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6. Asymmetric Reactions Enabled by Cooperative Enantioselective Amino‑ and Lewis Acid Catalysis

Author

Cozzi, Pier Giorgio, Gualandi, Andrea, Potenti, Simone, Calogero, Francesco, Rodeghiero, Giacomo, Olivucci, Massimo, Editor-in-Chief, Wong, Wai-Yeung, Editor-in-Chief, Bayley, Hagan, Series Editor, Hughes, Greg, Series Editor, Hunter, Christopher A., Series Editor, Hwang, Seong-Ju, Series Editor, Ishihara, Kazuaki, Series Editor, Kirchner, Barbara, Series Editor, Krische, Michael J., Series Editor, Larsen, Delmar, Series Editor, Lehn, Jean-Marie, Series Editor, Luque, Rafael, Series Editor, Siegel, Jay S., Series Editor, Thiem, Joachim, Series Editor, Venturi, Margherita, Series Editor, Wong, Chi-Huey, Series Editor, Wong, Henry N.C., Series Editor, Yam, Vivian Wing-Wah, Series Editor, Yan, Chunhua, Series Editor, You, Shu-Li, Series Editor, Arndtsen, Bruce A., editor, and Gong, Liu-Zhu, editor

Published
2020
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11. Reactivities of Photoredox Generated Nickel‐Nucleophilic Reactive Organometallic Species.

Author

Gualandi, Andrea, Calogero, Francesco, Corbisiero, Dario, Pinosa, Emanuele, and Cozzi, Pier Giorgio

Subjects
COUPLING reactions (Chemistry), NUCLEOPHILES, OXIDATIVE addition, OXIDATION states, ELECTROPHILES, CATALYSIS
Abstract

Dual photoredox catalysis has revolutionized the field of cross‐coupling reactions, enabling the discovery of numerous highly efficient reactions. This breakthrough is attributed to the exceptional combination of nickel catalysis with photoredox catalysis. Nickel exhibits both oxidative addition and reductive elimination processes, and a wide range of oxidation states (ranging from I to IV) accessible within a single catalytic cycle. Furthermore, nickel complexes are capable of catalyzing various processes through radical mechanisms. The latest feature has proven to be incredibly potent in facilitating the formation of new C−C and C−X bonds (X=H, O, S, N). The powerful combination of photoredox and nickel catalysis reveals an expansive domain of unexplored possibilities. It offers unparalleled opportunities for improving reactions and exploring innovative pathways. Under photoredox conditions, it is possible to form nucleophilic reactive organometallic intermediates, useful in reaction with electrophiles. We have devoted a research program towards the rediscovery and use of organometallic reagents, introduced by Corey, Hegedus, and Semmelack many years ago. The results unveiled the extraordinary capabilities of photoredox catalysis, enabling the creation and efficient utilization of potent nucleophilic organometallic reagents under mild conditions, free from the need for strong bases or stoichiometric metal reductants. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Dual Photoredox Catalysis with Vanadium Complexes in Low Oxidation State: Diastereoselective Pinacol Coupling.

Author

Pinosa, Emanuele, Gelato, Yuri, Calogero, Francesco, Moscogiuri, Matteo Maria, Gualandi, Andrea, Fermi, Andrea, Ceroni, Paola, and Cozzi, Pier Giorgio

Subjects
OXIDATION states, VANADIUM, CATALYSIS, VISIBLE spectra, AROMATIC aldehydes
Abstract

Dual photoredox catalysis is modifying the approach to sustainable metal catalysis based on metals in low oxidation state, as the use of stoichiometric metal as reductants are avoided. In this study, we showcase the potential use of vanadium in a dual photoredox process, allowing us to effectively control the formation of V(II) and its corresponding chemical reactions. A diastereoselective pinacol coupling with aromatic aldehydes is described. The process shows broad scope, and interestingly, unprotected salicylic aldehydes are compatible with the reaction protocol. Additionally, among all the ligands investigated we found that inexpensive bipyridines control the diastereoselection of the reaction favoring the d,l chiral compound (dr>20:1 for most of the aldehydes investigated). To promote the reaction and avoid an unproductive and not stereoselective radical coupling of the generated ketyl radical, the use of [DMQA]+, a stable organic dye, was found crucial. Furthermore, this dye possesses the remarkable capability of efficiently capturing light in the red segment of the visible spectrum, effectively raising efficiency of the protocol. The utilization of red light carries notable advantages in terms of penetration and safety, making it particularly significant. Moreover, careful photophysical investigations were able to give indications about the mechanism of the reaction. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Circularly Polarized Luminescence from New Heteroleptic Eu(III) and Tb(III) Complexes

Author

Ruggieri, Silvia, primary, Mizzoni, Silvia, additional, Nardon, Chiara, additional, Cavalli, Enrico, additional, Sissa, Cristina, additional, Anselmi, Michele, additional, Cozzi, Pier Giorgio, additional, Gualandi, Andrea, additional, Sanadar, Martina, additional, Melchior, Andrea, additional, Zinna, Francesco, additional, Willis, Oliver G., additional, Di Bari, Lorenzo, additional, and Piccinelli, Fabio, additional

Published
2023
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19. A Dual Photoredox‐ and Cp2TiCl2‐Catalyzed Approach for the Direct Access to α‐Vinyl‐β‐hydroxy Esters.

Author

Pinosa, Emanuele, Gualandi, Andrea, Fermi, Andrea, Ceroni, Paola, Cozzi, Pier Giorgio, and Calogero, Francesco

Subjects
*BARBIER reactions, *ESTERS, *AROMATIC aldehydes, *TRANSITION metals, *VISIBLE spectra
Abstract

For the first time, a dual photoredox‐ and titanocene‐catalyzed methodology for the regioselective access to α‐vinyl‐β‐hydroxy esters towards aldehyde allylation with 4‐bromobut‐2‐enoate is reported. The protocol is based on the Barbier‐type properties of the inexpensive and available Cp2TiCl2 in catalytic amount (5 mol%). The developed mild reaction conditions gave access to a library of differently functionalized α‐vinyl‐β‐hydroxy esters in moderate diastereoselectivity, employing the commercially available ethyl 4‐bromobut‐2‐enoate and both aromatic and aliphatic aldehydes. The reaction was realized under visible light irradiation, in the presence of an organophotocatalyst (3DPAFIPN, 2 mol%) combined with Hantzsch's ester as the sacrificial reductant. In contrast to other Barbier‐type reactions employing ethyl 4‐bromobut‐2‐enoate, the photoredox system ensures a better regioselectivity. Moreover, the use of preformed organometallic nucleophilic species (e. g. dienolborinates), and the need of metal reductants or stoichiometric amount of transition metals in low oxidation state for Barbier‐type reactions, is avoided. To support the experimental evidence, a detailed photophysical study shed light on the mechanism of the reaction. [ABSTRACT FROM AUTHOR]

Published
2023
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40. Asymmetric route to pyridines bearing a highly functionalized 2-alkyl substituent by aziridine ring-opening reactions

Author

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

Subjects
Pyridine -- Chemical properties, Ring-opening polymerization -- Research, Biological sciences, Chemistry
Abstract

The reactivity of the pyridyl-substituted aziridine with different N-, S-, and O-nucleophiles is examined in order to understand the optimal conditions allowing for a selective ring-opening. It is shown that complete or prevalent regioelectivity can be obtained by using cerium trichloride heptahydrate as a catalyst and the N-substituent can be removed by an oxidative protocol.

Published
2007

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

Author

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

Abstract

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined. © 2020 The Authors. Published by Wiley-VCH GmbH

Published
2020

47. Metallaphotoredox catalysis with organic dyes

Author

Gualandi, Andrea, primary, Anselmi, Michele, additional, Calogero, Francesco, additional, Potenti, Simone, additional, Bassan, Elena, additional, Ceroni, Paola, additional, and Cozzi, Pier Giorgio, additional

Published
2021
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