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Cation‐binding salen nickel catalysts were developed for the enantioselective alkynylation of trifluoromethyl ketones in high yield (up to 99%) and high enantioselectivity (up to 97% ee). The reaction proceeds with substoichiometric quantities of base (10‐20 mol% KOt‐Bu) and open to air. In the case of trifluoromethyl vinyl ketones, excellent chemo‐selectivity was observed, generating 1,2‐addition products exclusively over 1,4‐addition products. UV‐vis analysis revealed the pendant oligo‐ether group of the catalyst strongly binds to the potassium cation (K+) with 1:1 binding stoichiometry (Ka = 6.6 × 105 M‐1).
The design of solid‐state reference electrodes without liquid junction is of great importance to allow for miniature and cost‐effective electrochemical sensors in environmental and biomedical applications. To address this, we propose here a pulse control protocol using an Ag/AgI element as reliable solid‐state reference electrode. It involves the local release of iodide by a cathodic current that is immediately followed by an electromotive force (EMF) measurement that serves as the reference potential. The recapture of iodide ions is achieved by potentiostatic control. This results in intermittent potential values that are reproducible to less than one millivolt (SD = 0.27 mV, n = 50). The ionic strength is shown to influence the activity c.
Quantitative optical sensing of samples containing both enantiomeric and diastereomeric species of a chiral compound remains a major challenge. We have now developed an optical method for accurate concentration, er and dr analysis of amino alcohols based on a simple mix‐and‐measure workflow that is fully adaptable to multiwell plate technology and microscale analysis. We found that conversion of the four aminoindanol stereoisomers with salicylaldehyde to the corresponding Schiff base allows analysis of the dr based on a change in the UV maximum at approximately 420 nm that is very different for the homo‐ and heterochiral diastereomers and of the total amount (concentration) of the sample using a hypsochromic shift of another absorption band.
Controlling thermomechanical anisotropy is important for emerging heat management applications such as thermal interface and electronic packaging materials. Whereas many studies report on thermal transport in anisotropic nanocomposite materials, a fundamental understanding of the interplay between mechanical and thermal properties is missing, due to the lack of measurements of direction‐dependent mechanical properties. In this work, exceptionally coherent and transparent hybrid Bragg stacks made of strictly alternating mica‐type nanosheets (synthetic hectorite) and polymer layers (polyvinylpyrrolidone) were fabricated at large scale. Distinct from ordinary nanocomposites, these stacks display long‐range periodicity, which is tunable down to.
Lithium‐sulfur (Li‐S) batteries are well known as one of the most promising next‐generation batteries owing to its ultra‐high theoretical energy density and abundant sulfur resources. During the past 20 years, various sulfur materials have been reported. As the representative of molecular scale sulfur composite cathode, sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) exhibits several competitive advantages in terms of electrochemical behaviors. Currently, S@pPAN attracts increasing attentions although it was first reported in 2002. In this review, we firstly summarize its molecular model, which benefits to elucidate the correlation between structure property and exceptional electrochemical performance. Secondly, we classify the modificati.
N‐Alkenoxypyridinium salts have been used as synthons for umpolung enolates for the preparation of α‐functionalized carbonyl compounds. In contrast, we found that the photoreduction of N‐alkenoxypyridinium salts generates α‐carbonyl radicals after cleavage of the N−O bond, allowing the simultaneous incorporation of α‐keto and pyridyl groups across unactivated alkenes. In the process, the formed α‐carbonyl radicals engage unactivated alkenes to afford alkyl radical intermediates poised for subsequent addition to pyridinium salts, ultimately affording a variety of γ‐pyridyl ketones under mild reaction conditions. This transformation is characterized by a broad substrate scope, and good functional group compatibility, and the utility of this t.
Whole in one: A general method was developed for the synthesis of 2,5‐diaminoimidazoles through a thermal reaction between α‐aminoketones and substituted guanylhydrazines. This one‐step reaction works successfully on both cyclic and acyclic amino ketone starting materials, as well as a range of substituted guanylhydrazines. The method was applied to the efficient synthesis of the advanced glycation end product (AGE) methylglyoxal‐derived imidazolium crosslink (MODIC). Abstract. Here we describe a general method for the synthesis of 2,5‐diaminoimidazoles, which involves a thermal reaction between α‐aminoketones and substituted guanylhydrazines without the need for additives. As one of the few known ways to access the 2,5‐diaminoimidazole moti.
Chemical‐gradient‐driven concentration enhances the sensitivity and selectivity of chemical sensors. In their Communication (DOI: 10.1002/anie.201908647), P. V. Braun et al. show how hydrogel‐embedded radially symmetric cyclodextrin gradients direct transport of molecules including the nerve agent simulant 4‐methylumbelliferyl phosphate. To provide near real‐time read‐out of the analyte concentration an array of IR‐resonant metallic nanoantennas was used to enhance the IR signal generated by the analyte.
The separation of the liquid phase into solute‐rich and solute‐poor phases is an elementary step leading to the nucleation of supramolecular nanofibrils from amphiphilic amino acids and peptides. As X. Yan, T. P. J. Knowles et al. show in their Research Article (DOI: 10.1002/anie.201911782), the solute‐rich liquid droplets with low enthalpy act as nucleation sites, significantly decrease the nucleation barrier towards solid phase, and eventually form thermodynamically more favorable nanofibrils.
Sonodynamic therapy (SDT) has the advantages of high penetration, non‐invasiveness and controllability, and is suitable for deep‐seated tumors. However, there is still a lack of effective sonosensitizers with high sensitivity, safety and penetration. Herein, we designed ultrasound (US) and glutathione (GSH) dual responsive vesicles of Janus Au‐MnO nanoparticles (JNPs) coated with PEG and a ROS‐sensitive polymer. Upon US irradiation, the vesicles were disassembled into small Janus Au‐MnO nanoparticles (NPs) with promoted penetration ability. Subsequently, GSH‐triggered MnO degradation simultaneously released smaller Au NPs as numerous cavitation nucleation sites and Mn2+ for chemodynamic therapy (CDT), resulting in enhanced reactive oxygen s.
Acyclic ketone‐derived oxocarbenium ions, intermediates that are involved in numerous reactions providing valuable products, have thus far eluded efforts aimed at asymmetric catalysis. We report that a readily accessible chiral carboxylic acid catalyst exerts control over asymmetric cyclizations of acyclic ketone‐derived trisubstituted oxocarbenium ions, achieving the synthesis of highly enantioenriched dihydropyran products containing a tetrasubstituted stereogenic center. The high acidity of the carboxylic acid catalyst, exceeding that of the well‐known chiral phosphoric acid catalyst TRIP, is largely derived from stabilization of the carboxylate conjugate base via intramolecular anion‐binding to a thiourea site.
Reduction of the uranium(III) metallocene [(η 5 ‐C 5 i Pr 5 ) 2 UI] ( 1 ) with potassium graphite produces the 'second‐generation' uranocene [(η 5 ‐C 5 i Pr 5 ) 2 U] ( 2 ), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground‐state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f 3 6d 1 . Appreciable covalent contributions to the metal‐ligand bonds were determined from a computational study of 2 , including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth e.
Carbon nanotubes (CNTs) have unusual physical properties which are valuable for nanotechnology and electronics but the chemical synthesis of chirality‐ and diameter‐specified CNTs and π‐conjugated CNT segments is still a great challenge. Herein we report the selective synthesis, isolation, characterizations, and photophysical properties of two novel chiral conjugated macrocycles ([4]cyclo‐2,6‐anthracene, [4]CAn2,6) as (‐)/(+)‐(12,4) carbon nanotube segment. These conjugated macrocyclic molecules were achieved using a bottom‐up assembly approach and subsequent reductive elimination reaction. The hoop‐shaped molecules can be directly viewed by STM technique. In addition, chiral enantiomers with (‐)/(+)‐helicity of the [4]CAn2,6 were successfu.
Bpin it: A practical, atom‐economical method for the synthesis of 1,1,1‐triborylalkanes based on sequential dehydrogenative borylation and double hydroboration of terminal alkynes with HBpin is described. The 1,1,1‐triborylalkane products are useful synthetic intermediates for the construction of multiple C−C and C−O bonds to give carbocyclic organoboronates and unsymmetric tertiary alcohols. Abstract. A convenient and efficient one‐step synthesis of 1,1,1‐triborylalkanes was achieved via sequential dehydrogenative borylation and double hydroborations of terminal alkynes with HBpin (HBpin=pinacolborane) catalyzed by inexpensive and readily available Cu(OAc)2. This process proceeds under mild conditions, furnishing 1,1,1‐tris(boronates) with
Stereogenic trifluoromethyl‐substituted carbon centres are highly sought‐after moieties in pharmaceutical and agrochemical discovery. Here, we show that lithiation–borylation reactions of 2‐trifluoromethyl oxirane give densely functionalised and highly versatile trifluoromethyl‐substituted α‐tertiary boronic esters. The intermediate boronate complexes undergo the desired 1,2‐rearrangement of the carbon‐based group with complete retentive stereospecificity, a process that was only observed in non‐polar solvents in the presence of TESOTf. Although the trifluoromethyl group adversely affects subsequent transformations of the α‐boryl group, Zweifel olefinations provide trifluoromethyl‐bearing quaternary stereocenters substituted with alkenes, a.
The current research of thermally activated fluorescence (TADF) emitters is mainly based on the molecular levels, while the aggregation states of TADF emitters are to be explored deeply. Here we report two multifunctional emitters with simultaneous TADF, aggregation induced emission (AIE), and multicolor mechanochromic luminescence (MCL) features. Moreover, both emitters show polymorph‐dependent TADF emission. Crystal structure analysis reveals that the polymorphism is ascribed to the mutable conformations in different aggregation states. This work brings new insight into the TADF emitters from a perspective of aggregation states.

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