Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• The pKa values for the derivatives 1–5 dissolved in 50:50 water/acetonitrile solution were determined by potentiometric titration using a PHM210 Standard lab pH meter that had been calibrated against standards (pH 4 and pH 7). The electrode was first placed in 50 ml of a known concentration of an acid

Chiral recognition of macromolecules with cyclodextrins: pH- and thermosensitive copolymers from N-isopropylacrylamide and N-acryloyl-D/L-phenylalanine and their inclusion complexes with cyclodextrins

• Sabrina Gingter,
• Ella Bezdushna and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 204–209, doi:10.3762/bjoc.7.27

• Viscotek TSK GMHHR-M 7.8 mm (ID) × 30 cm (L) columns at 60 °C. N,N-Dimethylformamide (DMF, 0.1 M LiCl) was used as eluent at a flow rate of 1 mL·min−1. A Viscotek VE 3500 RI detector and a Viscotek Viscometer model 250 were used. The system was calibrated with polystyrene standards with a molecular range

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• product mixture, using the sum of 5-methyl (5-H) and 6-H signals as internal standards. The yields and the ratios of the two regioisomeric oxetanes were obtained from the peak areas of 5-methyl and 6-H for DMT system and those of 5-H and 6-H for DMU system in the 1H NMR spectra. The experimental error was

Hoveyda–Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

• Hynek Balcar,
• Tushar Shinde,
• Naděžda Žilková and
• Zdeněk Bastl

Beilstein J. Org. Chem. 2011, 7, 22–28, doi:10.3762/bjoc.7.4

• polystyrene standards. Grubbs 1 and Hoveyda–Grubbs 2 catalysts. Zhan catalyst-1B. Conversion curves for the RCM of DEDAM with 3 in CH2Cl2 (open squares), 3/SBA-15 in CH2Cl2 (inverted filled triangle), 3/SBA-15 in benzene (filled diamond), 3/SBA-15 in cyclohexane (filled triangle), and for the RCM of 1,7

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• performed relative to PMMA standards (Polymer Standards Service, Mp 1100–981.000 Da). Differential scanning calorimetry (DSC) experiments were carried out under a nitrogen atmosphere at a heating rate of 10 °C × min−1 with a DSC821e (Mettler Toledo) calorimeter up to a temperature of 150 °C with a sample

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

• Julia Theis and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 938–944, doi:10.3762/bjoc.6.105

• absorbance detector (λ = 256 nm) and a Waters 410 differential refractometer were used. The number average molecular weight (Mn), the weight average molecular weight (Mw) and the polydispersity (PD) were calculated by a calibration curve generated by polystyrene standards with a molar mass range from 580 to

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

• . For TGA, a Netzsch STA 449c in a He atmosphere was used with a heating rate of 10 K·min−1 between 30 and 600 °C. Gel permeation chromatography (GPC) elugrams were collected on THF (300 × 8 mm2 MZ Gel Sdplus columns, Waters 410 RI-detector) relative to polystyrene standards. NMR spectroscopy was

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine

• Lisa K. Thalén and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97

• ) as internal standards, and coupling constants (J) are given in Hz. The enantiomeric excess was determined by analytical GC employing a CP-Chirasil-DEX CB column (25 m Ø × 0.32 mm). Racemic compounds were used as references. Dynamic Kinetic Resolution 45 mmol scale: (R)-2-methoxy-N-(1-phenylethyl

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• -detector, indicating that the porphyrin has a lower RI than the eluent, and a positive signal in the UV-detector at 500 nm, where the porphyrin has a strong UV-absorption (Figure 9b). The Mn was calculated to be 1,580 g/mol with a polydispersity index (PDI) of 1.06 (against polystyrene standards). This PDI

• with the UV-detector at 500 nm revealed a relatively narrow molar mass distribution (Figure 9b), proving that the porphyrin is incorporated into the polymer. The SEC analysis with the UV-detector yielded a Mn of 10,700 g/mol and a PDI of 1.18 based on linear poly(ethylene glycol) standards. The Mn is

• lower than the theoretical molar mass (~21,000 g/mol) due to calibration with linear standards with a different molecular structure. The hydrodynamic volume, that determines the retention time, will be very different for a star-shaped polymer when compared to a linear polymer. Nonetheless, the narrow

Novel multi-responsive P2VP-block-PNIPAAm block copolymers via nitroxide-mediated radical polymerization

• Cathrin Corten,
• Katja Kretschmer and
• Dirk Kuckling

Beilstein J. Org. Chem. 2010, 6, 756–765, doi:10.3762/bjoc.6.89

• weight determined by MALDI-TOF MS only increased from Mn = 1530 g/mol to Mn = 2800 g/mol. One reason might be the laser energy used to desorb the polymer led to P2VP chain degradation or fragmentation. Since SEC calibration has been done with P2VP standards, one can assume that the different results can

Calix[4]arene-click-cyclodextrin and supramolecular structures with watersoluble NIPAAM-copolymers bearing adamantyl units: “Rings on ring on chain”

• Bernd Garska,
• Monir Tabatabai and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 784–788, doi:10.3762/bjoc.6.83

• weight (Mw) and the polydispersity (PD) were calculated by a calibration curve generated by polystyrene standards with a molecular weight range from 370 to 1000000 Da. DLS experiments were carried out on a Malvern HPPS-ET apparatus at a temperature value of 10 °C. The particle size distribution was

Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

• Florian K. Wolf,
• Anna M. Fischer and
• Holger Frey

Beilstein J. Org. Chem. 2010, 6, No. 67, doi:10.3762/bjoc.6.67

• via calibration with polyethylene glycol (PEG) standards. The obvious underestimation of the molecular weight by SEC is attributed to the peculiar spherical geometry of the multi-arm star copolymer and has also been observed with other star polymers. The polydispersities of the materials are in the

• series was used as an integrated instrument, including a PSS Gral column (104/104/102 Å porosity) and RI detector. Calibration was achieved with poly(ethylene glycol) standards provided by Polymer Standards Service (PSS)/Germany. Differential scanning calorimetry (DSC) measurements were carried out on a

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP

• Olubummo Adekunle,
• Susanne Tanner and
• Wolfgang H. Binder

Beilstein J. Org. Chem. 2010, 6, No. 59, doi:10.3762/bjoc.6.59

• analysis was performed on a Viscotek VE2001 system with THF as the eluant at a flow rate of 1 ml/min and an injection volume of 100 µL. Polystyrene standards were used for conventional external calibration using a Viscotek VE3580 refractive index detector. Positive ion MALDI-TOF (matrix-assisted laser

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

• determined using polystyrene standards. Thermal gravimetric analysis (TGA) was performed on Perkin–Elmer Diamond TA/TGA with a heating rate of 10 °C min under nitrogen flow. Preparation of the oligomers General procedure for the synthesis of polysulfone oligomer Bisphenol A (40 g, 175 mmol), bis(p

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

• Gajanan M. Pawar,
• Jochen Weckesser,
• Siegfried Blechert and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, No. 28, doi:10.3762/bjoc.6.28

• and λ2 = 343.600 nm, respectively. A 1000 ppm Rh standard (1N HNO3, Merck, Germany) was used to prepare standards of 0, 0.100, 1.00 and 10.00 ppm. General procedure for hydroformylation: The reaction was carried out in a 300 mL Parr high-pressure reactor. The reactor was evacuated, flushed with argon

Templated versus non-templated synthesis of benzo-21-crown-7 and the influence of substituents on its complexing properties

• Wei Jiang and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2010, 6, No. 14, doi:10.3762/bjoc.6.14

• required, developed in I2 vapor. Column chromatography was performed on silica gel 60 (Merck 40–60 nm, 230–400 mesh). 1H and 13C NMR spectra were recorded on Bruker ECX 400 MHz and Jeol Eclipse 500 MHz. All chemical shifts are reported in ppm with residual solvents as the internal standards, and the

Phaeochromycins F–H, three new polyketide metabolites from Streptomyces sp. DSS-18

• Jian Li,
• Chun-Hua Lu,
• Bao-Bing Zhao,
• Zhong-Hui Zheng and
• Yue-Mao Shen

Beilstein J. Org. Chem. 2008, 4, No. 46, doi:10.3762/bjoc.4.46

• , following the MTT standards [8] and using cisplatin (DDP) as a positive control. Phaeochromycins F and G were found to have weak cytotoxicities with inhibitory rates 9.4% and 1.0% at a concentration of 10 μg/ml. Phaeochromycin H showed a modest inhibitory rate of 46.0% at a concentration of 10 μg/ml