Structures of some hexa-1,5-diene-1,1,3,3,4,4,6,6-octacarboxylic esters

Abstract

The structures of the octamethyl ester, m.p. 139°, and the octaethyl ester, m.p. 86°, obtained by condensation of two molecules of methyl or ethyl sodiodicarboxyglutaconate, as derivatives of hexa-1,5-diene have been proved. The complete lack of normal electrophilic olefinic reactivity shown by these esters cannot be explained by intramolecular cyclisation to isomeric derivatives of bicyclo[2,1,1]hexane or bicyclo[2,2,0]hexane, and is regarded as arising from adverse polar and steric factors. The experimental work recorded by Ingold, Parekh, and Shoppee in 1936, where repeated, has been confirmed and the structures then assigned, with a single exception, proved by n.m.r. spectroscopy and mass spectrometry.