Effective prediction of organosilicon molecular structures and risks in aquatic environment with machine learning.

Until now, mass spectrometry databases lack molecular information of most organosilicon oligomers, and risk models needing accurate molecular descriptors are unavailable for these emerging contaminants with thousands of monomers. To address this issue, based on molecular/fragment ions and relative abundance from GC-Orbitrap-MS, this study developed appropriate classification (accuracies = 0.750-0.

ZIF-67-modified magnetic nanoparticles for extraction of phenoxy carboxylic acid herbicides.

Phenoxy carboxylic acid (PCA) herbicides are commonly used herbicides that can easily accumulate in soil, groundwater, crops, and vegetable surfaces. Thus, they pose a serious risk to human health. Accurate detection of trace amounts of PCAs in various matrixes is crucial.

Spatial distribution and seasonal variations of atmospheric organophosphate esters (OPEs) in Tianjin, China based on gridded field observations.

The atmospheric concentrations of 14 organophosphate esters (OPEs) were monitored by passive air sampling at 33 sites to determine their spatial distributions, and seasonal variations (summer and winter) in Tianjin, North China. The total concentrations of the OPEs (∑OPEs) in the summer ranged from 0.08 to 1113 ng/sample with a median of 98.

Synthesis of seven-membered heterocycles via copper-catalyzed cross-coupling of terminal alkynes with diazo compounds and sequential Michael addition.

A novel approach to synthesize seven-membered heterocycles is established by reacting amide tethered terminal alkynes with aryl diazoacetates in a one-pot reaction. This reaction involves copper-catalyzed cross coupling followed by base-promoted intramolecular Michael addition and yields products with a medium-sized ring.

Gold-Catalyzed Regiodivergent [2 + 2 + 2]-Cycloadditions of Allenes with Triazines.

Gold-catalyzed regiodivergent cycloadditions of functionalized allenes with 1,3,5-triazines, providing diverse N-heterocycles in moderate to excellent yields under mild reaction conditions, are reported. Importantly, different types of allenes exhibit distinct selectivity and reactivity for the reactions. Mechanistic investigations reveal that all of the cycloadditions proceed through a stepwise [2 + 2 + 2]-cycloaddition process.

Gold-catalyzed sequential annulations towards 3,4-fused bi/tri-cyclic furans involving a [3+2+2]-cycloaddition.

A gold-catalyzed sequential annulation reaction to prepare 3,4-fused bicyclic furan compounds has been realized by employing 2-(1-alkynyl)-2-alken-1-ones and 1,3,5-triazines as the starting materials under mild reaction conditions. This protocol features multiple bond formation in a single operation with the incorporation of two nitrogen and two carbon atoms into the final products. A mechanistic investigation reveals that the sequential annulations involved an unprecedented stepwise [3+2+2]-cycloaddition.

Synthesis of Polyheteroaromatic Compounds via Rhodium-Catalyzed Multiple C-H Bond Activation and Oxidative Annulation.

Polyheteroaromatic compounds are potential optoelectronic conjugated materials due to their electro- and photochemical properties. Transition-metal-catalyzed multiple C-H activation and sequential oxidative annulation allows rapidly assembling of those compounds from readily available starting materials. A rhodium-catalyzed cascade oxidative annulation of β-enamino esters or 4-aminocoumarins with internal alkynes is described to access those compounds, featuring multiple C-H/N-H bond cleavages and sequential C-C/C-N bond formations in one pot.

An efficient synthesis of isoquinolines via rhodium-catalyzed direct C-H functionalization of arylhydrazines.

A highly efficient rhodium-catalyzed C-H activation of arylhydrazines and coupling with internal alkynes has been realized under mild conditions. The isoquinolines have been prepared in moderate to excellent yields in high efficiency. This methodology features the use of readily available starting materials, and a simple hydrazine moiety as a directing group, in the absence of an external metal co-oxidant under an air atmosphere.