Search results for "Cyclohexane conformation"
showing 10 items of 52 documents
Derivatisation of Pyrogallarenes
2005
Derivatisation of upper-rim hydroxy groups of pyrogallarenes produced completely acylated and tosylated pyrogallarene derivatives. Mesitylation of pyrogallarene, however, resulted in a regioselective derivatisation of hydroxy groups, i.e. eight OH groups out of 12 were mesitylated. Crystal structures of the synthesised pyrogallarene derivatives indicate that completely substituted pyrogallarenes exist in a distorted crown conformation despite of the lack of stabilising intramolecular hydrogen bonds. In contrast, the partially substituted pyrogallarene adopts a boat conformation and has an open cavity for the inclusion of small guest molecules. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinh…
Synthesis and conformational analysis of tetrahydroisoquinoline- and piperidine-fused 1,3,4,2-oxadiazaphosphinanes, new ring systems
2006
Abstract Through cyclization of tetrahydroisoquinoline and piperidine 1,2-hydrazino alcohols with phenylphosphonic dichloride and phenyl dichlorophosphate, P-epimeric diastereomers of 1,6,7,11b-tetrahydro-4H-1,3,4,2-oxadiazaphosphino[5,4-a]isoquinoline-3-oxides ( 13 and 14 ), 1,6,11,11a-tetrahydro-4H-1,3,4,2-oxadiazaphosphino[4,5-b]isoquinoline-3-oxides ( 15 and 16 ) and 1,6,7,8,9,9a-hexahydro-4H-pyrido[1,2-d][1,3,4,2]oxadiazaphosphinane-3-oxides ( 17 and 18 ), the first representatives of these ring systems, were prepared. NMR and X-ray diffraction studies revealed that, independently of the P-substituent and the relative configuration of the phosphorus atom, 13 , 14 , 17 and 18 could be c…
Comparison of the crystal structures of 4,4′-bis[3-(4-methylpiperidin-1-yl)prop-1-yn-1-yl]-1,1′-biphenyl and 4,4′-bis[3-(2,2,6,6-tetramethylpiperidin…
2015
The crystal structures of the two title compounds display chair conformations of the piperidine rings in their molecules. In compound (I), the biphenyl system has a twisted conformation with a dihedral angle of 26.57 (6)° while in compound (II) the two phenyl rings are exactly coplanar.
Cation binding resorcinarene bis-crowns: the effect of lower rim alkyl chain length on crystal packing and solid lipid nanoparticles
2012
A group of seven resorcinarene bis-crown ethers (CNBC5) with two polyether bridges at the upper rim and either propyl, butyl, pentyl, heptyl, nonyl, decyl or undecyl groups at the lower rim were synthesized and their binding properties with Cs+ were investigated by NMR titration. The bis-crowns form 1:2 complexes with Cs+ with binding constants of logK 4–5. Crystal structures of bis-crowns and their Cs+ and K+ complexes were studied and different packing motifs were found depending on the alkyl chain length. Short ethyl, propyl and butyl alkyl chains gave a layer or pillar packing where the polar and non-polar regions cannot be distinguished, whereas longer pentyl and decyl chains formed bi…
Crystal structure and IR spectrum of 1-O-α-d-glucopyranosyl-d-mannitol–ethanol (2/1)
1999
Abstract 1- O - α - d -Glucopyranosyl- d -mannitol–ethanol (2/1), (C 12 H 24 O 11 ) 2 –C 2 H 5 OH, crystallizes in the monoclinic space group P2 1 with unit cell dimensions a =11.4230(8) A, b =9.525(4) A, c =15.854(2) A, β =102.751(7)° and V =1682.4(7) A 3 , Z =2, D x =1.45 Mg m −3 , λ (Mo-K α )=0.71069 A, μ=0.128 mm −1 , F (000)=788 and T =293(2) K. The structure was solved by direct methods and refined by least-squares calculations on F 2 to R 1 =0.0371[ I >2 σ ( I )], and 0.0930 (all data, 3542 independent reflections, R int =0.021). There are two molecules of glucopyranosylmannitol (GPM) and one ethanol molecule in the asymmetric unit, and the glucopyranosyl ring adopts a chair conforma…
Über blei-haltige Heterocyclen
1990
Abstract Crystal structures of alternating six-membered rings [Ph2PbS]3-P21/c and [Ph2SnS]3-P21/n have been determined by X-ray methods. Both heterocycles exhibit a C2-symmetric twisted boat conformation with tetrahedral coordination of the metal atoms [dPbS 2.491 A (dSnS 2.401 A, dPbC 2.19 A (dSnC 2.129 A)]. No additional intermolecular contacts have been found. A ring-segment exchange reaction in solution has been observed by NMR. In the resulting equilibrium new cyclic compounds containing both tin and lead atoms with coupling constants 2J(207PbS119Sn) 226 Hz have been detected. FD-mass spectra indicate formation of dimeric molecular units.
Zinn - Chalkogen - Heterocyclen. I. 2.4.6-Hexamethyl-1.3.5-triselena-2.4.6-tristannacyclohexan, Massen- und Schwingungsspektren
2010
The mass spectrum of the title compound exhibits very similar fragmentation patterns compared with the sulfur analogon. The high stability of triply coordinated organotin cations is remarkable. There is no evidence for any stabilisation effects by pπ-dπ bonding concerning the ring bonds. The assignment of the vibration spectra leads to the conclusion that the molecule of triselenastanninane possesses a boat conformation.
Theoretical and structural studies of lithium cyclic amide conformations. Monomers and aggregates
2000
High level ab initio calculations on the conformations of unsolvated and solvated lithium piperidide, 1, and lithium morpholide, 2, were carried out. It was found that both monomers exhibit a global minimum for a chair structure with a planar nitrogen, and 2 shows an additional stable pseudo boat conformation. Dimers and amine–lithium amide mixed aggregates were also calculated including discrete solvation; the role of aggregation is clearly shown both by the changes in geometries and in the stabilization energies. Semiempirical calculations carried out on a recently synthesized tetrameric mixed aggregate give a geometry very similar to the structure determined by X-ray diffraction. The pre…
Glycosylamines of 4,6-O-butylidene-α-d-glucopyranose: synthesis and characterization of glycosylamines, and the crystal structure of 4,6-O-butylidene…
2002
A total of nine glycosylamines of 4,6-O-butylidene-α-D-glucopyranose were synthesized using primary amines having various groups in their ortho- or para-positions. Among these, six are monoglycosylamines, including one primary glycosylamine, and three are bis-glycosylamines. All these compounds were characterized by 1H, 1H–1H COSY, 1H–13C COSY and 13C NMR spectroscopy and FTIR spectra. The FAB mass spectra provided the molecular weights of the products by exhibiting the corresponding molecular ion peaks. The crystal structure of 4,6-O-butylidene-N-(o-chlorophenyl)-β-D-glucopyranosylamine revealed the C-1 glycosylation, the β-anomeric nature, and the 4C1 chair conformation of the saccharide …
Crystal structure and theoretical study of (2E)-1-[4-hydroxy-3-(morpholin-4-ylmethyl)phenyl]-3-(thiophen-2-yl)prop-2-en-1-one
2018
WOS: 000437492100018