Showing papers by "Lucio Ronchin published in 2005"
TL;DR: In this article, selective oxidations by nitrous acid in aqueous sulfuric acid towards alkyl side chains of enolizable ketones are reported and the conversion reagents-products in different experimental conditions are explored and the reaction path of the compounds involved as intermediates is tested.
Abstract: Selective oxidations by nitrous acid in aqueous sulfuric acid towards alkyl side chains of enolizable ketones are reported. The conversion reagents–products in different experimental conditions is explored and the reaction path of the compounds involved as intermediates is tested. Side-chain oxidations are particularly successful for substrates with one site or with equivalent sites of oxidation. Thus, 95% of benzoylformic acid from acetophenone and 60% of 1,2-cyclohexanedione from cyclohexanone are obtained at ∼78 and at ∼40% H 2 SO 4 , respectively. Kinetic ( k obs ) and thermodynamic ( k °) rate constants of acetophenone are also determined, the latter by using the acidity dependence of the rates, the equilibria involving the reacting species and the departure from the ideality of the catalytic acid system. Details of the process between enolizable ketones and electrophilic species in concentrated aqueous acid solutions are discussed.
12 citations
TL;DR: In this article, the reactivity of a nitrosating agent (N2O3) on oxidations of alcohols and the methyl group of acetophenone were tested.
Abstract: The reactivity of a nitrosating agent (N2O3) on oxidations of alcohols and the methyl group of acetophenone were tested. Active electrophylic surface nitrosonium ions (NO+) was detected on H2SO4/SiO2 catalysts by Raman spectroscopy, suggesting a surface ionic mechanism of oxidation in agreement with the one proposed in acid aqueous solutions. Alcohols are selectively oxidized to ketones and aldehydes in high yield, useful for synthetic applications, at 25 °C in 1,2-dichlorethane and using commercial sulfonated styrene divinyl benzene resins (Amberlyst 15®) as catalysts. In addition, nitrous acid ester has been observed as intermediates according to an ionic mechanism by surface NO+. Under the same reaction conditions, acetophenone is selectively oxidized to benzoyl cyanide in high yield and selectivity. The comparison with oxidation carried out in aqueous solution of HNO2, where benzoyl formic acid was obtained, suggests that the differences in the final products are likely due to the specific stabilizing effect of each solvent. Moreover, the reactivity of the intermediates isolated in aqueous systems implies that α-nitroso-acetophenone is a probable reaction intermediate also in aprotic heterogeneous systems.
12 citations
TL;DR: In this paper, the title complex was synthesized by first reacting dppp with Pd(AcO)2 in acetone and then with NaHSO4 in water.
6 citations
TL;DR: In this paper, the influence of promoters and precipitants of the catalyst precursor on the activity and selectivity of the hydrogenation of benzene to cyclohexene catalyzed by highly loaded oxide-promoted Ru/ZrO2catalysts, carried out in a tetraphase reactor (in the presence of an aqueous solution of ZnSO4), at 423 K and 5 Mpa, was studied.
Abstract: The influence of promoters and precipitants of the catalyst precursor on the activity and selectivity of the hydrogenation of benzene to cyclohexene catalyzed by highly loaded oxide-promoted Ru/ZrO2catalysts, carried out in a tetraphase reactor (in the presence of an aqueous solution of ZnSO4), at 423 K and 5 Mpa, was studied. The effect of hydrogen diffusion on the reaction kinetics and on the selectivity has been taken into consideration, the internal pore diffusion being actually the limiting step. Hydrogen chemisorption measurements indicate that the catalyst activity is not influenced by the Ru dispersion, but rather by weakly chemisorbed species.
6 citations