The synthesis of amides is a long-term theme in chemistry and related areas. The use of readily available and cost-effective precursors for straightforward amide synthesis with atom economy under ...mild conditions is attractive yet challenging. Herein, we report the direct synthesis of amides from aldehydes and imines in a 100% atom-economical manner. The redox-neutral C–N bond-forming process was enabled by the dual catalysis of visible light and an N-heterocyclic carbene (NHC) at room temperature. This protocol features the unprecedented umpolung of imines to generate N-centered radicals. Mechanistic investigations reveal this reaction undergoes nontrivial radical–radical coupling between an N-centered radical and a C-centered radical to forge a C–N bond. This operationally simple protocol tolerates a wide range of functional groups, providing rapid access to amides from aromatic or aliphatic aldehydes with imines without producing any byproduct.
Organothianthrenium salts are a class of compounds containing a positively charged sulfur atom and a neutral sulfur atom. Over the past years, organothianthrenium salts have been emerging as ...attractive precursors for a myriad of transformations to forge new C-C and C-X bonds due to their unique structural characteristics and chemical behaviors. The use of the thianthrenation strategy selectively transforms C-H, C-O, and other chemical bonds into organothianthrenium salts in a predictable manner, providing a straightforward alternative for regioselective functionalizations for arenes, alkenes, alkanes, alcohols, amines and so on through diverse reaction mechanisms under mild conditions. In this review, the preparation of different organothianthrenium salts is summarized, including aryl, alkenyl and alkyl thianthrenium salts. Moreover, the utilization of organothianthrenium salts in different catalytic processes and their synthetic potentials are also discussed.
This review summarizes the synthesis of diverse organothianthrenium salts from various precursors and their applications in organic synthesis to forge new C-C, C-H and C-heteroatom bonds by C-S bond cleavage with different mechanistic considerations.
Three‐membered cyclic structures are widely existing in natural products and serve as enabling intermediates in organic synthesis. However, the efficient and straightforward access to such structures ...with diversity remains a formidable challenge. Herein, a general and practical protocol to aziridines and cyclopropanes synthesis using free XH2 (X=C or N) with alkenes by thianthrenation is presented. This metal‐free protocol features the direct aziridination and cyclopropanation with unprotected XH2. Free sulfonamides, amides, carbamates, amines, and methylene with acidic protons, are good precursors, providing an attractive alternative for straightforward synthesis of aziridines and cyclopropanes from easily available starting materials.
Herein, a general and practical protocol to aziridines and cyclopropanes using free XH2 (X=C or N) with alkenes by thianthrenation is presented under mild conditions. Free sulfonamides, amides, carbamates, amines, and acidic methylene with protons, are good precursors for three‐membered ring formation, providing an attractive alternative for straightforward synthesis of aziridines and cyclopropanes from easily available starting materials.
•As of 3 March 2020, COVID-19 has spread rapidly in 46 countries, causing >90 000 confirmed cases and >2946 deaths.•Detection methods for SARS-CoV-2 include RT-qPCR and SHERLOCK technique.•Four ...structural proteins are essential for SARS-CoV-2 assembly and infection, comprising the S, M, E and N proteins.•Pangolin may be a potential intermediate host for SARS-CoV-2.•Antiviral therapy, cellular therapy, immunotherapy and Chinese medicine may be promising therapeutic strategies.
Coronavirus disease 2019 (COVID-19) originated in the city of Wuhan, Hubei Province, Central China, and has spread quickly to 72 countries to date. COVID-19 is caused by a novel coronavirus, named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) previously provisionally known as 2019 novel coronavirus (2019-nCoV). At present, the newly identified SARS-CoV-2 has caused a large number of deaths with tens of thousands of confirmed cases worldwide, posing a serious threat to public health. However, there are no clinically approved vaccines or specific therapeutic drugs available for COVID-19. Intensive research on the newly emerged SARS-CoV-2 is urgently needed to elucidate the pathogenic mechanisms and epidemiological characteristics and to identify potential drug targets, which will contribute to the development of effective prevention and treatment strategies. Hence, this review will focus on recent progress regarding the structure of SARS-CoV-2 and the characteristics of COVID-19, such as the aetiology, pathogenesis and epidemiological characteristics.
Selective functionalization of allylic C-H bonds into other chemical bonds is among the most straightforward and attractive, yet challenging transformations. Herein, a transition-metal-free protocol ...for direct allylic C-H nitrogenation, oxygenation, and carbonation of alkenes by thianthrenation was developed. This operationally simple protocol allows for the unified allylic C-H amination, esterification, etherification, and arylation of vinyl thianthrenium salts. Notably, the reaction furnishes multialkyl substituted allylic amines, ammonium salts, sulfonyl amides, esters, and ethers in good yields. The reaction proceeds under mild conditions with excellent functional group tolerance and could be applied to late-stage allylation of natural products, drug molecules and peptides with excellent chemoselectivity.
The layered quasi‐2D perovskites are recognized as one of the effective strategies to resolve the big problem of intrinsic phase instability of the perovskites. However, in such configurations, their ...performance is fundamentally limited due to the correspondingly weakened out‐of‐plane charge mobility. Herein, the π‐conjugated p‐phenylenediamine (PPDA) is introduced as organic ligand ions for rationally designing lead‐free and tin‐based 2D perovskites with the aid of theoretical computation. It is evidenced that both out‐of‐plane charge transport capacity and stability can be significantly enhanced within as‐established quasi‐2D Dion‐Jacobson (DJ) (PPDA)Csn‐1SnnI3n+1 perovskites. The obviously increased electrical conductivity and reduced carrier effective masses are attributed to the enhanced interlayer interactions, limited structural distortions of diamine cations, as well as improved orbital coupling between Sn2+ and I− ions of (PPDA)Csn‐1SnnI3n+1 perovskites. Accordingly, by dimension engineering of the inorganic layer (n), the bandgap (Eg) of quasi‐2D perovskites can be linearly tailored toward the suitable Eg (1.387 eV) with optimal photoelectric conversion efficiency (PCE) of 18.52%, representing their great potential toward promising applications in advanced solar cells.
The photoelectric conversion efficiency (PCE) of (PPDA)Cs3Sn4I13 solar cell is calculated to be 18.52%, as a result of the optimal Eg, smaller carrier effective mass as well as the boosted charge transport. Meanwhile, the destruction of perovskite structure can promisingly be suppressed owing to the enhanced chemical bonding interactions. Thus, (PPDA)Cs3Sn4I13 perovskite exhibit enhanced structural stability and PCE.
Direct functionalizations of two distinct inert C–H bonds represent the most ideal ways to construct C–C bonds. Herein, we report an intermolecular vinylation of aldehydes using alkenes as the ...vinylating reagents through sequential two-fold C–H functionalizations. The merging of visible light and N-heterocyclic carbene catalysis allows for the coupling of alkenes with aldehydes through a dual catalysis relay enabled cross-dehydrogenative coupling mechanism. The use of diphenoquinone is essential for the success of this reaction, which plays an intriguing two-fold role in the reaction, as an electron acceptor as well as a radical reservoir for the radical coupling enabling the C–C forming process.
Aims
Patients with attention deficit hyperactivity disorder (ADHD) are prone to injury and frequently require treatment with hospital admission. This study aimed to evaluate the risk of injuries ...requiring hospitalization among children and adolescents with and without ADHD and assess the effects of medication on the risk reduction in patients with ADHD.
Methods
This is a retrospective population‐based cohort study by using data from the Taiwan National Health Insurance Research Database. We compared 4658 6–18 year‐old ADHD patients with 18 632 sex‐, age‐, and index day‐matched non‐ADHD controls between 2005 and 2012. Both groups were followed until the end of 2013 to compare the risk of injuries requiring hospitalization. Cox regression analysis was performed to determine the hazard ratio (HR) with 95% confidence intervals (CI) after adjusting for confounders.
Results
Children and adolescents with ADHD had a significantly higher risk of injuries requiring hospitalization than the non‐ADHD controls (HR = 1.39, 95% CI = 1.12–1.72), and a higher risk was especially observed in the male and adolescent subgroups. In ADHD patients, long‐term users of ADHD medication were associated with a lower risk of injuries requiring hospitalization than nonusers (HR = 0.51, 95% CI = 0.30–0.85).
Conclusion
Healthcare providers should be aware of the potential risk of injury in patients with ADHD and highlight the importance of the duration and compliance with medication treatment.
The non-stationary nature of electroencephalography (EEG) signals makes an EEG-based brain-computer interface (BCI) a dynamic system, thus improving its performance is a challenging task. In ...addition, it is well-known that due to non-stationarity based covariate shifts, the input data distributions of EEG-based BCI systems change during inter- and intra-session transitions, which poses great difficulty for developments of online adaptive data-driven systems. Ensemble learning approaches have been used previously to tackle this challenge. However, passive scheme based implementation leads to poor efficiency while increasing high computational cost. This paper presents a novel integration of covariate shift estimation and unsupervised adaptive ensemble learning (CSE-UAEL) to tackle non-stationarity in motor-imagery (MI) related EEG classification. The proposed method first employs an exponentially weighted moving average model to detect the covariate shifts in the common spatial pattern features extracted from MI related brain responses. Then, a classifier ensemble was created and updated over time to account for changes in streaming input data distribution wherein new classifiers are added to the ensemble in accordance with estimated shifts. Furthermore, using two publicly available BCI-related EEG datasets, the proposed method was extensively compared with the state-of-the-art single-classifier based passive scheme, single-classifier based active scheme and ensemble based passive schemes. The experimental results show that the proposed active scheme based ensemble learning algorithm significantly enhances the BCI performance in MI classifications.
A conventional phase-shift full-bridge (PSFB) converter suffers from easy failure of zero-voltage switching (ZVS) in the lagging leg under light load conditions. This poses a significant challenge to ...the optimal design of PSFB-based plug-in electric vehicle (PEV) onboard chargers. In this paper, a self-reconfigured integrated onboard charger architecture is proposed for PEVs to cope with this design challenge. In this architecture, the PSFB converter is adopted as the main topology to charge the high-voltage battery pack, while the half-bridge LLC resonant converter is employed to charge the low-voltage auxiliary battery. Under light-charging mode, the half-bridge LLC converter is reconfigured to be paralleled with the PSFB topology to guarantee the ZVS of the lagging leg MOSFETs. Moreover, a capacitor-diode-diode snubber is added to resolve the duty cycle loss issue of the PSFB converter and to reduce the circulating current. Practical design considerations are presented for both the PSFB and the half-bridge LLC converters. Frequency modulation and the phase-shift modulation provide two degrees of freedom to regulate the output voltage/current of both converters. The proposed charger architecture maintains low cost and high efficiency in this specific application. A 390 V input, 420 V/2.4 A, 14 V/21 A outputs, 1.3 kW rated converter prototype is designed, analyzed, and tested to verify the proof of concept.
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