35453
2012
2012
eng
3803
3811
9
17
13
article
Wiley-VCH
Weinheim
1
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Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine
On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity.
ChemPhysChem : a European journal of chemical physics and physical chemistry
10.1002/cphc.201200732
1439-4235
wos:2011-2013
WOS:000312038200010
Baranac-Stojanovic, M (reprint author), Univ Belgrade, Fac Chem, Studentski Trg 16,POB 158, Belgrade 11000, Serbia., mbaranac@chem.bg.ac.rs
Ministry of Education and Science of the Republic of Serbia [172020];
Deutscher Akademischer Austauschdienst (DAAD) [504 252 70]
Marija Baranac-Stojanovic
Andreas Koch
Erich Kleinpeter
eng
uncontrolled
anisotropic effects
eng
uncontrolled
aromaticity
eng
uncontrolled
B,N heterocycles
eng
uncontrolled
density functional calculations
eng
uncontrolled
NMR spectroscopy
Institut für Chemie
Referiert
36367
2012
2012
eng
370
376
7
1
18
article
Wiley-Blackwell
Malden
1
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Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct?
Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
Chemistry - a European journal
10.1002/chem.201101882
0947-6539
wos:2011-2013
WOS:000298547800044
Baranac-Stojanovic, M (reprint author), Univ Belgrade, Fac Chem, Studentski Trg 16,POB 158, Belgrade 11000, Serbia., mbaranac@chem.bg.ac.rs
Ministry of Science of the Republic of Serbia; Deutscher Akademischer
Austauschdienst (DAAD) [ID: 504 252 70]
Marija Baranac-Stojanovic
Andreas Koch
Erich Kleinpeter
eng
uncontrolled
ab initio calculations
eng
uncontrolled
anisotropic effects
eng
uncontrolled
NMR spectroscopy
eng
uncontrolled
nucleus-independent chemical shift
eng
uncontrolled
pi interactions
Institut für Chemie
Referiert
35707
2012
2012
eng
6284
6288
5
31
68
article
PERGAMON-ELSEVIER SCIENCE LTD
OXFORD
1
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Novel piperidine-fused benzoxazino- and
quinazolinonaphthoxazines-synthesis and conformational study
The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl) methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzox-azinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, G(tct)(1) for 4 and G(tct)(1) for 7, were corroborated by spatial NOE information relating to the H-7a-H-10a-H-15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements. (C) 2012 Elsevier Ltd. All rights reserved.
TETRAHEDRON
10.1016/j.tet.2012.05.048
0040-4020
wos:2011-2013
WOS:000306195800025
Fulop, F (reprint author), Univ Szeged, Inst Pharmaceut Chem, Hungarian Acad Sci, Eotvos U 6, H-6720 Szeged, Hungary.
, fulop@pharm.u-szeged.hu; ekleinp@uni-potsdam.de
Hungarian Research Foundation (OTKA) [K-75433,
TAMOP-4.2.1/B-09/KONV-2010-0005]; Deutsche Akademische Austauschdienst
(DAAD) [50368559]; Bolyai Janos Fellowship
Renata Csuetoertoeki
Istvan Szatmari
Matthias Heydenreich
Andreas Koch
Ines Starke
Ferenc Fueloep
Erich Kleinpeter
eng
uncontrolled
Quinazolines
eng
uncontrolled
Naphthoxazines
eng
uncontrolled
DFT structural study
eng
uncontrolled
Conformational analysis
eng
uncontrolled
NMR spectroscopy
35821
2012
2012
eng
4600
4608
9
24
68
article
Elsevier
Oxford
1
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Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c] quinazolin-13-ones
The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A(1), but also the rearranged chain form A(2) as a new tautomer were detected in DMSO at room temperature. The quantity of A(2) in the tautomeric mixture was changed with time.
Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS.
Tetrahedron
10.1016/j.tet.2012.04.026
0040-4020
wos:2011-2013
WOS:000304798800005
Kleinpeter, E (reprint author), Univ Potsdam, Dept Chem, Karl Liebknecht Str 24-25, D-14476 Potsdam, Golm, Germany., ekleinp@uni-potsdam.de; fulop@pharm.u-sze-ged.hu
Hungarian Research Foundation (OTKA) [K-75433]; Deutsche Akademische
Austauschdienst (DAAD) [50368559]; Bolyai Janos Fellowship;
[TAMOP-4.2.1/B-09/KONV-2010-0005]
Renata Csütörtöki
Istvan Szatmari
Andreas Koch
Matthias Heydenreich
Erich Kleinpeter
Ferenc Fulop
eng
uncontrolled
Naphthoxazinoquinazolinones
eng
uncontrolled
Aminonaphthols
eng
uncontrolled
NMR spectroscopy
eng
uncontrolled
Conformational analysis
eng
uncontrolled
Theoretical calculations
eng
uncontrolled
Ring current effect
Institut für Chemie
Referiert