Current understanding and applications of the cold sintering process

In traditional ceramic processing techniques, high sintering temperature is necessary to achieve fully dense microstructures. But it can cause various problems including warpage, overfiring, element evaporation, and polymorphic transformation. To overcome these drawbacks, a novel processing technique called “cold sintering process (CSP)” has been explored by Randall et al. CSP enables densification of ceramics at ultra-low temperature (≤ 300 °C) with the assistance of transient aqueous solution and applied pressure. In CSP, the processing conditions including aqueous solution, pressure, temperature, and sintering duration play critical roles in the densification and properties of ceramics, which will be reviewed. The review will also include the applications of CSP in solid-state rechargeable batteries. Finally, the perspectives about CSP is proposed

Palladium-Catalyzed Safe Cyanation of Aryl Iodides with Hexamethylenetetramine

A palladium-catalyzed cyanation of aryl halides with hexamethylenetetramine as a safe cyanide source is achieved, providing aromatic nitriles in moderate to good yields. This approach shows good functional group compatibilities and avoids the use of toxic cyanide source

Formal [3 + 2] Reaction of α,α-Diaryl Allylic Alcohols with <i>sec</i>-Alcohols: Proceeding with Sequential Radical Addition/Migration toward 2,3-Dihydrofurans Bearing Quaternary Carbon Centers

An unprecedented TBHP-promoted formal [3 + 2] annulation of <i>sec</i>-alcohols with α,α-diaryl allylic alcohols has been developed, leading to 2,3-dihydrofurans in moderate to excellent yields with good functional group tolerance. This procedure involves sequential radical addition, 1,2-aryl migration, and a dehydration process, where the migration of aryl with lower electron density is favored. Notably, cyclic reactions with <i>sec</i>-alcohols also ran smoothly, providing a novel method to access oxaspiro compounds

Silver-Mediated <i>N</i>‑Trifluoromethylation of Sulfoximines

An unprecedented approach to <i>N</i>-trifluoromethylations of electron-rich nucleophilic sites following a radical pathway is reported. Accordingly, various sulfoximines (19 examples) have been <i>N</i>-trifluoromethylated, providing previously unreported products with satisfying functionality tolerance in moderate to good yields. With a C–N bond length at the N–CF₃ moiety of 1.341 Å the respective linkage is shorter than a traditional C–N single bond and comparable with that of a C–N double bond

Synthesis of 2‑Amino-3-hydroxy‑3<i>H</i>‑indoles via Palladium-Catalyzed One-Pot Reaction of Isonitriles, Oxygen, and <i>N</i>‑Tosylhydrazones Derived from 2‑Acylanilines

A cyanide-free one-pot procedure was developed to access 2-amino-3-hydroxy-3<i>H</i>-indoles, which involved: (1) <i>in situ</i> formation of ketenimines by the reaction of <i>N</i>′-(1-(2-amino­phenyl)­ethylidene)-<i>p</i>-tosyl­hydrazones with isonitriles; (2) the intramolecular nucleophilic attack of ketenimines by the amino in phenyl furnishing the ring closure leading to 2-aminoindoles; (3) the oxidation of 2-aminoindoles by O₂ leading to 2-amino-3-hydroxy-3<i>H</i>-indoles. This strategy represents not only a key compliment to the sporadic synthetic methods toward 2-amino-3-hydroxy-3<i>H</i>-indoles but also progress in <i>N-</i>tosylhydrazone, isonitrile, and ketenimine chemistry

Synthesis of 2‑Amino-3-hydroxy‑3<i>H</i>‑indoles via Palladium-Catalyzed One-Pot Reaction of Isonitriles, Oxygen, and <i>N</i>‑Tosylhydrazones Derived from 2‑Acylanilines

A cyanide-free one-pot procedure was developed to access 2-amino-3-hydroxy-3<i>H</i>-indoles, which involved: (1) <i>in situ</i> formation of ketenimines by the reaction of <i>N</i>′-(1-(2-amino­phenyl)­ethylidene)-<i>p</i>-tosyl­hydrazones with isonitriles; (2) the intramolecular nucleophilic attack of ketenimines by the amino in phenyl furnishing the ring closure leading to 2-aminoindoles; (3) the oxidation of 2-aminoindoles by O₂ leading to 2-amino-3-hydroxy-3<i>H</i>-indoles. This strategy represents not only a key compliment to the sporadic synthetic methods toward 2-amino-3-hydroxy-3<i>H</i>-indoles but also progress in <i>N-</i>tosylhydrazone, isonitrile, and ketenimine chemistry

Cs₂CO₃‑Promoted Carboxylation of <i>N</i>‑Tosylhydrazones with Carbon Dioxide toward α‑Arylacrylic Acids

A Cs₂CO₃-promoted carboxylation of <i>N</i>-tosylhydrazones and CO₂ has been developed. The reaction proceeded efficiently at 80 °C under atmospheric CO₂, gave the corresponding α-arylacrylic acids in moderate to good yields. This method was featured with (1) the employment of Cs₂CO₃ rather than ^<i>n</i>BuLi as the base; (2) a reaction temperature of 80 °C rather than −78 °C

TBAI-Catalyzed Reaction between <i>N</i>‑Tosylhydrazones and Sulfur: A Procedure toward 1,2,3-Thiadiazole

A TBAI-catalyzed reaction between <i>N</i>-tosyl hydrazone and sulfur was developed, leading to 1,2,3-thiadiazoles in moderate to good yields. It represents a facile and practical procedure to access thiadiazole under metal-free conditions. This procedure serves as an improvement for the Hurd–Mori reaction

Base-Promoted Formal Arylation of Benzo[<i>d</i>]oxazoles with Acyl Chloride

A base-promoted formal arylation of benzo­[<i>d</i>]­oxazoles with acyl chloride was achieved in moderate to good yields. This reaction was triggered by the <i>N</i>-acylation of oxazole to form an iminium intermediate. Then, the addition of H₂O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure, the dehydration delivered the formal arylation product. In comparison with the transition-metal-catalyzed methodology, it represents an alternative arylation method leading to 2-arylbenzooxazole

Rhodium-Catalyzed Relay Carbenoid Functionalization of Aromatic C–H Bonds toward Fused Heteroarenes

A rhodium-catalyzed annulation between ethyl benzimidates and α- aroyl sulfur ylides was developed, affording a series of pyrano­[4,3,2-<i>ij</i>]­isoquinoline derivatives in moderate to good yields with good functional group compatibility. The procedure featured dual <i>ortho</i>-C–H functionalization and dual cyclization in one pot. The optoelectronic properties of those fused heteroarenes were tested by UV/vis and fluorescence spectrometers