323,161 research outputs found
Preghiera e letteratura nell'opera di Guido Casoni
No full textIl saggio percorre l'opera complessiva di Guido Casoni (1561-1642) per individuare in essa varie forme di preghiera, esaminando il rapporto fra la componente religiosa cristiana e la veste letterariaThe essay examines the entire work of Guido Casoni (1561-1642) to identify various forms of prayer, examining the relationship between the Christian religious component and the literary for
A mild and efficient synthesis of 3-Aminosubstituted Isothiazole S-Oxides and their 5-Sulfanylsubstituted derivatives
No full textThe present paper describes a mild and efficient method to synthesize 3-aminosubstituted isothiazole sulfoxides taking advantage of arylsulfonyloxaziridines. The reactivity of the resulting isothiazole sulfoxides toward sulfur nucleophiles has been studied and resulted in the formation of 5-sulfanylsubstituted isothiazoles in a fully diastereoselective way. From 3-benzylamino-5-chloro isothiazole S-oxide an addition-elimination reaction took place affording smoothly the corresponding unsaturated 5-sulfanyl derivatives
Fused isothiazole S-oxide systems from cycloaddition reactions of N-benzylisothiazol-3-amine 1-oxide
No full textThe racemic N-benzylisothiazol-3-amine 1-oxide (2) was demonstrated to be an efficient partner in Diels-Alder reactions (Schemes 2-4) and a good dipolarophile in 1,3-dipolar cycloaddition reactions with nitrile oxides (Scheme 5). Polycyclic isothiazole S-oxides with different substitution patterns were obtained from 2 in good yield and in a fully regioselective way. Improved diastereoselection was observed performing the Diels-Alder or 1,3-dipolar cycloaddition reactions in H 2O
Improved Analysis of Early Packet Discard
No full textIn a previous paper, one of the authors, gave a worst-case analysisfor the Early Packet Discard technique for maintaining packet integrityduring overload in ATM switches. This analysis showed that to ensure100% goodput during overload under worst-case conditions, requires a bufferwith enough storage for one maximum length packet from every active virtualcircuit. This paper refines that analysis, using assumptions that arecloser to what we expect to see in practice. Our principal result is that100% goodput can be achieved with substantially smaller buffers,although the required buffer space can be significant when the link speed issubstantially higher than the rate of the individual virtual circuits.These results are validated by comparison with simulation. We also givea simple analysis to determine the amount of buffering needed to boundthe probability of buffer overflow and underflow
Título: Commentaria in Primam Partem Tertij Libri Decretalium
No full textSign.: [ ]\p2\s, A-Z\p4\s, 2A-2Z\p4\s, 3A-3D\p4\s, 3E\p3\sTexto a dos colPort. con esc. pontificioPort. con esc. calc. pontifici
Título: Commentaria in quartum librum et in primam partem quinti libri Decretalium
No full textSign.: [ ]\p2\s, A-N\p4\s, O\p6\s, P-Z\p4\s, 2A-2V\p4\s, 2X\p3\sTexto a dos colPort. con esc. xilProsperi Fagnani Commentaria in primam partem quinti Libri Decretalium, segunda secuencia de pag., con port. propi
3-Amino-substituted isothiazole S,S-dioxides as dienophiles in Diels-Alder cycloaddition reactions with cyclic, acyclic and heterocyclic dienes
No full textThe Diels-Alder reactions of two 3-aminoisothiazole S,S-dioxides with various dienes, such as 2,3-dimethylbutadiene, cyclopentadiene or furan, under diverse reaction conditions are investigated. Differences of reactivity and selectivity between the studied isothiazoles and the influence of the reaction conditions on the outcome of the reactions are discusse
Asymmetric synthesis and absolute configuration of 3-aminosubstituted isothiazole S-oxides
No full textTaking into account the importance in medicinal- and agro-chemistry of optically active isothiazole
derivatives, we became interested in the asymmetric preparation of 3-aminosubstituted isothiazole 1-oxides [1]. A solution of 1 in CH2Cl2 with an equimolecular amount of (-)-2b was irradiated at 400W, 80°C.
Sulfoxide 3 was produced in 80% overall yield and 50% ee together with little amount of sulfone (8%) after 1h. (-)-2a gave much slower reactions.
In order to determine the absolute configuration (AC) of the new 3-aminosubstituted isothiazole Soxides,
we simulated [2,3] the ECD spectrum of (+)-3-aminomethyl isothiazole S-oxide, (+)-3b in the range 380-200 nm, both in the gas phase and ethanol at the TDDFT/B3LYP/aug-cc-pVDZ level of calculation. To this end we used (S)-3b which exists almost as a single conformer at the DFT/B3LYP/6-31G* level of calculation.
In Figure are reported the experimental (black line) ECD spectrum of (+)-3b and predicted ECD spectra of (S)-3b, taking into account the first 30 excited states both in the gas phase and ethanol. In the gas phase (green line), even if the positions and intensities of predicted ECD bands do not perfectly match the experimental data, the experimental spectrum shows a sequence of negative, positive, negative Cotton effects which is reproduced in the theoretical spectrum, indicating the (+)/(S) correlation. Including the ethanol effect (red line), significantly improves the agreement between calculated and experimental data, strongly supporting the (+)/(S) configurational correlation. We can conclude that (+)-3b possesses (S) AC and therefore the chiral auxiliaries (-)- 2b induces the preferential formation of the (S) antipode in the above asymmetric oxidation reaction.
1. Clerici, F.; Gelmi, M. L.; Pellegrino, S.; Pocar, D. “Chemistry of biologically active isothiazoles”, in Topics in Heterocyclic Chemistry, 9 (Bioactive Heterocycles III), 2007, 179-264. Publisher: Springer GmbH, 2. Frisch, M.J. et al., Gaussian 03; Gaussian, Inc.: Pittsburgh, PA, USA, 2003, http://www.gaussian.com/.
3. see, for instance: Tartaglia, S.; Padula, D.; Scafato, P.; Chiummiento, L.; Rosini, C.
Una nuova classe di 3-amminoisotiazol S-ossidi chirali : sintesi, assegnazione della configurazione assoluta tramite calcoli teorici e analisi computazionale del meccanismo di ossidazione
No full textA solution of 1a,b in CH2Cl2 with an equimolecular amount of (+) or (-)-2b was irradiated at 400W, 80°C. Sulfoxides (R)- and (S)-3a,b were produced in 70-80% overall yield and 44-55% ee together with little amount of sulfone (8-10%) after 1h. (-)-2a gave much slower reactions.
In order to determine the absolute configuration (AC) of the new 3-aminosubstituted isothiazole S-oxides, we simulated [2,3] the ECD spectrum of (+)-3-aminomethyl isothiazole S-oxide, (+)-3b in the range 380-200 nm, both in the gas phase and ethanol at the TDDFT/B3LYP/aug-cc-pVDZ level of calculation. To this end we used (S)-3b which exists almost as a single conformer at the DFT/B3LYP/6-31G* level of calculation.
In Figure are reported the experimental (black line) ECD spectrum of (+)-3b and predicted ECD spectra of (S)-3b, taking into account the first 30 excited states both in the gas phase and ethanol. In the gas phase (green line), even if the positions and intensities of predicted ECD bands do not perfectly match the experimental data, the experimental spectrum shows a sequence of negative, positive, negative Cotton effects which is reproduced in the theoretical spectrum, indicating the (+)/(S) correlation. Including the ethanol effect (red line), significantly improves the agreement between calculated and experimental data, strongly supporting the (+)/(S) configurational correlation.We can conclude that (+)-3b, which is the major enantiomer formed when using (+)-2b as the oxidant, possesses (S) AC
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