Florentina Neaţu

Heterogeneous Gold Catalysts for Efficient Access to Functionalized Lactones

A novel class of heterogeneous gold catalysts supported on zeolite beta-NH4+ was prepared by the deposition-precipitation method. This new class of catalyst showed interesting catalytic activities for the intramolecular cycloisomerization of gamma-acetylenic carboxylic acids leading to functionalized gamma-alkylidene gamma-butyrolactones. Analysis of the supported gold species with in situ X-ray photoelectron spectroscopy (in situ XPS) suggests that cationic Au (possibly AuIII) can play an important role in such reactions. The high discrepancy in catalyst stability in favor of the Au supported on the zeolite system over bulk Au2O3 is explained by 1) the size of the particles and 2) the reversibility of the redox deactivating process (AuIII-->AuI) in the presence of oxygen for the supported system. The efficiency of this system allowed reaction under mild heterogeneous conditions. The potential for catalyst recycling was also highlighted.

Gold imidazolium-based ionic liquids, efficient catalysts for cycloisomerization of γ-acetylenic carboxylic acids

Ionic liquid stabilized gold(III) chloride is shown to be a very active catalyst in the cyclization of sterically hindered and unhindered acetylenic carboxylic acid substrates even in the absence of a base.

Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds.

Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent. The process is general for aromatic and aliphatic, conjugated and isolated nitro groups, and occurs with low selectivity over hydrogenation of carbon-carbon double bonds.

Novel Pd heterogeneous catalysts for cycloisomerisation of acetylenic carboxylic acids

The Pd-TPPTS complex (TPPTS - trisodium salt of 3,3′,3′′-phosphanetriyl benzenesulfonic acid) and PdCl42− salt heterogenised onto Zn2AlNO3 layered double hydroxide (LDH) using an ion-exchange procedure, have been shown to be efficient green catalysts in the cycloisomerisation reaction of acetylenic carboxylic acids to the corresponding 5-membered heterocycles.

Heterogeneous Au and Rh catalysts for cycloisomerization reactions of γ-acetylenic carboxylic acids

Au- and Rh-based heterogeneized catalytic systems have been prepared and analyzed. Their efficiency has been evaluated for the cycloisomerization of γ-acetylenic carboxylic acids leading to valuable γ-alkylidene γ-butyrolactones. Bulk AuO3 was found to be a valuable and easy-to-handle catalyst for selective transformations, whereas [C6mim][AuCl4] presented a high activity and Au/β-zeolite was recyclable.

Rh-TPPTS/LDH : A new heterogeneous catalyst for the synthesis of functionalized γ-lactone

Abstract Well defined Zn 2 Al-NO 3 /CO 3 and Zn 2 Ga-NO 3 /CO 3 LDH were prepared using typical procedures starting from Zn(NO 3 ) 2 , Al(NO 3 ) 3 and Ga(NO 3 ) 3 . Rh-TPPTS complex was prepared by simple complexation of a Rh precursor [Rh(cod)Cl]2 and TPPTS (3,3′,″-phosphanetriyl benzenesulfonic acid) in water. The heterogeneization of the Rh-TPPTS complex was performed by anionic exchange between Rh-complex and Zn 2 Al-NO 3 /CO 3 or Zn 2 Ga-NO 3 /CO 3 LDH supports. The catalysts structures and the chemical composition were confirmed by XRD analysis, XPS and DRIFT spectroscopy. Triphenylphosphane-substituted Rh heterogeneous catalysts showed good catalytic activity and selectivity in the cycloisomerization of functionalized acetylenic acids.

Synthesis of Terephthalic Acid by p‐Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio‐Polyethylene Terephthalate

The synthesis of terephthalic acid from biomass remains an unsolved challenge. In this study, we conducted the selective oxidation of p-cymene (synthesized from biodegradable terpenes, limonene, or eucalyptol) into terephthalic acid over a Mn-Fe mixed-oxide heterogeneous catalyst. The impact of various process parameters (oxidant, temperature, reaction time, catalyst amount, oxygen pressure) on the selectivity to terephthalic acid was evaluated, and some mechanistic aspects were elucidated. An unprecedented synthesis of biobased terephthalic acid (51 % yield) in the presence of O2 is reported.