2022, Articolo in rivista, ENG
Ziccarelli I.; Mancuso R.; Giacalone F.; Calabrese C.; La Parola V.; De Salvo A.; Della Ca' N.; Gruttadauria M.; Gabriele B.
We report the first example of successful heterogenization of the classical PdI carbonylation catalyst, achieved in two simple steps from ionic liquid-functionalized multi-walled carbon nanotubes (MWCNTs). The newly developed materials (PdI@MWCNT-imi-X, X = Br, I) present the PdI anion supported on an imidazolium network (imi) grown on MWCNTs and have been fully characterized. The activity of PdI@MWCNT-imi-X has been successfully tested in a paradigmatic carbonylation reaction, the oxidative monoaminocarbonylation of 1-alkynes with amines to give high value added 2-ynamides (obtained in good yields, 50-84%, starting from various substrates). The heterogeneous catalyst could be easily recycled and showed a good efficiency even after the fourth recycle, when deactivation began to occur owing to the formation of inactive Pd(0) species, as confirmed by XPS analysis. Hot and cold filtration tests were compatible with an essentially heterogeneous catalytic process, and limited metal contamination in the final organic compounds occurred, as assessed by ICP-MS analysis of representative carbonylation products.
2019, Articolo in rivista, ENG
Antenucci, Achille; Flamini, Piergiorgio; Fornaiolo, Marco Valerio; Di Silvio, Sergio; Mazzetti, Sara; Mencarelli, Paolo; Salvio, Riccardo; Bassetti, Mauro
Alkylarylalkynes are converted with full regioselectivity into the corresponding arylketones by formal hydration of the triple bond under weak acidic conditions, at times and temperatures (<= 95 degrees C) comparable to those used for terminal alkynes. The process catalyzed by Fe-2(SO4)(3)nH(2)O in glacial acetic acid exhibits good functional group compatibility, including that with bulky triple bond substituents, and can be extended to the one-pot transformation of aryltrimethylsilylacetylenes into acetyl derivatives via a desilylation-hydration sequence. The overall reactivity pattern along with proton affinity data indicate that the triple bond is activated by proton transfer rather than by pi-interaction with the metal ion. This mechanistic feature, at variance with that of noble metal catalysts, accounts for the total regioselectivity and the insensitivity to steric hindrance exhibited by the Fe-2(SO4)(3)nH(2)O/AcOH catalytic system.
2017, Articolo in rivista, ENG
Monfredini A.; Santacroce V.; Marchio L.; Maggi R.; Bigi F.; Maestri G.; Malacria M.
Suitably delocalized metal-metal bonds can stabilize a particular class of discrete trinuclear complexes that are the transition-metal counterparts of carbon-based aromatics. This chemical stability has pivoted the development of an advantageous catalytic method for the semireduction of internal alkynes under transfer hydrogenation condition. The reaction does not require any additional solvent and a simple workup delivers pure products. This combines with broad functional group tolerance, complete cis-selectivity and catalytic charges down to 100 ppm on multigram scale.
2016, Articolo in rivista, ENG
Baglieri A.; Meschisi L.; De Sarlo F.; Machetti F.
Isoxazoles, mainly 3,5-disubstituted, are prepared by catalytic condensation of primary nitro compounds with terminal acetylenes by using a copper/base catalytic system. The additional catalytic effect of the copper(II) salts is evidenced by comparing the kinetic profiles. Selectivity dependence on reaction conditions is considered for phenylacetylene in the following competitive processes: oxidative coupling of terminal alkynes to conjugated diynes catalyzed by CuII and base in the presence of air; production of furazans beside condensation with benzoylnitromethane to 3-benzoylisoxazoles, as a result of the reaction of the dipolarophile with 3,4-dibenzoylfuroxan; addition of electron-poor alkynes (e.g., methyl propiolate) with themselves and with the nitro compound. Thus, oxidative coupling is negligible in reactions with "active" nitro compounds, whereas with nitroalkanes both products are observed: only trace amounts of isoxazoles are detected without copper. Similarly, in the presence of copper, 3-benzoyl-5-phenylisoxazole is predominant over the furazan. Furthermore, condensations of electron-poor alkynes give complex reaction mixtures in the presence of base alone, but cycloadducts are conveniently prepared with copper. The results indicate the practical and general utility of this catalytic method for synthetic practice.
2014, Articolo in rivista, ENG
Caporale, Andrea; Tartaggia, Stefano; Castellin, Andrea; De Lucchi, Ottorino
Two efficient protocols for the palladium-catalyzed synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides in the absence of copper were developed. A simple catalytic system consisting of Pd(OAc)2 and P(p-tol)3 using DBU as the base and THF as the solvent was found to be highly effective for the coupling reaction of 2-methyl-3-butyn-2-ol (4) with a wide range of aryl bromides in good to excellent yields. Analogously, the synthesis of aryl-2-methyl-3-butyn-2-ols was performed also through the decarboxylative coupling reaction of 4-hydroxy-4-methyl-2-pentynoic acid with aryl bromides, using a catalyst containing Pd(OAc)2 in combination with SPhos or XPhos in the presence of tetra-n-butylammonium fluoride (TBAF) as the base and THF as the solvent. Therefore, new efficient approaches to the synthesis of terminal acetylenes from widely available aryl bromides rather than expensive iodides and using 4 or propiolic acid rather than TMS-acetylene as inexpensive alkyne sources are described. © 2014 Caporale et al; licensee Beilstein-Institut. License and terms: See end of document.
2014, Articolo in rivista, ENG
M. Bassetti, S. Ciceri, F.Lancia, C. Pasquini
The hydration of aromatic terminal alkynes performed in acetic acid in the presence of catalytic hydrate ironIII sulfate, Fe2(SO4)3·nH2O (4-9 mol %), yields the derived aryl methyl ketones with good to excellent yields. Under comparable conditions (18 mol %, 95 °C, 24 h), bifunctional substrates were transformed into the monoacetyl or the diacetyl derivatives, depending on the structure of the aromatic diyne. The reaction is compatible with aryl substituents of different nature and ring positions, including hydroxyl, carbonyl groups, and cumulated hydrocarbons. The soft character of the non nucleophilic sulfate anion allows for activation of the triple bond toward carbonoxygen bond formation in the Brønsted acidic medium. The proposed protocol is based on readily available and non toxic materials, in the absence of chlorine atoms in either the solvent or the metal catalyst.
2013, Articolo in rivista, ENG
Zuccaccia, Daniele; Belpassi, Leonardo; Macchioni, Alceo; Tarantelli, Francesco
We critically review recent experimental and theoretical investigations into some key aspects of the chemistry of gold(I) complexes of the type [L-Au-S]X-+(-) (L = NHC carbenes and phosphanes, S = alkenes and alkynes, and X- = weakly coordinating counterion). These systems are important intermediates formed during gold-catalyzed nucleophilic additions to an unsaturated substrate, and their specific activity is largely governed by two fundamental factors: the nature of the gold-substrate bond and the role of the ion-pair structure in solution. Both are crucially influenced by the nature and properties of the auxiliary ligand L, and on this interplay we focus our discussion. The relative anion-cation orientation, investigated by NOE NMR spectroscopy and DFT calculations, shows that the exact position of the counterion is determined by the natures of the ancillary ligand and substrate: the counterion is located near the substrate in the phosphane complexes, while for the NHC complexes the preferred position of the counterion is near the ligand. This tunable interionic structure opens the way to greater control over the properties and activity of these catalysts. The bond between Au-I and the unsaturated substrate is investigated using an original and powerful theoretical method of analysis. Our approach permits a rigorous definition and assessment of the charge-displacement (CD) components at the heart of the Dewar-Chatt-Duncanson model: substrate-to-metal (sigma donation) and metal-to-substrate (back-donation) and how these change with different ligands. The results consistently reveal that back-donation is a large and crucially important component of the Au-I-substrate bond in all systems: back-donation penetrates the external side of coordinated alkynes, where nucleophile attack is directed, thus partially mitigating the electron depletion caused by sigma donation.
2013, Articolo in rivista, ENG
D'Auria, M.a , Guarnaccio, A.ab, Racioppi, R.a, Santagata, A.b, Teghil, R.a
The synthesis of a new fullerene-dithienylbenzo[c]thiophene (DTBT)-fullerene triad is reported. The synthetic approach involves the synthesis of a DTBT unit, a Sonogashira reaction to introduce two acetylenic groups, and the coupling with fullerene. The product showed an absorption at ? = 485 nm and a fluorescence band at ? = 575 nm.
2011, Articolo in rivista, ENG
Hassan Omar, Omar; Babudri, Francesco; Farinola, Gianluca M.; Naso, Francesco; Operamolla, Alessandra
A novel class of tetrathiolated aryleneethynylene oligomers was obtained by the Cassar-Heck-Sonogashira coupling between S,S'-(5-ethynyl-1,3-phenylene) bis(methylene) diethanethioate (1) and aryl diiodides or dibromides. Although standard coupling conditions are effective in the case of iodo derivatives, the addition of free triphenylphosphane to the reaction mixture was required to overcome the slower reaction rate of dibromoarenes. Oligomers with an extended conjugated system could be obtained starting from a higher homologue of 1 by applying the same synthetic approach. These oligomers represent interesting molecular wires, potentially able to self-assemble on various substrates, including gold and other noble metals in the form of thin films or nanoparticles. The chelating arrangement of the thiol functionalities should ensure stable anchoring and would also represent an interesting novel feature in the study of single molecule conduction with respect to traditional monodentate systems.
2010, Articolo in rivista, ENG
Chandanshive, Jay Zumbar; Bonini, Bianca Flavia; Gentili, Denis; Fochi, Mariafrancesca; Bernardi, Luca; Franchini, Mauro Comes
1,3-Dipolar cycloadditions of C-carboxymethyl-N-arylnitrile imines with substituted acetylenes bearing thiol or sulfone groups were studied. The sulfur controls the regiochemistry of the reaction, and this protocol was applied to the synthesis of ring-fused thieno[2,3-c]pyrazoles.
2008, Articolo in rivista, ENG
Chelucci G.; Baldino S.; Pinna G.A.; Sechi B.
A study on the synthesis of (Z)-1,2-bis(2-bromopyridin-3-yl)ethenes, key intermediates in the preparation of 1,10-phenanthrolines, based on selective Sonogashira and Suzuki-Miyaura cross-coupling reactions has been carried out. © 2008 Elsevier Ltd. All rights reserved.
1998, Articolo in rivista, ENG
Reginato, Gianna; Mordini, Alessandro; Capperucci, Antonella; Degl'Innocenti, Alessandro; Manganiello, Sonia
A new class of differently protected chiral ?-amino acetylenic esters have been synthesized using natural occurring amino acids as chiral source. Enantiomerically enriched propargylamines or vinyldibromides have been treated with BuLi at low temperature affording, after carboxylation, enantiomerically enriched derivatives of alkynologous amino esters