The substituent axial conformation in alkoxy- or siloxy-substituted six-membered cyclic compounds must be stabilized by the existence of an electron-withdrawing group or a double bond in their molecules, which can be rationalized in terms of the σ(C-H)→σ*(C-OR) or π(C=C)→σ*(C-OR) orbital overlap concept. The basicity of the oxygen atom of alkoxy and siloxy substituent groups may effect the relative stability of the substituent axial conformer.