DNA-Accelerated Catalysis of Carbene-Transfer Reactions by a DNA/Cationic Iron Porphyrin Hybrid

A novel DNA-based hybrid catalyst comprised of salmon testes DNA and an iron(III) complex of a cationic meso-tetrakis(N-alkylpyridyl)porphyrin was developed. When the N-methyl substituents were placed at the ortho position with respect to the porphyrin ring, high reactivity in catalytic carbene-transfer reactions was observed under mild conditions, as demonstrated in the catalytic enantioselective cyclopropanation of styrene derivatives with ethyl diazoacetate (EDA) as the carbene precursor. A remarkable feature of this catalytic system is the large DNA-induced rate acceleration observed in this reaction and the related dimerization of EDA. It is proposed that high effective molarity of all components of the reaction in or near the DNA is one of the key contributors to this unique reactivity. This study demonstrates that the concept of DNA-based asymmetric catalysis can be expanded into the realm of organometallic chemistry

A simple and versatile design concept for fluorophore derivatives with intramolecular photostabilization

Intramolecular photostabilization via triple-state quenching was recently revived as a tool to impart synthetic organic fluorophores with 'self-healing' properties. To date, utilization of such fluorophore derivatives is rare due to their elaborate multi-step synthesis. Here we present a general strategy to covalently link a synthetic organic fluorophore simultaneously to a photostabilizer and biomolecular target via unnatural amino acids. The modular approach uses commercially available starting materials and simple chemical transformations. The resulting photostabilizer-dye conjugates are based on rhodamines, carbopyronines and cyanines with excellent photophysical properties, that is, high photostability and minimal signal fluctuations. Their versatile use is demonstrated by single-step labelling of DNA, antibodies and proteins, as well as applications in single-molecule and super-resolution fluorescence microscopy. We are convinced that the presented scaffolding strategy and the improved characteristics of the conjugates in applications will trigger the broader use of intramolecular photostabilization and help to emerge this approach as a new gold standard

Bio-inspired catalysis in water

Bio-geïnspireerde katalyse in water Enzymen zijn katalysatoren in biologische systemen en kunnen reacties met hoge activiteit en selectiviteit uitvoeren. Synthetische katalysatoren uit het laboratorium werden meestal gemaakt voor reacties in organische oplosmiddelen. Dit heeft als voordeel dat de gekatalyseerde reacties goed controleerbaar en bestudeerbaar zijn. De reactiviteiten en selectiviteiten die bereikt worden met deze synthetische katalysatoren zijn vaak beduidend lager dan bij de biologische voorbeelden. In de laatste jaren is geprobeerd om artificiële enzymen (hybride katalysatoren) te maken waarbij de grote flexibiliteit van synthetische katalysatoren met de hoge activiteiten en selectiviteiten van biologische katalysatoren is gecombineerd. De in dit proefschrift omschreven DNA-gebaseerde katalysatoren zijn hier een voorbeeld van. Het hoofddoel van de studie die samengevat is in dit proefschrift was het ontwikkelen van unieke DNA-gebaseerde asymmetrische katalysatoren voor organometaalreacties in water. Bovendien werd gekeken naar nieuwe uitgangsstoffen voor bestaande DNA-gebaseerde asymmetrische katalysereacties en naar de ontwikkeling van nieuwe methoden voor organische synthese in waterige oplossingen. De belangrijkste vindingen zijn: • De eerste organometaalreactie met hoge selectiviteit voor één enantiomeer, gekatalyseerd door een DNA-gebaseerde katalysator. • De ontdekking van een ijzer porfyrine / duplex DNA hybride katalysator voor de intermoleculaire cyclopropanering van styrenen met ethyl diazoacetaat. Hierbij werden door aanwezigheid van DNA hoge reactieversnellingen verkregen. • De eerste substraten voor copper(II) gekatalyseerde reacties in DNA-gebaseerde asymmetrische katalyse die alleen zuurstof atomen bevatten voor de coördinatie aan copper(II). • De ontwikkeling van synthesemethoden voor de organische chemie in water die gebaseerd zijn op water oplosbare porfyrines en micellaire katalyse

Alkylidene malonates and α,β-unsaturated α'-hydroxyketones as practical substrates for vinylogous Friedel-Crafts alkylations in water catalysed by scandium(III) triflate/SDS

Alkylidene malonates and α,β-unsaturated α'-hydroxyketones are demonstrated to be efficient classes of electrophiles for the scandium(III) triflate/sodium dodecyl sulphate (SDS) catalysed vinylogous Friedel-Crafts alkylation of indoles and pyrroles in water. These substrates contain an easily removable auxiliary group that increases affinity for the catalytic metal ion in such a way that they can compete with water for binding to the catalytic metal ion. Thus, alkylidene malonates and α,β-unsaturated α'-hydroxyketones are attractive substitutes for, e.g., α,β-unsaturated carboxylic acids and -esters, which in aqueous media are not reactive enough in these reactions. The combination of Lewis acid and SDS in catalysis results in considerable acceleration of the reaction in water compared to organic solvents. The method presented is attractive because the reactions are fast, experimentally straightforward and give rise to high yields of products

Dramatic micellar rate enhancement of the Cu2+ catalyzed vinologous Friedel–Crafts alkylation in water

A dramatic rate enhancement of the Cu2+ catalyzed Friedel–Crafts alkylation in water was achieved in the presence of sodium dodecyl sulfate (SDS) micelles.

Separation and recycling of cotton from cotton/PET blends by depolymerization of PET catalyzed by bases and ionic liquids

The recycling of post consumer cotton textile waste is highly requested, due to the high environmental impact of cotton production. Often cotton is mixed in blends with polyethylene terephthalate (PET). For the generation of high value products from recycled cotton, it essential that PET is separated from the cotton first. In this contribution, the depolymerization of PET in cotton / PET blend is investigated for the separation of PET from cotton fibers. Ionic liquids and NaOH are used as catalysts for the depolymerization reaction in ethylene glycol (glycolysis). It will be shown that ionic liquids have no significant influence on the conversion of PET. However, 99% conversion is achieved in this process with 2 w/w % NaOH as catalyst. This enables the selective depolymerization of PET in presence of cotton and gives rise to an easy separation of cotton from cotton / PET blends. Paper for the 14th World Textile Conference, May 26th-28th2014, Bursa, Turkey

The life cycle assessment of cellulose pulp from waste cotton via the SaXcellTM process.

Recycling of cotton waste into high value products is a longstanding goal in textile research. The SaXcellTM process provides a chemical recycling route towards virgin fibres. In this study a Life cycle assessment (LCA) is conducted to measure the impact of the chemical recycling of cotton waste on the environment. Pure cotton waste and cotton containing 10 % of polyester are elaborated. The results show that chemical recycling via the SaXcellTM process can have a lower impact on climate change and other impact category than comparable pulping technologies.   doi:10.1088/1757-899X/254/19/19201