Study of molecular structures for arylidene derivatives of 3 R ‐methylcyclohexanone by 1 H NMR and molecular simulation

• Published in: Magnetic resonance in chemistry Vol. 41; no. 7; pp. 517 - 525
• Main Authors: Pivnenko, Nikolay S., Krivoshey, Alexander I., Kutulya, Lidiya A.
• Format: Journal Article
• Language: English
• Published: 01.07.2003
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.1199

Abstract Conformational states of the cyclohexanone ring were established for 3 R ‐methyl‐6‐(4‐phenylbenzylidene)cyclohexanone and several 2,6‐bis(4‐X‐benzylidene)‐3 R ‐methylcyclohexanones (X = Br, OCOCH 3 and C 6 H 5 ) by 1 H NMR spectroscopy combined with molecular simulation using the semi‐empirical methods AM1 and PM3. The first compound studied contains only one arylidene group, and exists predominantly in a chair conformation of the cyclohexanone ring with an equatorial orientation of the methyl substituent in C 6 D 6 and CDCl 3 solutions at room temperature (22–23 °C). In contrast, the 2,6‐bis(arylidene) derivatives of 3 R ‐methylcyclohexanone preferentially adopt conformations with an axially oriented methyl group. The extent of twisting of enone fragments was also characterized for the compounds studied based on simulation results and comparison of chemical shifts for the arylidene protons of appropriate model compounds. Copyright © 2003 John Wiley & Sons, Ltd.