Radical borylation using N‐heterocyclic carbene (NHC)‐BH3 complexes as boryl radical precursors has emerged as an important synthetic tool for organoboron assembly. However, the majority of reported ...methods are limited to reaction modes involving carbo‐ and/or hydroboration of specific alkenes and alkynes. Moreover, the generation of NHC‐boryl radicals relies principally on hydrogen atom ion with the aid of radical initiators. A distinct radical generation method is reported, as well as the reaction pathways of NHC‐boryl radicals enabled by photoredox catalysis. NHC‐boryl radicals are generated via a single‐electron oxidation and subsequently undergo cross‐coupling with the in‐situ‐generated radical anions to yield gem‐difluoroallylboronates. A photoredox‐catalyzed radical arylboration reaction of alkenes was achieved using cyanoarenes as arylating components from which elaborated organoborons were accessed. Mechanistic studies verified the oxidative formation of NHC‐boryl radicals through a single‐electron‐transfer pathway.
NHC‐boryl radicals are generated by single‐electron oxidation of NHC‐BH3 complexes using a photoredox catalytic system. New reaction modes of NHC‐boryl radicals were determined for the facile synthesis of highly elaborated organoboron molecules. Key: N‐heterocyclic carbene (NHC), leaving group (LG).
Understanding metabolism and dynamic biological events in cells, as well as physiological functions and pathological changes in organisms, is the major goal of biological investigations. It will ...improve our capability to diagnose and treat diseases, and will enhance personalized medicine. Fluorescence imaging is a powerful tool that plays an essential role in acquiring the comprehensive knowledge necessary to help reach this goal. Fluorescent molecules are crucial factors for obtaining high quality images. In contrast to conventional fluorogens with aggregation‐caused quenching (ACQ) effect, molecules that show aggregation‐induced emission (AIE) effect open up new avenues for fluorescence imaging. So far, a large variety of AIE probes have been developed and applied to bioimaging because of their outstanding characteristics, such as high fluorescence efficiency, excellent photostability and high signal‐to‐noise ratio (SNR). In this review, recent advances in AIE‐based probes for biomedical imaging of intracellular microenvironments, natural macromolecules, subcellular organelles, intracellular processes, living tissues, and diagnosis and therapeutic evaluation of diseases in vivo are summarized. It is hoped that this review generates great research enthusiasm for AIE‐based bioimaging, in order to promote the development of promising AIE probes and guide us to a better understanding of the biological essence of life.
Aggregation‐induced emission (AIE) probes have recently been considered as alternatives in the area of biological imaging to reveal the mysteries of life. This review summarizes and describes typical AIE‐based probes for sensing intracellular microenvironments and natural macromolecules, lighting up subcellular organelles, tracking cellular processes, monitoring living tissues, improving the diagnosis of disease, and evaluating therapies.
A synthetic method of isoquinolines from aryl ketone O-acyloxime derivatives and internal alkynes has been developed using Cp*RhCl22−NaOAc as the potential catalyst system. The present transformation ...is carried out by a redox-neutral sequence of C−H vinylation via ortho-rhodation and C−N bond formation of the putative vinyl rhodium intermediate on the oxime nitrogen, where the N−O bond of oxime derivatives could work as an internal oxidant to maintain the catalytic cycle.
The fluorine‐containing organic motif is becoming privileged in pharmaceuticals, agrochemicals, and functional materials, owing to its unique properties such as electron‐withdrawing character, ...metabolic stability, and lipophilicity. Described herein is the PhI(OAc)2‐mediated radical trifluoromethylation of vinyl azides with Me3SiCF3 to efficiently generate α‐trifluoromethyl azines. The resulting α‐trifluoromethyl azines were successfully transformed to valuable fluorine‐containing molecules such as α‐trifluoromethyl ketones, β‐trifluoromethyl amines, 5‐fluoropyrazoles, and trifluoroethyl isoquinolines.
Trifluoromethylated diversity: The title reaction (see scheme) efficiently leads to α‐trifluoromethyl azines, which were successfully transformed into valuable fluorine‐containing molecules such as α‐trifluoromethyl ketones, β‐trifluoromethyl amines, 5‐fluoropyrazoles, and trifluoroethyl isoquinolines.
According to the Mott's relation, the figure‐of‐merit of a thermoelectric material depends on the charge carrier concentration and carrier mobility. This explains the observation that low ...thermoelectric properties of GeTe‐based materials suffer from the degraded carrier mobility, on account of the fluctuation of electronegativity and ionicity of various elements. Here, high‐performance CuBiSe2 alloyed GeTe with high carrier mobility due to the small electronegativity difference between Cu and Ge atoms and the weak ionicity of CuTe and BiTe bonds, is developed. Density functional theory calculations indicate that CuBiSe2 alloying increases the formation energy of Ge vacancies and correspondingly reduces the amount of Ge vacancies, leading to an optimized carrier concentration and a high power factor of ≈37.4 µW cm−1 K−2 at 723 K. Moreover, CuBiSe2 alloying induces dense point defects and triggers ubiquitous lattice distortions, leading to a reduced lattice thermal conductivity of 0.39 W m−1 K−1 at 723 K. These synergistic effects result in an optimization of the carrier mobility, the carrier concentration, and the lattice thermal conductivity, which favors an enhanced peak figure‐of‐merit of ≈2.2 at 723 K in (GeTe)0.94(CuBiSe2)0.06. This study provides guidance for the screening of GeTe‐based thermoelectric materials with high carrier mobility.
The thermoelectric properties of GeTe‐based materials usually suffer from reduced carrier mobility. In this study, alloying CuBiSe2 into GeTe allows high intrinsic carrier mobility and a high zT of ≈2.2 at 723 K and an average zT of 1.4 from 300 to 723 K in (GeTe)0.94(CuBiSe2)0.06.
This paper presents a novel interleaved high-conversion-ratio bidirectional DC-DC converter based on switched capacitors and coupled inductors. Series-connected switched capacitor and inductor cells ...were used to increase the voltage conversion ratio, reduce voltage stresses on power switches, realize soft-charging/discharging of switched capacitors, and achieve autocurrent-sharing in parallel inductors. The interleaved structure combined with switched capacitors was adopted to reduce current ripple at the side having lower voltage, thus enabling applications that require high power levels. In this paper, we first review the status of high-voltage-ratio bidirectional dc-dc converters. Then, the evolution of the proposed extensible topologies and the steady-state operating principle under the inductor current continuous conduction mode is presented. Finally, the performance and features such as voltage gain, voltage and current stress, and the autocurrent-sharing mechanism that are realized by switched capacitors are verified; the optimal design of coupled-inductors, switched-capacitors, and the chip size of switches are given. A specific design of the driving circuit that facilitates actual applications is described. A 1-kW prototype converter, employing a hybrid configuration of SiC and Si mosfets, was constructed to verify the theoretical analysis, and achieved an optimal compromise between conversion efficiency and low cost.
In this work, a record high thermoelectric figure‐of‐merit ZT of 1.6 ± 0.2 at 873 K in p‐type polycrystalline Bi0.94Pb0.06CuSe1.01O0.99 by a synergy of rational band manipulation and novel ...nanostructural design is reported. First‐principles density functional theory calculation results indicate that the density of state at the Fermi level that crosses the valence band can be significantly reduced and the measured optical bandgap can be enlarged from 0.70 to 0.74 eV by simply replacing 1% O with 1% Se, both indicating a potentially reduced carrier concentration and in turn, an improved carrier mobility and a boosted power factor up to 9.0 µW cm−1 K−2. Meanwhile, comprehensive characterizations reveal that under Se‐rich condition, Cu2Se secondary microphases and significant lattice distortions triggered by Pb‐doping and Se‐substitution can be simultaneously achieved, contributing to a reduced lattice thermal conductivity of 0.4 W m−1 K−1. Furthermore, a unique shear exfoliation technique enables an effective grain refinement with higher anisotropy of the polycrystalline pellet, leading to a further improved power factor up to 10.9 µW cm−1 K−2 and a further reduced lattice thermal conductivity of 0.30 W m−1 K−1, which gives rise to record high ZT.
A record high thermoelectric figure‐of‐merit ZT of 1.6 ± 0.2 at 873 K in p‐type polycrystalline Bi0.94Pb0.06CuSe1.01O0.99 by a synergy of rational band manipulation and novel nanostructural design is reported.
A method for the synthesis of bi- and tricyclic amidines has been developed through copper-catalyzed aerobic 3+2-annulation reaction of N-alkenyl amidines. These cyclic amidines could be converted ...into mono-benzyl-protected vicinal diamines by the reduction with aluminum hydride.
Organoboron compounds are highly valuable in synthetic chemistry. In particular, α-borylcarbonyl compounds have shown versatile synthetic applications, owing to fruitful chemistries of both the boryl ...and carbonyl moieties. However, the synthesis of these molecules still remains tedious and time-consuming. Here we report a straightforward and practical route to synthesize α-borylcarbonyl molecules based on a regioselective radical α-borylation of α,β-unsaturated carbonyl compounds. The reaction features unusual α-regioselectivity and high functional-group compatibility. Further synthetic applications of new α-borylated products were also demonstrated. DFT and kinetic studies implicated that the α-regioselectivity of β-aryl-α,β-unsaturated carbonyl compounds was determined by the thermodynamically more favorable radical α-addition step, whereas the formation of α-addition products from β-alkyl-α,β-unsaturated carbonyl compounds was driven by an energetically favored hydrogen atom transfer step. Given that α,β-unsaturated carbonyl compounds can be easily obtained in abundance and variety, this method enjoys great advantages in diverse and economical synthesis of valuable α-borylcarbonyl molecules.
Catalysts in a relay: A synthetic method for delivering highly substituted isoquinolines has been developed (see scheme; Cp*=C5Me5, DMF=N,N‐dimethylformamide, ...TEMPO=2,2,6,6‐tetramethylpiperidine‐1‐oxyl). A preliminary mechanistic study showed that the rhodium and copper cooperate synergistically in the multistep sequence.
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