Anna Chrobok

Double bond migration in Sallyl systems catalysed by [RuClH(CO)(PPh3)3]

Abstract Reactions of S allyl systems (allyl sulphides of RSallyl type, where R=Et, allyl, Ph, Me 3 C, Ph 3 C, as well as of allyl phenyl sulphoxide, allyl phenyl sulphone, 2,5-dihydro-1,1-dioxothiophene) with [RuClH(CO)(PPh 3 ) 3 ] and other ruthenium compounds have been investigated. Double-bond migration was observed in the case of allyl trityl sulphide, allyl t -butyl sulphide and both sulphones, that is, where co-ordinating properties of sulphur were not too strong. High-yielded syntheses of ( E )- and ( Z )-RSCHCHCH 3 (R=Me 3 C, Z : E =96:4 and Ph 3 C, Z : E =92:8), ( E )PhS(O 2 )CHCHCH 3 and 2,3-dihydro-1,1-dioxothiophene from respective allyl systems are described. The binuclear Ru complex, formed in the model reaction of allyl phenyl sulphide with [RuClH(CO)(PPh 3 ) 3 ] has been isolated and its structure has been resolved. The mechanism of the reaction between S allyl systems and [RuClH(CO(PPh 3 ) 3 ] is proposed.

Tailoring ionic liquid catalysts: structure, acidity and catalytic activity of protonic ionic liquids based on anionic clusters, [(HSO4)(H2SO4)x]− (x = 0, 1, or 2)

Aiming at inexpensive Bronsted-acidic ionic liquids, suitable for industrial-scale catalysis, a family of protonic ionic liquids based on nitrogen bases and sulfuric acid has been developed. Variation of the molar ratio of sulfuric acid, χH2SO4, was used to tune acidity. The liquid structure was studied using 1H NMR and IR spectroscopies, revealing the existence of hydrogen-bonded clusters, [(HSO4)(H2SO4)]−, for χH2SO4 > 0.50. Acidity, quantified by Gutmann Acceptor Number (AN), was found to be closely related to the liquid structure. The ionic liquids were employed as acid catalysts in a model reaction; Fischer esterification of acetic acid with 1-butanol. The reaction rate depended on two factors; for χH2SO4 > 0.50, the key parameter was acidity (expressed as AN value), while for χH2SO4 > 0.50 it was the mass transport (solubility of starting materials in the ionic liquid phase). Building on this insight, the ionic liquid catalyst and reaction conditions have been chosen. Conversion values of over 95% were achieved under exceptionally mild conditions, and using an inexpensive ionic liquid, which could be recycled up to eight times without diminution in conversion or selectivity. It has been demonstrated how structural studies can underpin rational design and development of an ionic liquid catalyst, and in turn lead to a both greener and economically viable process.

Hydrogen-bond-rich ionic liquids as effective organocatalysts for Diels–Alder reactions

The synthesis and characterisation of new hydrogen-bond-rich ionic liquids and studies of their catalytic performance in Diels–Alder reactions are described. D-Glucose and chloroalcohols were used as the raw materials and as the sources of hydroxyl groups for the synthesis of ionic-liquid cations, whereas weakly coordinating bis(trifluoromethylsulfonyl)imide was used as the anion. The new ionic liquids were analysed by 1H and 13C NMR spectroscopy and by ESI-MS experiments, which confirmed their structures. In addition, the thermal data of the studied ionic liquids measured by differential scanning calorimetry and thermogravimetric analysis showed that these compounds tend to form a glass at temperatures in the range of −29 °C to −16 °C and are thermally stable from ambient temperature to at least 430 °C, most likely because of the presence of bis(trifluoromethylsulfonyl)imide anions. The performance of the ionic liquids in the model reaction of cyclopentadiene with diethyl maleate or methyl acrylate was investigated. The studied ionic liquids showed high activity even when present in catalytic amounts (4 mol% with respect to the dienophile). An increase in the number of hydroxyl groups present in the ionic liquid structure resulted in higher reaction rates.

Chemo-enzymatic Baeyer–Villiger oxidation in the presence of Candida antarctica lipase B and ionic liquids

A new method for the chemo-enzymatic Baeyer–Villiger oxidation of cyclic ketones to lactones has been developed. The influence of reaction parameters and the structure of various ionic liquids were studied. Free Candida antarctica lipase B or Novozyme-435 suspended in an ionic liquid was used as the catalytic phase. The reaction was carried out under mild conditions at room temperature using 30% aq. H2O2 as the oxidation agent. 1-Butyl-3-methyl bistriflimide was the most effective ionic liquid and increased the reaction rate compared to toluene. Lipase exhibited good stability, and the ionic liquid could be easily reused. Therefore, a general chemo-enzymatic method for the oxidation of cyclohexanones and cyclobutanones to obtain adequate lactones in high yields (79–95%) has been proposed.

The Baeyer–Villiger oxidation of ketones with bis(trimethylsilyl) peroxide in the presence of ionic liquids as the solvent and catalyst

A new method for lactone synthesis with bis(trimethylsilyl) peroxide as the oxidant and ionic liquids as solvents is reported. We propose two possibilities for the Baeyer–Villiger reaction course. The first of these is based on simply exchanging dichloromethane, the classical solvent for Baeyer–Villiger oxidation, for the ionic liquid bmimNTf2, which results in increased product yields. The second possibility is the elimination of the Baeyer–Villiger reaction catalyst and use of 1-butyl-3-methylimidazolium trifluoromethanesulfonate as both the solvent and catalyst. This method gives lactones in high yields with the possibility of ionic liquid recycling.

A new method for dialkyl peroxides synthesis in ionic liquids as solvents

Organic hydroperoxides undergo smooth nucleophilic displacement reactions with alkyl bromides in the presence of 30% water solution of NaOH in several ionic liquids (ILs) at room temperature to afford the corresponding dialkyl peroxides in excellent yields under extremely mild conditions. Additionally, symmetrical dialkyl peroxides were obtained in ionic liquids as solvent with good yields.

Herbicidal ionic liquids derived from renewable sources

A novel family of sugar-based herbicidal ionic liquids has been synthesized and the physical properties of the obtained salts were characterized. The herbicidal function was introduced to the new ionic liquids by the anion (4-chloro-2-methylphenoxyacetate or 2,4-dichlorophenoxyacetate) while the potential biodegradability and non-toxicity originated from the cation (based on D-glucose).

Friedel–Crafts alkylation catalysed by GaCl3-based liquid coordination complexes

Friedel–Crafts alkylation of benzene with 1-decene was catalysed by a new family of liquid Lewis acids: liquid coordination complexes (LCCs). LCCs are prepared by mixing a metal halide (e.g. GaCl3) and a donor molecule (e.g. N,N-dimethylacetamide, urea, or trioctylphosphine oxide), with the metal halide typically used in excess. This leads to the formation of a eutectic mixture comprised of charged and neutral species in a dynamic equilibrium. GaCl3-based LCCs were used in catalytic amounts, giving high reaction rates under ambient conditions, with selectivities to 2-phenyldecane superior to those previously reported in the literature. The influence of reaction conditions and catalyst composition on the reaction rate and selectivity was investigated. Optimised reaction conditions were suggested. This exploratory study offers promise with regard to the development of safer, LCC-based alternatives to HF in industrial alkylations.

New strategies for the synthesis of lactones using peroxymonosulphate salts, ionic liquids and microwave or ultrasound irradiation

A new method for the rapid synthesis of lactones via the one-pot oxidation of alcohols with potassium peroxymonosulphate in an ionic liquid was developed. The use of microwave or ultrasonic irradiation increased the reaction rates significantly. Additionally, new peroxymonosulphate ionic liquids were synthesised and used as effective oxidants in the synthesis of lactones.

Useful Application of Acidic Ionic Liquids as Solvents in Baeyer–Villiger Oxidation with Hydrogen Peroxide for the Synthesis of Lactones

Abstract Cyclic ketones have been efficiently oxidized with hydrogen peroxide using acidic ionic liquids (ILs) as solvents. This is a new method for the synthesis of lactones with high yields that does not utilize any additional catalysts and enables ILs to be recycled.