1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• and form linear (benzyl alcohol, ethylene glycol) and star-branched (glycerol, pentaerythritol) polyesters. In comparison to their linear analogues, star-branched polymers feature lower crystallinity, lower melt viscosities and smaller hydrodynamic volume [56][57][58]. The crystallinity (defined

• according to Equation 3 with ΔHc being the crystallization enthalpy, and ΔH' the enthalpy of fusion of PCL, ΔH' = 161.1 J·g−1) affects directly the melting temperature (Tm). Thus, a decrease of molecular weight causes a decrease of the Tm. Analysis of the crystallinity of the various polycaprolactones by

• differential scanning calorimetry is summarized in Table 4. DSC profiles are depicted in Supporting Information File 2 (Figure S1). Samples with molecular weight in the 1100–1500 Da range (Table 4), show similar Tm and Tc, although the endings of the chains are different. However, values for the crystallinity

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• . However, variable temperature experiments (−50 °C) produced a notable sharpening in both aromatic and aliphatic protons. Ultimately, elucidation of their structure was carried out by X-ray analysis, which was feasible due to their high crystallinity [54]. We found that in the solid state, compounds 19 and

The crystal structure of the Dess–Martin periodinane

• Albert Schröckeneder,
• Desiree Stichnoth,
• Peter Mayer and
• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 1523–1527, doi:10.3762/bjoc.8.172

• crystallinity of the compound. Indeed, microcrystalline 1 precipitates from the acetic anhydride solution upon cooling at the end of the procedure used for its preparation. Various recrystallization methods also yielded 1 as a microcrystalline powder that was unsuitable for single-crystal X-ray analysis

• synthesis. The similarity of our experimentally determined structure with a calculated gas-phase structure of monomeric 1 underscores the power of density functional theory. A network of halogen and hydrogen bonds in the supramolecular structure explains the high crystallinity of 1 and has implications with

Restructuring polymers via nanoconfinement and subsequent release

• Alan E. Tonelli

Beilstein J. Org. Chem. 2012, 8, 1318–1332, doi:10.3762/bjoc.8.151

• crystallizabilities were also observed for PCLs of various molecular weights when coalesced from their U ICs [68]. Density and DSC measurements [70] revealed a closer packing of chains in the noncrystalline sample regions, but this did not affect the overall crystallinity of the c-PCL films. Increased elastic storage

• suggest that p-PET readily attains higher crystallinity even when repeatedly cooled rapidly from the melt. Apparently the extended conformations of largely unentangled chains in p-PET do not become coiled and entangled even after spending substantial time in the melt. As a consequence, we have

• , each with ~10% crystallinity, reveals that the nuc-PET film has significantly increased density, hardness and Young’s modulus and is also much less permeable to CO2 than the asr-PET film. Undrawn nuc-PET fibers also exhibited significantly higher tenacities and moduli than undrawn asr-PET fibers. Self

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• ” in the middle, and thus unable to arrange themselves into a suitable mesophase structure. It is also worth briefly mentioning a couple of examples in which rodlike mesogenic or proto-mesogenic ligands have been grafted to NPs for studies focused on properties other than liquid crystallinity, in order

Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers

• Abigail Page and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1327–1333, doi:10.3762/bjoc.7.156

• d.r.'s may result from some electrophiles by competitive reaction with up to 15% retention (Table 1), and the effect of (−)-sparteine on the d.r.'s in Table 1 may be because its steric bulk helps to suppress this competing retentive pathway. Lack of crystallinity has meant that we cannot unequivocally

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

• polyesters such as polylactic acid (PLA) and poly(ε-caprolactone) [1] are of great interest due to their biodegradability, biocompatibility and permeability for many drugs. In contrast, poly(glycolic acid) (PGA) is scarcely used because of its high degree of crystallinity and its insolubility in all common

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• treatment of 7 with LDA in THF at −78 °C, followed by trapping with methyl chloroformate, a yield of 40% of the bicyclic hexahydroisoquinoline 8 was obtained (Scheme 3), which even after extensive experimentation could not be improved. Lack of crystallinity and overlapping 1H NMR signals prevented us from

• obtained by the use of an H-cube flow hydrogenation apparatus at 40 bar and 30 °C. Unfortunately, again the lack of crystallinity and the large number of overlapping signals in the 1H NMR spectrum frustrated an unequivocal assignment of the stereochemistry. However, hydrogenation of related fused

Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

• Gundula F. Starkulla,
• Elisabeth Kapatsina,
• Angelika Baro,
• Frank Giesselmann,
• Stefan Tussetschläger,
• Martin Kaller and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 63, doi:10.3762/bjoc.5.63

• the rigid rod core structure (Scheme 1) as exemplified by the derivative 1a which displays a SmA phase between 45 °C and 71 °C, while the corresponding biphenyl derivative 2a with the same terminal alkyl chains does not have any liquid crystallinity [1]. Whereas three regioisomeric phenylpyrimidines

Novel banana-discotic hybrid architectures

• Hari Krishna Bisoyi,
• H. T. Srinivasa and
• Sandeep Kumar

Beilstein J. Org. Chem. 2009, 5, No. 52, doi:10.3762/bjoc.5.52

• be the reason for absence of liquid crystallinity in compound 6. The banana discotic hybrid 8a melts at 92.6 °C to an isotropic liquid and on cooling it slowly crystallizes at 77.6 °C. Similarly, compound 8b on heating melts to isotropic liquid at 75.8 °C and on cooling slowly crystallizes at 54.9 °C

Synthesis of thienyl analogues of PCBM and investigation of morphology of mixtures in P3HT

• Fukashi Matsumoto,
• Kazuyuki Moriwaki,
• Yuko Takao and
• Toshinobu Ohno

Beilstein J. Org. Chem. 2008, 4, No. 33, doi:10.3762/bjoc.4.33

• crystallinity of the polymer [13][14], and controlling the growth rate of the organic film [15][16]. These studies reported that the morphology of the active layer is a critical factor that determines the device efficiency. Investigations have been performed for exploring new donor materials for bulk

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• preliminary guidelines for the observation of liquid crystallinity in those compounds. Among these is the necessity of the rings to fill their interior more or less with their own alkyl chains and the absence of bulky peripheral side groups, both in order to prevent an interlocking of the rings. However, the

• completely is common for all macrocycles, thus making them potential candidates for the observation of thermotropic liquid crystallinity according to the new design principle described above. Results and Discussion Synthesis Scheme 1 shows the synthesis of the macrocycles that have a reduced interior size

• mesophases. However, reports about shape-persistent macrocycles with extraannular PAH substituents are absent. If these compounds exhibit liquid crystallinity, the question about the mesogenic element (ring or PAH or both) arises. Additionally, biaxial nematic phases might be observable [31][32]. The