A liquid chromatography–atmospheric pressure photoionization tandem mass spectrometric method for the determination of azaarenes in atmospheric particulate matter

The development, optimization and validation of a liquid chromatography–atmospheric pressure photoionization tandem mass spectrometric (LC–APPI/MS/MS) method for the determination of 15 azaarenes (4-azafluorene, benzo[h] and -[f]quinoline, phenanthridine, acridine, 1-azafluoranthene, 4-azapyrene, benz[a]- and -[c]acridine, -10-azabenzo[a]pyrene, 7,9- and 7,10-dimethylbenz[c]acridine, dibenz[a,j]-, -[c,h] and [a,i]acridine) in airborne particulate matter is described. Each compound was detected and quantified operating in multiple reaction monitoring mode. Extraction of azaarenes was achieved using accelerated solvent extraction (ASE) with dichlormethane/methanol (50/50, v/v). After extraction, no additional clean-up procedure like solid phase or liquid/liquid extraction was necessary. Limits of quantification (S/N × 10) ranged from 0.2 pg/μl to 1.4 pg/μl, matrix dependent recoveries were between 57% and 94%, with relative standard deviations from 8% to 17%. Applicability of the method was demonstrated analyzing 10 samples of particulate matter (PM_2.5) collected in winter 2008. In all samples dimethylbenz[c]acridines as well as dibenzacridines were below the limit of quantification, concentration of the remaining analytes were in the range from 0.002 ng/m³ to 0.356 ng/m³.     

Catalytic Asymmetric Hydrophosphinylation of 2-Vinylazaarenes to Access P-Chiral 2-Azaaryl-Ethylphosphine Oxides

A chiral Brønsted acid-catalysed asymmetric hydrophosphinylation of 2-vinylazaarenes by secondary phosphine oxides is described. A variety of P-chiral 2-azaaryl-ethylphosphine oxides are synthesized with high yields and ees, of which both the substituents of phosphines and azaarenes can be flexibly modulated, underscoring an exceptionally broad scope of substrates. These adducts are valuable to asymmetric metal catalysis since the resultant P-chiral tertiary phosphines from the reduction of them are verified as a kind of effective C₁-symmetric chiral 1,5-hybrid P,N-ligands. Importantly, this catalysis platform enables the generic and efficient kinetic resolution of P-chiral secondary phosphine oxides. It thus provides an expedient approach to access the enantiomers of the P-chiral tertiary phosphine oxides derived from asymmetric hydrophosphinylation, further improving the utility of the method.     

Kinetic Resolution of Azaarylethynyl Tertiary Alcohols by Chiral Brønsted Acid Catalysed Phosphine-Mediated Deoxygenation

A chiral Brønsted acid catalysed phosphine-mediated deoxygenation protocol is reported. This metal-free method provides a precise kinetic resolution platform for azaarylethynyl tertiary alcohols, which are a broad category of biologically and synthetically important azaarene derivatives. In addition to providing an efficient method for the first asymmetric preparation of these tertiary alcohols, the strategy facilitates the construction of azaaryl-functionalized allenes with good to excellent enantioselectivities. The high selectivity factors (s up to 235), broad substrate scope, and ability to convert azaaryl compounds into both chiral tertiary alcohols and allenes robustly underscore the efficiency and promising utility of this method. The practicability is further validated by the successful synthesis of deuterated allenes with high ee values and substantial incorporation of deuterium using inexpensive D₂O as the deuterium source.     

Simple,One-Pot,and Three-Component Coupling Reactions of Azaarenes (Phenanthridine,Isoquinoline, and Quinoline), with Acetylenic Esters Involving Methyl Propiolate or Ethyl Propiolate in the Presence of NH-Heterocyclic or 1,3-Dicarbonyl Compounds

Three-component reactions involving azaarenes (quinoline, isoquinoline, and phenanthridine) with acetylenic esters such as methyl propiolate or ethyl propiolate in the presence of NH-heterocyclic compounds (carbazole, maleimide, 5-nitroindazole, 2-benzoxazolinone, indole, and 2-methylindole) or 1,3-dicarbonyl compounds involving acetylacetone and N,N′-dimethylbar bituric acid are described. The reactions proceeded smoothly at room temperature without a catalyst and with excellent yields. This method is very useful for functionalizing aza-aromatic compounds in a one-pot operation.     

氢原子转移与手性氢键协同催化共轭加成—不对称质子化构建氮杂芳烃α-三级立体中心

含亚胺氮杂芳烃(如吡啶、喹啉等)是一大类结构多样的芳香杂环,广泛存在于生物活性分子、天然产物、药物、催化剂、配体及功能材料等分子结构中.因此,发展氮杂芳烃衍生物合成方法学一直备受化学家的关注.其中,利用氮杂芳烃缺电子性质直接驱动氮杂芳烃底物参与化学转换一直是这一领域的研究重点.近年来,为了克服氮杂芳烃拉电子能力较羰基弱...     

Acid ionic liquid promoted addition of C(sp)–H bond to aldehyde

A novel protocol for acid ionic liquid promoted C(sp³)–H bond functionalization of alkyl azaarenes and nucleophilic addition to aldehydes was developed in good to excellent yields, which provides an efficient approach for the synthesis of alkyl-substituted azaarene derivatives. It is worthwhile to note that acid ionic liquid used for this reaction can be recycled and reused six times without a significant decrease in activity.     

Clean-up of polynuclear aromatic hydrocarbons and 3-ring azaarenes and their GC-analysis on whisker-walled open tubular columns

A modified clean-up of polynuclear aromatic (PNA) hydrocarbons on XAD-2 is described. n-Alkanes (C₁₆? C₂₈) are separated quantitatively from the PNA hydrocarbons and are eluted in one fraction. The distribution of 17 PNA hydrocarbons and four of their alkyl derivatives, two S-heterocyclic compounds and two azaarenes between the different fractions is reported. Azaarenes containing three rings are separated from PNA hydrocarbons and S-heterocyclic compounds. Whisker-walled open tubular columns coated with OV-215 and OV-25 were used in the separation of isomeric azaarenes and in PNA hydrocarbon profile analysis, respectively. The preparation of such columns is described in detail. Rinsing of capillary columns with cold, concentrated HCI after whisker growth removes much larger amounts of boron and sodium than subsequent leaching with HCI at 180°C. Whisker-walled open tubular columns are successfully applied to the characterization of isomeric benzofluoranthenes and other PNA hydrocarbons isolated from air particulate matter.     

Measurement of semi-volatile azaarenes in airborne particulate and vapor phase

In the atmosphere, exchanges between the gas and particle phases has a profound influence on the removal processes and residence times of semi-volatile compounds. This study describes analytical procedures for the reliable quantitation of both gas and particle phase azaarenes (two-, three- and four-rings). Samples of particulate material were collected on the glass fiber filters and gas phase material on polyurethane foam plugs. Azaarene compounds were isolated utilizing an acid/base partition method. Isolated azaarenes compounds were then characterized and quantified using gas chromatography with mass spectrometry (GC/MS). The analytical method described in this paper is the first procedure for the simultaneous determination of gas and particle phase azaarenes and allows 47 azaarene compounds to be reliably quantified despite the complexity of urban aerosols.     

Alumina-supported heteropoly acid: An effi cient catalyst for the synthesis of azaarene substituted 3-hydroxy-2-oxindole derivatives via C(sp3)H bond functionalization

A method of C(sp3)-H bond functionalization of methyl azaarenes catalyzed by alumina-supported heteropoly acid and addition to isatins was developed. This transformation could be used for the synthesis of biologically important 3-hydroxy-2-oxindole derivatives in good to excellent yields and the catalyst could be reused for six times without significant decrease in activity.     

The study of properties of HPLC determination of polycyclic aromatic nitrogen heterocycles

The study of the separation of polycyclic aromatic nitrogen heterocycles (PANHs) by reverse-phase liquid chromatography with an octadecyl stationary phase is presented. The retention behaviour of a mixture of PANHs was studied under different chromatographic conditions. A mixture of phosphate buffer/acetonitrile was used as mobile phase in isocratic and gradient modes. The effect of different pH mobile phase in the range from 2.5 to 6.5 has been investigated to describe retention changes of PANHs as a function of their acid/base properties. Different concentrations of phosphate buffer as a component of the mobile phase were used to study the effect of ionic strength. Very good RP-HPLC separation of 24 PANHs and 16 EPA polycyclic aromatic hydrocarbons (PAHs) was obtained without a pre-separation step in a test mixture and the extract of a real soil sample. Limits of detection of PANHs obtained by two detection techniques, ultraviolet-diode array detection (UV-DAD) and fluorescence detector (FD), are compared. The proposed method is tested with a real soil sample.