A concise,asymmetric synthesis of tetramic acid derivatives

[reaction: see text] A simple, asymmetric synthesis of tetramic acid derivatives is described in this paper. The key step is a carbonyl transfer from carbonyldiimidazole (CDI) to alpha-diimines (I) to form N-alkyl-4-alkylamino-5-methylenepyrrol-2-ones (II). In turn, these compounds can be easily transformed into tetramic acid derivatives (III) in two additional steps.     

Synthesis and Crystal Structure Study of Diethyl Aryl(benzo[d]thiazol‐2‐ylamino)methyl Phosphonates

A three‐component synthesis of α‐aminophosphonate is described from a reaction between aldehydes, 2‐aminobenzothiazole, and triethyl phosphite in the presence of InCl₃ as a catalyst under solvent‐free conditions for the generation of the particular α‐aminophosphonates. These products have two potentially biologically active parts, aminophosphonate and benzothiazole. This method offers advantages such as short reaction times, good yields, solvent‐free conditions, and easy workup with the green aspects by avoiding toxic catalysts and solvents. The crystal structure of 4b has been determined by X‐ray crystallography. This compound crystallizes in the monoclinic space group C2/c with cell parameters a = 21.9285(5) Å, b = 10.3221(2) Å, c = 18.5979(5) Å, β = 108.759(3)°, V = 3985.99(18) ų, D_calc = 1.301 mg m⁻³, and Z = 8. The final R value is 0.0501 for 3741 reflections. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:58–65, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21063     

Topological effects of a rigid chiral spacer on the electronic interactions in donor-acceptor ensembles

Two triads (donor-spacer-acceptor), exTTF-BN-C60 (6) and ZnP-BN-C60 (7), in which electron donors (i.e., exTTF or ZnP) are covalently linked to C60 through a chiral binaphthyl bridge (BN), have been prepared in a multistep synthetic procedure starting from a highly soluble enantiomerically pure binaphthyl building block (1). Unlike other oligomeric bridges, with binaphthyl bridges, the conjugation between the donor and the acceptor units is broken and geometric conformational changes are facilitated. Consequently, distances and electronic interactions between the donor and C60 are drastically changed. Both donor-spacer-acceptor (D-s-A) systems (i.e., 6 and 7) exhibit redox processes that correspond to all three constituent electroactive units, namely, donor, BN, and C60. Appreciable differences were, however, observed when comparing triad 6, in which no significant exTTF-C60 interactions were noted, with D-s-A 7, whose geometry favors donor-acceptor and pi-pi interactions that result in ZnP-C60 electronic communication. This through-space interaction is, for example, reflected in the redox potentials. Excited-state studies, carried out by fluorescence and transient absorption spectroscopy, also support through-space rather than through-bond interactions. Although both triads form the corresponding radical-ion pair, that is, exTTF*+-BN-C60*- and ZnP*+-BN-C60*-, dramatic differences were found in their lifetimes: 165 micros and 730 ns, respectively.     

Resolving Atomic-Scale Defects in Conjugated Polymers On-Surfaces

Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π-conjugated polymers. Here, isolated atomic-scale defects are deliberately introduced into a prototypical anthracene-ethynylene π-conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one-dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface-synthesized conjugated polymers.     

Metal-Free Formal Oxidative C−C Coupling by In Situ Generation of an Enolonium Species

Much contemporary organic synthesis relies on transformations that are driven by the intrinsic, so-called “natural”, polarity of chemical bonds and reactive centers. The design of unconventionally polarized synthons is a highly desirable strategy, as it generally enables unprecedented retrosynthetic disconnections for the synthesis of complex substances. Whereas the umpolung of carbonyl centers is a well-known strategy, polarity reversal at the α-position of a carbonyl group is much rarer. Herein, we report the design of a novel electrophilic enolonium species and its application in efficient and chemoselective, metal-free oxidative C−C coupling.     

Urinary excretion profiles of toremifene metabolites by liquid chromatography-mass spectrometry. Towards targeted analysis to relevant metabolites in doping control

In the present study, toremifene urinary excretion studies were evaluated in order to examine main metabolic reactions and to select target metabolites in doping control analysis. Urine samples from three female subjects were collected every 3 h for at least 15 days after the oral administration of a single dose of Fareston® (60 mg). The elemental compositions of the compounds detected were determined by liquid chromatography-mass spectrometry using a time-of-flight system with accurate mass measurement. More detailed structure elucidation was obtained by monitoring the presence or absence of structure-specific ions, using product ion scan and neutral loss acquisition modes, whereas the metabolites urinary profiles were evaluated in selected reaction monitoring acquisition mode. The results showed that the main routes of phase-I modifications involved carboxylation of the chlorinated side chain, N-demethylation and hydroxylation in different positions. Fifteen metabolites were found in all subjects studied, most of them were detected for more than 10 days in the free, glucuronide and sulphate fractions, with a maximum of excretion generally after 9–22 and 34–47 h from drug administration. These metabolites can be divided in two groups: metabolites with the characteristic chlorine isotope pattern and metabolites without the characteristic chlorine isotope pattern. The most abundant and long-term compounds were the carboxylated metabolites followed by the hydroxylated metabolites. Their product ions originating after collision-induced dissociation were observed to occur prevalently in the dimethylaminoethoxy and in the chlorinated side chains. These structure-specific ions were used to design screening and confirmation procedures to positively identify toremifene administration in doping control analysis.

Figure Suggested main metabolic routes of toremifene, as postulated by excretion studies followed by both LC-MS/MS assays with different acquisition modes and LC-QTOF

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Screening and confirmation analysis of stimulants, narcotics and beta-adrenergic agents in human urine by hydrophilic interaction liquid chromatography coupled to mass spectrometry

The chromatographic behaviour of 44 polar compounds (23 beta-adrenergic agents, 11 stimulants, 4 narcotics and 6 phenolalkylamines) included in the list of prohibited substances and methods of the World Anti-Doping Agency, has been investigated under hydrophilic interaction liquid chromatography conditions by application of different mobile phase compositions (percentage of the organic solvent, type and amount of mobile phase additive and ionic strength) and column temperatures. Detection of analytes was performed by a triple quadrupole mass spectrometer in positive ionization mode and selected reaction monitoring acquisition mode after liquid/liquid extraction. Data collected using as stationary phase type-B silica materials from different producers, showed that the best chromatographic conditions in terms of peak shape, selectivity and chromatographic retention were obtained using an initial percentage of acetonitrile of 90%, a column temperature of 35 °C, a mobile phase pH of 4.5 and ammonium acetate (5 mM) and acetic acid (0.1%) as mobile phase additives. The selected chromatographic conditions were used to develop screening and confirmation analytical procedures to detect polar compounds in human urine for antidoping purpose. The developed methods were validated in terms of specificity, matrix effect, linearity, precision, accuracy, sensitivity, robustness and repeatability of retention times and relative ion abundances. Such methods offer attractive alternatives and considerable advantages over traditional approaches especially for the analysis of the phenolalkylamines.     

Linking photo- and redoxactive phthalocyanines covalently to graphene

"Green" graphene: For the first time, the covalent attachment of a light-harvesting and electron-donating phthalocyanine to the basal plane of few-layer graphene is reported. Physicochemical characterizations reveal an ultrafast charge separation from the photoexcited phthalocyanine to few-layer graphene followed by a slower charge recombination.     

Modeling of metamagnetism in metallic-based materials with first-order transitions

During the past decade, the magnetic properties of metallic-based materials with first-order transitions have been extensively studied, motivated in part by the observation of large magnetocaloric effect (MCE) peaks displayed by these materials near room temperature. These large peaks are believed to be the result of the materials' magnetic properties at the metamagnetic region, characterized by (i) the thermal-induced transition from the ferromagnetic state (FM) to the paramagnetic state (PM) near the Curie temperature (T_C) and (ii) the field-induced transition from PM state to FM state above T_C. We developed a phenomenological model that utilizes the materials' mixed-state probability function to model the materials' complex hysteretic and properties at metamagnetic region. The approximate probability functions are obtained from the first and second derivatives of the magnetization curve. The probability functions are used to separate the materials' magnetization into a FM state component and a PM state component. The applicability of the model is demonstrated for a metallic-based metamagnetic material, Gd₅Si₂Ge₂ compound, where the modeled behaviors show remarkable agreement with the experimental data at the metamagnetic region and provide new physical insights in this mixed-state region. Specifically, in the region of metamagnetic transition, the PM state component is non-reversible and is a function of the FM state component.