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54. A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Author

Melli, Alessio, primary, Potenti, Simone, additional, Melosso, Mattia, additional, Herbers, Sven, additional, Spada, Lorenzo, additional, Gualandi, Andrea, additional, Lengsfeld, Kevin G., additional, Dore, Luca, additional, Buschmann, Philipp, additional, Cozzi, Pier Giorgio, additional, Grabow, Jens‐Uwe, additional, Barone, Vincenzo, additional, and Puzzarini, Cristina, additional

Published
2020
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62. Photoredox radical conjugate addition of dithiane-2-carboxylate promoted by an iridium(iii) phenyl-tetrazole complex: a formal radical methylation of Michael acceptors† †Electronic supplementary information (ESI) available: Experimental procedures, product characterizations, NMR spectra, compound preparation procedures, screening tests, and photophysical and electrochemical data. See DOI: 10.1039/c6sc03374a Click here for additional data file

Author

Gualandi, Andrea, Matteucci, Elia, Monti, Filippo, Baschieri, Andrea, Armaroli, Nicola, Sambri, Letizia, and Cozzi, Pier Giorgio

Subjects
Chemistry
Abstract

An iridium(iii) phenyl-tetrazole complex is a versatile catalyst for a new photocatalytic Michael reaction., A readily accessible iridium(iii) phenyl-tetrazole complex ([Ir(ptrz)2(tBu-bpy)]+, 2; Hptrz = 2-methyl-5-phenyl-tetrazole; tBu-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine) is shown to be a versatile catalyst for a new photocatalytic Michael reaction. Under light irradiation in the presence of 2, a dithiane 2-carboxylic acid, obtained by simple hydrolysis of a commercially available ethyl ester, generates a 1,3-dithiane radical capable of performing addition to a variety of Michael acceptors (e.g., unsaturated ketones, esters, amides and malonates). This broad scope reaction with high yields is a formal photo-redox addition of the elusive methyl radical and the adducts obtained can be starting materials for a variety of functionalized products. The excited-state oxidation potential of catalyst 2 allows selective formation of radicals only from α-heterosubstituted carboxylates. Chemical modification of this metal complex can tune the electrochemical properties, opening a route to new highly selective catalytic photo-oxidation reactions.

Published
2016

67. Allylation of aldehydes by dual photoredox and nickel catalysis

Author

Gualandi, Andrea, primary, Rodeghiero, Giacomo, additional, Faraone, Adriana, additional, Patuzzo, Filippo, additional, Marchini, Marianna, additional, Calogero, Francesco, additional, Perciaccante, Rossana, additional, Jansen, Thomas Paul, additional, Ceroni, Paola, additional, and Cozzi, Pier Giorgio, additional

Published
2019
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69. Octa-1,7-diene-4,5-diamine Derivatives: Useful Intermediates for the Stereoselective Synthesis of Nitrogen Heterocycles and Ligands for Asymmetric Catalysis

Author

GUALANDI, ANDREA, GRILLI, STEFANO, SAVOIA, DIEGO, Gualandi, Andrea, Grilli, Stefano, and Savoia, Diego

Subjects
Cyclohex-4-ene-1,2-diamine, Nitrogen heterocycle, Carbene ligand, Organic Chemistry, Asymmetric catalysi, Enantioselectivity, Physical and Theoretical Chemistry
Abstract

The octa-1,7-diene-4,5-diamine skeleton is usually prepared by the addition of allylic organometallic reagents to glyoxal diimines. The relative and absolute configurations of the C4 and C5 stereocenters are dependent on the nature of the (chiral) nitrogen substituents. These compounds are useful intermediates for the construction of NHC carbene complexes and nitrogen heterocycles, such as 2,2′-bipyrrolidines, 2,5-diazabicyclo[2.2.1]heptanes, amino- and hydroxy-substituted 7-azanorbornane, and diamino-substituted cyclohexanols and cyclohexanediols.

Published
2016

70. Catalytic Photoredox Allylation of Aldehydes Promoted by a Cobalt Complex.

Author

Gualandi, Andrea, Rodeghiero, Giacomo, Perciaccante, Rossana, Jansen, Thomas Paul, Moreno‐Cabrerizo, Cristina, Foucher, Charles, Marchini, Marianna, Ceroni, Paola, and Cozzi, Pier Giorgio

Subjects
*ALLYLATION, *COBALT, *ALLYL compounds, *ALDEHYDES, *ORGANIC chemistry
Abstract

The preparation of homoallylic alcohols by addition of organometallic allyl compounds to carbonyls is an important strategy in organic chemistry. Allylating organometallic cobalt species can be generated employing stoichiometric quantities of Zn acting as reductant. To avoid the employment of stoichiometric amount of Zn, we have developed an allylation reaction of aromatic and aliphatic aldehydes promoted by photoredox catalysis in the presence of a cobalt complex, and we present herein a full account of our research. In the presence of the abundant CoBr2 (10 mol %), 4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl (dtbbpy, 10 mol %), allyl acetate (3 equiv.), [Ir(dtbbpy)(ppy)2]PF6 (ppy=2‐phenylpyridine, 2 mol %), and N,N‐diisopropylethylamine (4 equiv.), an allylation of aldehydes is taking place, in moderate to good yields. Substrates scope, limitations, and photophysical investigations of this new process are reported. [ABSTRACT FROM AUTHOR]

Published
2021
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71. Tailored Coumarin Dyes for Photoredox Catalysis: Calculation, Synthesis, and Electronic Properties.

Author

Gualandi, Andrea, Nenov, Artur, Marchini, Marianna, Rodeghiero, Giacomo, Conti, Irene, Paltanin, Ettore, Balletti, Matteo, Ceroni, Paola, Garavelli, Marco, and Cozzi, Pier Giorgio

Subjects
*CATALYSIS, *REDUCTION potential, *TIME-dependent density functional theory, *COUMARINS, *TRANSITION metal catalysts, *COUMARIN derivatives, *ABSORPTION spectra, *PHOTOCATALYSTS
Abstract

High level time‐dependent density functional theory (TD‐DFT) computational modeling of coumarin dyes has been exploited for guiding the design of effective photocatalysts (PCs). A library of coumarins were investigated from the theoretical point of view and photophysical/electrochemical properties (absorption and emission spectra, E00, oxidation and reduction potentials) were evaluated. Comparison with literature values reported for a few candidates has been used for assessing the level of theory. On the basis of the results obtained, new strongly reducing PCs [Eox(PC.+/PC*)=−2.1 – −2.0 V vs SCE] were discovered. Through the computational study of structure‐properties relationships, a number of coumarins derivatives have been synthesized and evaluated in the pinacol coupling of aldehydes as the model reaction. The new organic photoredox catalysts show experimental photophysical and electrochemical data in accordance with the ones predicted by calculation, with excited state reduction potentials surpassing those of highly reducing transition metal‐based PCs. A careful investigation of their behavior as PC has revealed crucial issues that need to be taken into consideration in the general photoredox catalysis, shedding light on the use of these PC in the pinacol, as well as, in other photoredox reactions. [ABSTRACT FROM AUTHOR]

Published
2021
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72. Boron Compounds as Additives for the Cationic Polymerization Using Coumarin Derivatives in Epoxy Silicones.

Author

Abdallah, Mira, Hijazi, Akram, Cozzi, Pier Giorgio, Gualandi, Andrea, Dumur, Frederic, and Lalevée, Jacques

Subjects
ADDITION polymerization, FOOD additives, BORON compounds, COUMARIN derivatives, BORANE derivatives, SILICONES
Abstract

This work aims at using two borane derivatives, namely Borane A: B(C6F5)3 and Borate B: C32H12BF24Na as additives for the cationic polymerization of epoxy silicones under visible light, in the presence of coumarins as photosensitizers and 4‐isopropyl‐4′‐methyldiphenyl iodonium tetrakis(pentafluorophenyl)borate (SC939). The effect of boron compounds on the absorption and the emission spectra of a coumarin is particularly outlined. These two boron compounds can improve both the polymerization rate and the final monomer conversion. Moreover, the effect of adding water on the reactivity of the system is studied. It should be noted that the studied boron additives are able to enhance in an interesting way the polymerization rate when light irradiation is switched off through a dark polymerization (DP) mechanism. This latter behavior is highly desired for practical applications. Finally, the very high photoreactivity of boron compounds is employed for the development of new cationic 3D printing resins upon exposure to a light emitting diode (LED) projector at 405 nm, as well as for direct laser write experiments, by means of a laser diode at 405 nm. The 3D polymerization occurs through a cationic process which can be quite useful in order to reduce the shrinkage usually observed in radical polymerization. [ABSTRACT FROM AUTHOR]

Published
2021
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73. Shining Light on TiIV Complexes: Exceptional Tools for Metallaphotoredox Catalysis.

Author

Fermi, Andrea, Gualandi, Andrea, Bergamini, Giacomo, and Cozzi, Pier Giorgio

Subjects
*CATALYSIS, *OXIDATION-reduction reaction, *EXCITED states, *SUSTAINABLE development, *ORGANOMETALLIC compounds, *PHASE-transfer catalysis
Abstract

Titanium is one of the most abundant and environmentally innocuous metals. Ti‐based organometallic compounds have long been used as versatile homogeneous catalysts in synthetic chemistry and still remain highly attractive for the development of sustainable transformations. With the emerging role of photoredox catalysis, the selectivity of the radical initiation in electron transfer‐mediated reactions has been shown to be fundamental in terms of synthesis efficiency. Recent examples have displayed the effectiveness of inorganic and organic chromophores at the excited state in triggering the redox chemistry of TiIV/III complexes. In this minireview, we will illustrate the underlying principles and practicability of these – still uncommon – metallaphotoredox catalytic reactions. [ABSTRACT FROM AUTHOR]

Published
2020
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75. Aluminum(III) Salen Complexes as Active Photoredox Catalysts.

Author

Gualandi, Andrea, Marchini, Marianna, Mengozzi, Luca, Kidanu, Hagos Tesfay, Franc, Antoine, Ceroni, Paola, and Cozzi, Pier Giorgio

Subjects
*ASYMMETRIC synthesis, *CATALYSTS, *CHARGE exchange, *ALUMINUM, *ALUMINUM cans
Abstract

Metallosalen are privileged complexes that have found important applications in catalysis. In addition, their luminescent properties have also been studied and used for sensing and biological applications. Salen metal complexes can be efficient photosensitizers, but they can also participate to electron transfer processes. Indeed, we have found that commercially available [Al(Salen)Cl] is an efficient photoredox catalyst for the synergistic stereoselective reaction of alkyl aldehydes with different bromo ketones and malonates to give the corresponding enantioenriched α‐alkylated derivatives. The reaction was performed in the presence of a MacMillan catalyst. [Al(Salen)Cl] is able to replace ruthenium complexes, showing that also aluminum complexes can be used in promoting photoredox catalytic reactions. [ABSTRACT FROM AUTHOR]

Published
2020
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78. Self-Assembled Two-Dimensional Supramolecular Networks Characterized by Scanning Tunneling Microscopy and Spectroscopy in Air and under Vacuum

Author

Naydenov, Borislav, primary, Torsney, Samuel, additional, Bonilla, Alejandro Santana, additional, El Garah, Mohamed, additional, Ciesielski, Artur, additional, Gualandi, Andrea, additional, Mengozzi, Luca, additional, Cozzi, Pier Giorgio, additional, Gutierrez, Rafael, additional, Samorì, Paolo, additional, Cuniberti, Gianaurelio, additional, and Boland, John J., additional

Published
2018
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80. Application of coumarin dyes for organic photoredox catalysis

Author

Gualandi, Andrea, primary, Rodeghiero, Giacomo, additional, Della Rocca, Emanuele, additional, Bertoni, Francesco, additional, Marchini, Marianna, additional, Perciaccante, Rossana, additional, Jansen, Thomas Paul, additional, Ceroni, Paola, additional, and Cozzi, Pier Giorgio, additional

Published
2018
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83. The Facile and Direct Formylation of Organoboron Aromatic Compounds with Benzodithiolylium Tetrafluoroborate

Author

Diego Petruzziello, Hamza Jaffar, Veronica Lopez Carrillo, GUALANDI, ANDREA, COZZI, PIER GIORGIO, Diego Petruzziello, Andrea Gualandi, Hamza Jaffar, Veronica Lopez-Carrillo, and Pier Giorgio Cozzi

Subjects
SYNTHETIC METHODS, c-c coupling, SULFUR HETEROCYCLES, BORON, SUBSTITUENT EFFECTS
Abstract

Organoboron compounds can be used to effect a direct formylation in the absence of transition metals. We report that the direct reaction between boronic derivatives and benzodithiolylium tetrafluoroborate, a commercially available carbenium ionic compound, is possible and provides access to many interesting compounds without the use of transition metals. The direct reaction of the carbenium ion with boronic derivatives results in the formation of substituted arylcarbenium ions, a number of which can be further utilized in materials chemistry or for the direct transformation into other compounds. In addition to the rich chameleonic chemical nature of the benzodithiol intermediate, such species can also undergo a metallation reaction and subsequent treatment with a wide range of electrophiles to access a variety of functional groups (aldehyde, ketone, acid, and alkyl groups).

Published
2013
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84. A Practical Organocatalytic Alkylation Reaction with Benzodithiolylium Tetrafluoroborate

Author

COZZI, PIER GIORGIO, BANDINI, MARCO, GUALANDI, ANDREA, MENGOZZI, LUCA, Carlos A M Afonso, Nuno R Candeias, Dulce Pereira Simão, Alexandre F Trindade, Jaime A S Coelho, Bin Tan, Robert Franzén, Pier Giorgio, Cozzi, Marco, Bandini, Andrea, Gualandi, and Luca, Mengozzi

Subjects
Aldehyde alkylation, chiral HPLC, column chromatography, enamine, liquid–liquid extraction, methyl, NMR, organocatalysis
Abstract

The experiment is a simple and practical organocatalytic procedure for the enantiose- lective alkylation of aldehydes using a commercially available and stable carbenium ion. The alkylated adduct 4, obtained in high enantiomeric excess, is then transformed into the corresponding enantioen- riched alcohol 5 by reduction of the benzodithiole group with Raney®-nickel.

Published
2016

87. Asymmetric synthesis of 8-aminoindolizidine from chiral 2-pyrroleimines

Author

Albano, Vincenzo Giulio, Gualandi, Andrea, Monari, Magda, and Savoia, Diego

Subjects
Aldehydes -- Chemical properties, Azides -- Chemical properties, Schiff bases -- Chemical properties, Biological sciences, Chemistry
Abstract

The organometallic allylation of 2-pyrroleimines derived from (S)-valinol and (S)-phenylglycinol ring-closing metathesis (RCM) reaction and pyrrole ring hydrogenation are used to synthesize the N-protected 8-aminoindolizidines. The auxiliary based method starting from 2-pyrrolealdehydes could also be applied to prepare all the possible stereoisomers of amino-substituted fused bicyclic compounds containing the pyrrolidine nucleus.

Published
2008

89. Asymmetric synthesis of 2-(2-pyridyl)aziridines from 2-pyridineimines bearing stereogenic N-alkyl substituents and regioselective opening of the aziridine ring

Author

Savoia, Diego, Alvaro, Giuseppe, Di Fabio, Romano, Gualandi, Andrea, and Fiorelli, Claudio

Subjects
Schiff bases -- Research, Ring-opening polymerization -- Analysis, Halides -- Structure, Halides -- Chemical properties, Nucleophiles -- Structure, Nucleophiles -- Chemical properties, Biological sciences, Chemistry
Abstract

An aziridination procedure for 2-pyridineimines derived from [beta]-amino alcohols and [alpha]-aminoacid esters and the reactivity of the aziridine ring toward external nucleophiles is described. The findings suggest that the chemical functionality present in the nitrogen substituent could be exploited to achieve regioselective and stereoselective ring opening reactions by halide ions and an unusual rearrangement to a substituted pyrroline.

Published
2006

90. Can the pi-facial selectivity of solvation be predicted by atomistic simulation?

Author

Beradi, Roberto, Cainelli, Gianfranco, Galletti, Paola, Giacomini, Daria, Gualandi, Andrea, Zannoni, Claudio, and Muccioli, Luca

Subjects
Alkanes -- Chemical properties, Molecular dynamics -- Usage, Aldehydes -- Chemical properties, Chemistry
Abstract

The facial solvation of (R)-2-phenyl-propionaldehyde in n-pentane and n-octane at a number of temperatures is studied using molecular dynamics simulations and is compared with experimental selectivity data for the nBuLi addition leading to syn and anti-(2R)-2-phenyl-3-heptanol, which give nonlinear eyring plots with the presence of inversion temperatures. It is found from simulations that the facial solvation changes with temperature and alkane.

Published
2005

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