Chair–chair interconversion in some highly substituted 1,2,4-trioxanes and 1,3-dioxanes. A dynamic NMR study of a striking effect of skeletal substitution

Abstract

A dynamic NMR determination of barriers to chair–chair interconversion in some tetra- and hexa-substituted 1,2,4-trioxanes and 1,3-dioxanes is reported. Two comparisons of trioxanes and equivalently substituted dioxanes show that trioxane barriers are strikingly higher, and this is attributed to the high barrier to rotation about the oxygen–oxygen bond in the trioxane series.