An N.M.R. study of some esters and lactones derived from cineolic anhydride

Abstract

Cineolic anhydride is attacked by nucleophiles exclusively at its more exposed carbonyl group. The dimethyl ester of cineolic acid has been studied by proton N.M.R. spectroscopy and its conformation assigned. Similar assignments have been made for cineolic anhydride and two lactones derived from it, examples of the 3,6-dioxabicyclo[3,2,2]nonane ring system. In each case the N.M.R. signal of the methine proton is simplified by the use of a lanthanide shift reagent so that the conformation can be deduced. The shift reagent removes the effect of virtual coupling to the methine proton.