Membrane-assisted solvent extraction coupled to large volume injection–gas chromatography–mass spectrometry for the determination of a variety of endocrine disrupting compounds in environmental water samples

Membrane-assisted solvent extraction coupled to large volume injection in a programmable temperature vaporisation injector using gas chromatography–mass spectrometry analysis was optimised for the simultaneous determination of a variety of endocrine disrupting compounds in environmental water samples (estuarine, river and wastewater). Among the analytes studied, certain hormones, alkylphenols and bisphenol A were included. The nature of membranes, extraction solvent, extraction temperature, solvent volume, extraction time, ionic strength and methanol addition were evaluated during the optimisation of the extraction. Matrix effects during the extraction step were studied in different environmental water samples: estuarine water, river water and wastewater (influent and effluent). Strong matrix effects were observed for most of the compounds in influent and effluent samples. Different approaches were studied in order to correct or minimise matrix effects, which included the use of deuterated analogues, matrix-matched calibration, standard addition calibration, dilution of the sample and clean-up of the extract using solid-phase extraction (SPE). The use of deuterated analogues corrected satisfactorily matrix effect for estuarine and effluent samples for most of the compounds. However, in the case of influent samples, standard addition calibration and dilution of the sample were the best approaches. The SPE clean-up provided similar recoveries to those obtained after correction with the corresponding deuterated analogue but better chromatographic signal was obtained in the case of effluent samples. Method detection limits in the 5–54 ng L⁻¹ range and precision, calculated as relative standard deviation, in the 2–25% range were obtained.     

Organocatalytic enantioselective synthesis of 2,3-dihydropyridazines

We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the stereocentre is installed, followed by an intramolecular aldol reaction/dehydration step.     

Resolution and identification of co‐eluting alkylphenols in comprehensive two‐dimensional gas chromatography–mass spectrometry by multivariate curve resolution‐alternating least squares

The interest in the analysis of alkylphenols (APs) has widely increased in the last decades because of the endocrine disrupting features of these phenol derivatives. However, the isolation and identification of many of the multiple chemical structures of all APs is a very challenging task because of their similar physicochemical properties. In this work, the co‐elution of the isomers present in technical mixtures and using comprehensive two‐dimensional gas chromatography coupled to quadrupole mass spectrometry was resolved using multivariate curve resolution‐alternating least squares algorithm. The mass spectrum of each resolved compound was compared with the theoretical mass spectrum obtained from the literature, in order to assign the appropriate identification of each isomer. Two commercial mixtures were studied; in one of them, 34 compounds were resolved, and in the second mixture, 40 compounds were resolved. The relative abundances of the compounds were also calculated in both mixtures. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Pyrrolo[2,3‐d]pyrimidines by Copper‐Mediated Carbomagnesiations of N‐Sulfonyl Ynamides and Application to the Preparation of Rigidin A and a 7‐Azaserotonin Derivative

The treatment of readily available N‐alkynyl‐5‐iodo‐6‐sulfamido‐pyrimidines with iPrMgCl?LiCl followed by a transmetalation with CuCN?2 LiCl produces, after intramolecular carbocupration, metalated py r rolo[2,3‐d]pyrimidines. Quenching of these pyrimidines with allylic halides or acid chlorides results in polyfunctional pyrrolo[2,3‐d]pyrimidines. Further reaction with ICl and a Negishi cross‐coupling, using PEPPSI‐iPr as the catalyst, furnishes fully substituted N‐heterocycles. A formal synthesis of the marine alkaloid rigidin A has been achieved as well as the preparation of a derivative of 7‐azaserotonine, related to the natural hormone serotonin.     

New In Situ Trapping Metalations of Functionalized Arenes and Heteroarenes with TMPLi in the Presence of ZnCl2 and Other Metal Salts

The addition of TMPLi to a mixture of an aromatic or heteroaromatic substrate with a metal salt such as MgCl₂, ZnCl₂, or CuCN at ?78 °C first leads to lithiation of the arene followed by transmetalation with the metal salt to afford functionalized organometallic compounds of Mg, Zn, or Cu. This in situ trapping method allows an expedited metalation (?78 °C, 5 min) of a range of sensitive pyridines (bearing a nitro, ester, or cyano group) and allows the preparation of kinetic regioisomers of functionalized aromatic compounds or heterocycles not otherwise available by standard metalating agents, such as TMPMgCl?LiCl or TMPZnCl?LiCl.