Relative stabilities and conformational ring inversion potentials in heterocyclic decalin systems and stereoelectronic implications

Abstract The energy differences between stereoisomers and the ring inversion potential surfaces of decalin ( 1 ) and various oxadecalins ( 2, 3 ), dioxadecalins ( 4–7 ), trioxadecalins ( 8, 9 ) and tetraoxadecalins ( 10, 11 ) were interrogated following the generally accepted scheme of a stepwise conformational six-ring inversion process and using molecular mechanics techniques (MM3 and MM3-GE, i.e. MM3 reparametrized for treatment of the “gauche effect”). The results were compared with some available experimental data and were also used to probe the validity of a recently elaborated protocol for ring-fragment analysis of oxygen-containing bicyclic systems in terms of their interannular fragment components: CCCC, CCCO, CCOC, COCOC and OCCO, the latter two with their corresponding stereoelectronic effects, namely, the “anomeric effect” and the “gauche effect”, respectively.