A convenient tandem one-pot synthesis of donor-acceptor-type triphenylene 2,3-dicarboxylic esters from diarylacetylene

A tandem one-pot method for the direct synthesis of polysubstituted triphenylene 2,3-dicarboxylic esters with different substitution patterns was developed by enyne metathesis of diarylacetylene, followed by Diels–Alder, aromatization and a cyclization cascade

Study of synthesis of 2-(2-alkoxyphenyl)-1H-imidazoles. Comparison of oxidative aromatization reactions of imidazolines

The reaction of methyl salicylate with ethane-1,2-diamine has been used to prepare 2-(2-hydroxyphenyl)-1H-imidazoline. This compound was alkylated with alkyl halides to give five new 2-(2-alkoxyphenyl)-1H-imidazolines (alkyl = propyl, isopropyl, isobutyl, sec-butyl, benzyl). Seven types of transformation reactions of imidazolines into the respective imidazoles were tested. Out of them successful were the dehydrogenation on palladium in toluene (several-day refluxing), oxidation with activated manganese dioxide in toluene (several-hour heating at 60 °C), and the oxidation with potassium nitrosodisulfonate (Fremy’s salt) at room temperature. Seven new 2-(2-alkoxyphenyl)-1H-imidazoles were synthesized (alkyl = ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, benzyl) via mentioned methods. Comparison of individual oxidative aromatization reactions is discussed from the point of view of experimental arrangement, reaction time and conditions, purity of the products obtained, and yields

Effect of zeolite topology and reactor configuration on the direct conversion of CO2 to light olefins and aromatics

The direct transformation of CO2 into high-value-added hydrocarbons (i.e., olefins and aromatics) has the potential to make a decisive impact in our society. However, despite the efforts of the scientific community, no direct synthetic route exists today to synthesize olefins and aromatics from CO2 with high productivities and low undesired CO selectivity. Herein, we report the combination of a series of catalysts comprising potassium superoxide doped iron oxide and a highly acidic zeolite (ZSM-5 and MOR) that directly convert CO2 to either light olefins (in MOR) or aromatics (in ZSM-5) with high space–time yields (STYC2-C4= = 11.4 mmol·g–1·h–1; STYAROM = 9.2 mmol·g–1·h–1) at CO selectivities as low as 12.8% and a CO2 conversion of 49.8% (reaction conditions: T = 375 °C, P = 30 bar, H2/CO2 = 3, and 5000 mL·g–1·h–1). Comprehensive solid-state nuclear magnetic resonance characterization of the zeolite component reveals that the key for the low CO selectivity is the formation of surface formate species on the zeolite framework. The remarkable difference in selectivity between the two zeolites is further rationalized by first-principles simulations, which show a difference in reactivity for crucial carbenium ion intermediates in MOR and ZSM-5

Resonance Raman Spectroscopy of the Oxygenated Intermediates of Human CYP19A1 Implicates a Compound I Intermediate in the Final Lyase Step

CYP19A1, or aromatase, a cytochrome P450 responsible for estrogen biosynthesis in humans, is an important therapeutic target for the treatment of breast cancer. There is still controversy surrounding the identity of reaction intermediate that catalyzes carbon–carbon scission in this key enzyme. Probing the oxy-complexes of CYP19A1 poised for hydroxylase and lyase chemistries using resonance Raman spectroscopy and drawing a comparison with CYP17A1, we have found no significant difference in the frequencies or isotopic shifts for these two steps in CYP19A1. Our experiments implicate the involvement of Compound I in the terminal lyase step of CYP19A1 catalysis

Synthesis and Structure of 1,2-Dimethylene[2.10]metacyclophane and Its Conversion into Chiral [10]Benzenometacyclophanes: Synthesis and Structure of 1,2-Dimethylene[2.10]metacyclophane and Its Conversion into Chiral [10]Benzenometacyclophanes

Bromination of 5,21-di-tert-butyl-8,24-dimethoxy-1,2-dimethyl[2.10]metacyclophan-1-ene (MCP-1-ene; 1) with benzyltrimethylammonium tribromide exclusively afforded 1,2-bis(bromomethyl)-5,21-di-tert-butyl-8,24-dimethoxy[2.10]MCP-1-ene (2). Debromination of 2 with Zn and AcOH in CH₂Cl solution at room temperature for 24 h produced dimethylene[2.10]MCP 7 in 92 % yield, which is a stable solid compound. Compound 7 was treated with dimethyl acetylenedicarboxylate (DMAD) to provide 1,2-(3′,6′-dihydrobenzo)-5,21-di-tert-butyl-8,24-dimethoxy[2.10]MCP-4′,5′-dimethylcarboxylate (8) in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno-bridged dimethoxy[2.10]MCP-4′,5′-dimethylcarboxylate 9, possessing C₁ symmetry, by aromatization with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). A new type of N-phenyl-maleimide substituted 1,2-(3′,6′-dihydrobenzo)-5,21-di-tert-butyl-8,24-dimethoxy[2.10]MCP-4′,5′-N-phenylmaleimide 10 was also synthesized from 7 through treatment with N-phenylmaleimide in toluene at 110 °C followed by aromatization with DDQ. Single-crystal X-ray analysis of 9 revealed the formation of a syn-isomer

Biological variables in forager fertility performance: a critique of Bongaarts' model

African Studies Center Working Paper No. 60During the period of the 1960s and 1970s, a considerable amount of scholarly energy was devoted to studying the process of "modernization." Scholars, particularly political scientists and anthropologists, theorized extensively over exactly what modernization was and debated how it could best be quantified and measured.1 By the 1980s, however, the very notion of the "modern," along with its antithesis, the "traditional" was falling out of favor. Indeed, by declaring the new era "post-modern," the academic avant-guard signaled that the concept of modernity had effectively been relegated to the past. The past, however, is the turf of historians, so perhaps now that the concept of modernity has become old-fashioned it is time for historians to take their turn at examining its meaning. This paper will approach the concept of the "modern" by examining the role of advertising in creating notions of modernity in independence-era Ghana. Ghana, at the time of independence in 1957, was a country of supreme optimism about the future. Not only did Ghanaians see themselves as being on the cutting edge politically (as the first sub-Saharan colony to achieve independence), but they also believed that independence would bring a new era of economic development and wealth. Ghana, as a country, was "going places." The new nation's optimism found many manifestations, but this paper will focus on only one aspect of this exuberance—representations of transportation as modernity in the advertisements and articles of Ghana's premier newspaper, the Daily Graphic. As stated before, early scholarship on modernization was concerned primarily with developing a way of measuring the demise of the traditional and the rise of the modern. Such studies focused on examining populations of "traditional" or "transitional" peoples to attempt to discern just how "modern" they had or had not become. What the previous studies did not consider, and what this paper seeks to examine, is exactly how modernity was presented to and by such populations. No single factor seems to represent modernity more than motion itself—be it actual movement across space or be it social and economic change. Indeed, Daniel Lerner, the prominent scholar of modernity, defined the key aspect of being modern as having... [TRUNCATED

Development of autoclavable polyimides

A poly(Diels-Alder) (PDA) resin approach was investigated as a means to achieve autoclavability of high temperature resistant resin/fiber composites under mild fabrication procedures. Low void content Type A-S graphite reinforced composites were autoclave fabricated from a PDA resin/fiber prepared from an acetone:methanol:dioxane varnish. Autoclave conditions were 477K (400F) and 0.7 MN/sq m (100 psi) for up to two hours duration. After postcure at temperatures up to 589K (600F), the composites demonstrated high initial mechanical properties at temperatures up to 561K (550F). The results from isothermal aging studies in air for 1000 hours indicated potential for long-term ( 1000 hours) use at 533K (500F) and shorter-term (up to 1000 hours) at 561K (550F)

Sex hormone-binding globulin regulation of androgen bioactivity in vivo : validation of the free hormone hypothesis

Sex hormone-binding globulin (SHBG) is the high-affinity binding protein for androgens and estrogens. According to the free hormone hypothesis, SHBG modulates the bioactivity of sex steroids by limiting their diffusion into target tissues. Still, the in vivo physiological role of circulating SHBG remains unclear, especially since mice and rats lack circulating SHBG post-natally. To test the free hormone hypothesis in vivo, we examined total and free sex steroid concentrations and bioactivity on target organs in mice expressing a human SHBG transgene. SHBG increased total androgen and estrogen concentrations via hypothalamic-pituitary feedback regulation and prolonged ligand half-life. Despite markedly raised total sex steroid concentrations, free testosterone was unaffected while sex steroid bioactivity on male and female reproductive organs was attenuated. This occurred via a liganddependent, genotype-independent mechanism according to in vitro seminal vesicle organ cultures. These results provide compelling support for the determination of free or bioavailable sex steroid concentrations in medicine, and clarify important comparative differences between translational mouse models and human endocrinology

Polar Diels-Alder Reactions using Heterocycles as Electrophiles. Influence of Microwave Irradiation

In this work we studied a series of polar Diels-Alder reactions using different heterocycles derivatives acting as electrophiles joint to dienes of different nucleophilicity, analyzing the effect of the microwave irradiation in these processes. We employ the technique in two conditions: benzene as solvent and solvent free reactions. The last one presents the better yield in shorter time of reaction. Using microwave heating the aromatic cycloadducts are clearly predominant. It is possible to demonstrate that the microwave irradiation has a better influence on these cycloaddition reactions respect to those developed in thermal classical conditions.Fil: Kneeteman, Maria Nelida. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: López Baena, Anna Francesca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Della Rosa, Claudia Daniela. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentin