TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Kirpichenko, Svetlana V.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational analysis of 1,3-azasilinanes
JF  - Tetrahedron
N2  - 1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature H-1/C-13 NMR spectroscopy, iteration of the H-1 NMR spectra and quantum chemical calculations showed slight predominance of the PheqMeax over the PhaxMeeq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol.
KW  - 1,3-Azasilinanes
KW  - Conformational analysis
KW  - Dynamic NMR spectroscopy
KW  - Quantum chemical calculations
KW  - Ring current effect
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.05.106
SN  - 0040-4020
VL  - 68
IS  - 36
SP  - 7494
EP  - 7501
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Csütörtöki, Renata
A1  - Szatmari, Istvan
A1  - Koch, Andreas
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
A1  - Fulop, Ferenc
T1  - Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c] quinazolin-13-ones
JF  - Tetrahedron
N2  - 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.
KW  - Naphthoxazinoquinazolinones
KW  - Aminonaphthols
KW  - NMR spectroscopy
KW  - Conformational analysis
KW  - Theoretical calculations
KW  - Ring current effect
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.04.026
SN  - 0040-4020
VL  - 68
IS  - 24
SP  - 4600
EP  - 4608
PB  - Elsevier
CY  - Oxford
ER  -