Stefan Jopp

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Verified

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• Dr. rer. nat. habil.
• Group Leader at University of Rostock

The diversity in structure, the variety in chirality, as well as the large occurrence of carbohydrates in nature, led to the development of the next generation of ionic liquids (ILs). These carbohydrate-based ionic liquids, also known as CHILs, are expected to overcome limitations such as aquatic ecotoxicity and poor biodegradability. In this work,...

The incorporation of carbohydrate based ionic liquids as a support for Novozym 435 was previously studied by the authors for the acrylation of n‐butanol as the target substrate, which was used as the foundation for the design of experiments. The combination of carbohydrate based ionic liquids and Novozym 435 remains a key aspect of this work. Build...

This work presents the synthesis of glucose-based vinyl imidazolium monomers and the hydrogels produced thereof. These novel semisynthetic, cationic hydrogels were prepared by radical polymerization with different types of commercial cross-linkers such as N,N′-methylenebis(acrylamide) or poly(ethylene glycol) diacrylate. Both the type and the amoun...

The authors of this work have optimized a novel synthetic route towards glucose‐based PdII‐bis(NHC) complexes in only 4 steps with total yields up to 73 %. The synthesis route encompasses an Appel reaction towards 6‐iodo‐glucopyranosides, followed by acyl‐protection, then quaternization with imidazoles and finally the conversion of these acyl‐prote...

Carbohydrate‐based ionic liquids and salts (CHILS) have recently emerged as an uprising sub‐class of ionic liquids. Their starting materials are available in abundant natural resources from plants and fauna. Carbohydrates are not only sustainable; they also exhibit natural chirality. To use this, novel glucosyl imidazolium NTf2 ionic liquids were s...

Hydrogels have gained significant interest in the last decades, especially in the medical sector, due to their versatile properties. While hydrogels from naturally occurring polysaccharides (e.g. cellulose) are well-known, those produced from polymerizable carbohydrate-based monomers remain underexplored. However, these semi-synthetic hydrogels off...

The interest in hydrogels has grown considerably across a number of disciplines, including but not limited to the immobilization of (bio)catalysts in matrices and in the medical sector, for example, in drug delivery systems, contact lenses, biosensors, electrodes, and tissue engineering. Consequently, the characterization of these materials is freq...

Three bis- or tris-brominated 2-trifluoromethylquinolines have been successfully applied in palladium-catalysed Sonogashira reactions, leading to several examples of alkynylated quinolines in good to excellent yields. Optical properties of selected products have been studied by steady state absorption and fluorescence spectroscopy which give insigh...

The authors of this work have optimized a novel synthetic route towards glucose-based Pd(II)-bis(NHC) complexes in only 4 steps with total yields up to 73 %. The synthesis route encompasses an Appel reaction towards 6-iodo-glucopyranosides, followed by acyl-protection, then quaternization with imidazoles and finally the conversion of these acyl-pro...

This research article focuses on the synthesis of ionic liquids from glucosamine, a renewable material obtained from chitin. Our group previously experienced some obstacles in the synthesis of these glucosamine‐based ionic liquids, often due to the sterical hindrance induced by the dimethylated amino‐group. In this work we present a method using Bo...

The Cover Picture shows the conversion of acrylic acid and n-butanol into butyl acrylate through an engine of Novozym 435, in which the powering piston CalB (Candida antarctica lipase B) is supported by the newly developed GMIM-I (glucosyl-methyl-imidazolium iodide). The authors acknowledge Dr. Johanna Meyer (University of Hannover) for the creatio...

A series of novel ionic liquids based on glucose was synthesized in high yields in simple two or three‐step reaction procedures. These carbohydrate‐based ionic liquids were studied and compared to commercially available imidazolium‐based ionic liquids as supports for Novozym 435 in the acrylation of n‐butanol. A direct correlation between the avail...

The title solvated molecular salt, [MeGluVIm]I (MeGluVIm = 1-(methyl-α-d-gluco­pyran­osid-6-yl)-3-vinyl­imidazolium), or C12H19N2O5⁺·I⁻·C3H7NO, was synthesized from methyl-α-d-6-iodo­gluco­pyran­oside and vinyl­imidazole in DMF. It crystallizes through precipitation from ethyl acetate solution directly after the reaction procedure. The crystal stru...

Hygroscopic effects in ionic liquids and salts in general, and how to suppress said hygroscopy, often needs to be considered during the everyday work routine. Chemicals that decompose, undergo hydrolysis or in any way change their composition when exposed to air are generally not considered to be bench-stable. In this study, we synthesized a low-hy...

Acridine derivatives have attracted considerable interest in numerous areas owing to their attractive physical and chemical properties. Herein, starting from readily available anthranilic acid, an efficient synthesis of 2,4-bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridine derivatives was accomplished via a one-pot double Sonogashira cross-coupl...

The authors of this work have successfully synthesized a broad choice of new ribose based ionic liquids, using several varying protecting groups (methyl, ethyl, allyl and benzyl) at the various positions of the carbohydrate, as well as different quarternised N-heterocycles and different anions. These consistent variations of the carbohydrate based...

CHILs! A series of carbohydrate‐based ionic liquids have been successfully synthesized from glucosamine, an abundant and regrowing resource, which can be obtained through shell refinery from chitin and chitosan. The synthesis of these CHILs is straightforward and performed in high yields. Their thermal properties as well as their potential as catal...

In this article the authors investigated a new synthetic strategy to convert glucosamine, a natural resource produced from chitin, into several trimethylammonium glucosamine salts. The thermal properties of the new carbohydrate based ionic liquids (CHILs) have been measured to further investigate the structure‐property relationships. The authors fu...

Carbohydrate based ionic liquids (CHILs) are a sub‐class of ionic liquids which first emerged in 2007 and has since then attracted a steadily growing community of organic chemists. Since carbohydrates are naturally occurring materials with a broad spectrum of diastereomers, they are fitting materials for ionic liquids bearing stereochemical informa...

The large pool of naturally occurring carbohydrates with their diversity in chirality and structure led to the idea of a systematic investigation of carbohydrate based ILs. To this end, we investigated the influence of different ether groups, mainly methyl or ethyl ether, on the secondary OH groups as well as different configurations on physical pr...

In the work presented herein a new derivative of the anticoagulant dabigatran, bearing a tosyl group at the amidine function, was prepared. The desired final product was achieved after a 7 step synthesis in overall good yields. A main part of the strategy was the selective tosylation of 4‐aminobenzamidine, which was proven via NMR and crystal struc...

A catalytic system for the chlorination of alcohols under Appel conditions was developed. Benzotrichloride is used as a cheap and readily available chlorinating agent in combination with trioctylphosphane as the catalyst and phenylsilane as the terminal reductant. The reaction has several advantages over other variants of the Appel reaction, e.g. n...

A straightforward, site-selective arylation of the bis(triflate) of estrone by Suzuki–Miyaura reactions has been developed. Monoarylation occurs selectively at the D-ring with good to excellent yield. Such products were exemplarily employed for the synthesis of estrones containing two different aryl substituents.

4-Bromo-3-O-triflyl-estrone has been synthesized in 2 steps from estrone and was successfully employed in chemoselective palladium catalysed Suzuki-Miyaura reactions. Mono- and bis-arylations were carried out selectively by variation of ligands and solvents. Overall 19 derivatives of mono- and bis-arylated estrones were synthesized under optimized...

The Suzuki-Miyaura reactions of 16-E-(triflyloxymethylidene)-3-methoxy-α-estrone allow for a convenient synthesis of various 16-E-(arylidene)-3-methoxy-α-estrones in good to high yields and with excellent E-selectivity. Both electron-rich and electron-poor boronic acids could be successfully employed.

Sonogashira reactions of steroids have been studied. The reaction of α-estron-16-methylidenyloxy triflate with various alkynes afforded novel alkynylvinylidene steroids. The reactions proceeded in good to quantitative yields, with excellent E-selectivity and with a broad synthetic scope.

16-E-Arylidene-3-methoxy-estrones were synthesized using a palladium catalysed Mizoroki-Heck reaction. This methodology tolerates various functional groups and gives the corresponding products in yields between 14 and 99%, which were strongly dependent on the electronic character of the aryl halides.

A novel selective catalytic reduction method of tertiary phosphine oxides to the corresponding phosphines has been developed. Notably, the reaction proceeds smoothly with low catalyst loadings of 1–5 mol% even at low temperature (70 °C). Under the optimized conditions various phosphine oxides could be selectively reduced and the desired phosphines...

The palladium‐catalyzed CH activation and arylation of N‐methylpyrrole and N‐phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand‐free catalytic system by using simple palladium salts or polyvinylpyrrolidone...