Modular Design of Functional Glucose Monomer and Block Co-Polymer toward Stable Zn Anodes.

Aqueous Zn batteries employing mildly acidic electrolytes have emerged as promising contenders for safe and cost-effective energy storage solutions. Nevertheless, the intrinsic reversibility of the Zn anode becomes a focal concern due to the involvement of acidic electrolyte, which triggers Zn corrosion and facilitates the deposition of insulating byproducts. Moreover, the unregulated growth of Zn over cycling amplifies the risk of internal short-circuiting, primarily induced by the formation of Zn dendrites. In this study, a class of glucose-derived monomers and a block copolymer are synthesized through a building-block assembly strategy, ultimately leading to uncover the optimal polymer structure that suppresses the Zn corrosion while allowing efficient ion conduction with a substantial contribution from cation transport. Leveraging these advancements, remarkable enhancements are achieved in the realm of Zn reversibility, exemplified by a spectrum of performance metrics, including robust cycling stability without voltage overshoot and short-circuiting during 3000 h of cycling, stable operation at a high depth of charge/discharge of 75% and a high current density, >95% Coulombic efficiency over 2000 cycles, successful translation of the anode improvement to full cell performance. These polymer designs offer a transformative path based on the modular synthesis of polymeric coatings toward highly reversible Zn anode.

Effects of Storage in an Active and Spontaneous Controlled O2/CO2 Atmosphere on Volatile Flavor Components and the Microbiome of Truffles.

This study explored the potential to improve the storage quality and prolong the shelf life of truffles by storing them in a modified atmosphere fresh-keeping box with sealed gas components of Active Modified Atmosphere Packaging (AMAP, 40% O2 + 60% CO2) at 4 °C. During the storage period, a total of 63 volatile components in 10 categories were detected, with aldehydes being the most abundant and the relative content of ethers being the highest. The relative odor activity value and principal component analysis revealed that isovaleraldehyde, 1-octen-3-ol, 1-octen-3-one, and dimethyl sulfide were the characteristic flavor components of fresh truffles. However, 3-methylthiopropionaldehyde and (E, E)-2,4-nonadienal were the components that caused the deterioration of truffle flavor and could potentially serve as markers of truffle decay characteristics. 16S rDNA high-throughput sequencing showed that Leuconostoc and Lactococcus were dominant in the truffle samples stored for 14 days, but the abundance of putrefactive pathogenic bacteria showed an increasing trend in the truffle samples stored for 28 days. During the whole storage period, the common fungi detected in the different treatment groups were Candida and Aspergillus. The relative abundance of the former decreased, while the relative abundance of the latter decreased initially and then increased. The correlation between volatile components and the microbial flora was further analyzed, which indicated that Lactococcus and Lactobacillus had the same contributions to the same flavor, while Pseudomonas and Glutamicibacter had the opposite contributions to the same flavor. The results provide a reference for the storage and preservation of truffles.

Transition-Metal-Free Electrochemical Selenylative Cyclization of Alkynyl Phosphonates.

Unprecedented regioselective electrochemical tandem selenation/cyclization of alkynyl phosphonates with diselenide is described here. These obtained selenoether products can be chemo-selectively converted into halogen-functionalized cyclic enol phosphonates under our electrochemical conditions. These protocols provide straightforward access to valuable cyclic enol phosphonate or phosphaisocoumarins under the electrochemical and transition-metal-free conditions. The robustness of these transformations was illustrated by their compatibility with various complex natural products and bioactive molecules. The selenoether and halogen functional groups allow the further diversification of the phosphorus heterocycles thus obtained.

Palladium-catalyzed distal selective C-H chalcogenation of biphenyl amines.

A palladium-catalyzed distal C(sp2)-H chalcogenation of biphenyl amines is described. This protocol demonstrates scalability, excellent chemo- and regio-selectivity, and broad functional group tolerance, providing efficient access to valuable aryl chalcogenides. Notably, the chalcogenated biphenyl amines could be further transformed to 8-membered N, Se(S)-heterocycles through copper-catalyzed intramolecular C-N cyclization.

A recyclable stereoauxiliary aminocatalyzed strategy for one-pot synthesis of indolizine-2-carbaldehydes.

Indolizine-carbaldehydes with the easily modifiable carbaldehyde group are important synthetic targets as versatile precursors for distinct indolizines. However, the efficient one-pot construction of trisubstituted indolizine-2-carbaldehydes represents a long-standing challenge. Herein, we report an unprecedented recyclable stereoauxiliary aminocatalytic approach via aminosugars derived from biomass, which enable the efficient one-pot synthesis of desired trisubstituted indolizine-2-carbaldehydes via [3+2] annulations of acyl pyridines and α,ß-unsaturated aldehyde. Compared to the steric shielding effect from α-anomer, a stereoauxiliary effect favored by ß-anomer of D-glucosamine is supported by control experiments. Furthermore, polymeric chitosan containing predominantly ß-D-anhydroglucosamine units also shows excellent catalytic performance in aqueous solutions for the conversion of various substrates, large-scale synthesis and catalytic cycling experiments. Thus, our approach advances the existing methodologies by providing a rich library of indolizine-2-aldehydes. In addition, it delivers an efficient protocol for a set of late-stage diversification and targeted modifications of bioactive molecules or drugs, as showcased with 1,2,3-trisubstituted indolizine-2-carbaldehydes.

Electrochemical selenium-π-acid promoted hydration of alkynyl phosphonates.

An unprecedented electrochemical selenium-π-acid promoted hydration of internal alkynes bearing a phosphonate auxiliary was described. Thus, valuable (hetero)aryl and alkyl ketones could be accessed under mild, metal- and external oxidant-free conditions. This protocol features high atom-economy, good chemo- and regio-selectivity, excellent functional group tolerance and easily transformable products. Control experiments demonstrate that phosphonate assistance is essential for this transformation.

Direct nitrogen interception from chitin/chitosan for imidazo[1,5-a]pyridines.

A catalyst-free one-pot methodology that enables direct nitrogen interception of chitosan/chitin for imidazo[1,5-a]pyridines was developed. This strategy features direct synthesis of important deuterated imidazo[1,5-a]pyridines and tridentate ligands. In particular, a broad group of previously inaccessible products including saturated 1-alkylimidazo[1,5-a]pyridines are unprecedently synthesized by this protocol.

Hydroxyl-Directed Ruthenium-Catalyzed peri-Selective C-H Acylmethylation and Annulation of Naphthols with Sulfoxonium Ylides.

Herein, we report a highly efficient ruthenium-catalyzed peri-selective C(sp2)-H acylmethylation of 1-naphthols with α-carbonyl sulfoxonium ylides by utilizing hydroxyl as a weakly coordinating directing group. This new method imparts good reactivity, excellent chemo- and regioselectivity, and broad functional group tolerance and involves mild reaction conditions. The C-H acylmethylated products can be readily cyclized into fluorescent annulated pyrans by a one-pot process.

Copper-mediated oxidative C-H/N-H activations with alkynes by removable hydrazides.

The efficient copper-mediated oxidative C-H alkynylation of benzhydrazides was accomplished with terminal alkynes. Thus, a heteroaromatic removable N-2-pyridylhydrazide allowed for domino C-H/N-H functionalization. The approach featured remarkable functional group compatibility and ample substrate scope. Thereby, highly functionalized aromatic and heteroaromatic isoindolin-1-ones were accessed with high efficacy with rate-limiting C-H cleavage.

Cobalt-Catalyzed Oxidative C-H Activation: Strategies and Concepts.

Inexpensive cobalt-catalyzed oxidative C-H functionalization has emerged as a powerful tool for the construction of C-C and C-Het bonds, which offers unique potential for transformative applications to modern organic synthesis. In the early stage, these transformations typically required stoichiometric and toxic transition metals as sacrificial oxidants; thus, the formation of metal-containing waste was inevitable. In contrast, naturally abundant molecular O2 has more recently been successfully employed as a green oxidant in cobalt catalysis, thus considerably improving the sustainability of such transformations. Recently, a significant momentum was gained by the use of electricity as a sustainable and environmentally benign redox reagent in cobalt-catalyzed C-H functionalization, thereby preventing the consumption of cost-intensive chemicals while at the same time addressing the considerable safety hazards related to the use of molecular oxygen in combination with flammable organic solvents. Considering the unparalleled potential of the aforementioned approaches for sustainable green synthesis, this Review summarizes the recent progress in cobalt-catalyzed oxidative C-H activation until early 2020.

Cobaltaelectro-catalyzed oxidative allene annulation by electro-removable hydrazides.

An efficient C-H/N-H functionalization with allenes was enabled via versatile electro-oxidative cobalt catalysis. Thus, electrochemical C-H activations were accomplished with high levels of chemoselectivity and regioselectivity in an operationally simple undivided cell setup. The user-friendly nature of this protocol was highlighted by excellent functional group tolerance, an electro-reductive removable hydrazide directing group and easy scalability. Experimental mechanistic studies were indicative of a facile BIES C-H cobaltation event.

Cobaltaelectro-Catalyzed Oxidative C-H/N-H Activation with 1,3-Diynes by Electro-Removable Hydrazides.

An efficient electro-oxidative C-H/N-H activation with 1,3-diynes has been achieved with a robust earth-abundant cobalt catalyst. The electrochemical C-H functionalization was accomplished with ample scope and remarkable functional group compatibility in a simple undivided cell. This protocol avoids the utilization of stoichiometric and cost-intensive chemical oxidants in C-H activation, thus forming hydrogen as the only byproduct.

Cobaltaelectro-Catalyzed C-H Activation with Carbon Monoxide or Isocyanides.

Electrochemical oxidative C-H/N-H activations with isocyanides have been realized with a versatile cobalt catalyst. The widely applicable cobalt catalysis manifold further enabled electrooxidative C-H/N-H carbonylations with carbon monoxide under ambient conditions. The C-H functionalizations were efficiently realized with ample scope and outstanding functional group tolerance in a user-friendly undivided cell setup.

Electrochemical ruthenium-catalyzed alkyne annulations by C-H/Het-H activation of aryl carbamates or phenols in protic media.

Electrooxidative peri-C-H activation was accomplished by versatile ruthenium(ii) catalysis in terms of C-H/N-H and C-H/O-H functionalization. Thus, alkyne annulations proved viable with ample scope by organometallic C-H activation. The sustainable electrocatalysis exploited electricity, thereby avoiding the use of toxic transition metals as sacrificial oxidants. The robust ruthenium(ii)-electrocatalysis was operative in a protic alcohol/H2O reaction medium with excellent levels of position-, regio- and chemo-selectivity.

Electroremovable Traceless Hydrazides for Cobalt-Catalyzed Electro-Oxidative C-H/N-H Activation with Internal Alkynes.

Electrochemical oxidative C-H/N-H activations have been accomplished with a versatile cobalt catalyst in terms of [4 + 2] annulations of internal alkynes. The electro-oxidative C-H activation manifold proved viable with an undivided cell setup under exceedingly mild reaction conditions at room temperature using earth-abundant cobalt catalysts. The electrochemical cobalt catalysis prevents the use of transition metal oxidants in C-H activation catalysis, generating H2 as the sole byproduct. Detailed mechanistic studies provided strong support for a facile C-H cobaltation by an initially formed cobalt(III) catalyst. The subsequent alkyne migratory insertion was interrogated by mass spectrometry and DFT calculations, providing strong support for a facile C-H activation and the formation of a key seven-membered cobalta(III) cycle in a regioselective fashion. Key to success for the unprecedented use of internal alkynes in electrochemical C-H/N-H activations was represented by the use of N-2-pyridylhydrazides, for which we developed a traceless electrocleavage strategy by electroreductive samarium catalysis at room temperature.

Electrochemical C-H Amination by Cobalt Catalysis in a Renewable Solvent.

Syntheses of substituted anilines primarily rely on palladium-catalyzed coupling chemistry with prefunctionalized aryl electrophiles. While oxidative aminations have emerged as powerful alternatives, they largely produce undesired metal-containing by-products in stoichiometric quantities. In contrast, described herein is the unprecedented electrochemical C-H amination by cobalt-catalyzed C-H activation. The environmentally benign electrocatalysis avoids stoichiometric metal oxidants, can be conducted under ambient air, and employs a biomass-derived, renewable solvent for sustainable aminations in an atom- and step-economical manner with H2 as the sole byproduct.

Ruthenium(II)-Catalyzed C-H Alkynylation of Weakly Coordinating Benzoic Acids.

C-H alkynylations with weakly coordinating acids were accomplished by the aid of an expedient ruthenium(II) catalysis manifold. The user-friendly C-H alkynylation occurred under mild conditions with the weak base K2CO3. The versatility of the ruthenium(II) catalysis was reflected by providing step-economical access to phthalides as well as enabling unprecedented decarboxylative ortho-C-H alkynylations.

Ruthenium(ii)-catalyzed C-H functionalizations on benzoic acids with aryl, alkenyl and alkynyl halides by weak-O-coordination.

C-H arylations of weakly coordinating benzoic acids were achieved by versatile ruthenium(ii) catalysis with ample substrate scope. Thus, user-friendly ruthenium(ii) biscarboxylate complexes modified with tricyclohexylphosphine enabled C-H functionalizations with aryl electrophiles. The unique versatility of the ruthenium(ii) catalysis manifold was reflected by facilitating effective C-H activations with aryl, alkenyl and alkynyl halides.

Synergistic Heterobimetallic Manifold for Expedient Manganese(I)-Catalyzed C-H Cyanation.

The manganese-catalyzed cyanation of inert C-H bonds was achieved within a heterobimetallic catalysis regime. The manganese(I) catalysis proved widely applicable and enabled C-H cyanations on indoles, pyrroles and thiophenes by facile C-H manganesation. The robustness of the manganese catalyst set the stage for the racemization-free C-H cyanation of amino acids with excellent levels of positional and chemo selectivity by the new cyanating agent NCFS. Experimental and computational mechanistic studies provided strong support for a synergistic heterobimetallic activation mode, facilitating the key C-C formation.

Cobalt-Catalyzed Oxidase C-H/N-H Alkyne Annulation: Mechanistic Insights and Access to Anticancer Agents.

Cp*-free cobalt-catalyzed alkyne annulations by C-H/N-H functionalizations were accomplished with molecular O2 as the sole oxidant. The user-friendly oxidase strategy proved viable with various internal and terminal alkynes through kinetically relevant C-H cobaltation, providing among others step-economical access to the anticancer topoisomerase-I inhibitor 21,22-dimethoxyrosettacin. DFT calculations suggest that electronic effects control the regioselectivity of the alkyne insertion step.