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239 results on '"Pisano, Luisa"'

52. Green and convenient arene-catalized reductive lithiation of heterocyclic compounds

Author

Mamuye, Ashenafi Damtew, Azzena, Ugo Gavino, Pisano, Luisa, Carraro, Massimo, and Pittalis, Mario

Subjects
CHIM/06 Chimica organica
Abstract

In the last decades reductive lithiation established itself as a particularly powerful procedure for the generation of functionalized organometals. In addition, the enormous role of this reaction in the reductive ring opening and functionalization of heterocycles has been reported. Accordingly, critical experiments were performed for the generation of lithium radical anions of several PAHs and a diene in both solvents, under both CA and SA protocols. Almost all of the above mentioned hydrocarbons rapidly generate radical anions with different fascinating visible colors at 0 °C. Based on this, influence of different electron shuttles and their efficiency in the reductive lithiation of N-phenylaziridine, phthalan will be disclosed. Moreover, we will report an interesting example of chemoselectivity concerning to the reductive lithiation of 4-chlorobenzyl methyl ether in a green solvent.

Published
2013

53. Lithiation of 4-membered heterocycles as useful strategy for the preparation of new molecular scaffolds: addressing the regioselectivity in azetidines and thietanes

Author

Degennaro, Leonardo, Zenzola, Marina, Trinchera, Piera, Carroccia, Laura, Giovine, Arianna, Falcicchio, Aurelia, Pisano, Luisa, and Luisi, Renzo

Subjects
CHIM/06 Chimica organica
Abstract

Four-membered heterocycles (4-MH) with one or two heteroatoms are of great importance in medicinal chemistry and synthetic organic chemistry. This kind of scaffolds show peculiar structural features, related to the ring “puckering”, and biological properties. Our recent research efforts have been focused on the stereoselective synthesis and functionalization of some 4-MH such as azetidines, thietanes and oxazetidines.

Published
2013

58. ChemInform Abstract: Harnessing the ortho-Directing Ability of the Azetidine Ring for the Regioselective and Exhaustive Functionalization of Arenes.

Author

Zenzola, Marina, primary, Degennaro, Leonardo, additional, Trinchera, Piera, additional, Carroccia, Laura, additional, Giovine, Arianna, additional, Romanazzi, Giuseppe, additional, Mastrorilli, Piero, additional, Rizzi, Rosanna, additional, Pisano, Luisa, additional, and Luisi, Renzo, additional

Published
2015
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59. Riduzione regioselettiva del 3,4,5-trimetossibenzil metil etere: sintesi di resorcinoli 2,5-dialchilsostituiti

Author

Dettori, Giovanna, Azzena, Ugo Gavino, Pittalis, Mario, Pisano, Luisa, and Mascia, Ilaria

Subjects
CHIM/06 Chimica organica
Abstract

Vista l'esperienza maturata nel nostro laboratorio nella generazione di reattivi organometallici di tipo benzilico e aromatico attraverso reazioni di metallazione riduttiva di alchil benzil eteri, abbiamo ritenuto che il metil etere dell'alcool 3,4,5-trimetossibenzilico, fosse un substrato adatto alle nostre necessità sintetiche.

Published
2006

60. Metallazione riduttiva di 1,2-diarileteni: applicazioni sintetiche

Author

Pittalis, Mario, Azzena, Ugo Gavino, Dettori, Giovanna, Madeddu, Simona, and Pisano, Luisa

Subjects
CHIM/06 Chimica organica
Abstract

Proseguendo nella nostra ricerca di nuove ed efficienti procedure basate sull’utilizzo di metalli alcalini in sintesi organica, abbiamo studiato la reazione di metallazione riduttiva di una serie di 1,2-diariletileni, e le possibili applicazioni sintetiche dei derivati vicdiorganometallici così ottenuti.

Published
2006

61. Silica Gel Stabilized Na and Na/K Alloys: Highly Effective, Versatile and Environmentally Friendly Reducing Agents.

Author

Carraro, Massimo, Pisano, Luisa, and Azzena, Ugo

Subjects
*SILICA gel, *AMMONIA, *CARBON-carbon bonds, *ALLOYS, *CHEMICAL synthesis
Abstract

Na and Na/K alloys in the liquid phase can be absorbed into amorphous silica gel at loadings up to 40 wt%. Further heating of these so-called stage 0 materials at 150 or 400 °C furnishes stage I and stage II materials, respectively, as free-flowing powders that can be handled under much safer conditions than the corresponding starting materials. Stage I Na and Na2K possess valuable reducing properties and they have found a variety of low impact applications in organic synthesis, including, e.g., the reductive deprotection of several functional groups, the development of safer protocols to operate the Bouveault-Blanc and the Birch reductions, and a new and particularly efficient approach to the Grignard and Darzens reactions. 1 Introduction 2 Reductive Deprotection Procedures 3 Bouveault-Blanc Reduction of Esters 4 Ammonia-Free Birch Reductions 5 Synthesis of Alkyldiaryl- and Dialkylarylphosphines 6 C-C Bond Forming Reactions 7 Further Applications 8 Conclusion. [ABSTRACT FROM AUTHOR]

Published
2017
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62. Nuove prospettive nella sintesi degli acidi peptido nucleici

Author

Azzena, Ugo Gavino, Dettori, Giovanna, Lubinu, Maria Caterina, and Pisano, Luisa

Subjects
CHIM/06 Chimica organica
Abstract

Gli acidi peptido nucleici, comunemente chiamati PNA (Peptide Nucleic Acids), sono mimetici del DNA, in cui la sequenza delle nucleobasi (le stesse del DNA), è inserita in uno scheletro poliammidico achirale. Data la notevole importanza dei PNA, il nostro gruppo di ricerca ha studiato la messa a punto di un processo di sintesi dei singoli monomeri PNA, efficiente e riproducibile, privo, per quanto possibile, di purificazioni cromatografiche degli intermedi, che consenta di ottenere i monomeri su larga scala. Si è inoltre cercato di ottenere monomeri in cui fosse rispettata l’ortogonalità tra i vari gruppi protettori (Pg1, Pg2, Pg3) dello scheletro e delle nucleobasi.

Published
2004

65. Electron-transfer-induced reductive dealkoxylation of alkyl aryl ethers. III. Reductive cleavage of methoxy-substituted N,N-dimethylanilines (N,N-dimethylanisidines)

Author

Azzena, Ugo Gavino, Dessanti, Francesca, Melloni, Giovanni, and Pisano, Luisa

Subjects
CHIM/06 Chimica organica
Abstract

The reactivity of the three isomeric methoxy-substituted N,N-dimethylanilines (N,N-dimethylanisidines) and of N,N-dimethyl-2,6-dimethoxyaniline in the reduction with alkali metals in aprotic solvents was investigated. N,N-Dimethyl-p-methoxyaniline was found to be unreactive, while the other substrates underwent exclusive cleavage of carbon-oxygen bond(s), with the following order of reactivity: 2,6-dimethoxy > o-methoxy > m-methoxy > p-methoxy. Both the relative reactivity and the regioselectivity of cleavage (demethoxylation vs. demethylation) was found to parallel closely that of the corresponding di- and trimethoxysubstituted substrates. These results suggest that intermediates with different electron distribution or even different intermediates are involved in the reductive cleavage of aryl-oxygen and arylnitrogen bonds.

Published
2002

83. Cyclopentyl methyl ether–NH4X: a novel solvent/catalyst system for low impact acetalization reactions.

Author

Azzena, Ugo, Carraro, Massimo, Mamuye, Ashenafi Damtew, Murgia, Irene, Pisano, Luisa, and Zedde, Giuseppe

Subjects
METHYL ether, AMMONIUM, SOLVENTS, ACETAL resins, CHEMICAL reactions, AZEOTROPES, ACID catalysts
Abstract

Cyclopentyl methyl ether, a low impact ether forming a positive azeotrope with water, was successfully employed as a solvent in the synthesis of 1,3-dioxanes and 1,3-dioxolanes carried out under Dean-Stark conditions by the acetalization of aliphatic and aromatic aldehydes or ketones, employing ammonium salts as environmentally friendly acidic catalysts. [ABSTRACT FROM AUTHOR]

Published
2015
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93. Harnessing the ortho-Directing Ability of the Azetidine Ring for the Regioselective and Exhaustive Functionalization of Arenes.

Author

Zenzola, Marina, Degennaro, Leonardo, Trinchera, Piera, Carroccia, Laura, Giovine, Arianna, Romanazzi, Giuseppe, Mastrorilli, Piero, Rizzi, Rosanna, Pisano, Luisa, and Luisi, Renzo

Subjects
AROMATIC compounds, AZETIDINE, REGIOSELECTIVITY (Chemistry), ORGANOMETALLIC chemistry, LITHIATION, LITHIUM
Abstract

This work demonstrates how the directing ability of the azetidine ring could be useful for regioselective ortho- C-H functionalization of aryl compounds. Robust polar organometallic (lithiated) intermediates are involved in this synthetic strategy. The reagent n-hexyllithium emerged as a safer, yet still effective, basic reagent for the hydrogen/lithium permutation relative to the widely used reagent nBuLi. Two different reaction protocols were discovered for regioselective lithiation at the ortho positions adjacent to the azetidine ring, which served as a toolbox when other competing directing groups were installed on the aromatic ring. The coordinating ability of the azetidine nitrogen atom, as well as the involvement of dynamic phenomena related to the preferential conformations of 2-arylazetidine derivatives, were recognized to be responsible for the observed reactivity and regioselectivity. A site-selective functionalization of the aromatic ring was achieved for aryl azetidines with either coordinatively competent groups (e.g. methoxy) or inductively electron-withdrawing substituents (e.g. chlorine and fluorine). By fine-tuning the reaction conditions, regioselective introduction of several substituents on the aromatic ring could be realized. Several substitution patterns were accomplished, which included 1,2,3-trisubstitution, 1,2,3,4-tetrasubstitution, and 1,2,3,4,5-pentasubstitution, up to the exhaustive substitution of the aromatic ring. [ABSTRACT FROM AUTHOR]

Published
2014
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99. VIVO Versus VIV Complex Formation by Tridentate (O, Narom, O) Ligands: Prediction of Geometry, EPR 51V Hyperfine Coupling Constants, and UV-Vis Spectra.

Author

Pisano, Luisa, Várnagy, Katalin, Timari, Sarolta, Hegetschweiler, Kaspar, Micera, Giovanni, and Garribba, Eugenio

Subjects
*VANADIUM compounds, *LIGANDS (Chemistry), *CRYSTAL structure, *PYRIDINE, *INFRARED spectroscopy, *METAL complexes, *COUPLING constants, *ULTRAVIOLET spectroscopy
Abstract

Systems formed using the VIVO2+ ion with tridentate ligands containing a (O, Narom, O) donor set were described. Examined ligands were 3,5-bis(2-hydroxyphenyl)-l-phenyl-lH-l,2,4-triazole (H2hyphPh), 4-[3,5-bis(2-hydroxyphenyl)-lH-l,2,4-triazol-l-yl]benzoic acid (H3hyphC), 4-[3,5-bis(2-hydroxyphenyl)-lH-l,2,4-triazol-l-yl]benzenesulfonic acid (H3hyphS), and 2,6-bis(2-hydroxyphenyl)pyridine (Hsub>2bhpp), with H3hyphc being an orally active iron chelator that is commercially available under the name Exjade (Novartis) for treatment of chronic iron overload arising from blood transfusions. The systems were studied using EPR, UV-Vis, and IR spectroscopies, pH potentiometry, and DFT methods. The ligands bind vanadium with the two terminal deprotonated phenol groups and the central aromatic nitrogen to give six-membered chelate rings. In aqueous solution the main species were the mono- and bis-chelated VIVO complexes, whereas in the solid state neutral non-oxido VIV compounds were formed. [V(hyphPh)2] and [V(bhpp)2] are hexacoordinated, with a geometry dose to the octahedral and a meridional arrangement of the ligands. DFT calculations allow distinguishing VIVO and VIV spedes and predicting their structure, the SIV hyperfine coupling constant tensor A1 and the electronic absorption spectra. Finally, EPR spectra of several non-oxido VIV speaes were compared using relevant geometrical parameters to demonstrate that in the case of tridentate ligands the 5IV hyperfine coupling constant is related to the geometric isomerism (meridional or fecial) rather than the twist angle f1 which measures the distortion of the hexacoordinated structure toward a trigonal prism. [ABSTRACT FROM AUTHOR]

Published
2013
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