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IJC-B Vol.47B(03) [March 2008] >


Title: Stereochemistry and stereodynamics of N-chloroacetyl-r-2,c-6- diarylpiperidin-4-ones - NMR studies and semi-empirical molecular orbital calculations
Authors: Venkatraj, M
Ponnuswamy, S
Jeyaraman, R
Keywords: N chloroacetyl r 2,c 6 diarylpiperidin-4 one
NMR spectra
Semiempirical MO calculation
Boat conformation
syn and anti rotamers
Variable temperature ¹H NMR spectra
Energy barrier
Issue Date: Mar-2008
Publisher: CSIR
Abstract: The preferred conformations of N chloroacetyl r 2,c 6 diarylpiperidin-4 ones 8-14 have been determined using NMR spectral techniques, X ray crystallography and semi-empirical molecular orbital calculations (AM1 method). The NMR spectral data indicates that the N chloroacetyl r 2,c 6 diarylpiperidin 4 ones 8-14 are found to exist in conformational equilibrium between the syn rotamer of boat conformations B1 and anti rotamer of boat conformations B2 in solution. The preferred conformation of 12 obtained through X ray crystallography is found to be the syn rotamer of boat conformation B1 with C2 and C5 occupying the prow and stern positions. The barriers for the N CO rotation determined using variable temperature ¹H NMR spectral studies for the N chloroacetyl derivatives 8 and 12 are 54.2 and 50.3 kJ mol⁻¹, respectively. The semi-empirical calculations (AM1 method) for the N-chloroacetyl derivatives 8-14 also support the conformational equilibrium between syn rotamer of boat conformations B1 and anti rotamer of boat conformations B2.
Page(s): 411-426
ISSN: 0376-4699
Source:IJC-B Vol.47B(03) [March 2008]

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