Synthesis and NMR spectroscopic conformational analysis of benzoic acid esters of mono- and 1, 4-dihydroxycyclohexane, 4-hydroxycyclohexanone and the -ene analogue – The more polar the molecule the more stable the axial conformer. Issue 27 (6th July 2017)

• Record Type: Journal Article
• Authors: Kleinpeter, Erich; Werner, Peter; Linker, Torsten
• Is Part Of: Tetrahedron. Volume 73:Issue 27/28(2017)
• Page Start: 3801
• Page End: 3809
• Publication Date: 2017-07-06
• Subjects: Conformational analysis -- A-values of COOAr on cyclohexane -- Benzoic acid esters -- Dynamic NMR -- DFT calculations; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2017.04.029
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: para -Substituted benzoic acid esters of cyclohexanol, 1, 4-dihydroxycyclohexane, 4-hydroxy-cyclohexanone and of the corresponding exo -methylene derivative were synthesized and the conformational equilibria of the cyclohexane skeleton studied by low temperature 1 H and 13 C NMR spectroscopy. The geometry optimized structures of the axial/equatorial chair conformers were computed at the DFT level of theory. Only one preferred conformation of the ester group was obtained for both the axial and the equatorial conformer, respectively. The content of the axial conformer increases with growing polarity of the 6-membered ring moiety; hereby, in addition, the effect of sp 2 hybridization/polarity of C(4)=O/C(4)=CH2 on the present conformational equilibria is critically evaluated. Another dynamic process could be studied, for the first time in this kind of compounds. Graphical abstract: