Mild and convenient one-pot synthesis of 1,3,4-oxadiazoles

A mild, general, convenient, and efficient one-pot synthesis of 2-phenyl-5-substituted-1,3,4-oxadiazoles is described. Both (hetero)aryl and alkyl carboxylic acids were efficiently condensed with benzohydrazide in the presence of TBTU to give diacylhydrazine intermediates. The latter underwent a smooth TsCl-mediated cyclodehydration reaction to afford 2-phenyl-5-substituted-1,3,4-oxadiazoles in good to very good yields.     

Double pi(0) Photoproduction on the Proton at GRAAL

The double pi(0) photoproduction off the proton has been measured in the beam energy range of 0.65-1.5 GeV. The total and differential cross sections and the Sigma beam asymmetry were extracted. The total cross section measured for the first time in the third resonance region of the nucleon shows a prominent peak. The interpretation of these results by two independent theoretical models infers mostly the selective excitation of P11- and D13-nucleon resonances.     

Thermodynamics of the intercalation of acridines in DNA

Summary The thermodynamical quantities ΔG ⁰, ΔH ⁰, ΔS ⁰ and ΔC _p ⁰ have been evaluated for quinacrine, an acridine derivative, bound to different native DNAs: calf thymus, E. Coli and M. Luteus. Optical-absorption spectroscopy at theS ₁ singlet of quinacrine has been employed in order to determine the equilibrium association ?constant? of the complexes between 20 and 70°C. A nearly constant value of ΔG ⁰ has been evaluated, close to −7 kcal/mol, whereas ΔH ⁰ has been found to display a large change with temperature, from ∼−3 to ∼−7 kcal/mol. The data show also that at lower temperatures the association is both enthalpy and entropy controlled, whereas at higher temperatures the enthalpy becomes the dominant contribution to the intercalation process.

---

Riassunto Sono state determinate le grandezze ΔG ⁰, ΔH ⁰, ΔS ⁰ and ΔC _p ⁰ relative alla chinacrina, un derivato acridinico, legata ai seguenti DNA nativi: timo di vitello, Escherichia Coli e Micrococcus Luteus. Al fine di determinare la ?costante? di associazione all'equilibrio per complessi tra 20 e 70°C si è fatto uso della spettrofotometria del singolettoS ₁ della chinacrina. I valori di ΔG ⁰ sono stati trovati quasi costanti attorno a −7 kcal/mol, mentre ΔH ⁰ mostra una grande variazione nei suoi valori, da ∼−3 a ∼−7 kcal/mol. I dati mostrano anche che l'associazione alle piú basse temperature è governata sia da entalpia che entropia, mentre alle piú alte temperature il contributo entalpico domina il meccanismo d'intercalazione.

---

Реэюме Вычисляются термодинамические величины ΔG ⁰, ΔH ⁰, ΔS ⁰ и ΔC _p ⁰ для хинакрина, проиэводной акридина, свяэанного в раэличных природных DNA. Испольэуется спектроскопия оптического поглощения в областиS ₁ синглета хинакрина для определения ?постоянных? равновесной ассоции комплексов в интервале температур между 20 и 70°C. Получена почти постоянная величина ΔG ⁰, блиэкая к ∼−7 ккая/моль, тогда как величина ΔH ⁰ обнаруживает большое иэменение с темиературой от ∼−3 до ∼−7 ккал/моль. Полученные данные покаэывают, что при более ниэких температурах ассоциация определяется и энтальпией и энтропией, тогда как при более высоких температурах энтальпия определяет доминирующий вклад в механиэм внедрения.

     

Probing the order-to-chaos region in superdeformed 151Tb and 196Pb nuclei with continuum gamma transitions

The gamma decay associated with the warm rotation of the superdeformed nuclei 151Tb and 196Pb has been measured with the EUROBALL IV array. Several independent quantities provide a stringent test of the population and decay dynamics in the superdeformed well. A Monte Carlo simulation of the gamma decay based on microscopic calculations gives remarkable agreement with the data only assuming a large enhancement of the B(E1) strength for 1-2 MeV gamma rays, which may be related to the evidence for octupole vibrations in both mass regions.     

Electrophilic Vinylation of Thiols under Mild and Transition Metal-Free Conditions

The iodine(III) reagents vinylbenziodoxolones (VBX) were employed to vinylate a series of aliphatic and aromatic thiols, providing E-alkenyl sulfides with complete chemo- and regioselectivity, as well as excellent stereoselectivity. The methodology displays high functional group tolerance and proceeds under mild and transition metal-free conditions without the need for excess substrate or reagents. Mercaptothiazoles could be vinylated under modified conditions, resulting in opposite stereoselectivity compared to previous reactions with vinyliodonium salts. Novel VBX reagents with substituted benziodoxolone cores were prepared, and improved reactivity was discovered with a dimethyl-substituted core.     

Mild, convenient and versatile Cu-mediated synthesis of N-aryl-2-imidazolidinones

A mild, general, convenient and practical methodology for the selective copper-mediated mono N-arylation of unprotected 2-imidazolidinone was developed. Strong electron-donating groups and free hydroxy and amino groups on the aryl iodide substrates were well tolerated. The use of n-butanol as the solvent for the copper-catalysed mono-arylation of 2-imidazolidinone is unprecedented.     

Strong coupling limit of the gφ4 theory

The strong coupling limit of the gφ⁴ theory in the framework of the path integral formalism. An expansion of the Green's functions in negative powers of the coupling constant is obtained; at each order the dependence on the external momenta is of polynomial type. A renormalization procedure is proposed; the asymptotic behaviour of the Callan-Symanzik β function is studied and the existence of a stable ultraviolet fixed point is established.     

The graal experiment: Beam polarization asymmetries in pseudoscalar meson photoproduction

The GRAAL tagged and polarized γ beam has been operating with a maximum energy of 1100 MeV. For the first time asymmetry results in ν photoproduction were obtained and will be shown. Interesting results have also been obtained for π⁰ and π⁺ photo-production, that largely confirm the already existing ones, but also extend in not yet explored angular and energetic regions, especially for backward scattering and energies greater than 900 MeV.     

Measurement of beam-recoil observables Ox , Oz and target asymmetry T for the reaction \gammap → K+ \Lambda

The double polarization (beam-recoil) observables $\ensuremath O_x$ and $\ensuremath O_z$ have been measured for the reaction $ \gamma$ p → K ⁺ $ \Lambda$ from threshold production to $\ensuremath E_{\gamma} \sim 1500$ MeV. The data were obtained with the linearly polarized beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900MeV mass region.