Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone

• Miroslav Mrsevic,
• David Düsselberg and
• Claudia Staudt

Beilstein J. Org. Chem. 2012, 8, 776–786, doi:10.3762/bjoc.8.88

• air leading to a change in optical properties, which often causes undesired optical aberrations [9]. It has been shown that cross-linking can significantly inhibit swelling phenomena in membranes prepared from DABA (3,5-diaminobenzoic acid) functionalized (co)polyimides [10][11][12]. This approach is

• simultaneously good solubility in organic solvents appears to be very valuable. If this material additionally acquires functional groups, i.e., carboxyl groups of the 3,5-diaminobenzoic acid (DABA) monomer, cross-linking is possible in order to decrease the water sorption. It is also possible to use carboxyl

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

• over a wide range of solvents and under reasonable pressure due to the high degree of cross linking, making them easier to use in flow processes. Historically monoliths have traditionally been used to facilitate the isocratic separation of peptides [19]; however, our group and others have shown

• phosphine monomer with a cross-linking component and a porogen [32][33]. A stock solution of the functionalised monomer (diphenyl(4-vinylphenyl)phosphine), cross-linking material (divinylbenzene and styrene) and porogen (1-dodecanol) was heated to 50 °C until a homogeneous solution was obtained. The

• hours in a Vapourtec R4 heater to give a white polymeric solid, which filled the column. It was noted that the addition of styrene as part of the cross-linking component was necessary to increase the active loading of the monolith during the reactions. Dibenzoyl peroxide was chosen as a radical

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

• activity, resin 1a, containing only 1% of the cross-linking agent DVB, exhibited consistently better productivities with the different substrates. It is also worth noting that in the case of catalyst 1a the conversions registered for the different substrates were not dependent on the chain length (Table 1

• in the conversion being observed with time in both cases. Contrary to our expectations based on the different degrees of cross-linking, no significant difference in stability was detected between resin 1a and resin 1b (the one with 8% DVB being only slightly more stable, as indicated by the

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• recovered and re-used in hydrogenation reactions in batch systems. We then developed polysilane-supported Pd/metal oxide hybrid catalysts [13] using the PI method (microencapsulation and cross-linking), which were then applied in these microreactor systems [14]. The hybrid catalysts were insoluble, did not

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• cross linking the diacetylene functional groups. Therefore, we have also synthesized and studied several diacetylene containing sugar lipids. Esterification of sugar headgroups with diacetylene containing long chain carboxylic acids can give the desired diacetylene containing lipids. Previously we had

Amphiphilic dendritic peptides: Synthesis and behavior as an organogelator and liquid crystal

• Baoxiang Gao,
• Hongxia Li,
• Defang Xia,
• Sufang Sun and
• Xinwu Ba

Beilstein J. Org. Chem. 2011, 7, 198–203, doi:10.3762/bjoc.7.26

• bonds. The absorption intensity at 3081 cm−1 decreases in the organogelator which indicates the loss of hydrogen bonds. Hydrogen bonds as physical cross-linking points in these compounds are an essential factor for gelling. With more physical cross-linking points, compound G3 gels more easily. Compound

Hybrid biofunctional nanostructures as stimuli-responsive catalytic systems

• Gernot U. Marten,
• Thorsten Gelbrich and
• Annette M. Schmidt

Beilstein J. Org. Chem. 2010, 6, 922–931, doi:10.3762/bjoc.6.98

• particle cross-linking or agglomeration due to multiple attachment of a single protein molecule by several nano-objects. Figure 3b compares the ATR-IR spectra of trypsin-functional nanoparticles (Fe3O4@P(M8O84S8)-Try) to free trypsin. In both samples, we observe similar amide signals (ν = 1620, 1578 cm−1

Kinetic studies and predictions on the hydrolysis and aminolysis of esters of 2-S-phosphorylacetates

• Milena Trmčić and
• David R. W. Hodgson

Beilstein J. Org. Chem. 2010, 6, 732–741, doi:10.3762/bjoc.6.87

• Milena Trmcic David R. W. Hodgson Centre for Bioactive Chemistry, Department of Chemistry, Durham University, Science Laboratories, South Road, Durham DH1 3LE, United Kingdom 10.3762/bjoc.6.87 Abstract Background: Heterobifunctional cross-linking agents are useful in both protein science and

• a thiophosphate nucleophile from commonly used bromoacetate ester cross-linking agents. Results: We found cross-linking between uridine-5′-monophosphorothioate and D-glucosamine using N-hydroxybenzotriazole and N-hydroxysuccinimde bromoacetates to be ineffective. In order to gain insight into these

• ; heterobifunctional cross-linker; hydrolysis; kinetics; thiophosphate; Introduction Heterobifunctional cross-linking agents are used widely in protein science for forming covalently-bonded protein-protein complexes [1] and protein-small molecule systems [2]. S-Alkylation and N-acylation processes are used together

Functionalized copolyimide membranes for the separation of gaseous and liquid mixtures

• Nadine Schmeling,
• Roman Konietzny,
• Daniel Sieffert,
• Patrick Rölling and
• Claudia Staudt

Beilstein J. Org. Chem. 2010, 6, 789–800, doi:10.3762/bjoc.6.86

• /aliphatics; copolyimides; cross-linking; gas separation; membranes; natural gas treatment; olefins/paraffins; pervaporation; Introduction Over 50% of energy costs in the chemical industry are used for the separation of gaseous or liquid mixtures [1]. Separations in petrochemical processes, e.g. low

• it will be definitely necessary to develop new plasticization resistant, robust membrane materials. Cross-linking of polymer structures has been found to be a suitable method to improve plasticization resistance as well as the separation characteristics for pervaporation [29][30][31][32][33] and gas

• polymerization reaction and can be used in further reactions, e.g., cross-linking. Polymerization takes place in a two step reaction. Firstly, the purified diamino monomers were dissolved in dry N,N-dimethylacetamide and the 6FDA dianhydride is added under a nitrogen atmosphere in order to form the polyamic acid

Synthesis, characterization and photoinduced curing of polysulfones with (meth)acrylate functionalities

• Cemil Dizman,
• Sahin Ates,
• Lokman Torun and
• Yusuf Yagci

Beilstein J. Org. Chem. 2010, 6, No. 56, doi:10.3762/bjoc.6.56

• demonstrate the structural and molecular weight effects on the curing behavior. Finally, the durability of the cross-linking material was investigated by TGA. Results and Discussion UV-Curable PSU telechelics were synthesized by condensation polymerization and subsequent esterification. First of all, PSU-2000

• -4000 exhibit no plateau region indicating the absence of the rapid auto acceleration at the very beginning of the reaction. This behavior may be due to factors related to the cross-linking nature of the samples and solid-state measurements. Since the obtained telechelics exhibit high melting points and

• polymerization rates at room temperature [30]. The cross-linking capability of the oligomers increased with the molecular weight of the macromonomer as a result of the increased flexibility of the longer chains. Therefore, PSU-DA-4000 displays a slightly higher conversion and a faster rate of polymerization

Functionalized polymers: synthesis and properties

• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, No. 55, doi:10.3762/bjoc.6.55

• , naturally occurring polymers as cellulose or polyisoprene were simply modified, for example by esterification or cross-linking to obtain the desired properties. Hermann Staudinger, for instance, chemically modified starch to prove the existence of high molecular weight substances. Nowadays, the development

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• themselves can be regarded as strands 1 and 3 of a three-stranded β-sheet, with cross-linking between the chains through the 4-position of adjacent phenylalanine residues. We also report on the conformational equilibria of these receptors in solution as well as on their tendency to dimerize. 1H NMR titration

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• alkylation and cross-linking. The success of mitomycin C in cancer treatment is due to a great cytotoxic selectivity for hypoxic (O2-deficient) cells characteristic of solid tumors [33][34]. Mitomycin C itself is indeed relatively unreactive toward DNA [35][36] but becomes remarkably reactive upon reduction

Ru-catalyzed dehydrogenative coupling of carboxylic acids and silanes - a new method for the preparation of silyl ester

• Guo-Bin Liu and
• Hong-Yun Zhao

Beilstein J. Org. Chem. 2008, 4, No. 27, doi:10.3762/bjoc.4.27

• ester)s were found to be an ideal family of degradable polymers [1]. Also, multifunctional silyl esters have been found to be ideal cross-linking agents since they require only mild reaction conditions, especially for silicone elastomers. The demand for degradable poly(silyl ester)s has been increasing