oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Synthesis and Molecular Structure of 4′,9′,4″,9″-Tetra-tert-butyl-1′,6′,1″,6″-tetramethoxy-2,5-dioxa[3.3]metabiphenylophane  [PDF]
Tetsuji Moriguchi,Tatsuya Egami,Akihiko Tsuge
Journal of Crystallography , 2014, DOI: 10.1155/2014/695701
Abstract: A large calixarene-like metacyclophane, 4′,9′,4″,9″-tetra-tert-butyl-1′,6′,1″,6″-tetramethoxy-2,5-dioxa[3.3]metabiphenylophane, was synthesized by an intermolecular condensation reaction of its corresponding bischloromethyl-biphenyl and bishydroxymethyl-biphenyl precursors. After molecular characterization by 1H NMR spectroscopy and mass spectrometry, the compound generated single crystals by recrystallization from a dichloromethane/hexane mixture, facilitating an exact conformational determination via X-ray diffraction analysis. The crystal was found to belong to the monoclinic space group with cell parameters a = 19.908(2)??, b = 9.7193(11)??, c = 23.350(3)??, β = 109.594(1)°, and ?g/cm3 at 90?K. The compound adopted quite strained 1,2-alternate-like conformations because its biphenyl parts displayed large dihedral angles and rigidity. The crystal did not incorporate any solvent molecule but its molecular cavity and crystal space were effectively filled by the substituents. 1. Introduction Calixarenes are cyclic compounds consisting of aromatic rings and methylene bridge chains. In search for novel supramolecular hosts, numerous efforts have been deployed to decorate the upper or lower rim of calixarenes with various functional groups [1–3]. However, the nature of their cyclic skeleton clearly plays a central role in their remarkable performance as host molecules. Members of the metacyclophane family [4–8], calixarenes, are readily obtained by base-assisted condensation of tert-butylphenol and formaldehyde into methylene-based bridges exclusively. In addition, several calixarene analogues such as []metacyclophanes containing oxygen [9, 10] or nitrogen [11, 12] instead of methylene groups in their bridges have been prepared. Cyclic compounds such as calix[4]arenes and large metacyclophanes present various conformations derived from the orientations of the aromatic parts [13]. In addition, the crystal structures of several cyclophanes have been reported using an alternative synthetic pathway [14] and cesium ion template effect [15–19]. Although large metacyclophanes comprising ether bridges and biphenyl units have been synthesized and their host-guest properties were reported [20, 21], their structures in the crystals were not determined. In this study, we report the synthesis of “oxametabiphenilophanes,” a new class of metacyclophanes that incorporate oxygen atoms in bridges and two biphenyl parts thus giving rigidity to the molecules (Scheme 1). A precursor mixture of bischloromethyl-biphenyl and bishidroxymethyl-biphenyl reacted under alkaline
tert-Butyl 3-(4-Cyano-5-phenylisothiazol-3-yl)carbazate  [PDF]
Heraklidia A. Ioannidou,Panayiotis A. Koutentis
Molbank , 2009, DOI: 10.3390/m628
Abstract: 3-Iodo-5-phenylisothiazole-4-carbonitrile 1 reacts with tert-butyl carbazate via a Buchwald C-N style coupling to afford tert-butyl 3-(4-cyano-5-phenylisothiazol-3-yl)- carbazate 2 in 70% yield. [...]
High Birefringence Liquid Crystals  [PDF]
Roman D?browski,Przemys?aw Kula,Jakub Herman
Crystals , 2013, DOI: 10.3390/cryst3030443
Abstract: Liquid crystals, compounds and mixtures with positive dielectric anisotropies are reviewed. The mesogenic properties and physical chemical properties (viscosity, birefringence, refractive indices, dielectric anisotropy and elastic constants) of compounds being cyano, fluoro, isothiocyanato derivatives of biphenyl, terphenyl, quaterphenyl, tolane, phenyl tolane, phenyl ethynyl tolane, and biphenyl tolane are compared. The question of how to obtain liquid crystal with a broad range of nematic phases is discussed in detail. Influence of lateral substituent of different kinds of mesogenic and physicochemical properties is presented (demonstrated). Examples of mixtures with birefringence ?n in the range of 0.2–0.5 are given.
Di-tert-butyl 2,2′-(biphenyl-2,2′-diyldioxy)diacetate  [cached]
Qamar Ali,Farooq Ibad,Muhammad Raza Shah,Donald VanDerveer
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808019764
Abstract: The title compound, C24H30O6, does not exhibit π–π interactions due to the steric effect of the bulky tert-butyl groups present in the molecule. The presence of these groups at the 2 and 2′ positions hinders the free motion of the benzene rings relative to each other, causing them to adopt an antiperiplanar arrangement. The benzene rings are twisted by just under 50.96 (17)° with respect to each other. The carbonyl groups within the molecule are directed in different directions, one towards the biphenyl group and the other away from it. The molecules are linked together by C=O...H—C hydrogen bonds.
N′-[(Biphenyl-4-yl)methylene]-2-[(3,5-di-tert-butyl-4-hydroxybenzyl)sulfanyl]acetohydrazide  [cached]
Wagee A. Yehye,Azhar Ariffin,Noorsaadah Abdul Rahman,Seik Weng Ng
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810006884
Abstract: In the title compound, C30H36N2O2S, the dihedral angle between the two aromatic rings of the biphenyl residue is 31.2 (1)°. The two methylene C atoms subtend an angle of 99.9 (1)° at the S atom. In the crystal, molecules form inversion dimers linked by pairs of N—H...O hydrogen bonds. The hydroxyl group is shielded by the tert-butyl residues and is therefore not involved in any hydrogen bonding.
3,3′,5,5′-Tetra-tert-butyl-2′-hydroxy-[1,1′-biphenyl]-2-yl 4-methylbenzenesulfonate  [cached]
Chunli Jian,Jinjin Zhang,Lei Wang,Ning Tang
Acta Crystallographica Section E , 2013, DOI: 10.1107/s1600536812051938
Abstract: In the title molecule, C37H48O4S, the benzene rings in the biphenyl fragment are inclined to each other at 61.1 (1)°. The hydroxy group is involved in a weak intramolecular O—H...Osulfonate hydrogen bond. One tert-butyl group is disodered over two orientations in a 0.682 (17):0.318 (17) ratio. In the crystal, weak C—H...O hydrogen bonds link the molecules into columns in direction [100].
tert-Butyl 6-amino-5-cyano-2-(2-methoxyethyl)nicotinate  [cached]
Yi-Ning Chen,Xing-Dong Zhao,Jie Deng,Qin-Geng Li
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812014328
Abstract: The title compound, C14H19N3O3, was synthesized by the reaction of 3-methoxypropionitrile, tert-butyl bromoacetate and ethoxymethylenemalononitrile. In the crystal, N—H...O hydrogen bonds link the molecules into chains propagating along the b axis.
Synthesis and Crystal Structure Determination of 4’,9’,4”,9”-Tetra-t-Butyl- 1’,6’,1”,6”-Tetramethoxy-2,5-Dithia[3.3] Metabiphenylophane  [PDF]
Tetsuji Moriguchi, Tatsuya Egami, Daisuke Yakeya, Venkataprasad Jalli, Kenji Yoza, Akihiko Tsuge
Crystal Structure Theory and Applications (CSTA) , 2016, DOI: 10.4236/csta.2016.53005
Abstract: The title compound 4’,9’,4”,9”-tetra-tert-butyl-1’,6’,1”,6”-tetramethoxy-2,5-dithia[3.3] metabiphenylophane was synthesized as a calixarene like large-sized metacyclophane from the corresponding 3,3’-bis(chloromethyl)-5,5’-bis(1,1-dimethylethyl)-2,2’-dimethoxy-1,1’-biphenyl and 3,3’-bis (mercaptomethyl)-5,5’-bis(1,1-dimethylethyl)-2,2’-dimethoxy-1,1’-biphenyl via an intermolecular condensation reaction. The compound was characterized using 1H NMR spectroscopy and mass spectrometry. Its exact conformational structure was determined via single crystal X-ray diffraction analysis. The compound has quite strained 1,2-alternate like structure because of its two high dihedral angled and rigid biphenyl parts in the crystal. The crystal includes the two isomers as two different 1,2-alternate like conformers, and the ratio of the two isomers is 78:22.
Ferroelectric ordering in chiral smectic C^* liquid crystals determined by nonchiral intermolecular interactions  [PDF]
M. A. Osipov,M. V. Gorkunov
Physics , 2007, DOI: 10.1103/PhysRevE.77.031701
Abstract: General microscopic mechanism of ferroelectric ordering in chiral smectic C* liquid crystals is considered. It is shown that if the mesogenic molecules have a sufficiently low symmetry, the spontaneous polarization is proportional to one of the biaxial vector order parameters of the smectic C phase. This order parameter may be determined by intermolecular interactions which are not sensitive to molecular chirality. At the same time, the polarization is also proportional to a pseudoscalar parameter which vanishes if the molecules are nonchiral. The general statistical theory of ferroelectric ordering is illustrated by two particular models. The first model is based on electrostatic quadrupole-quadrupole interactions, and it enables one to obtain explicit analytical expressions for the spontaneous polarization. In the second model, the molecular chirality and polarity are determined by a pair of off-center nonparallel dipoles. For this case, the spontaneous polarization is calculated numerically as a function of temperature. The theory provides a more general interpretation of the previous approaches including the classical Boulder model.
Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals  [PDF]
Yoriko Sonoda
Molecules , 2011, DOI: 10.3390/molecules16010119
Abstract: [2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of α,ω-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.