A protocol for the highly enantioselective synthesis of 9‐substituted tetrahydroxanthenones by means of asymmetric Brønsted acid catalysis has been developed. A chiral binol‐based ...N‐triflyphosphoramide was found to promote the in situ generation of ortho‐quinone methides and their subsequent reaction with 1,3‐cyclohexanedione to provide the desired products with excellent enantioselectivities. In addition, a highly enantio‐ and diastereoselective Brønsted acid catalyzed desymmetrization of 5‐monosubstituted 1,3‐dicarbonyl substrates with ortho‐quinone methides gives rise to valuable tetrahydroxanthenes containing two distant stereocenters.
Procedures for the Brønsted acid catalyzed asymmetric synthesis of 9‐substituted tetrahydroxanthenones and 3,9‐disubstituted tetrahydroxanthenone derivatives have been developed. The procedures are based on the in situ generation of ortho‐quinone methides and their subsequent reaction with 1,3‐dicarbonyl compounds. The reaction provides products with a high level of asymmetric induction.
A nickel catalyzed cross‐coupling protocol for the straightforward C−S bond formation has been developed. Various mercaptans and a wide range of ester and amide substrates bearing various ...substituents were tolerated in this process which afforded products in good to excellent yields. Furthermore, an intramolecular protocol for the synthesis of thioethers starting from thioesters has been developed. The utility of this protocol has been demonstrated in a new synthetic protocol of benzothiophene.
A nickel catalyzed cross‐coupling protocol for facile C−S bond formation was developed. Various thiols and a wide range of ester and amide substrates bearing various substituents were tolerated in this process which afforded products in good to excellent yields. An intramolecular protocol for the synthesis of thioethers starting from thioesters was also developed and its utility was demonstrated in the synthesis of benzothiophene on the bench top.
An efficient nickel‐catalyzed decarbonylative amination reaction of aryl and heteroaryl esters has been achieved for the first time. The new amination protocol allows the direct interconversion of ...esters and amides into the corresponding amines and represents a good alternative to classical rearrangements as well as cross coupling reactions.
An efficient nickel‐catalyzed decarbonylative amination reaction of readily available aryl and heteroaryl esters has been developed. This new amination procedure shows high tolerance towards a variety of aryl and heteroaryl esters, thus providing a practical and versatile access to valuable primary amines. cod=1,5‐cyclooctadiene.
Despite the recent progress in the synthesis of crystalline boronate ester covalent organic frameworks (BECOFs) in powder and thin‐film through solvothermal method and on‐solid‐surface synthesis, ...respectively, their applications in electronics, remain less explored due to the challenges in thin‐film processability and device integration associated with the control of film thickness, layer orientation, stability and crystallinity. Moreover, although the crystalline domain sizes of the powder samples can reach micrometer scale (up to ≈1.5 μm), the reported thin‐film samples have so far rather small crystalline domains up to 100 nm. Here we demonstrate a general and efficient synthesis of crystalline two‐dimensional (2D) BECOF films composed of porphyrin macrocycles and phenyl or naphthyl linkers (named as 2D BECOF‐PP or 2D BECOF‐PN) by employing a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) on the water surface. The achieved 2D BECOF‐PP is featured as free‐standing thin film with large single‐crystalline domains up to ≈60 μm2 and tunable thickness from 6 to 16 nm. A hybrid memory device composed of 2D BECOF‐PP film on silicon nanowire‐based field‐effect transistor is demonstrated as a bio‐inspired system to mimic neuronal synapses, displaying a learning–erasing–forgetting memory process.
Mimicking synaptic plasticity: A free‐standing boronate ester‐linked 2D COF thin film has been achieved with record crystalline domain size as large as ≈60 μm2 via an interfacial synthesis method. This film was integrated into an organic thin film/Si nanowire‐based field effect transistor to mimic neuronal synapses capable of learning–erasing–forgetting memory process.
Aza‐ortho‐quinone methides allow the straightforward asymmetric synthesis of natural‐product‐inspired indole scaffolds possessing a quaternary stereocenter. Our approach provides access to diverse ...communesin and spiroindoline derivatives with high enantioselectivity under mild reaction conditions. Predictable substitution patterns are found to be the key to our regiodivergent protocols.
Two protocols have been developed for the regiodivergent, asymmetric Brønsted acid catalyzed addition of indoles to in situ generated aza‐ortho‐quinone methides. Furthermore, a new addition spirocyclization sequence leads, depending on the indole derivative, to communesin and spiroindoline cores with quaternary stereocenters.
An efficient method for the highly enantioselective synthesis of chiral chromanes bearing multiple stereogenic centers was developed. A chiral BINOL‐based N‐triflylphosphoramide proved to be an ...effective catalyst for the in situ generation of ortho‐quinone methides (o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes provided chromanes with excellent diastereo‐ and enantioselectivity.
Exclusive chemistry: An efficient method for the highly enantioselective synthesis of chiral chromanes bearing multiple stereogenic centers was developed. A chiral BINOL‐based N‐triflylphosphoramide proved to be an effective catalyst for the in situ generation of ortho‐quinone methides (o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes provided chromanes with excellent diastereo‐ and enantioselectivity.
The aza‐ortho‐quinone methide (aza‐o‐QM) chemistry has overwhelmingly progressed in the past few decades. This review aims to integrate various transition metal‐catalyzed and organocatalytic ...strategies in taming aza‐o‐QM intermediates, including the aza‐ortho‐vinylidene quinone methide (aza‐o‐VQM), aza‐ortho‐alkynyl quinone methide (aza‐o‐AQM), aza‐para‐quinone methide (aza‐p‐QM), and indole‐based aza‐o‐QM analog. These transient species are often utilized for the direct and enantioselective synthesis of complex (hetero)polycyclic or fused‐ring molecular scaffolds such as tetrahydroquinoline and indoline, among others, which are abundant in many natural products, bioactive compounds, and pharmaceuticals.
The aza‐ortho‐quinone methide (aza‐o‐QM) chemistry has been showing budding progress in the past years. Herein, the asymmetric catalysis involving these transient intermediates is highlighted, which was made possible by well‐designed catalysts as well as new aza‐o‐QM precursors/substrates.
A ligand-controlled and site-selective nickel catalyzed Suzuki–Miyaura cross-coupling reaction with aromatic esters and alkyl organoboron reagents as coupling partners was developed. This methodology ...provides a facile route for C(sp2)–C(sp3) bond formation in a straightforward fashion by successful suppression of the undesired β-hydride elimination process. By simply switching the phosphorus ligand, the ester substrates are converted into the alkylated arenes and ketone products, respectively. The utility of this newly developed protocol was demonstrated by its wide substrate scope, broad functional group tolerance and application in the synthesis of key intermediates for the synthesis of bioactive compounds. DFT studies on the oxidative addition step helped rationalizing this intriguing reaction chemoselectivity: whereas nickel complexes with bidentate ligands favor the C(aryl)–C bond cleavage in the oxidative addition step leading to the alkylated product via a decarbonylative process, nickel complexes with monodentate phosphorus ligands favor activation of the C(acyl)–O bond, which later generates the ketone product.
Rechargeable lithium metal batteries are next generation energy storage devices with high energy density, but face challenges in achieving high energy density, high safety, and long cycle life. Here, ...lithium metal batteries in a novel nonflammable ionic‐liquid (IL) electrolyte composed of 1‐ethyl‐3‐methylimidazolium (EMIm) cations and high‐concentration bis(fluorosulfonyl)imide (FSI) anions, with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a key additive are reported. The Na ion participates in the formation of hybrid passivation interphases and contributes to dendrite‐free Li deposition and reversible cathode electrochemistry. The electrolyte of low viscosity allows practically useful cathode mass loading up to ≈16 mg cm−2. Li anodes paired with lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (LiNi0.8Co0.1Mn0.1O2, NCM 811) cathodes exhibit 99.6–99.9% Coulombic efficiencies, high discharge voltages up to 4.4 V, high specific capacity and energy density up to ≈199 mAh g−1 and ≈765 Wh kg−1 respectively, with impressive cycling performances over up to 1200 cycles. Highly stable passivation interphases formed on both electrodes in the novel IL electrolyte are the key to highly reversible lithium metal batteries, especially for Li–NMC 811 full batteries.
A nonflammable ionic‐liquid electrolyte is developed for high‐safety and high‐energy‐density Li metal batteries, allowing practically useful cathode mass loading up to 16 mg cm−2, realizing high specific capacity and energy density (199 mAh g−1 and 765 Wh kg−1) with impressive cycling performances. The robust passivation interphases formed on both electrodes are key to realizing impressive battery performances.
π-Conjugated two-dimensional covalent organic frameworks (2D COFs) are emerging as a novel class of electroactive materials for (opto)electronic and chemiresistive sensing applications. However, ...understanding the intricate interplay between chemistry, structure, and conductivity in π-conjugated 2D COFs remains elusive. Here, we report a detailed characterization for the electronic properties of two novel samples consisting of Zn– and Cu–phthalocyanine-based pyrazine-linked 2D COFs. These 2D COFs are synthesized by condensation of metal–phthalocyanine (M = Zn and Cu) and pyrene derivatives. The obtained polycrystalline-layered COFs are p-type semiconductors both with a band gap of ∼1.2 eV. A record device-relevant mobility up to ∼5 cm2/(V s) is resolved in the dc limit, which represents a lower threshold induced by charge carrier localization at crystalline grain boundaries. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10–7 S/cm), charge carrier density (∼1012 cm–3), charge carrier scattering rate (∼3 × 1013 s–1), and effective mass (∼2.3m 0) of majority carriers (holes). Notably, charge carrier transport is found to be anisotropic, with hole mobilities being practically null in-plane and finite out-of-plane for these 2D COFs.
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