Cu(II) detection by a fluorometric probe based on thiazoline-amidoquinoline derivative and its application to water and food samples.

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).

KOtBu-Catalyzed Synthesis of Isoindole Derivatives from N-Benzyl Amides Bearing an Ortho Alkynyl Group via 1,2-Acyl Shift.

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%.

Unimolecular Fragment Coupling: A New Bond-Forming Methodology via the Deletion of Atom(s).

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.

Palladium-Catalyzed Addition of Trifluoroacetylsilanes to Alkenes and Allenes via the Cleavage of C-Si Bonds.

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.

A novel "turn-on" fluorescent probe based on thiocarbamoyl-DHP for Hg2+ detection in water samples and living cells.

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.

Synthesis of γ-Lactams from Acrylamides by Single-Carbon Atom Doping Annulation.

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.

Nickel/Photoredox Dual-Catalyzed Conversion of Allyl Esters to Ketones via the Formal Deletion of Oxygen.

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.

Synthesis and Host-Guest Chemistry of Chiral Spirobifluorene-Based Macrocycles Soluble in Basic Aqueous Solution.

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.

Nickel-catalyzed direct methylation of arylphosphines via carbon-phosphorus bond cleavage using AlMe3.

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.

Open-Shell Germylene Stabilized by a Phenalenyl-Based Ligand.

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.

Synthesis, Structure, and Reactivity of a Gallylene Derivative Bearing a Phenalenyl-Based Ligand.

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.

Palladium-catalyzed addition of acylsilanes across alkynes via the activation of a C-Si bond.

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.

Cationic Rhodium(I) Tetrafluoroborate Catalyzed Intramolecular Carbofluorination of Alkenes via Acyl Fluoride C-F Bond Activation.

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.

Single-carbon atom transfer to α,ß-unsaturated amides from N-heterocyclic carbenes.

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.

1,2-Diacylation of Alkynes Using Acyl Fluorides and Acylsilanes by P(III)/P(V) Catalysis.

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.

Correction: Nickel-catalyzed 1,4-aryl rearrangement of aryl N-benzylimidates via C-O and C-H bond cleavage.

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.

Palladium-Catalyzed Unimolecular Fragment Coupling of N-Allylamides via Elimination of Isocyanate.

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.

Nickel-catalyzed skeletal transformation of tropone derivatives via C-C bond activation: catalyst-controlled access to diverse ring systems.

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.

Nickel-catalyzed 1,4-aryl rearrangement of aryl N-benzylimidates via C-O and C-H bond cleavage.

We report herein that nickel-catalyzed reaction of aryl imidates bearing an N-benzyl group results in 1,4-migration of an O-aryl group via the cleavage of C-O and C-H bonds. This protocol allows for the benzylic C-H bond arylation of benzylamine building blocks using phenols as an aryl source to form elaborate diarylmethylamine derivatives.