Conformational analysis of some 1R,4S-2-arylidene-p-menthan-3-ones by H-1 NMR spectroscopy and molecular simulation

摘要

Based on H-1 NMR spectral analysis combined with molecular simulation, conformational states of the cyclohexanone ring were studied for some 1R,4S-2-(4-X-benzylidene)-p-menthan-3-ones (X = COOCH3 or C6H5) in CDCl3 and C6D6. The co-existence of chair conformers with an axial orientation of both alkyl substituents and twist-boat forms was established for the compounds studied at room temperature (22-23degreesC). The substituent X does not influence appreciably the ratio of these conformers, but the fraction of twist-boat forms increases noticeably in benzene solutions as compared with CDCl3 solutions. Rotameric states of the isopropyl fragment were also characterised for the compounds studied. Distinctions in conformational states for the 1R,4S-2-arylidene-p-menthan-3-ones and (-)-menthone were revealed and are discussed. Copyright (C) 2002 John Wiley Sons, Ltd. [References: 39]