20-May-2013
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NISCAIR ONLINE PERIODICALS REPOSITORY (NOPR) >
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Indian Journal of Chemistry -Section B (IJC-B) >
IJC-B Vol.51B [2012] >
IJC-B Vol.51B(08) [August 2012] >
| Title: | Effect of A1,3-strain on the stereochemistry of N-acetyl and N,O-diacetyl-r-2,c-6-diphenylpiperidin-4-one oximes |
| Authors: | Vijayalakshmi, R
Muthukumar, M
Ponnuswamy, S
Jeyaraman, R |
| Keywords: | A1,3-strain
N-acetylpiperidin-4-one oximes
N,O-diacetylpiperidin-4-one oximes
NMR spectra
Semiempirical MO calculation
X-ray crystal structure
Variable temperature 1H NMR spectra |
| Issue Date: | Aug-2012 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | The
stereochemical consequences of the introduction of A1,3-strain by
means of acetyl groups in r-2,c-6-diphenylpiperidin-4-one oximes have
been studied using various NMR spectral techniques, X-ray crystallographic
analysis and semiempirical MO calculations. The NMR spectral results show that
the N,O-diacetylpiperidin-4-one oximes 12-15 prefer to adopt twist-boat conformation with an equilibrium
between syn and anti rotamers. From the variable temperature 1H NMR
spectral studies carried out on N,O-diacetyl-t-3-methyl-r-2,c-6-diphenylpiperidin-4-one oxime 13, the syn-anti rotational
barriers DG#AB and DG#BA have been found to be 44.2 and 43.5 kJ
mol-1, respectively. The X-ray crystal structure of N,O-diacetyl-t-3-isopropyl-r-2,c-6-diphenylpiperidin-4-one
oxime 14 also show twist-boat
conformation. The conformational preferences obtained from the semiempirical MO
calculations for N,O-diacetylpiperidin-4-one oximes 12-15 have been found to be similar to
those predicted from the NMR spectral studies and X-ray crystallographic
analysis. Similarly, the N-acetyl-r-2,c-6-diphenylpiperidin-4-one
oximes 5-7 have been found to adopt
twist-boat conformations.
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| Page(s): | 1151-1162 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-0983(Online); 0376-4699(Print) |
| Source: | IJC-B Vol.51B(08) [August 2012]
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