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http://nopr.niscpr.res.in/handle/123456789/16312| Title: | Influence of A 1,3 -strain on the conformational preferences and stereodynamics of N-formyl-cis-2,6-diarylpiperidines |
| Authors: | Jeyaraman, R Thenmozhiyal, J C Murugadoss, R Venkatraj, M |
| Issue Date: | Mar-1999 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | Ten N-formyl-cis-2,6-diarylpiperidines
have been prepared and their preferred conformations are determined using NMR spectral
studies and semiempirical calculations (AM1 and PM3 of MOPAC 6). The severe A 1,3 -strain due to the
interaction between the N-C=O group (coplanar to the C2-N1-C6 plane) and the
adjacent aryl group forces the N-forrnyl-cis-2,6- diarylpiperidines 19-28
to prefer
flattened boat conformations with nitrogen at one of the base positions (VIA
and VIB;
Figure1). Employing variable
temperature NMR studies, the barriers for N-C rotation in the N-formylpiperidin-4-one 19 and
the N-formylpiperidine 28 are found to be 72.5 and 65.8
kJ mol-1, respectively, which are in general, lower than those of the
corresponding N-nitrosopiperidines.
The lower energy barrier (ΔG#) of the N-formylpiperidine 28 compared to the N-formylpiperidin- 4-one 19 (by 6.7 kJ mol-l)
is attributed to the larger ground state destabilization of N- formylpiperidine 28
than 19. Semiempirical calculations
show a hydrogen bond type of attraction between the electron-rich oxygen atom
of N-C=O group and the electron deficient hydrogen at  -position (H2). |
| Page(s): | 325-336 |
| Appears in Collections: | IJC-B Vol.38B(03) [March 1999] |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| IJCB 38B(3) 325-336.pdf | 2.31 MB | Adobe PDF | View/Open |
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