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The application of N-doped carbon as a basic, heterogeneous catalyst in a continuous-flow process is described for the first time. The Knoevenagel condensation reaction was chosen to demonstrate the potential of N-doped carbon toward the development of sustainable, scalable processes that require a basic catalyst. The practical potential and performance advantages of the flow approach compared to a conventional batch system were envisioned. Under flow conditions, products were continuously synthesized for 200 h with high conversions up to 95%. The presented metal-free flow system successfully operated under mild reaction conditions, with temperatures ranging from 25 to 70 °C and ethanol as a solvent, which embody key principles of green chemistry.

Based on MS analysis, the mechanism of the Baeyer–Villiger oxidation of cyclic ketones with hydrogen peroxide using metal triflates (Ga(OTf)3 and Er(OTf)3) as catalysts was proposed. In the case of cyclohexanone as a substrate, dimeric, trimeric and tetrameric peroxide structures were detected.

In this work an enzymatic method for the synthesis of alkyl levulinates from α-angelica lactone has been reported for the first time. Lipase B from Candida antarctica was immobilized via interfacial activation on the surface of a hybrid support, consisting of commercially available multi-walled carbon nanotubes (MWCNTs) and polytetrafluoroethylene (PTFE). Among the biocatalysts with various contents of PTFE in the support, the CALB/MWCNT–PTFE (0.10 wt%) biocatalyst with 22.5 wt% CALB loading was determined as the most active one in the model synthesis of the n-butyl levulinate in toluene. n-Butyl levulinate was obtained quantitively after 120 min of the reaction under the selected reaction conditions (2-fold molar excess of n-butanol, 0.150 g of biocatalyst per 1 mmol of α-angelica lactone, 20 °C). The yield of n-butyl levulinate was found to be higher than that in the presence of accurate amounts of sulfuric acid or Novozyme-435. Additionally, the unique stability of the developed biocatalyst was demonstrated over 6 reaction cycles at 20 °C. The biocatalyst remained stable over 3 reaction cycles at 60 °C as well. The essence of the proposed approach lies in the possibility to overcome the equilibrium limitations occurring in the conventional Fisher esterification. The activity of the elaborated hybrid biocatalyst in the reactions non-specific for lipases is a clear proof of the versatility of the novel system.

As a result of strict regulations of phthalate plasticizers, alternative non-phthalate forms are desired and increasingly used. This work presents a synthetic method for alternative plasticizers (dialkyl succinates and adipates) via esterification of succinic and adipic acid with alcohols: butan-1-ol and 2-ethylhexan-1-ol. Ionic liquids were synthesized by the reaction of triethylamine with over-equimolar (1:2.7) amounts of sulfuric(VI) acid, which were used as an acidic catalyst and solvent. The two-phase liquid–liquid system was formed during the reaction due to immiscibility of the esters with the ionic liquid. This phenomenon is a driving force of this process, shifting the equilibrium toward the product formation. As a result, dialkyl succinates and adipates were obtained in high yields (99%) and selectivities (&gt, 99%), under mild reaction conditions at 70–80 °C and using a 4:1 molar ratio of alcohol to acid and 15 mol% of catalyst. The catalyst was recycled 10 times without any loss of activity. This alternative method is highly competitive: it involves a simple procedure for product isolation as well as a high yield and purity of the resulting esters. These advantages make this method sustainable and promising for industrial applications.

Following our previous studies on the molecular level structure of (co)oligoesters obtained via anionic homo- and co-polymerization of novel β-substituted β-lactones, prepared by the atmospheric pressure carbonylation reaction of respective epoxides, the boric acid biocatalyzed ring-opening (co)polymerization of δ-valerolactone has been studied. As a co-monomer the 6-methy-ε-caprolactone, prepared by the one-pot oxidation of respective alcohol, and ethylene glycol as polymerization initiator were used. The obtained copolymers were characterized by 1H-NMR, GPC and ESI-MS, respectively in order to confirm their chemical structures and identity. Subsequently, tandem mass spectrometry (MS-MS studies) via collision-induced dissociation were utilized to characterize the fragmentation pattern. ESI-MS and NMR analyses confirmed the formation of random linear copolymer chains composed of different polyester repeat units. MS-MS experiments showed that fragmentation proceeds via ester bound cleavage along the (co)polyester chains. The innovative aspect of this contribution is related to the elaboration of the telechelic (co)polymers end-capped with hydroxyl end groups and well-defined molecular architectures, which could facilitate the development of new flexible macromolecular systems for potential biomedical applications.

Levulinic acid esters (LAEs) were synthesized from α-angelica lactone and alcohols, in a reaction catalyzed by a new family of chloride-free Lewis acidic ionic liquids, containing trifloaluminate anions, [Al(OTf)3+n]n−. Changing the catalyst from poorly soluble Al(OTf)3 (used as suspension) to fully homogeneous trifloaluminate ionic liquids resulted in shorter reaction times required for full α-AL conversion (60 min at 60 °C for 0.1 mol % catalyst loading) and unprecedented selectivities to LAEs, reaching >99%. Supporting the trifloaluminate ionic liquid on multiwalled carbon nanotubes gave an easily recyclable system, with no leaching observed over six cycles. Mechanistic considerations suggest that the propensity of Al(OTf)3 to undergo very slow hydrolysis results in the correct balance of Brønsted and Lewis acidic sites in the system, which inhibit byproduct formation.

An effective method for the synthesis of 2,3,6-trimethyl-1,4-benzoquinone via the oxidation of 2,3,6-trimethylphenol as the key step in the in the preparation of vitamin E was presented. An aqueous solution of H2O2 was used as the oxidant and Lewis acidic trifloaluminate ionic liquids [emim][OTf]-Al(OTf)3, &chi, Al(OTf)3 = 0.25 or 0.15 as catalysts. Trifloaluminate ionic liquids were synthesised by the simple reaction between 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (triflate) [emim][OTf] and aluminium triflate used in sub-stoichiometric quantities. The influence of the reaction parameters on the reaction course, such as the amount and concentration of the oxidant, the amount of catalyst, the amount and the type of organic solvent, temperature, and the reaction time was investigated. Finally, 2,3,6-trimethyl-1,4-benzoquinone was obtained in high selectivity (99%) and high 2,3,6-trimethylphenol conversion (84%) at 70 &deg, C after 2 h of oxidation using a 4-fold excess of 60% aqueous H2O2 and acetic acid as the solvent. The catalytic performance of trifloaluminate ionic liquids supported on multiwalled carbon nanotubes (loading of active phase: 9.1 wt.%) was also demonstrated. The heterogeneous ionic liquids not only retained their activity compared to the homogenous counterparts, but also proved to be a highly recyclable catalysts.

Inexpensive Br&oslash, nsted acidic ionic liquids based on trimethylamine and sulfuric acid are proposed as both solvents and catalysts in the synthesis of alternative plasticizer bis(2-ethylhexyl) terephthalate, which has a broad spectrum of applications in plasticization processes. The utilization of 50 mol % of Br&oslash, nsted ionic liquid led to the full conversion of terephthalic acid after 8 h of reaction at 120 &deg, C. Additionally, a 100% selectivity of bis(2-ethylhexyl) terephthalate was obtained. The advantage of the presented reaction system is based on the formation of a biphasic system during the reaction. The bottom phase consists of an ionic liquid and water, and the upper phase is created by the ester and unreacted alcohol. This phenomenon helps overcome the equilibrium of the reaction and drives it towards a high yield of product. The presented new approach is proposed as a safe, cost-effective, and alternative method to conventional processes with organometallic compounds that, in turn, leads to greener and a more economically viable technology.

The first example of triflometallate ionic liquids, named in analogy to chlorometallate ionic liquids, is reported. Trifloaluminate ionic liquids, synthesised from 1-alkyl-3-methylimidazolium triflates and aluminium triflate, were characterised by multinuclear NMR spectroscopy and FT-IR spectroscopy, revealing the existence of oligonuclear, multiply-charged trifloaluminate anions, with multiple bridging triflate modes. Acceptor numbers were determined to quantify their Lewis acidity, rendering trifloaluminate ionic liquids as medium-strength Lewis acids (AN = ca. 65). Used as acidic catalysts in the cycloaddition of 2,4-dimethylphenol and isoprene (molar ratio 2:1) to prepare chromane, trifloaluminate systems outperformed literature systems, showing high activity (conversions 94-99%, selectivities 80-89%) and at low loadings (0.2 mol%) at 35 °C. Using these new systems as supported ionic liquid phase (SILP) on multi-walled carbon nanotubes (ionic liquid loading 16 wt%) delivered a recyclable catalytic system, with activity enhanced with respect to the homogenous regime.

A range of Lewis acidic metal chlorides were tested as homogeneous catalysts in a model Diels–Alder reaction; AlCl3 and GaCl3 performed best in terms of conversion and endo : exo selectivity. Based on this outcome, the corresponding chlorometallate(III) ionic liquids were tested as homogeneous catalysts, without a decrease in performance compared to the chlorides. Finally, these ionic liquids were heterogenised by covalent tethering of the cation onto a multimodal porous silica support; such supported chlorogallate(III) ionic liquids are reported for the first time. Supported chlorometallate(III) ionic liquids were used as recyclable heterogeneous catalysts for the Diels–Alder reaction under solventless conditions. High yields (99%) and high endo-selectivities (95%) were obtained after very short reaction times (5 min) at near-ambient temperature (25 °C).