Developing highly
active and stable nonprecious metal catalysts
for electrochemical reactions is desirable but remains a great challenge.
Herein, we report a novel metal-ion adsorption-pyrolysis strategy
for the controllable zeolitic imidazolate framework-8 derived synthesis
of individual high-quality N-doped carbon nanotubes embedded with
well-dispersed nonprecious metal nanoparticles, which exhibit superior
electrocatalytic activity and stability for electrochemical CO2 reduction reaction, oxygen reduction reaction, and oxygen
evolution reaction. Experimental analysis and density functional theory
calculations indicate that the remarkable electrocatalytic activities
are mainly attributed to the interface effects for the efficient electron
transfer from metal nanoparticles to the N-doped carbon shell, as
well as the large specific areas, unique tube structures, appropriate
doping, high graphitization degree, and robust frameworks. The high
reaction stability is attributed to the multiwalled graphitic carbon
shells efficiently preventing metal nanoparticles from aggregation,
corrosion, and oxidation. This novel synthetic strategy presents a
facile universality for synthesizing N-doped carbon nanotube structures
and will provide a guideline for developing low-cost, highly active,
and stable electrocatalytic materials for sustainable energy conversion.
To
explore insecticides targeting the γ-aminobutyric acid
(GABA) receptor, two series of novel isoxazoline derivatives containing
sulfonic and carboxylic esters were designed and synthesized. Their
insecticidal activities against Plutella xylostella, Mythimna separata, and Aedes aegypti larvae and their structure–activity
relationship were investigated. The sulfonate-containing isoxazoline
derivatives (10k–q) exhibited promising insecticidal
activities against the three insect larvae. Compound 10o displayed excellent activities with LC50 values of 8.32,
5.23, and 0.35 μg/mL at 48 h against P. xylostella, M. separata, and A. aegypti larvae, respectively, which were better
than or similar to those of avermectin. Furthermore, compound 10o exhibited a faster insecticidal effect than avermectin
against M. separata. The mode of action
of 10o was preliminarily verified by molecular docking,
theoretical calculations, and measurement of glutamate decarboxylase
and glutamic pyruvic transaminase activities. Compound 10o is a novel insecticidal candidate acting on GABA receptors, which
could guide the discovery of isoxazoline insecticides.
We report the Sonogashira cross-coupling of aryl ammonium
salts
catalyzed by air- and moisture-stable [Pd(NHC)(3-CF3-An)Cl2] (An = aniline). This highly active Pd(II)–NHC complex
features broad scope and excellent C–N activation selectivity
in the challenging alkynylative cross-coupling of aryl ammonium salts.
Full structural characterization and computational studies demonstrate
the effect of pyridine to aniline replacement as highly effective
stabilizing ancillary ligand in well-defined Pd(II)–NHCs. Considering
the high reactivity and the recent commercialization of [Pd(NHC)(3-CF3-An)Cl2] (Millipore Sigma, no. 915165), this catalyst
represents an attractive approach to the activation of C–N
bonds of broad synthetic interest.
We report the first Suzuki−Miyaura cross-coupling of 2-pyridyl ammonium salts by highly selective N−C activation catalyzed by air-and moisture-stable Pd(II)−NHC (NHC = Nheterocyclic carbene) precatalysts. The use of well-defined and highly reactive [Pd(IPr)(3-CF 3 -An)Cl 2 ] (An = aniline) or [Pd(IPr)(cin)Cl] (cin = cinnamyl) Pd(II)−NHC catalysts permits an exceptionally broad scope of the cross-coupling to furnish valuable biaryl and heterobiarylpyridines that are ubiquitous in medicinal chemistry and agrochemistry research. The overall process leverages the Chichibabin C−H amination of pyridines with N−C activation to enable an attractive strategy to the 2-pyridyl problem. The utility of the method to the discovery of potent agrochemicals is presented. Considering the importance of 2-pyridines and the versatility of N−C activation methods, we envision that this new C−H/N−C activation strategy will find broad application.
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