1H and 13C NMR spectral study of some 3-aryl-5r-aryl-6t-carbethoxycyclohex-2-enones-a study of four-bond 1H1H couplings

• Published in: Magnetic resonance in chemistry Vol. 49; no. 5; pp. 253 - 257
• Main Authors: Yuvaraj, C., Pandiarajan, K.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-05-2011
• Subjects: 13C NMR; 1H NMR; cyclohex-2-enones; four-bond 1H1H coupling
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.2724

Nine 3‐aryl‐5r‐aryl‐6t‐carbethoxycyclohex‐2‐enones 2a–2i have been synthesized. For all these compounds, 1H and 13C NMR spectra have been recorded. For two compounds, 2D spectra have been recorded. The spectral data suggest that these compounds adopt sofa conformation in solution with H‐5, H‐6 and H‐4t occupying axial‐like positions and H‐4c occupying equatorial‐like positions. In 3‐phenyl‐5r‐(o‐chlorophenyl)‐6t‐carbethoxycylohex‐2‐enone (2b), the o‐chlorophenyl group is oriented such that the chlorine atom is in between H‐4c and H‐5. Allylic coupling of H‐2 is observed only with H‐4t. Evidence has been obtained for four‐bond coupling between 1,3‐diaxial and 1,3‐axial–equatorial protons. Copyright © 2011 John Wiley & Sons, Ltd.
The title compounds adopt sofa conformation shown in figure in solution. Allylic coupling of H–2 has been observed only with H–4t. Evidence has been obtained for four‐bond coupling between H–6 and H–4t and between H–6 and H–4c.