Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

• Sebastian Reinelt,
• Monir Tabatabai,
• Urs Karl Fischer,
• Norbert Moszner,
• Andreas Utterodt and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 1733–1740, doi:10.3762/bjoc.10.180

• organic matrix used in the formulation of dental composites [1][2][3][4]. The shrinkage stress and the leachability of unreacted monomers due to an insufficient double bond conversion are two of the main drawbacks of dimethacrylate based dental resins and are still a driving force for dental researches [2

Orthogonal dual thiol–chloroacetyl and thiol–ene couplings for the sequential one-pot assembly of heteroglycoclusters

• Michele Fiore,
• Gour Chand Daskhan,
• Baptiste Thomas and
• Olivier Renaudet

Beilstein J. Org. Chem. 2014, 10, 1557–1563, doi:10.3762/bjoc.10.160

• directly upon acid cleavage (1% TFA in CH2Cl2). The resins were treated for 3 min repeatedly until the resin beads became dark purple. The combined washings were concentrated under reduced pressure, and white solid peptides were obtained by precipitation from diethyl ether. General procedure for peptide

Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

• Xuanshu Xia and
• Patrick H. Toy

Beilstein J. Org. Chem. 2014, 10, 1397–1405, doi:10.3762/bjoc.10.143

• to be an efficient and highly recyclable catalyst for aldehyde and ketone cyanosilylation reactions from which the products could also be obtained pure after only filtration and solvent removal [30]. It should be noted that the grafts of the rasta resins reported are random co-polymers, and the

• ), which bears both triphenylphosphine oxide and tertiary amine moieties, in order to increase the efficiency and appeal of our method. We have extensive experience in preparing functionalized resins with two different catalytic groups [35][36][37][38], and prepared 18 by oxidation of 19, which we

• to the substrate. Use of our rasta resins 16 and 18 required only a 20 mol % excess. Rasta resins 14 and 15. The Masaki–Fukui reaction and halophosphonium salt reduction. Representative reactions involving halophosphonium salts 3a,b. Catalytic Appel reactions reported by Denton and co-workers

Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• ) group [43]). For a precise overview, the review of Isidro-Llobet 2009 and detailed manuals of major companies are recommended [44][45][46]. Optimal resins and linkers for peptide synthesis: The solid phase has to meet a number of requirements to be suitable for peptide synthesis. It has to be insoluble

• styrene and cross-linked divinylbenzene [20]. At present, there are mainly three classes of solid carriers: traditional polystyrene (PS), polyethylene glycol (PEG)-functionalized PS (such as TentaGel-supports [47]) and pure PEG-based resins such as PEGA resin [48] and ChemMatrix [49]. Shelton et al

• . recently published a collection of commonly used resins, together with their individual swelling and loading (is defined by the equivalents of amino acid in mmol/g, which can be attached to the resin) properties [50]. With respect to PEG-functionalized linkers, peptide synthesis yields can be improved by

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

• Oliver Goerz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 902–909, doi:10.3762/bjoc.10.88

• -dipolar cycloaddition with unsaturated bio-based polyester poly(isosorbide itaconate -co- succinate). Results and Discussion N-Alkylated dinitrones derived from acrylates and crotonates were prepared and evaluated in respect to their 1,3-cycloaddition with itaconic acid containing polyester resins. To

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• of nitric acid consumed during aromatic nitration is directed towards the synthesis of aniline derivatives, which are produced by nitration followed by reduction. These aniline derivatives find applications in insecticides, pigments, dyes, resins, textiles, elastomers, plant growth regulators

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• -critical ethanol. It is thought that the resins act as catalysts to release active palladium-species into solution. It also appeared that the IL-like unit was capable of capturing and stabilising the catalytically active soluble palladium species that are generated during the reaction. The reaction system

Oligomeric epoxide–amine adducts based on 2-amino-N-isopropylacetamide and α-amino-ε-caprolactam: Solubility in presence of cyclodextrin and curing properties

• Julian Fischer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2803–2811, doi:10.3762/bjoc.9.315

• resins exhibit poor solubility in water [15][16][17]. Accordingly, epoxide–amine polymers are not yet deeply investigated in respect to LCST behavior [18][19]. At present, most available bio-based and water soluble epoxy resins are expensive and use petroleum-based curing agents [20]. Thus, in the

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

• Quynh Pham Bao Nguyen and
• Taek Hyeon Kim

Beilstein J. Org. Chem. 2013, 9, 2113–2119, doi:10.3762/bjoc.9.248

• -linked, insoluble polymer supports, such as Merrifield and Wang resins, have been mainly explored [3][4][5]. However, the unavoidable heterogeneous-phase reaction and the spectroscopic analysis of the functionally supported products are extremely problematic. In an attempt to bridge the gap between the

• ]. Additionally, in the solid phase asymmetric alkylation reactions, in which Evans' 2-oxazolidinone chiral auxiliaries were used, the yield and stereoselectivity were too dependent on the base, reaction time, and supported resins. As an example, the base-catalyzed epimerization of the chiral center was

Flow synthesis of a versatile fructosamine mimic and quenching studies of a fructose transport probe

• Matthew B. Plutschack,
• D. Tyler McQuade,
• Giulio Valenti and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 2022–2027, doi:10.3762/bjoc.9.238

• basic approach, but improved throughput significantly [19]. The synthesis began with a Tiffeneau–Demjanov rearrangement of glucosamine·HCl using an acidic resin and NaNO2 to make nitrous acid in situ (Scheme 2). The original conditions required neutralization by a basic resin. After rinsing both resins

Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

• Mayeul Collot,
• Steffen Eller,
• Markus Weishaupt and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 97–105, doi:10.3762/bjoc.9.13

• /bjoc.9.13 Abstract Automated oligosaccharide assembly requires suitable linkers to connect the first monosaccharide to a solid support. A new hydrogenolysis-labile linker that is stable under both acidic and basic conditions was designed, synthesized and coupled to different resins. Glycosylation and

• cleavage efficiencies on these functionalized solid supports were investigated, and restrictions for the choice of solid support for oligosaccharide synthesis were found. Keywords: glycosylation; hydrogenolysis; linkers; oligosaccharides; resins; solid-phase synthesis; Findings Since Bruce Merrifield

• different resins were briefly explored [26]. However, for automated solid-phase oligosaccharide synthesis, Merrifield polystyrene resin has almost exclusively been used as the solid support. Here, we describe the development of a new linker system that was tested in the context of different solid supports

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

• Daniel Fürniss,
• Timo Mack,
• Frank Hahn,
• Sidonie B. L. Vollrath,
• Katarzyna Koroniak,
• Ute Schepers and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 56–63, doi:10.3762/bjoc.9.7

• both resins, the peptoid synthesis was successful; the only differences are the functional groups on the C-terminus. After cleavage from Rink-amide resin with trifluoroacetic acid, an amide is obtained, whereas cleavage from 2-chlorotrityl chloride resin with hexafluoroisopropanol (HFIP) gives the

Multivalent display of the antimicrobial peptides BP100 and BP143

• Imma Güell,
• Rafael Ferre,
• Kasper K. Sørensen,
• Esther Badosa,
• Iteng Ng-Choi,
• Emilio Montesinos,
• Eduard Bardají,
• Lidia Feliu,
• Knud J. Jensen and
• Marta Planas

Beilstein J. Org. Chem. 2012, 8, 2106–2117, doi:10.3762/bjoc.8.237

• was obtained. It has been previously reported that silanes under acidic conditions can promote the reduction of aldehydes [27]. Cleavage of the peptidyl resins with TFA/H2O (95:5) followed by purification by reversed-phase high-performance liquid chromatography (RP-HPLC) afforded peptide aldehydes 4

Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

• Jian Yin,
• Steffen Eller,
• Mayeul Collot and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 2067–2071, doi:10.3762/bjoc.8.232

• cleavage products revealed shortcomings for oligosaccharide synthesis. Keywords: glycosaminoglycans (GAGs); glycosylation; resins; safety-catch linker; solid-phase synthesis; Findings Solid-phase oligosaccharide synthesis [1][2] has been automated [3][4][5] to rapidly assemble complex oligosaccharides

• ] afforded linker 10. To support oligosaccharide synthesis, the safety-catch linker was first coupled to different resins (Scheme 2). In addition, since the activation and cleavage of safety-catch linkers is typically quite slow, a second, base-labile (Zemplén [24]) cleavage site was integrated to facilitate

• acid 13 with oxalyl chloride yielded acyl chloride 14, which, in turn, was coupled to linker 10 under the conditions established for the construction of resins 11 and 12, and afforded modified TentaGel resin 16 with both cleavage sites (Scheme 2). Functionalized resins 11 and 16, both containing

Photochemistry with laser radiation in condensed phase using miniaturized photoreactors

• Elke Bremus-Köbberling,
• Arnold Gillner,
• Frank Avemaria,
• Céline Réthoré and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1213–1218, doi:10.3762/bjoc.8.135

• , and several side-products, such as the corresponding azo-derivatives, are usually formed [36][40][41][42][43][44]. During the past few years, we successfully employed triazene resins, such as 4, which are readily available from aniline in the synthesis of a library of aromatic derivatives [45][46][47

• ][48]. Moreover, triazene-resins are perfectly suitable for the synthesis of arylazides 5 (Scheme 2) [49]. The photochemical decomposition of arylazides into carbazoles is appropriate for application in miniaturized photoreactors, since significant results can be observed by an online analysis through

Synthesis of diverse indole libraries on polystyrene resin – Scope and limitations of an organometallic reaction on solid supports

• Kerstin Knepper,
• Sylvia Vanderheiden and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1191–1199, doi:10.3762/bjoc.8.132

• distilled dichloromethane; IR spectra of resins were recorded in KBr on Bruker IFS88 IR. EI-MS (electron impact mass spectrometry): Kratos MS 50 (70 eV) and Thermo Quest Finnigan MAT 95 XL (70 eV). The molecular fragments are quoted as the relation between mass and charge (m/z), the intensities as a

• purchased from CalBiochem-NovaBiochem. General washing procedure for resins: After reaction the resins are subsequently washed according to the following procedure: (MeOH, THF, n-pentane, CH2Cl2) three times, (MeOH, DMF, n-pentane, THF) once, (n-pentane, CH2Cl2, n-pentane) twice. GP 1 - Immobilization of

Combined bead polymerization and Cinchona organocatalyst immobilization by thiol–ene addition

• Kim A. Fredriksen,
• Tor E. Kristensen and
• Tore Hansen

Beilstein J. Org. Chem. 2012, 8, 1126–1133, doi:10.3762/bjoc.8.125

• acrylonitrile, directly in a bottom-up fashion to give linear copolymers [1][8], or anchored to prefabricated cross-linked and thiol-funtionalized resins in a traditional post-modification approach [1][9]. However, for the preparation of the preferred beaded and cross-linked polymer resins, so easily handled

• organocatalyst precursors. Results and Discussion Building blocks for the preparation of cross-linked thiol–ene resins Research oriented towards thiol–ene chemistry has experienced near explosive growth in the past few years, perhaps due to its efficiency and functional tolerance, but possibly even more due to

• in several organic solvents, particularly in THF and CH2Cl2, despite their significant degree of cross-linking. As such, they have much in common with the CLEAR (cross-linked ethoxylate acrylate resin) resins, a type of polymer support with all the characteristics of a microporous polymer that also

Parallel solid-phase synthesis of diaryltriazoles

• Matthias Wrobel,
• Jeffrey Aubé and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

• potential inhibitors of protein–protein interactions. Results and Discussion Synthesis of azide-functionalized Wang resins Two azide-functionalized resins were prepared for the solid-phase synthesis of diaryl-triazoles. The commercially available 4-(bromomethyl)benzoic acid (5) was converted into azide 6 in

• of water occurred in the presence of TFA. The dehydrated products were obtained in 57 and 71%. The remaining material was the corresponding hydroxylated product. Parallel synthesis of a compound library A larger compound library was prepared by using resins 7 and 9, 15 different terminal alkynes 10f

• , 4.25; N, 23.75. Terphenyl scaffold 1 [13][14]; oxazole-pyridazine-piperazine 2 [14][15] and aryl-triazoles 3 and 4 [15][16] as α-helix mimetics. Synthesis of azido-functionalized resins 7 and 9. Copper-catalyzed [2 + 3] cycloadditions of resin-bound azide 7 with five terminal alkynes. Copper-catalyzed

Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

• Branislav Husár,
• Norbert Moszner and
• Ivan Lukáč

Beilstein J. Org. Chem. 2012, 8, 337–343, doi:10.3762/bjoc.8.37

• (CQ) in the presence of H-atom donors such as ethers (H abstraction), or more efficiently tertiary amines (electron/proton transfer), is known to be an effective photoinitiator for curing methacrylate-based dental restorative resins [1][2][3][4][5][6][7][8][9]. CQ photochemistry in solution in the

Ion-exchange-resin-catalyzed adamantylation of phenol derivatives with adamantanols: Developing a clean process for synthesis of 2-(1-adamantyl)-4-bromophenol, a key intermediate of adapalene

• Nan Wang,
• Ronghua Wang,
• Xia Shi and
• Gang Zou

Beilstein J. Org. Chem. 2012, 8, 227–233, doi:10.3762/bjoc.8.23

• acid [19], could circumvent the drawbacks associated with using concentrated H2SO4. However, these strong organic protic acids are expensive and volatile, and thus their recovery poses many difficulties. Strongly acidic ion-exchange sulfonic acid resins have been extensively exploited as recyclable

• acid catalysts for organic syntheses in both laboratory and industry since they became commercially available [23][24][25][26]. The success of recyclable ion-exchange resins as substitutes for mineral acids in organic syntheses prompted us to study the possibility of using acidic sulfonic acid resin as

• resins, could be easily converted into acetic acid by the addition of an equivalent amount of acetic anhydride during the work-up procedure. Further, after the sole byproduct, water, is converted into the solvent acetic acid, the resulting process is waste-free except for regeneration of the resin at its

Continuous proline catalysis via leaching of solid proline

• Suzanne M. Opalka,
• Ashley R. Longstreet and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2011, 7, 1671–1679, doi:10.3762/bjoc.7.197

• strategies involving the use of catalysts with limited solubility in flow rely on them being supported on resins or polymers (Figure 1A and B). This can be an attractive method as the catalysts are often easily recycled [20][21][22][23][24]. Finding a suitable solid support for a reaction, however, can prove

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors

• Kimberley A. Roper,
• Heiko Lange,
• Anastasios Polyzos,
• Malcolm B. Berry,
• Ian R. Baxendale and
• Steven V. Ley

Beilstein J. Org. Chem. 2011, 7, 1648–1655, doi:10.3762/bjoc.7.194

• ideal for use in a flow-chemistry setup. Elemental analysis showed an approximate loading of 1.87 mmol of phosphorus per gram, giving a calculated loading of 4.68 mmol of phosphorus per monolith, which is comparable to commercially available triphenylphosphine resins. Loading the monolith The monolith

Continuous-flow enantioselective α-aminoxylation of aldehydes catalyzed by a polystyrene-immobilized hydroxyproline

• Xacobe C. Cambeiro,
• Rafael Martín-Rapún,
• Pedro O. Miranda,
• Sonia Sayalero,
• Esther Alza,
• Patricia Llanes and
• Miquel A. Pericàs

Beilstein J. Org. Chem. 2011, 7, 1486–1493, doi:10.3762/bjoc.7.172

• Merrifield resin, and propargyloxyproline derivative 2, which was readily obtained in two steps from commercially available (2S,4R)-N-Boc-4-hydroxyproline (Scheme 2). Based on previous experience, we considered that variations in the degree of cross-linking of the support resins could have an important

• nature and readily swells in a variety of solvents, leading to gel formation. For catalytic resins, this ensures contact of the reactants in solution with essentially all the catalytic sites and, accordingly, high activity. This positive characteristic, however, can be countered by a poor mechanical

• macroporous resins. We accordingly expected that the catalyst immobilized on such a more heavily cross-linked resin, such as 1b, would retain an important level of activity while having less of a tendency for structural collapse under the flow conditions, and that, as a consequence, the useful lifetime of the