Search Results (7)

Polycyclic aromatic hydrocarbon (PAH) derivatives, specifically azaarenes and nitrated and oxygenated PAHs, are emerging contaminants of concern due to their increased toxicity and persistence compared to the parent PAHs. Despite their toxicity, their simultaneous analysis in complex matrices, such as in fumes emitted from bituminous mixtures, remains challenging due to limitations of conventional analytical techniques. To address this, an advanced methodology was developed using Ultra-High-Performance Liquid Chromatography coupled with High-Resolution Mass Spectrometry (UHPLC-HRMS Orbitrap Eclipse) equipped with an APCI source for the simultaneous identification and quantification of 14 PAH derivatives. Chromatographic and ionization parameters were optimized to ensure maximum sensitivity and selectivity. Following ICH Q2(R2) guidelines, the method was validated, demonstrating excellent linearity (R² > 0.99), high mass accuracy (≤5 ppm), strong precision (<15%), and excellent sensitivity. Limits of detection (LODs) ranged from 0.1 µg L⁻¹ to 0.6 µg L⁻¹ and limits of quantification (LOQs) ranged from 0.26 µg L⁻¹ to 1.87 µg L⁻¹. The validated method was successfully applied to emissions from asphalt pavement materials collected on quartz filters under controlled conditions, enabling the identification and quantification of all 14 targeted compounds. These results confirm the method’s robustness and suitability for trace-level analysis of PAH derivatives in complex environmental matrices. Full article

Heteroaromatic motifs are prevalent in natural products and numerous high-value drug molecules. Consequently, the construction of alkylated heterocyclic frameworks holds significant importance. The Minisci reaction of heteroarenes has evolved into a flexible technique for the synthesis of substituted heterocyclic derivatives. However, the use of strong oxidants and external acid is inevitable during the reaction process. Herein, we present a versatile and accessible method for achieving cross dehydrogenation coupling between quinoline derivatives and inactive ether. This strategy utilizes inexpensive NaI and PPh₃ to support the reaction, obviating the need for metal complexes or sacrificial oxidants, and enables the straightforward synthesis of a diverse library of alkyl-substituted N-heteroarenes. Additionally, radical trapping experiments and fluorescence quenching experiments have been conducted to gain a more comprehensive understanding of the reaction mechanism. Full article

A practical method was developed for the convenient synthesis of isoxazole-fused tricyclic quinazoline alkaloids. This procedure accesses diverse isoxazole-fused tricyclic quinazoline alkaloids and their derivatives via intramolecular cycloaddition of methyl azaarenes with tert-butyl nitrite (TBN). In this method, TBN acts as the radical initiator and the source of N–O. Moreover, this protocol forms new C–N, C–C, and C–O bonds via sequence nitration and annulation in a one-pot process with broad substrate scope and functionalization of natural products. Full article

Heat treatment of meat can lead to the formation of carcinogenic organic compounds. The influence of dried fruits on the formation of non-polar heterocyclic aromatic amines (carbolines) and nitrogen derivatives of polycyclic aromatic hydrocarbons (azaarenes) in roasted pork loin was elucidated. Two hundred grams of fruit per 1 kg of meat were used as stuffing. Carbolines, derivatives of pyridoimidazole and pyridoindole, and azaarenes (benzoacridines and dibenzoacridines) were determined by means of high-performance liquid chromatography with fluorescence detection. The total concentration of six δ-, γ- and α-carbolines in roasted pork loin was 1.3 ng/g. This content decreased by 64%, 58%, and 54% in pork loin stuffed with prunes, apricots, and cranberries, respectively. Concentrations of β-carbolines (harmane and norharmane) increased under the influence of added fruits. The norharmane content increased the most, from 2.2 ng/g in the control sample to 12.3 ng/g in meat prepared with cranberries. The harmane content increased from 1.0 ng/g to 3.6 ng/g in meat with prunes. The total concentration of azaarenes (two benzoacridines and dibenzo[a,c]acridine), which was close to 0.1 ng/g, decreased in dishes with prunes and apricots by 54% and 12%, respectively. Azaarenes were not found in samples of meat stuffed with cranberries. Full article

Nucleophilic dearomatization of azaarenium salts is a powerful strategy to access 3D scaffolds of interest from easily accessible planar aromatic azaarene compounds. Moreover, this approach yields complex dihydroazaarenes by allowing the functionalization of the scaffold simultaneously to the dearomatization step. On the other side, organocatalysis is nowadays recognized as one of the pillars of the asymmetric catalysis field of research and is well-known to afford a high level of enantioselectivity for a myriad of transformations thanks to well-organized transition states resulting from low-energy interactions (electrostatic and/or H-bonding interactions…). Consequently, in the last fifteen years, organocatalysis has met great success in nucleophilic dearomatization of azaarenium salts. This review summarizes the work achieved up to date in the field of organocatalyzed nucleophilic dearomatization of azaarenium salts (mainly pyridinium, quinolinium, quinolinium and acridinium salts). A classification by organocatalytic mode of activation will be disclosed by shedding light on their related advantages and drawbacks. The versatility of the dearomatization approach will also be demonstrated by discussing several chemical transformations of the resulting dihydroazaarenes towards the synthesis of structurally complex compounds. Full article

Heterocyclic amines (HCAs) are carcinogenic food toxicants formed in cooked meats, which may increase the risk of cancer development in humans. Therefore, in this study, the effect of stingless bee honey from different botanical origins on the formation of HCAs in grilled beef satay was investigated. HCAs concentration in grilled beef satay was determined by using high performance liquid chromatography (HPLC). In total, six of the most toxigenic HCAs representing aminoimidazo-azaarenes (AIAs) (MeIQx, 4,8-DiMeIQx, and PhIP) and amino carbolines (norharman, harman, and AαC) groups were identified in all the beef samples investigated. A significant reduction in HCAs was observed in grilled beef marinated in honey as compared to beef samples marinated in table sugar (control), in which the reduction of 95.14%, 88.45%, 85.65%, and 57.22% was observed in gelam, starfruit, acacia, and Apis honey marinades, respectively. According to the partial least squares regression (PLS) model, the inhibition of HCAs in grilled beef was shown to be significantly correlated to the antioxidant activity (IC₅₀) of the honey samples. Therefore, the results of this study revealed that the addition of stingless bee honey could play an important role in reducing HCAs in grilled beef. Full article

The totality of chemical space is so immense that only a small fraction can ever be explored. Computational searching has indicated that bioactivity is associated with a comparatively small number of ring-containing structures. Pyrrole, indole, pyridine, quinoline, quinazoline and related 6-membered ring-containing aza-arenes figure prominently. This review focuses on the search for fast, efficient and environmentally friendly preparative methods for these rings with specific emphasis on iminyl radical-mediated procedures. Oxime derivatives, particularly oxime esters and oxime ethers, are attractive precursors for these radicals. Their use is described in conventional thermolytic, microwave-assisted and UV-vis based preparative procedures. Photoredox-catalyzed protocols involving designer oxime ethers are also covered. Choice can be made amongst these synthetic strategies for a wide variety of 5- and 6-membered ring heterocycles including phenanthridine and related aza-arenes. Applications to selected natural products and bioactive molecules, including trispheridine, vasconine, luotonin A and rutaecarpine, are included. Full article