Factors influencing the performance of organocatalysts immobilised on solid supports: A review

• Zsuzsanna Fehér,
• Dóra Richter,
• Gyula Dargó and
• József Kupai

Beilstein J. Org. Chem. 2024, 20, 2129–2142, doi:10.3762/bjoc.20.183

• , providing a cost-effective alternative to traditional catalytic methods. The immobilisation of organocatalysts offers the potential to increase catalyst reusability and efficiency in organic reactions. This article reviews the key parameters that influence the effectiveness of immobilised organocatalysts

• , including the type of support, immobilisation techniques and the resulting interactions. In addition, the influence of these factors on catalytic activity, selectivity and recyclability is discussed, providing an insight into optimising the performance of immobilised organocatalysts for practical

• insoluble materials preferably with a large surface area to maximise the number of active sites for catalyst attachment. The advantages of such supports have been demonstrated by numerous reports on immobilised catalysts [12][13][14]. The type of support and the immobilisation technique have a major

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• engineering, cell culture and microbiology, or specific chemicals to aid in chemical, environmental, and medicinal filtration, and purification applications [5][19][42][60][61]. This also aids cell immobilisation, putting cryogels forward for potential use in bioreactors [5][42]. Cells can be included within

• the hydrophobic state of the polymer network at physiological temperature and the method of drug immobilisation. Additionally, cryogels based on other polymers such as polyacrylamide (PAAm), PNIPAM and poly(2-hydroxyethyl methacrylate) (PHEMA), obtained via the same method reported by Kostava et al

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• the catalyst expense. As enantioselective catalysts require expensive structural modifications, the possibility of immobilisation would facilitate catalyst recovery/recycle and drastically reduce the cost of the associated process. In 2012, silica-supported 5-(pyrrolidin-2-yl)tetrazole 63 was used to

• , the (S)-enantioselectivity could be reversed by inversion of stereochemistry at the terminal proline moiety of the supported peptide. Ötvös’ protocol highlights some of the key advantages of this immobilisation approach, i.e., improved reaction kinetics over batch (higher effective catalyst loading

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• solution, completing the photocatalyst cycle. Charge carriers must overcome competing processes that result in the immobilisation and recombination of charge carriers. The photogenerated electron/hole pair will spontaneously undergo bulk or surface recombination if they cannot efficiently separate, which

• accessible to the reaction media and the excitation photons, preventing the photocatalyst from being wasted in the bulk material. The immobilisation will generally reduce the reaction kinetics of the homogeneous photocatalyst as it is no longer dispersed in solution, but this can be mitigated through flow

• porphyrin colour from a purple powder to green when immobilised. The immobilisation of porphyrins onto polystyrene supports has been reported prior to this through covalent and electrostatic attractions but often suffered from poor coupling yields and low loadings [133][134][135][136]. Similarly, ionic

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• combination of properties has enabled numerous applications in the life sciences, for example, for protein binding [5][6], stabilization [7], immobilisation [8], isolation [9], self-assembly [10][11], and regulation [12], or for drug solubilisation and delivery [13][14][15]. The combination of CBs with

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• strategies to realise heterogeneous palladium catalysis [21]. Immobilisation of catalytic systems on solid supports can mitigate a lot of problems of homogeneous catalysts, for example, it allows a straightforward removal of the catalyst from the reaction system. However, most heterogeneous approaches

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

• Raimondo Maggi,
• N. Raveendran Shiju,
• Veronica Santacroce,
• Giovanni Maestri,
• Franca Bigi and
• Gadi Rothenberg

Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207

• consists of the immobilisation of a functional moiety on an inorganic support via covalent bonds ensured by a suitable linker [35]. In preliminary experiments reactions were carried out with a five-fold molar excess of alcohol. We started from this ratio as in the literature we did not retrieve any

Economical and scalable synthesis of 6-amino-2-cyanobenzothiazole

• Jacob R. Hauser,
• Hester A. Beard,
• Mary E. Bayana,
• Katherine E. Jolley,
• Stuart L. Warriner and
• Robin S. Bon

Beilstein J. Org. Chem. 2016, 12, 2019–2025, doi:10.3762/bjoc.12.189

• bioorthogonal reaction (k ≈ 10 M−1s−1) [9] for site-specific labelling or immobilisation of proteins 4, either at an N-terminal cysteine residue or at a 1,2-aminothiol group incorporated into a non-natural amino acid (Scheme 1) [10][11]. In addition, CBT derivatives have been used for the synthesis of polymeric

• ligations such as the site-specific labelling/immobilisation of proteins 4. Reported synthetic routes to ACBT 8: A) Original route reported by Takakura et al. [14] and Wang et al. [15]. B) The improved route reported by McCutcheon et al. [7]. Scale-up of ACBT synthesis. DABCO-catalysed cyanation of 6

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• metathesis and subsequent reduction of the obtained double bond in one pot. Keywords: catalysis; immobilisation; N-heterocyclic carbenes; olefin metathesis; ruthenium; Introduction Over the past decade olefin metathesis has undergone a grand development. The design of stable and active ruthenium-based

• of remotely functionalised ligands within the metal coordination sphere. A very efficient covalent immobilisation through anionic ligands was reported by Buchmeiser et al., who synthesised a series of monolith-supported catalysts (such as 1) which gave metathesis products with extremely low residual

• to the solution. A different valuable concept is the covalent or electrostatic immobilisation of ruthenium initiators on magnetically active nanoparticles. Complexes 5 [37] and 6 [38] presented in Figure 1 can serve as an examples, but others were also prepared [39]. These compounds are carefully

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• modified stereoselective catalysts were described [5][6][7][8]. Over the last few years, considerable attention has also been paid to immobilisation and tagging of catalysts and especially on making them more environmentally friendly [9][10][11][12][13][14]. Alkene cross-metathesis (CM) is a convenient

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• for eventual immobilisation of the final thymine glycoconjugate on a surface or for conjugation to another multivalent compound. For the click reaction of 5 with the thymine derivative 6, copper sulfate and sodium ascorbate were used. The conjugation product 7 was obtained in 71% yield and showed good

Removal of volatile organic compounds using amphiphilic cyclodextrin-coated polypropylene

• Ludmilla Lumholdt,
• Sophie Fourmentin,
• Thorbjørn T. Nielsen and
• Kim L. Larsen

Beilstein J. Org. Chem. 2014, 10, 2743–2750, doi:10.3762/bjoc.10.290

• Framework Directive). However, the fibres are exclusively produced for this purpose which might require the wastewater plant to change their existing setup and/or to buy specific equipment, all of which result in increased production costs. A method for simple and fast immobilisation of CDs onto various

The application of a monolithic triphenylphosphine reagent for conducting Ramirez gem-dibromoolefination reactions in flow

• Kimberley A. Roper,
• Malcolm B. Berry and
• Steven V. Ley

Beilstein J. Org. Chem. 2013, 9, 1781–1790, doi:10.3762/bjoc.9.207

• -Wittig and Appel reactions in flow [37][38][39][40]. The immobilisation of triphenylphosphine in this manner allowed the facile production of a collection of pure compounds using flow chemistry technologies with no need for further offline purification. Following the successful application of this

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• favourable physiological properties are considered, such as low toxicity [36] and receptor specificity of the azobenzene aglycon [37]. It will be our next goal to employ derivatives of azobenzene mannobioside 2 for immobilisation to test the photoswitching of adhesion on surfaces. Experimental Materials and

Formation of carbohydrate-functionalised polystyrene and glass slides and their analysis by MALDI-TOF MS

• Martin J. Weissenborn,
• Johannes W. Wehner,
• Christopher J. Gray,
• Robert Šardzík,
• Claire E. Eyers,
• Thisbe K. Lindhorst and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2012, 8, 753–762, doi:10.3762/bjoc.8.86

• ligands, such as protein, peptide and carbohydrate arrays [2][3]. An important aspect of this field is the immobilisation of such ligands on solid array surfaces, which can be polymers, such as polystyrene, or glass or gold, i.a. [4][5][6][7]. The challenge for immobilisations is in the efficiency of

• applied to the surface and the solvent was allowed to evaporate under atmospheric conditions. Unless otherwise stated, the spots were washed by following procedure 1. Carbohydrate arrays on polystyrene slides can be obtained by noncovalent immobilisation of tritylated saccharide derivatives. (A) Lectin

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• synthesised products could be valuable tools to follow glycan immobilisation on biomaterial surfaces. Preliminary results already demonstrate that biotinylated poly-LacNAc oligosaccharides (with deprotected NH2-linker) are detectable by streptavidin-peroxidase-detection after immobilisation on amine-reactive

Synthesis of glycosylated β³-homo-threonine conjugates for mucin-like glycopeptide antigen analogues

• Florian Karch and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2010, 6, No. 47, doi:10.3762/bjoc.6.47

• of the epithelial mucin MUC1 and an N-terminal non-immunogenic triethylene glycol spacer. The latter can be used for further conjugation to immunostimulants (e.g., BSA [35] or tetanus toxoid [36]) and for immobilisation onto microarray platforms [37] within functional immunological studies. The MUC1

Continuous flow based catch and release protocol for the synthesis of α-ketoesters

• Alessandro Palmieri,
• Steven V. Ley,
• Anastasios Polyzos,
• Mark Ladlow and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2009, 5, No. 23, doi:10.3762/bjoc.5.23

• purification. The average yield for the nitroolefins 1a–j prepared as described in Scheme 2 was approximately 60% by LCMS. Impurities were readily removed following immobilisation of nitroolefinic esters 1 on the QP-BZA resin. In addition, the flow synthesis of two representative compounds was undertaken to

A practical synthesis of the ¹³C/¹⁵N- labelled tripeptide N-formyl- Met-Leu-Phe, useful as a reference in solid- state NMR spectroscopy

• Sven T. Breitung,
• Jakob J. Lopez,
• Gerd Dürner,
• Clemens Glaubitz,
• Michael W. Göbel and
• Marcel Suhartono

Beilstein J. Org. Chem. 2008, 4, No. 35, doi:10.3762/bjoc.4.35

• . Results and Discussion Peptide Synthesis The synthesis of the MLF tripeptide started with the immobilisation of 13C/15N-labelled Fmoc-Phe-OH to the solid support (Wang resin 2). This esterification step, leading to 3 quantitatively, was performed by activating the COOH group with MSNT under mild reaction

• ; 13C: 75.5 MHz). Immobilisation of the first monomer: Wang resin (485 mg, 0.315 mmol, capacity: 0.65 mmol/g) was swelled under argon with dry CH2Cl2 (1.5 mL) in an oven dried reaction vessel for 15 min. In a second dry vessel, 13C/15N-labelled Fmoc-Phe-OH (250 mg, 0.63 mmol) was dissolved in dry CH2Cl2