scholarly journals Squaraine Rotaxanes with Boat Conformation Macrocycles

2009 ◽  
Vol 74 (17) ◽  
pp. 6462-6468 ◽  
Author(s):  
Na Fu ◽  
Jeffrey M. Baumes ◽  
Easwaran Arunkumar ◽  
Bruce C. Noll ◽  
Bradley D. Smith
Keyword(s):  
Boat Conformation ◽  
Squaraine Rotaxanes

The Crystal and Molecular Structure of sym-fac-(1,4,7-Triazaheptane)-(S)-aspartatocobalt(III) Diperchlorate Dihydrate

1994 ◽  
Vol 59 (5) ◽  
pp. 1052-1058 ◽  
Author(s):  
Jan Ondráček ◽  
Jana Ondráčková ◽  
Jaroslav Maixner ◽  
František Jursík
Keyword(s):  
Molecular Structure ◽  
Aspartic Acid ◽  
Crystal And Molecular Structure ◽  
Heavy Atom ◽  
Membered Ring ◽  
Boat Conformation ◽  
Hydrogen Atoms ◽  
Orthorhombic System ◽  
Anisotropic Temperature ◽  
Heavy Atom Method

The crystal and molecular structure of s-fac-[Co((S)-Asp)(dien)]ClO4 . HClO4 .2 H2O (dien = 1,4,7-triazaheptane) was solved by the heavy atom method. The position parameters of the non-hydrogen atoms and their anisotropic temperature parameters were refined based on 1 726 observed reflections with a final value of R = 0.073. The substance crystallizes in the orthorhombic system in the space group P212121, Z = 4, a = 8.506(1), b = 17.171(2), c = 13.277(1) Å. The structure involves hydrogen bonds between the O2, O4 and HN2 atoms of aspartic acid and the two molecules of water. The five-membered dien chelate rings take the asymmetric envelope conformations. The five-membered ring of (S)-aspartic acid possesses the symmetric envelope conformation whereas the six-membered ring exhibits the skew boat conformation.

The Structure and Photochromism of 2,4,4,6-Tetraphenyl-4H-thiopyran

1992 ◽  
Vol 57 (6) ◽  
pp. 1326-1334 ◽  
Author(s):  
Jaroslav Vojtěchovský ◽  
Jindřich Hašek ◽  
Stanislav Nešpůrek ◽  
Mojmír Adamec
Keyword(s):  
Solid State ◽  
Uv Light ◽  
Order Reaction ◽  
Boat Conformation ◽  
X Rays ◽  
Exponential Time ◽  
First Order ◽  
Double Plane ◽  
The Mean ◽  
Independent Molecules

2,4,4,6-Tetraphenyl-4H-thiopyran, C29H22S, orthorhombic, Pna21, a = 17.980(4), b = 6.956(2), c = 34.562(11) Å, V = 4323(2) Å3, Z = 8, Dx = 1.237 g cm-3, F(000) = 1696, λ(CuKα) = 1.54184 A, μ = 1.372 mm-2, T = 294 K. The final R was 0.050 for the unique set of 3103 observed reflections. The central 4H-thiopyran ring forms a boat conformation for both symmetrically independent molecules with average boat angles 4.4(3) and 6.8(3)° at S and C(sp3), respectively. The mean planes of phenyls at the position 2 and 6 are turned from the double plane of 4H-thiopyran by 42.5(5) and 35.8(3)°, respectively. The investigated material undergoes a photochromic change in the solid state after irradiation with UV light or X-rays. The maximum of the new absorption band is situated at 564 nm. The non-exponential time dependence of photochromic bleaching is analysed in terms of a dispersive first-order reaction.

The structure of 1,2,4,4,6-pentaphenyl-1,4-dihydropyridine

1990 ◽  
Vol 55 (8) ◽  
pp. 2059-2065 ◽  
Author(s):  
Jaroslav Vojtěchovský ◽  
Jindřich Hašek ◽  
Jiří Ječný ◽  
Karel Huml
Keyword(s):  
Title Compound ◽  
Cambridge Structural Database ◽  
Boat Conformation ◽  
Planar Conformation ◽  
Structural Database ◽  
Independent Molecules ◽  
Dihydropyridine Ring

Title compound is triclinic, Mr = 461.60; P1, a = 9.158(1), b = 16.062(3), c = 19.472(3) Å, α = 110.69(1)°, β = 89.70(1)°, γ = 103.17(1)°, V = 2 600(1) Å3, Z = 4, Do = 1.15(3), Dc = 1.179(1) Mg m-3, λ(CuKα) = 1.5418 Å, μ = 0.509 mm-1, F(000) = 976 K, R = 0.040 for 8 059 unique observed reflections. Both symmetrically independent molecules show a different geometry of the 1,4-dihydropyridine ring: either the boat conformation with apexes C(sp3), N and boat angles 14.7(3)° and 10.3(2)° respectively, or the planar conformation. The conformation has been compared with similar dihydropyridines obtained from Cambridge Structural Database.

Cyclization Dichotomy of D-xylo-Hex-5-ulosonamides and Synthesis of Piperidine Analogs of Aldohexoses and Aldohexono-1,5-lactones

1999 ◽  
Vol 64 (4) ◽  
pp. 673-684 ◽  
Author(s):  
Radka Kováříková ◽  
Miroslav Ledvina ◽  
David Šaman
Keyword(s):  
Boat Conformation ◽  
Direct Transformation

The preparation of 2,3,4,6-tetra-O-benzyl-5-D-xylo-hex-5-ulosonamides 3a and 3b and their cyclization to 5-amino-2,3,4,6-tetra-O-benzyl-5-deoxy-D-glucono-1,5-lactam (4) and 5-amino- 2,3,4,6-tetra-O-benzyl-5-deoxy-D-talono-1,5-lactam (5) or to 2,3,4,6-tetra-O-benzyl-1,5-dideoxy-1,5-imino-D-glucitol (9), and also their direct transformation into 2,3,4,6-tetra-O-benzyl- D-talono-1,5-lactone (6), are described and discussed. The atypical boat conformation of D-talonolactam 5 and D-talonolactone 6 was found.

Crystal Structure and Conformation of Ring A of 2β-Bromo-19β,28-epoxy-18α-oleanan-3-one

1993 ◽  
Vol 58 (11) ◽  
pp. 2737-2744 ◽  
Author(s):  
Jiří Novotný ◽  
Jaroslav Podlaha ◽  
Jiří Klinot
Keyword(s):  
Crystal Structure ◽  
Opposite Direction ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Form Ring ◽  
Twist Boat

The crystal structure of β-bromo-19β,28-epoxy-18α-oleanan-3-one was elucidated. The crystal is orthorhombic, P212121, a = 9.686(1), b = 14.355(2), c = 19.687(4) Å, Z = 4, R = 0.042 for 2 410 observed reflections. Rings B, C, D and E adopt the chair conformation, the five membered ether cycle in ring E occurs in the envelope form. Ring A takes the twist-boat conformation turned towards the classical boat with C2 and C5 in the stem-stern position, in contrast to the conformation in solution, which is turned in the opposite direction towards the classical boat with C3 and C10 in the stem-stern positions.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

The Boat Conformation in Pyrazaboles. A Theoretical and Experimental Study†

2008 ◽  
Vol 8 (3) ◽  
pp. 838-847 ◽  
Author(s):  
Emma Cavero ◽  
Raquel Giménez ◽  
Santiago Uriel ◽  
Eduardo Beltrán ◽  
José Luis Serrano ◽  
...  
Keyword(s):  
Experimental Study ◽  
Boat Conformation

scholarly journals 7′-Amino-1′H-spiro[cycloheptane-1,2′-pyrimido[4,5-d]pyrimidin]-4′(3′H)-one

2012 ◽  
Vol 68 (8) ◽  
pp. o2546-o2546
Author(s):  
Shu Chen ◽  
Daxin Shi ◽  
Mingxing Liu ◽  
Jiarong Li
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Three Dimensional ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Compound C ◽  
Dimensional Network

The title compound, C12H17N5O, was obtained by cyclocondensation of 2,4-diaminopyrimidine-5-carbonitrile with cycloheptanone. The tetrahydropyrimidine ring has a distorted boat conformation and the cycloheptane ring adopts a chair conformation. In the crystal, molecules are linkedviaN—H...O and N—H...N hydrogen bonds generating a three-dimensional network.

scholarly journals 6-Amino-3-methyl-4-(3,4,5-trimethoxyphenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile

2014 ◽  
Vol 70 (8) ◽  
pp. o875-o876 ◽  
Author(s):  
Naresh Sharma ◽  
Goutam Brahmachari ◽  
Bubun Banerjee ◽  
Rajni Kant ◽  
Vivek K. Gupta
Keyword(s):  
Hydrogen Bonds ◽  
Benzene Ring ◽  
Title Compound ◽  
Pyrazole Ring ◽  
Ring System ◽  
Boat Conformation ◽  
Two Dimensional ◽  
Compound C ◽  
Dimensional Network ◽  
Centroid Distance

In the title compound, C17H18N4O4, the dihedral angle between the benzene ring and 2,4-dihydropyrano[2,3-c]pyrazole ring system is 89.41 (7)°. The pyran moiety adopts a strongly flattened boat conformation. In the crystal, molecules are linked by N—H...N, N—H...O, C—H...N and C—H...O hydrogen bonds into an infinite two-dimensional network parallel to (110). There are π–π interactions between the pyrazole rings in neighbouring layers [centroid–centroid distance = 3.621 (1) Å].

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