varieties i.e., Ujala-2016 and Anaj-2017 were sown in sand filled plastic pots. Cadmium (CdCl2) stress i.e., 0 and 0.5 mM CdCl2 was applied in full strength Hoagland's nutrient solution after 4 weeks of seed germination. Foliar spray of varying ZnSO4 levels i.e., 0, 2, 4, 6 and 8 mM was applied after 2 weeks of CdCl2 stress induction (of 6 week old plants). After 3 weeks of foliar treatment leaf samples of 9 week old wheat plants were collected for the determination of changes in various growth and physiobiochemical attributes. Results obtained showed that cadmium stress (0.5 mM CdCl2) significantly decreased shoot and root fresh and dry weights, shoot and root lengths, yield attributes, chlorophyll a contents and total phenolics, while increased hydrogen peroxide (H2O2), total soluble proteins, free proline, glycinebetaine (GB) contents, and activities of antioxidant enzymes i.e., catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD). Foliar application of varying ZnSO4 levels significantly increased various growth attributes, chlorophyll b contents, H2O2, free proline, GB and activities of antioxidant enzymes i.e., CAT, POD and APX, while decreased relative water contents and total phenolics under Cd stress or non stress conditions. Furthermore, both wheat varieties showed differential response under Cd stress and towards foliar application of ZnSO4 e.g., wheat var. Ujala-2016 was higher in shoot dry weight, root length, root fresh and dry weights, total leaf area per plant, 100 grains weight, number of tillers per plant, chlorophyll b, hydrogen peroxide (H2O2), activities of APX, POD, glycinebetaine and leaf free proline contents, while var. Anaj-2017 exhibited high shoot fresh weight, grain yield per plant, no. of grains per plant, chlorophyll contents, chlorophyll a/b ratio, total phenolics, MDA and total soluble protein contents under cadmium stress or non stress conditions.

Antibacterial activity of eco-friendly zinc nanoparticles prepared from leaf extract of Mentha piperita L.

The study aims to prepare reliable, ecofriendly and cost efficient zinc nanoparticles (Zn NPs) by Mentha piperita L. leaf extract and zinc sulfate heptahydrate, for four pathogenic bacteria. Synthesized NPs were investigated by using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Zeta Potential. Disc diffusion method was used to check their antibacterial activity. For synthesizing Zn NPs leaf extract was used as a biological reducing agent. During reaction, appearance of cloudy white solution due to reduction in the number of zinc ions, indicated the Zn NPs formation. XRD determined the average NPs size i.e. 9.8 nm. FTIR confirmed the presence of functional groups in the leaf extract sample. Spherical shape of the NPs was confirmed by the SEM analysis. Antibacterial activity of the Zn NPs was measured by the inhibition zones against various bacteria (E. coli, P. aeruginosa, S. aureus and S. pneumoniae). Inhibition zones were observed in the range of 2.9 to 12.9 mm.

Distinctive reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under photoredox conditions.

A simple photocatalytic method was developed for the synthesis of unsymmetrical 1,2-diamines by the unprecedented reductive coupling of N-benzylidene-[1,1'-biphenyl]-2-amines with an aliphatic amine. The presence of a phenyl substituent in the aniline moiety of the substrate was critical for the reactivity. The reaction proceeded via radical-radical cross-coupling of α-amino radicals generated by proton-coupled single-electron transfer in the presence of an Ir photocatalyst. On the other hand, symmetrical 1,2-diamines were selectively produced from the same starting materials by the judicious choice of the reaction conditions, showcasing the distinct reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines. The developed method can be employed for the synthesis of various bulky vicinal diamines, which are potential ligands in stereoselective synthesis.

Synthesis of fluoroalkylated alkynes via visible-light photocatalysis.

Fluoroalkylated alkynes, which are versatile building blocks for the synthesis of various biologically active organofluorine compounds, were synthesized from easily available alkynyl halides and fluoroalkyl halides by visible-light photocatalysis. Addition of fluoroalkyl radicals to alkynes and subsequent dehalogenation selectively yielded fluoroalkylated alkynes.

Chemical control of polyphagous pests on their auxiliary hosts can minimize insecticide resistance: A case study of Spodoptera exigua Hübner (Lepidoptera: Noctuidae) in cotton agroecosystem.

Use of insecticides for agricultural pest management have significant environmental impacts. Using integrated approaches to minimize the frequency of insecticide application by incorporating cultural control tactics can keep environmental hazards to the minimum. The alternate hosts of polyphagous pests have significant role in population development and success of chemical control. Spodoptera exigua Hübner is a polyphagous insect pest of frequently cultivated crops (castor, cauliflower, okra and spinach) in cotton agroecosystem of Pakistan. Since the timeline of cultivation of these crops coincide and the field are often adjoining, S. exigua therefore keeps on migrating from one crop to the other both in winter and summer. Such shifting has a significant effect on the susceptibility of the larvae against the commonly used insecticides. To reveal these effects, toxicity of chlorpyrifos and cypermethrin were tested against the larvae fed on their natal hosts, then shifted to their auxiliary hosts and finally upon their reversal to the natal host. Results have demonstrated that resistance of S. exigua decreased significantly when the populations are cultured on a single host in the laboratory. Field population collected from castor crop demonstrated the highest decrease in resistance ratios against chlorpyrifos and cypermethrin (i.e., 210- and 403-folds, respectively) compared to its field population. Moreover, alternation of generations among cotton and alternate crops, in general, decreased the resistance against chlorpyrifos and cypermethrin. But when these populations return to cotton again, their resistance has been found to be increased significantly. A similar but more obvious change in resistance ratio is observed when the pest population from cotton hosts is fed on spinach (a host available in the later developmental stages of cotton) and vice versa upon their return to cotton. Hence it is suggested that for effective management of S. exigua a continual routine of pest control on available alternate hosts, especially castor and spinach should be administered at critical stages of cotton crop development, i.e. early seedling stage and the late fruiting stage.

Access to Multifunctionalized Benzofurans by Aryl Nickelation of Alkynes: Efficient Synthesis of the Anti-Arrhythmic Drug Amiodarone.

An unconventional nickel-catalyzed reaction was developed for the synthesis of multifunctionalized benzofurans from alkyne-tethered phenolic esters. The transformation involves the generation of a nucleophilic vinyl NiII species by the regioselective syn-aryl nickelation of an alkyne, which then undergoes an intramolecular cyclization with phenol ester to yield highly functionalized 1,1-disubstituted alkenes with 3-benzofuranyl and (hetero)aryl substituents. The methodology can be used for the late-stage benzofuran incorporation of various drug molecules and natural products, such as 2-propylvaleric acid, gemfibrozil, biotin, and lithocholic acid. Furthermore, this arylative cyclization method was successfully applied for the efficient synthesis of the anti-arrhythmic drug amiodarone.

Mitochondrial Phylogenomics Resolves the Global Spread of Higher Termites, Ecosystem Engineers of the Tropics.

The higher termites (Termitidae) are keystone species and ecosystem engineers. They have exceptional biomass and play important roles in decomposition of dead plant matter, in soil manipulation, and as the primary food for many animals, especially in the tropics. Higher termites are most diverse in rainforests, with estimated origins in the late Eocene (∼54 Ma), postdating the breakup of Pangaea and Gondwana when most continents became separated. Since termites are poor fliers, their origin and spread across the globe requires alternative explanation. Here, we show that higher termites originated 42-54 Ma in Africa and subsequently underwent at least 24 dispersal events between the continents in two main periods. Using phylogenetic analyses of mitochondrial genomes from 415 species, including all higher termite taxonomic and feeding groups, we inferred 10 dispersal events to South America and Asia 35-23 Ma, coinciding with the sharp decrease in global temperature, sea level, and rainforest cover in the Oligocene. After global temperatures increased, 23-5 Ma, there was only one more dispersal to South America but 11 to Asia and Australia, and one dispersal back to Africa. Most of these dispersal events were transoceanic and might have occurred via floating logs. The spread of higher termites across oceans was helped by the novel ecological opportunities brought about by environmental and ecosystem change, and led termites to become one of the few insect groups with specialized mammal predators. This has parallels with modern invasive species that have been able to thrive in human-impacted ecosystems.

Controlled Fluoroalkylation Reactions by Visible-Light Photoredox Catalysis.

Owing to their unique biological, physical, and chemical properties, fluoroalkylated organic substances have attracted significant attention from researchers in a variety of disciplines. Fluoroalkylated compounds are considered particularly important in pharmaceutical chemistry because of their superior lipophilicity, binding selectivity, metabolic stability, and bioavailability to those of their nonfluoroalkylated analogues. We have developed various methods for the synthesis of fluoroalkylated substances that rely on the use of visible-light photoredox catalysis, a powerful preparative tool owing to its environmental benignity and mechanistic versatility in promoting a large number of synthetically important reactions with high levels of selectivity. In this Account, we describe the results of our efforts, which have led to the development of visible-light photocatalytic methods for the introduction of a variety of fluoroalkyl groups (such as, -CF3, -CF2R, -CH2CF3, -C3F7, and -C4F9) and arylthiofluoroalkyl groups (such as, -CF2SPh, -C2F4SAr, and -C4F8SAr) to organic substances. In these studies, electron-deficient carbon-centered fluoroalkyl radicals were successfully generated by the appropriate choice of fluoroalkyl source, photocatalyst, additives, and solvent. The redox potentials of the photocatalysts and the fluoroalkyl sources and the choice of sacrificial electron donor or acceptor as the additive affected the photocatalytic pathway, determining whether an oxidative or reductive quenching pathway was operative for the generation of key fluoroalkyl radicals. Notably, we have observed that additives significantly affect the efficiencies and selectivities of these reactions and can even change the outcome of the reaction by playing additional roles during its course. For instance, a tertiary amine as an additive in the reaction medium can act not only as a sacrificial electron donor in photoredox catalysis but also as a hydrogen atom source, an elimination base for dehydrohalogenation of the intermediate, and also a Brønsted base for deprotonation. In the same context, the selection of solvent is also critical since it affects the rate and selectivity of reactions depending upon its polarity and reagent solubilizing ability and plays additional roles in the process, for example, as a hydrogen atom source. By clearly understanding the roles of additives and solvent, we designed several controlled fluoroalkylation reactions where different products were formed selectively from the same starting substrates. In addition, we could exploit one of the most important advantages of radical reactions, that is, the use of unactivated π-systems such as alkenes, alkynes, arenes, and heteroarenes as radical acceptors without prefunctionalization. Furthermore, fluoroalkylation processes under mild room-temperature reaction conditions tolerate various functional groups and are therefore easily applicable to late-stage modifications of highly functionalized advanced intermediates.