Conformational Aspects of Some Methoxysubstituted Hexacarbocyclic Derivatives

The quantitative conformational behaviour of a methoxy group is studied in a series of hexacarbocyclic compounds I, II, III and VII depicted in SCHEME 1. It is found (Table I) that the equatorial preference of that group is accentuated in polar solvents such as freon 21, propably for entropy reasons. The conformational behaviour is normal for the spiro derivative II, but in the 2‐methoxy cis‐decalane a complex situation arises from additional no‐bond interactions in the decalane skeleton itself. Some derivatives in which the conformational behaviour of a hydroxy group could be weighted against that of a methoxy group were also investigated, and show results in accordance with expectations. Finally the barrier for ring reversal between equienergetic conformer possessing various types of methoxy substitutions were studied by different methods (Table III). The unreliability in the calculation of ΔH∦ and ΔS∦ was noted.