Anna Maria Caporusso

(η6-Cyclohepta-1,3,5-triene)(η4-cycloocta-1,5-diene)iron(0) complex as attractive precursor in catalysis

The catalytic activity of the complex Fe(η6-CHT)(η4-COD), (CHT=1,3,5-cycloheptatriene; COD=1,5-cyclooctadiene), 1, has been evaluated in some reference reactions such as the hydroformylation of 1-hexene and styrene and the cyclotrimerisation of a wide range of terminal and internal acetylenes. The title complex has been found to be a convenient catalytic precursor and it resulted more active than other iron catalysts in the investigated reactions.

Hydrosilylation of aromatic nitriles promoted by solvated rhodium atom-derived catalysts

Abstract Rhodium metal particles, isolated as supported or unsupported powder starting from mesitylene solvated rhodium atoms, catalyse the hydrosilylation of aromatic nitriles to N , N -disilylamines in high conversion at 100°C. Different hydrosilanes (HSiMe 3 , HSi(OEt) 3 ) can be employed. In the case of cinnamonitrile, the chemoselectivity of the reaction to 2-trimethylsilyl-3-phenylpropionitrile and ( E )- and ( Z )-1-di(trimethylsilyl)amino-3-phenyl-1-propene is strongly dependent on the reaction temperature. The commercial rhodium on γ-Al 2 O 3 catalyst is considerably less active and selective than the analogous catalyst prepared via Metal Vapour Synthesis (MVS) probably owing to the different dimension and distribution of the metal particles in the two samples as shown by HRTEM analysis.

Silylformylation of Chiral 1‐Alkynes, Catalysed by Solvated Rhodium Atoms

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.

Reactions of 3-alkyl- and 3,3-dialkyl-1-bromoallenes with organocuprates: Effects of the nature of the cuprate reagent on the regio- and stereoselectivity

Abstract Organocuprates induce 1,3- and direct substitution in 3-alkyl- and 3,3-dialkyl-1-bromo-1,2-dienes leading respectively to either terminal acetylenes or allenic hydrocarbons. The nature of the cuprate exerts a prominent role in determining both the regio- and the stereochemistry of these reactions.

Supported Rhodium Nanoparticles in Catalysis: the role of stabilizers on catalytic activity and structural features

Abstract Rhodium nanoparticles supported on γ-Al 2 O 3 , 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.

Supported platinum atoms derived catalysts in the hydrosilylation of unsaturated substrates

Abstract Supported Pt systems, prepared by treatment of supports as carbon, graphite and γ-Al 2 O 3 with mesitylene solvated Pt atoms, are quite good catalysts for the selective hydrosilylation of 1-hexyne and 2-hexyne to vinyl silanes and of isoprene to allyl derivatives. The catalyst can be recycled for several runs, even after months, without loss of activity.

Copper catalyzed aminolysis of bromoallenes as a new efficient route to propargylamines

Abstract An efficient procedure of general applicability for the synthesis of secondary and tertiary propargylamines by copper mediated aminolysis of 1-bromo-1,2-dienes is described.

A new method for the enantiomeric excess determination of chiral trisubstituted allenes by 195Pt NMR of trans-dichloro[(S)-α-methylbenzylamine](allene)platinum(II) complexes

The formation of diastereoisomeric complexes trans-dichloro[(S)-α-methylbenzylamine](allene)platinum(II) and detection by 195Pt NMR of their concentrations in CDCl3 solution allow the enantiomeric purity of chiral trisubstituted allenes to be determined easily.

New synthesis of α-benzylaldehydes from 2-(dimethylphenylsilylmethylene)alkanals by fluoride promoted phenyl migration

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-phenyl migration from the silicon to the adjacent carbon atom.

Metal catalysis in organic reactions. X. Nickel-catalyzed dimerization of 1-alkynes to 1,3-dialkylbutenynes

An efficient method for the selective synthesis of 1,3-dialkylbutenynes is described via reaction between terminal acetylenes and isolated diisobutylzinc in the presence of a nickel catalyst.