Oxygen Coordination Promotes Single-Atom Cu(II)-Catalyzed Azide-Alkyne Click Chemistry without Reducing Agents.

Unique active sites make single-atom (SA) catalysts promising to overcome obstacles in homogeneous catalysis but challenging due to their fixed coordination environment. Click chemistry is restricted by the low activity of more available Cu(II) catalysts without reducing agents. Herein, we develop efficient, O-coordinated SA Cu(II) directly catalyzed click chemistry. As revealed by theoretical calculations of the superior coordination structure to promote the click reaction, an organic molecule-assisted strategy is applied to prepare the corresponding SA Cu catalysts with respective O and N coordination. Although they both belong to Cu(II) centers, the O-coordinated one exhibits a 5-fold higher activity than the other and even much better activity than traditional homogeneous and heterogeneous Cu(II) catalysts. Control experiments further proved that the O-coordinated SA Cu(II) catalyst tends to be reduced by alkyne into Cu acetylide rather than the N-coordinated catalyst and thus facilitates click chemistry.

Nasal Respiratory Epithelial Adenomatoid Hamartoma: Three Case Reports and Review of the Literature.

Hamartomas, as non-true tumors, are commonly found in the lungs, digestive tract, and kidneys, and there are few clinical reports on nasal cases. Nasal histiocytosis accompanied by lymphatic lesions is a common feature of nasal hamartoma. Three patients with nasal cavity hamartoma were treated in our department, including 1 male and 2 females, with nasal obstruction or epistaxis. The imaging (computed tomography, magnetic resonance imaging) of 2 patients showed a soft tissue mass in the nasal cavity and no erosion of bone, while in 1 patient, the imaging was inconclusive. The excised material in all patients was found to be a soft mass. The 3 cases showed the same pattern under histological examination, and all 3 patients were diagnosed with nasal cavity respiratory epithelial adenomatoid hamartoma (REAH). Nasal hamartoma is a rare disease with nonspecific clinical manifestations and imaging features and is often misdiagnosed. Only by a better understanding of this disease can the rate of correct clinical diagnosis be improved.

Decreasing the coordinated N atoms in a single-atom Cu catalyst to achieve selective transfer hydrogenation of alkynes.

Single-atom (SA) catalysts have attracted broad attention due to their distinctive catalytic properties in diverse reactions. Increasing the unsaturated coordination sites of active centers is a valid and challenging approach to improve the performance of such catalysts. Herein, we report an oxide compounding strategy to decrease the N coordination number of a SA Cu catalyst by reducing the thickness of the N-doped carbon carrier with a lower density of N atoms. The SA Cu catalyst with a more unsaturated N coordination structure can achieve transfer hydrogenation of alkynes with good activity and selectivity, which is disabled over the common N coordinated SA Cu catalyst on pure CN. It is found that individual Cu centers coordinated by fewer N atoms can accelerate the hydrogen transfer from ammonia-borane and still leave proper adsorption sites for alkynes to realize the entire hydrogenation reaction. This work will open up new opportunities to modulate the unsaturated coordination structure of SA catalysts for creating better-performing heterogeneous catalysts.