| | 1 | Author
| Ulrike Holzgrabe, Willy Friedrichsen, Rl-FH. Esse | Requires cookie* | | | Title
| Keto-Enol-Tautomerism and Configurational Isomerism of 2,6-Disubstituted 4-Piperidone-3,5-dicarboxylates [1]  | | | | Abstract
| The dialkyl 2,6-dialkylsubstituted 4-piperidone-3,5-dicarboxylates were synthesized by a M annich procedure. Depending on the substitution at the nitrogen keto-enol-tautomerism and a configurational isomerism at C 2 is observed. The structure o f the N-substituted piperi-done 24 E (C 18H 29N 0 5) has been determined by X-ray analysis: it is characterized by an enol structure o f the /?-ketoester and an axial position o f the alkyl group at C 2 and an equatorial one o f the alkyl group at C 6. The O -H -O hydrogen bond shows characteristic values o f a strong hydrogen bond. The N-unsubstituted piperidones adopt a ketone structure with the all-equatorial position o f all substituents. This stereochemistry is confirmed for other enolic and ketone analogues by N M R spectroscopic methods. To work out the reason for the different thermodynamic stabilities o f the different stereochemical structures o f N-substituted and N-unsubstituted piperidones, various semiempirical calculations were done for series o f simple pairs o f carbonyl/enol tautomers, substituted acetoacetates, oxoglutarate as well as o f syste matically varied substituted cyclohexanone, 4-oxacyclohexanone and 4-piperidone deriva tives. | | | |
Reference
| Z. Naturforsch. 46b, 1237—1250 (1991); received Novem ber 2 1990 | | | |
Published
| 1991 | | | |
Keywords
| 2, 6-Disubstituted 4-Piperidone-3, 5-dicarboxylates, High-resolution N M R, X-Ray, Theoretical Calculations | | | |
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| default:Reihe_B/46/ZNB-1991-46b-1237.pdf | | | | Identifier
| ZNB-1991-46b-1237 | | | | Volume
| 46 | |
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