Reversal of aryl bromide reactivity in Pd-catalysed aryl amination reactions promoted by a hemilabile aminophosphine ligand

Incorporation of a hemilabile amino group with a bulky, electron-rich phosphorus ligand led to a reversal in the order of aryl bromide reactivity in Pd-catalysed aryl amination reactions.     

Photodegradation of tetramethylpolycarbonate (TMPC): Correlation of properties with chemical modifications

The consequences of tetramethylpolycarbonate (TMPC) photoageing (λ > 300 nm) on the surface modifications of the material have been analysed. Roughness and stiffness measurements were performed using AFM (Atomic Force Microscopy). Gel fraction measurements, DMTA (Dynamic Mechanical Thermal Analysis) measurements and infrared analyses were also performed. The results indicate that the three-dimensional network forms as a result of crosslinking reactions. The modifications of the properties measured using each technique were followed as functions of the irradiation time, and the influence of oxygen was characterised. The surface modifications are explained in light of the modifications of the chemical structure. Quantitative correlations were obtained between the main relevant criteria characterizing the surface degradation from the chemical structure to the mechanical properties.     

Large yet Flexible N‐Heterocyclic Carbene Ligands for Palladium Catalysis

A straightforward and scalable eight‐step synthesis of new N‐heterocyclic carbenes (NHCs) has been developed from inexpensive and readily available 2‐nitro‐m‐xylene. This process allows for the preparation of a novel class of NHCs coined ITent (“Tent” for “tentacular”) of which the well‐known IMes (N,N′‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene), IPr (N,N′‐bis(2,6‐di(2‐propyl)phenyl)imidazol‐2‐ylidene) and IPent (N,N′‐bis(2,6‐di(3‐pentyl)phenyl)imidazol‐2‐ylidene) NHCs are the simplest and already known congeners. The synthetic route was successfully used for the preparation of three members of the ITent family: IPent (N,N′‐bis(2,6‐di(3‐pentyl)phenyl)imidazol‐2‐ylidene), IHept (N,N′‐bis(2,6‐di(4‐heptyl)phenyl)imidazol‐2‐ylidene) and INon (N,N′‐bis(2,6‐di(5‐nonyl)phenyl)imidazol‐2‐ylidene). The electronic and steric properties of each NHC were studied through the preparation of both nickel and palladium complexes. Finally the effect of these new ITent ligands in Pd‐catalyzed Suzuki–Miyaura and Buchwald–Hartwig cross‐couplings was investigated.     

Oral fluid cannabinoid concentrations following controlled smoked cannabis in chronic frequent and occasional smokers

Oral fluid (OF) is an alternative biological matrix for monitoring cannabis intake in drug testing, and drugged driving (DUID) programs, but OF cannabinoid test interpretation is challenging. Controlled cannabinoid administration studies provide a scientific database for interpreting cannabinoid OF tests. We compared differences in OF cannabinoid concentrations from 19 h before to 30 h after smoking a 6.8 % THC cigarette in chronic frequent and occasional cannabis smokers. OF was collected with the Statsure Saliva Sampler? OF device. 2D-GC-MS was used to quantify cannabinoids in 357 OF specimens; 65 had inadequate OF volume within 3 h after smoking. All OF specimens were THC-positive for up to 13.5 h after smoking, without significant differences between frequent and occasional smokers over 30 h. Cannabidiol (CBD) and cannabinol (CBN) had short median last detection times (2.5–4 h for CBD and 6–8 h for CBN) in both groups. THCCOOH was detected in 25 and 212 occasional and frequent smokers’ OF samples, respectively. THCCOOH provided longer detection windows than THC in all frequent smokers. As THCCOOH is not present in cannabis smoke, its presence in OF minimizes the potential for false positive results from passive environmental smoke exposure, and can identify oral THC ingestion, while OF THC cannot. THC?≥?1 μg/L, in addition to CBD?≥?1 μg/L or CBN?≥?1 μg/L suggested recent cannabis intake (≤13.5 h), important for DUID cases, whereas THC?≥?1 μg/L or THC?≥?2 μg/L cutoffs had longer detection windows (≥30 h), important for workplace testing. THCCOOH windows of detection for chronic, frequent cannabis smokers extended beyond 30 h, while they were shorter (0–24 h) for occasional cannabis smokers.     

Simultaneous quantification of 28 synthetic cathinones and metabolites in urine by liquid chromatography-high resolution mass spectrometry

Synthetic cathinones are novel stimulants derived from cathinone, with amphetamines or cocaine-like effects, often labeled “not for human consumption” and considered “legal highs”. Emergence of these new designer drugs complicate interpretation of forensic and clinical cases, with introduction of many new analogs designed to circumvent legislation and vary effects and potencies. We developed a method for the simultaneous quantification of 28 synthetic cathinones, including four metabolites, in urine by liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). These cathinones include cathinone, methcathinone, and synthetic cathinones position-3’-substituted, N-alkyl-substituted, ring-substituted, methylenedioxy-substituted, and pyrrolidinyl-substituted. One mL phosphate buffer pH 6 and 25 μL IStd solution were combined with 0.25 mL urine, and subjected to solid phase cation exchange extraction (SOLA SCX). The chromatographic reverse-phase separation was achieved with a gradient mobile phase of 0.1 % formic acid in water and in acetonitrile in 20 min. We employed a Q Exactive high resolution mass spectrometer, with compounds identified and quantified by target-MSMS experiments. The assay was linear from 0.5–1 to 100 μg/L, with limits of detection of 0.25–1 μg/L. Imprecision (n?=?20) was <15.9 % and accuracy (n?=?20) 85.2–118.1 %. Extraction efficiency was 78.9–116.7 % (CV 1.4–16.7 %, n?=?5), process efficiency 57.7–104.9 %, and matrix effects from ?29.5 % to 1.5 % (CV 1.9–13.1 %, n?=?10). Most synthetic cathinones were stable at 4 °C for 72 h (n?=?27) and after 3 freeze-thaw cycles (n?=?26), but many (n?=?19) were not stable at room temperature for 24 h (losses up to ?67.6 %). The method was applied to authentic urine specimens from synthetic cathinone users. This method provides a comprehensive confirmation method for 28 synthetic cathinones in urine, with good selectivity and specificity.     

Light‐Induced Bistability in the 2 D Coordination Network {[Fe(bbtr)3][BF4]2}∞: Wavelength‐Selective Addressing of Molecular Spin States

Whereas the neat polymeric Fe^II compound {[Fe(bbtr)₃][ClO₄]₂}_∞ (bbtr=1,4‐di(1,2,3‐triazol‐1‐yl)butane) shows an abrupt spin transition centered at 107 K facilitated by a crystallographic symmetry breaking, in the covalently linked 2D coordination network of {[Fe(bbtr)₃][BF₄]₂}_∞, Fe^II stays in the high‐spin state down to 10 K. However, strong cooperative effects of elastic origin result in reversible, persistent, and wavelength‐selective photoswitching between the low‐spin and high‐spin manifolds. This compound thus shows true light‐induced bistability below 100 K. The persistent bidirectional optical switching behavior is discussed as a function of temperature, irradiation time, and intensity. Crystallographic studies reveal a photoinduced symmetry breaking and serve to establish the correlation between structure and cooperative effects. The static and kinetic behavior is explicated within the framework of the mean‐field approximation.     

Studies on pyrrolidones. Synthesis and reactivity of β-enaminomono-esters and β-enaminomononitriles derived from pyroglutamic acid

In the pyroglutamic acid series, β-enaminoesters 3 were formed in the 2-position by opening of the corresponding Meldrum's derivative 6 , and β-enaminonitriles 4 were obtained by treating carbamate vinylogous 5 by trimethytsilyl iodide. Alkylation and acylation of β-enaminoester 3a was briefly examined.     

Acetylcholinesterase-inhibiting alkaloids from Zephyranthes concolor

The bulbs and aerial parts of Zephyranthes concolor (Lindl.) Benth. & Hook. f. (Amaryllidaceae), an endemic species to Mexico, were found to contain the alkaloids chlidanthine, galanthamine, galanthamine N-oxide, lycorine, galwesine, and epinorgalanthamine. Since currently only partial and low resolution (1)H-NMR data for chlidanthine acetate are available, and none for chlidanthine, its 1D and 2D high resolution (1)H- and (13)C-NMR spectra were recorded. Unambiguous assignations were achieved with HMBC, and HSQC experiments, and its structure was corroborated by X-ray diffraction. Minimum energy conformation for structures of chlidanthine, and its positional isomer galanthamine, were calculated by molecular modelling. Galanthamine is a well known acetylcholinesterase inhibitor; therefore, the isolated alkaloids were tested for this activity. Chlidanthine and galanthamine N-oxide inhibited electric eel acetylcholinesterase (2.4 and 2.6 × 10(-5) M, respectively), indicating they are about five times less potent than galanthamine, while galwesine was inactive at 10(-3) M. Inhibitory activity of HIV-1 replication, and cytotoxicity of the isolated alkaloids were evaluated in human MT-4 cells; however, the alkaloids showed poor activity as compared with standard anti-HIV drugs, but most of them were not cytotoxic.