- Rhodium-catalyzed intermolecular silylcarbamoylation of acetylenic bonds
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α,β-Unsaturated amides are readily formed by silylcarbamoylation of an acetylenic bond which is accomplished intermolecularly by a one-pot reaction of four components, an alkyne, a hydrosilane, an amine, and CO in the presence of a catalytic amount of Rh
- Matsuda, Isamu,Takeuchi, Kiyoshi,Itoh, Kenji
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- Cationic complexes of dirhodium(II) with 1,8-naphthyridine: Catalysis of reactions involving silanes
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The synthesis of cationic dirhodium(II) complexes by partial or total substitution of the acetate groups of [Rh2(OAc)4] with different homoleptic neutral bidentate ligands has been attempted. The ligand 1,8-naphthyridine gave the bes
- Basato, Marino,Biffis, Andrea,Martinati, Gianluca,Tubaro, Cristina,Graiff, Claudia,Tiripicchio, Antonio,Aronica, Laura A.,Caporusso, Anna M.
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- Silylformylation catalyzed by Rh and Rh-Co mixed metal complexes and its application to the synthesis of pyrrolizidine alkaloids
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Reactions of hydrosilanes with 1-hexyne catalyzed by Co2Rh2(CO)12, Rh4(CO)12, (BuNC)4RhCo(CO)4, and Rh(acac)(CO)2 at 25°C and atmospheric pressure to 10 atm of carbon
- Ojima,Donovan,Eguchi,Shay,Ingallina,Korda,Zeng
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- Metal vapour derived supported rhodium nanoparticles in the synthesis of β-lactams and β-lactones derivatives
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Functionalised β-lactones and β-lactams were prepared starting from propargyl alcohols and propargyl tosyl amides by means of efficient silylcarbocyclisation reactions catalysed by rhodium nanoparticles derived from mesitylene-solvated Rh atoms (Metal Vapour Synthesis technique, MVS) and deposited on inorganic (C, γ-Al2O3 Fe 2O3) and organic matrices (PBI). All the MVS supported nanoclusters resulted more active than the analogous commercial Rh/C and Rh/γ-Al2O3, as well as homogeneous Rh 4(CO)12 used as reference catalyst. In particular, metal vapour derived Rh/C afforded the β-lactones and β-lactams in high yields and chemoselectivity. Preliminary investigations on the nature of the real active metal species involved in the catalytic process showed that rhodium(0) naked nanoparticles are leached by the support. The high catalytic activity encountered with Rh/C could be ascribed to the easy leaching of metal nanoparticles from carbon into solution. Indeed, the presence of a more polar matrix determined a minor catalytic efficiency probably due to a stronger interaction between the metal and the support. Therefore MVS Rh/C species represents a source, stable with ageing at room temperature, of highly active metal nanoparticles.
- Aronica, Laura Antonella,Caporusso, Anna Maria,Evangelisti, Claudio,Botavina, Maria,Alberto, Gabriele,Martra, Gianmario
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experimental part
p. 20 - 28
(2012/03/12)
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- Fluoride-Promoted Rearrangement of Organo Silicon Compounds: A New Synthesis of 2-(Arylmethyl)aldehydes from 1-Alkynes
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A new approach to 2-(arylmethyl)aldehydes 4 based upon a 1,2-anionotropic rearrangement of an aryl group is presented. The synthetic sequence begins with a silylformylation reaction of terminal acetylenes 5 with aryl and heteroaryl silanes 6, followed by treatment of the products (Z)-1 with TBAF. The optimization of the experimental conditions of the fluoride-promoted step is described, together with the synthetic potentialities of the process. A plausible mechanism of the rearrangement reaction is reported that suggests the addition of the fluoride ion to the arylsilicon moiety of β-silylalkenals (Z)-1 and the consequent migration of the aryl group to the adjacent carbon atom. Both aryl and heteroaryl substituents can rearrange without any loss of configuration. Bromofunctionalized substrates undergo an intramolecular reaction that affords exclusively carbacyclobenzyl aldehydes, further enhancing the high synthetic value of this method.
- Aronica, Laura Antonella,Raffa, Patrizio,Caporusso, Anna Maria,Salvadori, Piero
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p. 9292 - 9298
(2007/10/03)
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- Supported rhodium nanoparticles in catalysis: The role of stabilizers on catalytic activity and structural features
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Rhodium nanoparticles supported on γ-Al2O3, derived from arene-solvated Rh atoms stabilized by trioctylamine (TOA), are valuable catalysts in hydrogenation and silylformylation reactions. They are largely more active than the analogous commercial catalyst, as well as of a sample similarly prepared in the absence of TOA. HRTEM measurements, IR studies on adsorbed CO species and extended X-ray absorption fine structure analyses evidenced the role of TOA in controlling the particle growth in the preparative process and in stabilizing the resulting Rh particles against erosion by CO and oxidation.
- Vitulli, Giovanni,Evangelisti, Claudio,Pertici, Paolo,Caporusso, Anna Maria,Panziera, Nicoletta,Salvadori, Piero,Faga, Maria Giulia,Manfredotti, Chiara,Martra, Gianmario,Coluccia, Salvatore,Balerna, Antonella,Colonna, Stefano,Mobilio, Settimio
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- New synthesis of α-benzylaldehydes from 2-(dimethylphenylsilylmethylene)alkanals by fluoride promoted phenyl migration
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α-Benzyl aldehydes are prepared from easily available β-silylalkenals and fluoride reagents, under mild experimental conditions; the reaction occurs instantaneously with almost quantitative yields. A plausible mechanism is suggested, which involves a 1,2-
- Aronica, Laura Antonella,Morini, Francesca,Caporusso, Anna Maria,Salvadori, Piero
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p. 5813 - 5815
(2007/10/03)
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- Silylformylation of chiral 1-alkynes, catalysed by solvated rhodium atoms
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Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R1R2CH(CH2)nC≡CH, with catalytic activities comparable with and even higher than more common species such as Rh4(CO)12. Z-Silylalkenals are exclusively formed in high yields (60-95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the α-position of the unsaturated moiety, to afford enantiomerically enriched β-silylalkenals.
- Aronica, Laura Antonella,Terreni, Silvia,Caporusso, Anna Maria,Salvadori, Piero
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p. 4321 - 4329
(2007/10/03)
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