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http://nopr.niscpr.res.in/handle/123456789/14513| 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. |
| Page(s): | 1151-1162 |
| ISSN: | 0975-0983(Online); 0376-4699(Print) |
| Appears in Collections: | IJC-B Vol.51B(08) [August 2012] |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| IJCB 51B(8) 1151-1162.pdf | 114.42 kB | Adobe PDF | View/Open |
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