Štefan Toma

Catalysts with ionic tag and their use in ionic liquids

The concept of homogeneous supported catalysts has emerged as a useful alternative to homogeneous as well as heterogeneous catalysis, possibly combining positive aspects of both. Designing catalysts with respect to not only their catalytic activity but also their physical-chemical properties, appears to be a possible way towards sustainable chemical synthesis. Such tailored catalytic systems would ideally have high catalytic activities and some property enabling their efficient recycling. We reviewed the field of specifically designed ionic catalysts used mostly in ionic liquids.

Comparison of conventional and ultrasonically assisted extractions of pharmaceutically active compounds from Salvia officinalis.

Conventional as well as ultrasonically assisted extractions of biologically active compounds from Salvia officinalis using 65% ethanol have been studied. Cineole, Thujone and Borneol were used as standards for the GLC-MS evaluation of the extracts. The effect of temperature, stirring and mode of sonication (ultrasonic bath or horn system) have been studied. The results indicate that ultrasonically assisted extraction with mechanical stirring at room temperature in a period of 12 h produces a substantial improvement over conventional methodology.

L-Proline Catalyzed Michael Additions of Thiophenols to α,β-Unsaturated Compounds, Particularly α-Enones, in the Ionic Liquid [bmim]PF6

L-proline catalyzed additions of 13 different thiols to 11 different alpha-enone Michael acceptors in [bmim] PF(6 )are reported. Reasonable to high yields of the reaction products were isolated in most cases.

Dry synthesis under microwave irradiation: Synthesis of ferrocenylenones

Abstract Acetylferrocene and ferrocene carboxaldehyde were condensed with aldehydes or ketones without solvent in presence of solid KOH, Slow reactions were accelerated by microwave irradiation.

Study of ligand and base effects on enantioselective allylation catalyzed by Pd(0) phosphine complexes in [bmim][PF6] ionic liquid

Enantioselective Pd-catalyzed allylic substitution of (rac)-(E)-1,3-diphenyl-3-acetoxyprop-1-ene with dimethyl malonate was studied in 3-butyl-1-methylimidazolium hexafluorophosphate ([bmim][PF6]) as an ionic liquid. The reactions were catalyzed by Pd(0) complexes of three homochiral ferrocenylphosphine ligands, (S,S)-iPr-Phosferrox, (S,R)-iPr-Phosferrox, (R,S)-BCyPFA and (R)-BINAP. Potassium carbonate and bis(trimethylsilyl)acetamide (BSA)/AcOK were tested as the bases and simple optimization of the reaction procedure was performed. Experiments with other soft nucleophiles also were carried out under optimized conditions.

Enantioselective allylic substitution catalyzed by Pd0–ferrocenylphosphine complexes in [bmim][PF6] ionic liquid

Enantioselective allylic substitution reactions of (rac)-(E)-1,3-diphenyl-3-acetoxyprop-1-ene with dimethyl malonate (DMM) are studied in 1-butyl-3-methylimidazolinium hexafluorophosphate ([bmim][PF6]) as an ionic solvent; the reactions are catalyzed by Pd0 complexes of two homochiral ferrocenylphosphine ligands, (S,R)-BPPFA and (R,S)-BPPFDEA with the recycling of the catalytic system being tested. A similar reaction with 1-phenyl-3-acetoxyprop-1-ene is also studied with only a linear achiral product being isolated.

Michael addition of thiols to α-enones in ionic liquids with and without organocatalysts

Seventeen organocatalyts were tested for their ability to catalyst the addition of thiophenols to chalcones in [bmim]PF6. The products were isolated in high yield after a short reaction time, but no stereoselectivity was observed. The reactions also proceeded (without any stereoselectivity) in four other ionic liquids. In contrast, 16% and 26% ee were observed when L-proline and cinchonine, respectively, were used as the catalysts in CH2Cl2. Addition of thiophenols is also catalysed by HCl, as well as D-mandelic and L-tartaric acids. Addition of thiophenols to chalcones also occurred in neat ionic liquids, without any additional catalyst, but the rate of the reaction depended considerably on the structure of ionic liquid. The scope of the non-catalysed reaction in ionic liquids was tested by the reactions of 5 different thiols and 3 different α-enones.

Knoevenagel condensation of ferrocenyl substituted carboxaldehydes with methylene active compounds on inorganic supports and the NLO properties of the resulting push–pull alkenes

Abstract We report a new method for the condensation of nonamethylferrocenecarboxaldehyde, 3-ferrocenylacrolein, 5-ferrocenylthiophene-2-carboxaldehyde and 5′-ferrocenyl-2,2′-bithienyl-5-carboxaldehyde inorganic supports, with methylene active compounds on the inorganic supports. In this way, conditions leading to very high yield (>70%) of the product could be achieved. The effect of sonication during the synthesis of nonamethylferrocenecarboxaldehyde is reported and appears to be of great importance. We also report a new method for the synthesis of 3-ferrocenylacrolein. The second-order non-linear optical (NLO) properties of these ferrocenecarboxaldehyde condensation products are measured with the hyper-Rayleigh scattering (HRS) technique. The results of a similar study made for the condensation products of the above-mentioned aldehydes with malononitrile and indan-1,3-indandione are also given.

Ultrasound effect on the aromatic nucleophilic substitution reactions on some haloarenes

The sonochemical nucleophilic aromatic substitutions on haloarenes with different amines have been studied. A beneficial ultrasound effect was observed and high yields of the products were obtained after 15-30 min sonication. The reaction course of the nucleophilic aromatic substitution was found to be strongly dependent on nucleophilicity, bulkiness, and boiling point of amines as well as on the electron-withdrawing property of the substituents on the haloarenes.

The effect of ultrasound on photochemical reactions

Sonochemistry and photochemistry are based on very different physical phenomena, which a priori seems to exclude any possibility to observe more than a simple superposition of their respective effects. Literature data are examined, first the few studies devoted to sonochemical and photochemical reactions in cases where a direct comparison is possible. The second part is devoted to an analysis of experiments in which both irradiations are effected simultaneously. Cases exist from which it can be concluded, at least provisionally, that sonication is able to quench long-lived excited states, because of the intense streaming which enhances strongly the probability of collisional deactivations.