On-line solid phase microextraction derivatization for the sensitive determination of multi-oxygenated volatile compounds in air

Multi-oxygenated volatile organic compounds are important markers of air pollution and precursors of ozone and secondary aerosols in both polluted and remote environments. Herein, their accurate determination was enhanced. The approach was based on an automated system for active sampling and on-fibre derivatization coupled with the gas chromatography–mass spectrometry (GC–MS) technique. The method capability was determined for different compound families, such as aldehydes, ketones, α-dicarbonyls, hydroxy-aldehydes, hydroxy-ketones, and carboxylic acids. A good accuracy (<7 %) was demonstrated from the results compared to Fourier-transform infrared spectroscopy (FTIR). Limits of detection (LODs) of 6–100 pptV were achieved with a time resolution lower than 20 min. The developed method was successfully applied to the determination of multi-oxygenated compounds in air samples collected during an intercomparison campaign (EUROCHAMP-2020 project). Also, its capability and accuracy for atmospheric monitoring was demonstrated in an isoprene ozonolysis experiment. Both were carried out in the high-volume outdoor atmospheric simulation chambers (EUPHORE, 200 m3). In summary, our developed technique offers near-real-time monitoring with direct sampling, which is an advantage in terms of handling and labour time for a proper quantification of trace levels of atmospheric multi-oxygenated compounds.

On-line SPME derivatization for the sensitive determination of multi-oxygenated volatile compounds in air

Multi-oxygenated volatile organic compounds are important markers of air pollution and precursors of ozone and secondary aerosols in both polluted and remote environments. Herein, their accurate determination was enhanced. The approach was based on an automated system for active sampling and on-fiber derivatization coupled with GC-MS technique. The method capability was determined for different compound families, such as aldehydes, ketones, α-dicarbonyls, hydroxy-aldehydes, hydroxy-ketones and, carboxylic acids. A good accuracy (

Substituted Pyridopyrimidinones. Part 3. Synthesis of Some Novel Ether Derivatives of 4H-Pyrido[1,2-a]pyrimidin-4-one

A series of novel bis-heterocyclic ethers, containing 4Hpyrido[1,2-a]pyrimidin-4-one along with other five and six-membered heterocyclic rings, was obtained utilizing ethyl [(4-oxo-4Hpyrido[1,2-a]pyrimidin-2-yl)oxy]acetate (1), [(4-oxo-4H-pyrido[1,2a]pyrimidin-2-yl)oxy]acetic acid (2) and/or [(4-oxo-4H-pyrido[1,2a]pyrimidin-2-yl)oxy]acetohydrazide (3). Reaction of ester 1 with some ortho-hydroxy-aldehydes furnished the corresponding pyridopyrimidyloxypyrones. Reaction of ester 1 or acid 2 with 1,2-diamines led to some imidazoles. Also, some pyrazole, triazole, and oxadiazoline derivatives have been prepared from hydrazide 3.

Stereoselective Allylation of Linear and Chiral β-Amino-α-Hydroxy Aldehydes: Total Syntheses of Tetraacetyl d-lyxo-, d-ribo-, and d-arabino-Phytosphingosines

The stereoselective allylations of β-amino-α-hydroxy aldehydes­ are described. Several Lewis acids (BF3·OEt2, SnCl4, TiCl4, ZnCl2­, and MgBr2·OEt2) were utilized in the allylations. The allylation of anti-β-NHCbz-α-OTBS substrate mediated by SnCl4 afforded the syn-selective­ product, while its allylation mediated by BF3·OEt2 afforded the anti-selective product. The allylation of syn-β-NHCbz-α-OTBS mediated by SnCl4 afforded the anti-selective product. The mechanism involves the chelation between the amido group and aldehyde oxygen by SnCl4, and the Felkin–Anh model by BF3·OEt2. The resulting allylation products were used for the total syntheses of tetraacetyl d-lyxo-, d-ribo-, and d-arabino-phytosphingosines.