ABSTRACT
Although lithium-oxygen batteries (LOBs) hold the promise of high gravimetric energy density, this potential is hindered by high charging voltages. To ensure that the charging voltage remains low, it is crucial to generate discharge products that can be easily decomposed during the successive charging process. In this study, we discovered that the use of amide-based electrolyte solvents containing a fluorinated moiety can notably establish a sustained voltage plateau at low-charging voltages at around 3.5 V. This occurs under conditions that can verify the feasibility of achieving a benchmark energy density value of 500 Wh kg-1. Notably, the achievement of the low-voltage plateau was accomplished solely by relying on the intrinsic properties of the electrolyte solvent. Indeed, synchrotron X-ray diffraction measurements have shown that the use of fluorine-containing amide-based electrolyte solvents results in the formation of highly decomposable discharge products, such as amorphous and Li-deficient lithium peroxides.
ABSTRACT
Two novel fluorescent probes for Cu2+ detection have been developed based on thiazoline-quinoline conjugates bearing a 4-ethynyl-N,N-dimethylaniline unit (QT1 and QT2). QT2 exhibits instantaneous fluorescence quenching of Cu2+ with an emissive change from bright orange to arctic blue under UV light irradiation (365 nm). The plots of I0/I against Cu2+ concentrations show a good linear relationship that ranges from 0 to 50 µM with a coefficient of determination (R2) = 0.9906 and a limit of detection (LOD) of 76 nM, which is considered low (4.84 ppb). A 1:1 complexation between QT2 and Cu2+ was confirmed by UV-Vis titration, ESI-MS, and SC-XRD. The QT2·Cu2+ complex was dissociated by the addition of EDTA. The fluorescence quenching mechanism involves the ligand-to-metal charge transfer (LMCT) of a paramagnetic Cu2+ complex. The QT2 probe on a paper-based strip was used to determine the amount of Cu2+ in water and food samples (shiitake mushrooms and oysters).
Subject(s)
Copper , Fluorescent Dyes , Quinolines , Spectrometry, Fluorescence , Water , Copper/analysis , Copper/chemistry , Fluorescent Dyes/chemistry , Quinolines/chemistry , Water/chemistry , Limit of Detection , Food Analysis/methods , Thiazoles/chemistry , Thiazoles/analysis , Fluorometry/methods , Ostreidae/chemistryABSTRACT
In this study, we present the catalytic conversion of benzylamides featuring an ortho alkynyl moiety into 1-acylisoindole derivatives via a 1,2-acyl shift. Remarkably, this transformation proceeds without the need for transition-metal catalysts; instead, KOtBu alone serves as the catalyst. This method enables the efficient synthesis of isoindoles from easily accessible amides with an atom economy of 100%.
ABSTRACT
Unimolecular fragment coupling (UFC) is defined as a reaction format, wherein atom(s) located in the middle of a molecule are extruded, and the remaining fragments are coupled. UFC is a potentially powerful strategy that is an alternative to transition-metal-catalyzed cross-coupling because the target chemical bond is formed in an intramolecular fashion, which is inherently beneficial for chemoselectivity and stereoselectivity issues. In this Perspective, we will present an overview of the recent advances in UFC reactions, which encompass those proceeding through the elimination of CO2, CO, SO2, isocyanates, N2, or single atoms primarily via transition metal catalysis.
ABSTRACT
The palladium-catalyzed addition of trifluoroacetylsilanes to alkenes and allenes via the cleavage of the C-Si bonds is reported. When alkenes are used, cyclopropanation occurs to afford cyclopropane derivatives bearing CF3 and siloxy groups with a high degree of stereoselectivity. When allenes are used, silylacylation occurs to form alkenylsilane derivatives bearing a trifluoroacetyl group at the allylic position with complete regioselectivity. Both reactions allow for highly atom-economical access to densely functionalized fluorinated organosilane derivatives using simple building blocks.
ABSTRACT
In this study, two fluorescent sensing probes, dihydropyridine (DHP) derivatives (DHP-CT1 and DHP-CT2) bearing phenoxy thiocarbonyl group, have been developed for Hg2+ detection. The tandem trimerization-cyclization of methylpropiolate with ammonium acetate gave 1.4-DHP and 1,2-DHP derivatives, which were reacted with O-phenylcarbonochloridothioate to produce DHP-CT1 and DHP-CT2, respectively. DHP-CT1 exhibits superior sensitivity and selectivity of fluorescence enhancement towards Hg2+ in aqueous media. The fluorescence intensity shows a good linear relationship with the concentration of Hg2+ in the range of 0-10 µM providing the extremely low LOD of 346 nM (69.4 ppb). The fluorescence enhancement is caused by the Hg2+ promoted hydrolysis of the thioamide bond releasing the fluorescent 1,4-DHP that was confirmed by NMR and HRMS. The quantitative analysis of Hg2+ in water samples using DHP-CT1 probe was demonstrated in aqueous solution and paper-based sensing strips. Furthermore, DHP-CT1 was also applied for monitoring intracellular Hg2+ in living RAW264.7 macrophages through fluorescence cell imaging.
Subject(s)
Fluorescent Dyes , Mercury , Fluorescent Dyes/chemistry , Water , Spectrometry, Fluorescence/methods , Magnetic Resonance Spectroscopy , Mercury/analysisABSTRACT
A protocol for single-carbon atom doping annulation is reported, which enables the conversion of acrylamides into homologated γ-lactams through the cleavage of two σ-bonds and the formation of four new σ-bonds at the single carbon center. The key strategy is the use of N-heterocyclic carbenes as an atomic carbon equivalent by acting as carbon atom donors through the loss of a 1,2-diimine moiety. Experimental and computational studies reveal that the reaction proceeds through a spirocyclic intermediate, followed by the disassembly of the N-heterocyclic carbene skeleton via proton transfer.
ABSTRACT
We report herein the catalytic conversion of allylic esters into the corresponding ketones by the formal deletion of an oxygen atom. The key to the success of the reaction is the dual use of nickel and photoredox catalysts; the former mediates C-O bond activation and C-C bond formation, while the latter is responsible for deoxygenation of the acyloxy group using PPh3 as a stoichiometric reductant. Catalytic replacement of an oxygen atom of an allyl ester with a tethered alkene is also accomplished.
ABSTRACT
Synthesis and host-guest chemistry of water-soluble (pH 12.5) chiral spirobifluorene-based macrocycles 2-[n] were carried out. Cationic guests, such as quaternary ammonium salts, were accommodated well in the hosts. Cp2Co+ was especially strongly bound in 2-[4] (Ka of up to 3.0 × 105 M-1). Enantioselective recognition with (l)-carnitine was also achieved.
ABSTRACT
We report herein on the nickel-catalyzed methylation of arylphosphines using AlMe3via the cleavage of unactivated C(aryl)-P bonds. This reaction allows for the direct, catalytic substitution of an aryl group on a phosphorus center with a methyl group. This catalytic methylation can proceed, when phosphine oxides and sulfides are used as a substrate.
ABSTRACT
An open-shell germylene 1 stabilized by a phenalenyl-based bidentate ligand was synthesized and characterized. Because of the high thermal stability originating from spin delocalization over the phenalenyl moiety, it was possible to isolate compound 1 in crystalline form by sublimation at ca. 300 °C. Electron spin resonance (ESR) spectra, crystallographic analysis, theoretical calculations, and reactivities with carbon radicals suggest that the spin of 1 is distributed on the phenalenyl moiety, while 1 reacted with C2Cl6, PhSSPh, and p-benzoquinone at the germanium center to form Ge-E (E = Cl, S, O) bonds. Furthermore, compound 1 is featured by its reactivity as a "formal germylyne", which allows for the formation of three new σ-bonds or one σ-bond with metal complexation on the germanium center.
ABSTRACT
Phenalenyl-based N,N-bidentate ligand-stabilized monovalent gallium(I) complex 1 was synthesized and characterized by NMR spectroscopies, single-crystal X-ray diffraction, and theoretical calculations. In solution, complex 1 has a high thermal stability at 80 °C, with an absorption maximum at 505 nm. Complex 1 promotes the oxidative addition of I-I, Si-Cl, C-I, and S-S bonds and oxidative cyclization with various π components. Complex 1 can also coordinate to a tungsten complex to form a Ga-W bond.
ABSTRACT
Palladium-catalyzed addition of a C-Si bond in acylsilanes across the triple bonds in an alkyne bearing a carbonyl group at one terminal is reported. The reaction proceeds with excellent regioselectivity, in which a silyl group is incorporated into the carbon α to the carbonyl group, allowing for straightforward access to a variety of functionalized alkenylsilane derivatives. Catalytic synthesis of indanones by annulation between acylsilanes and alkynes with an identical catalytic system is also reported.
ABSTRACT
The C-F bond of acyl fluorides can be cleaved and added across tethered alkenes in the presence of a cationic rhodium(I) tetrafluoroborate catalyst. This 1,2-carbofluorination reaction offers a powerful method for the synthesis of tertiary alkyl fluoride derivatives with an atom economy of 100 %. Mechanistic studies indicate that the concerted action of a rhodium cation and a tetrafluoroborate anion is key for the success of this catalytic cleavage and formation of C-F bonds in a controlled manner.
ABSTRACT
Single-carbon atom transfer reactions are lacking in organic synthesis, partly because of the absence of atomic carbon sources under standard solution-phase conditions. We report here that N-heterocyclic carbenes can serve as atomic carbon donors through the loss of a 1,2-diimine moiety. This strategy is applicable to single-carbon atom transfer to α,ß-unsaturated amides, which can be converted into homologated γ-lactams through the formation of four single bonds to one carbon center in one operation.
ABSTRACT
We report herein the phosphine-catalyzed 1,2-diacylation of alkynes using acyl fluorides and acylsilanes as acyl sources. The key to the success of the reaction is a formal oxidative addition-ligand metathesis-reductive elimination cycle based on phosphine redox catalysis, which allows for the installation of two different acyl groups into an alkyne in a regioselective manner.
ABSTRACT
Correction for 'Nickel-catalyzed 1,4-aryl rearrangement of aryl N-benzylimidates via C-O and C-H bond cleavage' by Satoshi Ogawa et al., Chem. Commun., 2022, 58, 7909-7911, https://doi.org/10.1039/D2CC02355E.
ABSTRACT
We report herein on nickel-catalyzed carbon-carbon bond cleavage reactions of 2,4,6-cycloheptatrien-1-one (tropone) derivatives. When a Ni/N-heterocyclic carbene catalyst is used, decarbonylation proceeds with the formation of a benzene ring, while the use of bidentate ligands in conjunction with an alcohol additive results in a two-carbon ring contraction with the generation of cyclopentadiene derivatives. The latter reaction involves a nickel-ketene complex as an intermediate, which was characterized by X-ray crystallography. The choice of an appropriate ligand allows for selective synthesis of four different products via the cleavage of a seven-membered carbocyclic skeleton. Reaction mechanisms and ligand-controlled selectivity for both types of ring contraction reactions were also investigated computationally.
ABSTRACT
Transition metal-catalyzed unimolecular fragment coupling (UFC) is defined as processes that forge new chemical bonds through the extrusion of molecules, such as CO and CO2, and the subsequent recombination of the remaining fragments. Herein, we report on a new UFC reaction that involves the palladium-catalyzed elimination of an isocyanate fragment from an amide, with the formation of carbon-carbon and carbon-heteroatom bonds. An organometallic intermediate that is relevant to the catalytic reaction was characterized by X-ray crystallography. This UFC reaction enables the late-stage transformation of an amide functionality, allowing amides to be used as a convertible directing or protecting group.